combo 12
"Good evidence for an original Big Bang that ""created"" our Universe comes from:"
" a background ""glow"" of microwaves with blackbody temperature of about 3 K. "
The number of comets in the Oort Cloud is probably about
1 Trillion
The diagram below illustrates two stars in a visual binary system and the center of mass of this system. Based on this diagram, what is the ratio of the mass of star A to the mass of star B?
1 to 2
The total number of Comets orbiting the sun is estimated to be about
1 trillion
How long will the Sun have spent as a main sequence star when it finally begins to evolve toward the red giant phase?
1010 years
The typical diameter of a spiral galaxy is about:
105 light years.
The total lifespan of the Sun is believed to be
12 billion years.
If the stars at the turnoff point of a cluster have a mass of 3 M, what is the age of the cluster?
6.4×10^8 years
RR Lyrae variable
A type of pulsating star with a period of less than one day.
Cepheid variable
A type of yellow, supergiant, pulsating star.
Why is the fact that the cosmic background radiation (CBR) is near smooth considered a problem?
A universe as smooth as predicted by the CBR should never have occurred because quantum mechanics states that the universe had to have started with fluctuations too great to have smoothed out
If you lived today on the farthest quasar we can see and looked around, what would you see?
A universe much as we see it today
long-period variable
A variable star with a period longer than about 100 days.
What is the Hubble flow?
Distant superclusters of galaxies are all moving away from us, their speed increasing with increasing distance.
What is the relationship between the mass of a protostar and the time needed for it to reach the main sequence, after it forms inside an interstellar cloud?
More massive protostars reach the main sequence in a shorter time than less massive protostars.
At the end of a high-mass star's life, it produces new elements through a series of helium capture reactions.
Observations show that elements with atomic mass numbers divisible by 4 (such as oxygen-16, neon-20, and magnesium-24) tend to be more abundant in the universe than elements with atomic mass numbers in between. Why do we think this is the case?
The phase of matter in the sun is?
Plasma
Which of the following stars are metal poor?
Population II stars
Why wont pluto collide with neptune
The two planets have an orbital resonance that prevents them from colliding
Which statement about dark dust clouds is true?
They can be penetrated only with longer wavelengths such as radio and infrared.
What characteristic of Cepheid variables makes them extremely useful to astronomers?
Their absolute magnitude is related directly to their metal content (heavy element abundance).
Which statement about black holes is true
Their escape velocity is greater than the speed of light.
T/F 1. The sun at a absolute magniture + 4.8, would be one of the brightest stars in the sky if seen from 32 light years distance.
True
T/F A parsec is about 3.3 light years.
True
T/F A type B star is bluer than a type G star
True
T/F A type b9 star is hotter than a type A0 star
True
T/F About 90% of that star's total life is spent on the main sequence
True
T/F Almost all stars on the main sequence range from 15 to 0.1 solar radius
True
T/F Although sunspots are cooler areas in the photosphere, an increase in their number tells us the Sun is becoming more active
True
T/F As a main-sequence star, the Sun's hydrogen supply should last about 10 billion years from ZAMS until its evolution to the giant stages
True
T/F Carbon will be the last, heaviest element formed in stage 11 by our sun
True
T/F Chandrasekhar's limit is 1.4 times more massive than our Sun.
True
T/F Dark dust clouds are cooler than their surroundings True Young open clusters contain a lot of hot, young blue white stars
True
T/F During the fusion process, mass is converted into energy.
True
T/F Elements heavier than iron are formed mainly in supernovae
True
T/F Emission Nebulae are created by gas absorbing ultraviolet energy from the hot young stars within them, such as in the Orion Nebula
True
T/F For bright stars to form, the protostars must condense in a dense, dark nebulae
True
T/F Globular clusters are dominated by bright red supergiants at the top right of the H-R diagram
True
T/F Gold is rare since the only time it can be formed is during the core collapse of a supernova
True
T/F Granulation is the most obvious proof of solar convective energy transport
True
T/F Helium fusion requires a higher temperature than hydrogen fusion
True
T/F Hydrogen lines are strongest in a class A stars
True
T/F In describing other stellar properties, almost everything is relative to our sun
True
T/F In the proton proton chain, helium atoms are fused into hydrogen.
True
T/F Interstellar matter is distributed uniformly throughout the Milky Way
True
T/F Less than 100 stars lie within 5 parsecs of the sun.
True
T/F Main sequence stars are fusing hydrogen into helium in their cores
True
T/F Most naked eye stars would fall to the top left on the H-R diagram
True
T/F O and B type stars are usually found associated with emission nebulae
True
T/F Once the helium flash occurs at stage 10, the star stabilizes again on the horizontal branch of the H-R diagram, but now hundreds of times as bright as on the main sequence.
True
T/F Our nearest stellar neighbor is a little less than 1 parsec away.
True
T/F Paradoxically, while the core of the red giant is contracting and heating up, its radiation pressure causes its photosphere to swell up and cool off.
True
T/F Prominences are extensions of the solar magnetic fields above sunspots
True
T/F Sunspots usually come in pairs, each a magnetic pole.
True
T/F Supergiants are burning different fuels in several shells around the core.
True
T/F The blue stragglers represent the horizontal branch for globular clusters
True
T/F The density of white dwarf stars is about a million times that of the Sun
True
T/F The final step in transporting energy to the surface of the sun is via convection
True
T/F The granules in the photosphere are about as big as texas, or around 1,00 km across.
True
T/F The least massive red main sequence stars may be lifetimes of a trillion years
True
T/F The mass of a newly formed star will determine its position on the main sequence
True
T/F The photosphere is the coolest layer close to the sun, for the radiation of visible light allows it to cool off efficiently.
True
T/F The solar corona is best studied using x-ray telescopes
True
T/F The solar wind is constantly removing mass from the sun
True
T/F The sun produces energy by fusing hydrogen into helium.
True
T/F The sun's density is about the same as Jupiter's suggesting a similar composition.
True
T/F The sun's magnetic field is very weak compared to Earth's
True
T/F There is as much mass in the voids between the stars as in the stars themselves
True
T/F To get to space velocity of a star in three dimensions, you need its proper motion, distance, and radial velocity.
True
T/F While more massive than most of our neighbors, our sun is still technically a low mass star
True
T/F While there are none yet, in the very distant future, most normal matter will be in the form of black dwarfs
True
T/F White dwarfs were once the cores of stars that produced planetary nebulae
True
The proton-proton chain converts four hydrogen nuclei into one helium nucleus.
True
The total mass of the Kuiper Belt is greater than that of the asteroid belt
True
The upper limit to the mass of a white dwarf is 1.4 solar masses.
True
In the verification of the Hubble law for the expansion of the universe and the determination of the constant H0, the greatest difficulty has been
accurate determination of distances to very distant galaxies.
Seyfert galaxies are:
active galaxies with very bright star-like nuclei.
Among discovered meteorites, we have found some with all the following origins except
being a fragment from Comet Halley
The carbon-nitrogen-oxygen cycle
combines four hydrogen nuclei to form one helium nucleus, which produces energy.
Sunspots...
come in pairs, representing the north and south magnetic fields
Which statement is not thought to be true of all comets in our solar system?
comets always have tails
How can we determine an asteroid's reflectivity?
comparing its infrared thermal emission to its visible-light reflection
Two important properties of young neutron stars are made of
compressed neutrons in contact with each other.
If dark matter is not visible, how have scientists inferred its presence?
dark matter curves spacetime
The one component of the material of the Milky Way galaxy that prevents us from seeing and photographing the galactic center at optical wavelengths is:
interstellar dust.
What is the physical reason for the appearance of periodic splitting and recombining of spectral lines in the spectra of binary stars?
Doppler shift of light from stars orbiting each other and moving toward and away from Earth during this orbital motion
When particle-antiparticle pairs are created just outside the event horizon of a black hole, one member can escape while the other enters the black hole. What is the name of this stream of particles leaving a black hole?
Hawking radiation
stellar spectra tell us that blank is the second most abundant element in the sun
Helium
As a main sequence star burns its core supply of hydrogen, what happens?
Helium builds up as ash in the core
____ are small luminous nebulae excited by nearby young stars.
Herbig-Haro objects
it is a low density gaseous object
the fact that Jupiter has a volume of 1000x that of the Earth but only 300x the mass of the Earth implies that
Most stars in our part of the Galaxy are formed in associations
thousands of stars in the galaxy's spiral arms.
Approximately, what basic composition are all stars born with?
three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements
The effect of interstellar dust on starlight is
to dim and redden distant stars by preferentially scattering their blue light.
The effect of interstellar dust on starlight is:
to dim and redden distant stars by preferentially scattering their blue light.
An astronomer plots the H-R diagram of a star cluster and finds that it contains hot B-type stars on the main sequence and cooler G and K-type stars noticeably above the main sequence. This cluster is:
very young because the G and K stars are still evolving toward the main sequence.
Molecular clouds can be observed
using radio telescopes to observe the CO emission from the clouds.
Protostars are
very young objects, still contracting before becoming true stars.
Sometimes particle-antiparticle pairs are created and then annihilate so quickly that we cannot know that they ever existed. What are these particles (or antiparticles) called?
virtual particles
Binary stars separated enough to be resolved in a telescope are called
visual binaries
it is held up by the pressure of the very high temperature gas within it.
what stops the Sun from collapsing under the force of its own gravity?
not enough neutrinos are seen to explain the fusion reactions we believe are taking place in the sun's core.
what was the Solar Neutrino Problem?
its small size compared to Earth
what's the fundamental reason that the Moon, unlike the Earth, has become virtually geologically dead?
nuclear fission
when a large atomic nucleus breaks into two smaller pieces, this is called
earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere.
why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
high temperatures mean high collisional velocities, which can allow protons to overcome their mutual electrical repulsion
why does fusion only take place at very high temperatures
high temperatures mean high collisional velocities, which can allow protons to overcome their mutual electrical repulsion.
why does fusion only take place at very high temperatures?
venus because of its dense carbon dioxide atmosphere
which planet has the highest average surface temperature, and why?
pluto
which planet will be visited by the recently-launched New Horizons mission?
the water was lost when ultraviolet light broke apart water molecules and the hydrogen escaped to space.
venus may have started with an ocean's worth of water. Where is its water now?
Quasars appear to be:
very distant intrinsically bright objects moving away from Earth at very high speeds.
The typical optical spectrum of a quasar shows:
very redshifted emission lines superimposed upon a weak continuum of radiation.
In astronomical terms planetary nebulae are:
very short lived with lifetimes of about 50 000 years.
simple ones are found in the atmospheres of some stars.
which statement is true of molecules?
venus
which terrestrial planet has a dense atmosphere of CO2, surface temperatures over 450 C and a thick cloud cover obscuring the surface?q
The chandraeskhar limit is the upper mass limit of a
white dwarf
The stars with masses comparable to our Sun's, but sizes like the Earth are a
white dwarf
When the outer envelope of a red giant recedes, the remaining carbon core is called a
white dwarf
Black dwarfs are hypothetical stellar remnant, formed when a
white dwarf becomes sufficiently cool to no longer emit significant heat or light. Since the time required for a white dwarf to reach this state is calculated to be longer than the current age of the universe (about 13.7 billion years old) no black dwarfs are expected to exist yet.
The final remnant of the evolution of a red giant star that has ejected a planetary nebula is a
white dwarf star.
The Chandrasekhar limit tells us that
white dwarfs more massive than 1.4 solar masses are not stable.
Stars that have ejected a planetary nebula eventually become
white dwarfs.
Stars that have ejected a planetary nebula go on to become:
white dwarfs.
because the stars never get hot enough inside to fuse heavier nuclei
why can't stars like our sun fuse elements heavier than carbon and oxygen?
because all the heavy elements (e.g. carbon, oxygen) in our cells were formed inside stars by nuclear fusion
why did astronomer and TV personality Carl Sagan say we are all "star stuff?"
because the fuel for energy production at this stage of the star's life is hydrogen, and the star has lots of it in its core
why do all stars spend most of their lives on the main sequence?
because the rotation period of the Moon has been made equal to its orbital period by gravitational interaction with Earth
why does the Moon keep the same face towards the Earth?
much larger radius
why is a cool, red star like Betelgeuse so much more luminous than the cool, red star Proxima Centauri? Note: the use of the word luminous implies that distance is not a factor.
If the sun were replaced by a one solar mass black hole we
would still orbit it in a period of one year.
Cen X-3 shows regular X-ray pulses every 4.84 seconds. What causes these periodic pulses?
x ray hot spots on the surface of a rotating neutron star
What is the origin of the diffuse X-ray background?
x rays from accreting black holes
The mechanism that gives rise to the phenomenon of the nova is:
matter from a companion star falling onto a white dwarf in a close binary system eventually causing a nuclear explosion on the dwarf's surface.
The spectra of most galaxies tell us that
most galaxies appear to be moving away from us
If we could put all the asteroids together, their total mass would be
much less than the mass of any terrestrial planet
A black hole is so named because:
no light can escape from it due to its powerful gravitational field.
Compared to a cluster containing type O and B stars, a cluster with only type F and cooler stars will be
older
The fact that we live in an accelerating universe indicates that the age of the universe is ____________ the Hubble time.
older than
12 hours day; 12 hours night
on September 22nd, approximately how long was day and night in New York?
grapefruit, ballpoint
on a scale of 10 billion to one, the Sun would be the size of a _______ and the Earth the size of a ________ 50 feet away
how long does the sunspot cycle last,
on average 11 years
Astronomers use millimeter wavelength radiation to find giant molecular clouds. What is the source of this millimeter radiation?
rotational energy changes in the CO molecule
As a high-mass main sequence star evolves off the main sequence, it follows a ___________ the HR diagram.
roughly horizontal path
increase by 256 times
suppose the surface of the Sun suddenly got four times hotter, but somehow did not change its size. How would the Sun's luminosity change?
20 m/s
the acceleration of gravity on Earth is approximately 10 m/s2 (more precisely, 9.8m/s2). If you drop a rock from a tall building, about how fast will it be falling after 2 seconds?
The event which marks the end of the main sequence lifetime of a star is
the end of hydrogen fusion in the core.
white dwarf.
the end state of a one-half solar mass star is a
A planetary nebula is
the expelled outer envelope of a medium mass star.
A Type II supernova is:
the explosion of a massive star after silicon burning has produced a core of iron nuclei.
A Type Ib supernova is believed to result from:
the explosion of a massive star that has lost its hydrogen-rich outer layers through a stellar wind or mass transfer in a binary star.
A Type Ia supernova is:
the explosion of a white dwarf in a binary star system after mass has been transferred onto it from its companion.
detached binary
A binary star system in which neither star fills its Roche lobe.
semidetached binary
A binary star system in which one star fills its Roche lobe.
____ occurs when most of the material collapsing to form a protostar has fallen into a disk around the star, and a strong wind from the warm protostar ejects material from its poles.
A bipolar outflow
What is a brown dwarf?
A brown dwarf is a celestial body that doesn't have sufficient mass to initiate hydrogen fusion and thereby become a true star. They have heat due to their initial gravitational contraction or maybe even a brief deuterium, lithium fusion stage but are now little more than a (hot) giant planet.
overcontact binary
A close binary system in which the two stars share a common atmosphere.
After what evolutionary stage does a star become a white dwarf?
Giant
If a star with an absolute magnitude of −5 has an apparent magnitude of +5, then its distance is
1000 pc.
The question asked in Olbers's paradox of cosmology is:
"Why is the sky dark at night?"
What mechanism is thought to allow material to spiral into a black hole?
(Due to differential rotation in the accretion disk) magnetic viscosity transfers angular momentum outward (allowing material to fall inwards)
At a redshift of z = 1,000, the universe was
1000 times smaller than it is today
How does the efficiency of accretion depend on the nature of the black hole?
(theory predicts) large efficiency of accretion onto spinning black holes
Which of the following apparent magnitudes is the brightest?
*** -1.4
In which star's spectrum are the hydrogen lines strongest?
*** A;ApM 3;AbM 1;ST A2
Which star has the bluest color?
*** B;ApM 5;AbM 2;ST 09
Which star appears the brightest?
*** C;ApM 1;AbM 5;ST G5
Which star is closer to us than 10 parsecs?
*** C;ApM 1;AbM 5;ST G5
Which star has the greatest intrinsic luminosity?
*** D;ApM 10;AbM -4;ST K5
Which star is reddest?
*** D;ApM 10;AbM -4;ST K5
Which star is the most distant?
*** E;ApM 15;AbM 0;ST F3
Which of the following spectral types is the hottest?
*** G2,lesson 15 speedback
Which of the following distances is the largest?
*** One parsec
1. the temperature of the photosphere is about
5800K
The lowest mass object that can initiate thermonuclear fusion of hydrogen has a mass of about
0.08 solar masses.
Which of the following stars spend the longest time on their Hayashi tracks?
0.1 M₀ stars
In what range of masses are most stars found?
0.1 to 100 ? (not 0.1-20?)
Assuming a Hubble time of 13.6 billion years and a constant rate of expansion, what was the scale factor (R₀) of the universe 10.2 billion years ago (compared to today)?
0.25
List the three types of objects a star's core can collapse to, and give the mass limits for each
1) White Dwarf: Mass <1.4 solar masses 2) Neutron Star: Mass 1.41 up to 3.0 solar masses (scientific uncertainty on upper mass limit) 3) Black Hole: Mass > 3.0 solar masses (Some suspect there is another between Neutron and Black Hole called a Quark Star but it is not proven)
The temperature of the cosmic background radiation 2.73 K corresponds to a peak wavelength of around
1,000 um
Stars with masses less than ____ produce most of their energy via the proton-proton chain.
1.1 solar masses
The mass range of a neutron stars is
1.35 Solar masses (2.69e+30 kg) to 2.40 Solar masses (4.16e+30 kg).
A Type I supernova occurs when a white dwarf exceeds a mass of ____________.
1.4 M₀
There is a mass limit for a star in the white dwarf phase the Chandrasekhar limit beyond which the star can no longer support itself against its own weight. This mass limit in terms of solar mass is:
1.4.
There is a mass limit for a star in the white dwarf phase, the Chandrasekhar limit, beyond which the star can no longer support its own weight. This mass limit, in terms of solar mass, is
1.4.
What is the lifetime on the main sequence of a 2 solar mass star compared to the approximately 10 billion year life of our Sun? Pick the best answer.
1.8×10^9 years
If, at the time of recombination, the wavelength of the background radiation peaked at 1 um, how old was the universe, compared to today?
1/1,000th as old
Approximately what fraction of the Sun's main-sequence lifetime has been completed at the present time?
1/2 •half
What is the approximate age of the star cluster in the H-R diagram below? Hint: Main sequence stars of spectral types between A and B core's supply of hydrogen is sufficient to last about 250 million years. Between A and F about 2 billion years. Type G about 10 billion years. Between K and M about 30 billion years.
10 billion years
The critical temperature to initiate the proton-proton cycle in the cores of stars is
10 million K
Which is closest to the temperature of the core of the Sun?
10 million K
Measurements suggest that light first arrived at Earth from the Cassiopeia A supernova about 300 years ago and that this supernova is about 10,000 light years away from Earth. When did the explosion actually occur?
10,300 years ago, or about 8300 BC
Two stars that differ from each other by five magnitudes differ in brightness by a factor of:
100
Two stars that differ from each other by five magnitudes have a ratio of brightness of:
100
If the dust around a protostar radiates most strongly at 30 microns or 30,000 nm, what is the approximate temperature of that dust? Hint: T in K =3,000,000/wavelength in nm.
100 K
Fred and Joanne both measure the length of a particular spaceship to be 100 m when it is on Earth. Joanne then gets into the spaceship and, after visiting the Moon, hurtles past Earth at a speed close to the speed of light. Fred, still on Earth, measures the length of the moving spaceship to be about 90 m. At the same time, Joanne (using her own meterstick) measures the length of the spaceship to be
100 m because she is "at rest" on the spaceship.
What temperature is needed to fuse helium into carbon?
100 million K
If the Hipparchos satellite measures the parallax motion of a star against the background stars and concludes that the star has a parallax of 0.01 arc second how far is that star from us?
100 pc
The energy output of a bright quasar is equivalent to:
1000 bright galaxies.
The diagram below shows a light curve from a supernova. How many days after maximum light did it take for the supernova to decrease in brightness by a factor of 100?
150
The first search for radio signals from extraterrestrial civilizations was made in:
1960.
In what year was the first pulsar discovered?
1967
The distance to the bright quasar 3C 273 is estimated to be:
2 billion light years.
What is the total mass of a binary star system with P = 20 yr and a = 10 AU?
2.5 solar masses
The star that exploded to form supernova SN1987A probably had before it blew up a mass of about:
20 solar masses.
The estimated rate at which supernovae occur in our Galaxy is about once every:
20 years.
A jet has an angular length of 10 seconds of arc and flows from a star at a distance of 2,000 pc. How far does this jet extend away from the star?
20,000 AU
Neutral hydrogen atoms are best studied from their energy given off as
21 cm waves in the radio region
The spiral-arm structure of the Milky Way galaxy has been measured and evaluated most effectively by observations of:
21cm radiation from interstellar hydrogen and the positions of young stars.
The time taken for the Sun to orbit the galactic center once in its motion in the Galaxy is
220 million years.
A planetary nebula has a radius of 0.5 pc and is expanding at 20 km/sec. What is the approximate age of this planetary nebula? (1 pc is equal to 3×1013 km, and 1 year is equal to 3.15×107 seconds.)
24,000 years
What fraction of the mass of the Universe is helium (as represented by the "standard cosmic abundances" in the interstellar medium)?
25%
What is the dominant nuclear reaction during helium burning in a star?
3 He fusing into C
The evolutionary cutoff between low- and high-mass stars occurs around
3 M₀
The sketch below shows groups of stars on the H-R diagram labeled (a) through (e). Note that (a) represents the entire main sequence while (c) and (d) represent only small parts of the main sequence. https://bcc.blackboard.com/courses/1/PHY-120-300_2014SP/ppg/Chapter15FullPool0101141354/f1q21g1.jpg The approximate main-sequence lifetime of a star of spectral type O is
3 million years.
What is the lifetime of a 10 solar mass star on the main sequence?
3.2×107 years
The absolute magnitude of a star is the brightness the star would appear to have if it were placed at what distance from Earth?
32.6 light years
A star's absolute magnitude is its apparent brightness as seen from
33 light years difference
At what point in the light curve below is the cooler star in front of the hotter star?
4
The diagram below is an H-R diagram. The line indicates the location of the main sequence. Which of the five labeled locations on the HR diagram indicates a luminosity and temperature similar to that of a T Tauri star?
4
The stars that eventually become white dwarfs are those that start life with masses of less than about
4 solar masses.
The stars that eventually become white dwarfs are those that start life with masses of less than:
4 solar masses.
The diameter of our Galaxy is about:
49 kpc.
In the diagram below, which point indicates the location on the H-R diagram of a one solar mass star when it undergoes helium flash?
5
The Sun will exhaust its nuclear fuel in about
5 billion years
The sun will likely stop being a main sequence star in
5 billion years
A nearby star has a parallax of 0.2 arc seconds. What is its distance?
5 pc
If a star has a parallax of 0.02 seconds of arc, then its distance is
50 pc
About how long will a 0.5 star spend on the main sequence?
57 billion years
37. From the data given,, which star in Table 13-1 has the greatest luminosity?
58 Ori
40. From the data given,, which star in Table 13-1 has the greatest diameter?
58 Ori
The Sun's average surface (photosphere) temperature is about
5800 k
36. From the data given, which star in Table 13-1 would appear the faintest in the night sky?
65 Tau
What is the sun made of (by mass)?
70% hydrogen, 28% helium, 2% other elements
What fraction of the mass of the Universe is hydrogen (as represented by the "standard cosmic abundances" in the interstellar medium)?
74%
At about what mass do we distinguish between high-mass and low-mass stars?
8 M₀
41. Which star in Table 13-2 is the closest to Earth?
9 CMa
Dark unknown forms of matter appear to make up about what fraction of the mass of a typical rich cluster of galaxies?
90%
The average star spends ____ of its lifetime on the main sequence.
90%
Interstellar gas is composed mainly of
90% hydrogen, 9% helium by weight.
"Standard candles," which are essential standard units of brightness for measuring distances to remote galaxies, are A. stars and other objects of known intrinsic brightness whose apparent brightness can then be used to find the distance. B. standard laboratory light sources with which the brightness of a galaxy can be compared. C. heat sources of standard intensity used to calibrate infrared observations of galaxies. D. laboratory light sources with accurately measured spectra for calibrating stellar and galactic spectra.
A
A Bok globule is a A. cold, compact cloud of gas and dust. B. large region of ionized hydrogen gas. C. compact knot of ionized gas where a jet from a T Tauri star is colliding with an interstellar cloud. D. giant molecular cloud containing up to two million solar masses of gas and dust.
A
A series of helium shell flashes (also called thermal pulses) causes A. old low-mass stars to produce planetary nebulae. B. young low-mass stars to settle into main-sequence stars. C. asymptotic giant branch stars to settle into the helium core-burning phase. D. degeneracy to be removed from a helium core.
A
A temperature map of the cosmic microwave background, such as that produced by the WMAP probe, shows small-scale fluctuations in the temperature. What do these fluctuations signify, and why? A. Cooler regions are denser because the denser a region, the greater is the gravitational redshift in the light leaving it. B. Warmer regions are denser because the compression raised its temperature. C. Warmer regions surround low-mass primordial black holes because low-mass black holes release energy as they evaporate. D. Cooler regions surround supermassive black holes because these black holes remove mass and energy from the surrounding matter.
A
A virtual particle is any particle that A. exists for such a short time that we cannot detect it by direct measurement. B. exists for such a short time that it has no effect whatsoever on the universe. C. has no mass and no charge. D. cannot act through the gravitational or electromagnetic force.
A
A wormhole is a A. bridge or tunnel connecting two different parts of our universe to each other. B. bridge or tunnel connecting our universe to a parallel universe. C. ring-shaped singularity inside a rotating black hole. D. string-shaped black hole of zero diameter and often thousands of parsecs in length.
A
Almost no sunspots were observed by astronomers between 1645 and 1715 A.D. What effect did this have on weather on the Earth? A. lower than normal temperatures in Europe and a drought in the western United States B. higher than normal temperatures in Europe and heavy rainfall in the western United States C. no detectable effect at all D. heavy rainfall in Europe and higher than normal temperatures in the western United States
A
An elliptical galaxy with a bright, starlike nucleus that has an almost featureless spectrum would be called a A. BL Lacertae object or blazar. B. quasar. C. Seyfert galaxy. D. Herbig-Haro object.
A
An important process that occurs at the end of the life of a massive star is photodisintegration. To what does this term refer? A. absorption of high-energy gamma rays by atomic nuclei, causing the nuclei to split apart B. ejection of protons or neutrons from atomic nuclei, accompanied by emission of high-energy gamma rays C. destruction of the star's core by radiation pressure D. destruction of high-energy gamma rays and consequent production of positive and negative proton pairs
A
An object in the center of an active galaxy with the same diameter as that of Jupiter's orbit brightens in a very short burst of energy that lasts for about 10 seconds. Of what duration would this burst of energy appear to be if observed from Earth, 100 million light-years away? A. 1.5 hours, or 5200 seconds. B. 1 light-day, or 86,400 seconds. C. No burst would be seen since it would be smoothed out over 100 million years of travel time. D. length of the original burst, 10 seconds
A
Astronomers today conclude that the early atmosphere of the Earth was composed of A. carbon dioxide (CO2), nitrogen (N2), water (H2O), and hydrogen (H2). B. hydrogen (H2), ammonia (NH3), methane (CH4), and water (H2O). C. hydrogen (H2), oxygen (O2), and water (H2O). D. carbon dioxide (CO2), water (H2O), helium (He), and argon (Ar).
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Evidence of spiral structure in our Galaxy has been found by measuring the distribution of A. young O and B stars and emission nebulae. B. bright, highly evolved, red giant stars and planetary nebulae. C. globular clusters. D. low-mass red dwarf stars.
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Except for the nearby galaxies in our own cluster, we see all galaxies moving away from us, with more distant galaxies moving faster. What would an observer in a distant galaxy see? A. the same thing we see—all distant galaxies moving away, with more distant galaxies moving faster B. all distant galaxies on one side moving closer and all galaxies on the other side moving away, with more distant galaxies moving faster C. all distant galaxies moving away, with more distant galaxies moving more slowly D. all distant galaxies moving closer, with more distant galaxies moving faster
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For a nonrotating black hole, what is the singularity? A. a location in space (a point) having mass but no volume B. a location in space having volume but no mass C. a location where the escape velocity is equal to the speed of light D. a volume inside which the directions of space and time are interchanged
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For a remote object such as a quasar, the comoving radial distance is the distance A. from the Earth to where the object is actually located now. B. from the Earth to where we see the object now (the distance the light traveled to get here). C. traveled by the object during the time the light took to get here (the difference between where we see it and where it is now). D. traveled by the object from the Big Bang until the end of the universe.
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For many years, neutrino detectors on the Earth detected only about one-third as many neutrinos from the Sun as was expected from theory. The reason for this discrepancy was recently proven to be that the A. neutrinos change from one type to another while in flight. B. Sun's core is 10% cooler than had earlier been thought. C. Sun's core contains less hydrogen than had earlier been thought. D. majority of solar neutrinos pass through the detectors undetected.
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Galactic radio emission at the specific wavelength of 21 cm is produced by A. the rearrangement of the "spins" of proton and electron from parallel (spin axes aligned) to antiparallel (spin axes opposite in direction) in atoms of atomic hydrogen. B. transitions in which electrons fall from the level n = 100 to n = 99 in atomic hydrogen atoms. C. electrons recombining with protons to form neutral atomic hydrogen, where the electron falls from outside the atom into the n = 21 level. D. transitions in which the hydrogen H2 molecule changes its rate of vibration.
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Globular clusters in our Galaxy are distributed in A. a spherical halo centered on the galactic center, moving in elliptical orbits around the center. B. the spiral arms and disk of the Galaxy, moving in circular orbits around the galactic center. C. a broad plane tilted at 55° to the plane of the Galaxy, moving around the galactic center in circular orbits. D. the central bulge, moving in elliptical orbits around the galactic center.
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How do we know that there is at least a small proportion of protons mixed in with the neutrons in the interior of a neutron star? A. The magnetic field of a neutron star is anchored in its interior, and magnetic fields are generated by charged particles in motion. B. The neutron star would collapse to a black hole if it weren't supported by the mutual repulsion of charged particles. C. Protons are produced continuously by pair production in the neutron star's magnetosphere, and they are expected to sink into the interior. D. The universe is predominantly hydrogen, and the nucleus of a hydrogen atom is a proton.
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How does the intensity of typical synchrotron radiation from an active galaxy vary with frequency of the radiation? A. Intensity falls off uniformly with increasing frequency. B. Intensity reaches a peak at some frequency that depends on the temperature of the source and falls off at higher and lower frequencies. C. Intensity increases uniformly with increasing frequency. D. Intensity is the same at all wavelengths (flat spectrum).
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Hydrogen is the most abundant atomic species in the Sun. Why then are absorption lines from hydrogen very weak in the solar spectrum? A. The Sun's temperature is so low that very few electrons in hydrogen atoms are excited to the second energy level, from which absorption of visible light can occur. B. The Sun's temperature is so high that most electrons in hydrogen atoms are at levels above the second level and therefore cannot absorb at visible wavelengths. C. The Sun's temperature is so low that the hydrogen is mostly in molecular form, and Balmer absorption does not occur in molecular hydrogen. D. The Sun's temperature is so high that most hydrogen atoms are completely ionized and therefore have no electrons that can absorb light.
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Hydrostatic equilibrium is a balance between A. gravity and gas pressure. B. gravity and nuclear reactions. C. gas pressure and temperature. D. convection and radiation.
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Hydrostatic equilibrium tells us that A. the force of gas pressure outward is balanced by the pull of gravity inward. B. convectively moving gas is always replaced by an equal amount of fresh gas. C. the energy produced in the core of the Sun is balanced by the flow of energy from the Sun's surface into space. D. the centripetal force outward due to the Sun's rotation is balanced by the force of gravity inward.
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If the Hertzsprung-Russell diagram of all the stars in a cluster is plotted as the cluster evolves, the main sequence A. becomes progressively shorter as high-mass stars exhaust all the hydrogen in their cores and evolve away from the upper end. B. moves slowly across the H-R diagram from left to right, as the stars in it evolve toward the giant branch. C. becomes progressively shorter as low-mass stars exhaust all the hydrogen in their cores and evolve away from the lower red end. D. gradually becomes thinner and disappears as the stars in it evolve from it toward the giant branch.
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If we compare white dwarfs of the same composition, which one of the following statements is correct? A. More massive white dwarfs are smaller. B. More massive white dwarfs are larger. C. Cooler white dwarfs of the same mass are smaller. D. Cooler white dwarfs of the same mass are larger.
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In 2005, the discovery by the NASA rover Opportunity of vast numbers of millimeter-sized spheres of the mineral hematite ("blueberries") on the Meridiani Planum on Mars is significant because A. hematite on the Earth is most commonly produced on the floor of a body of water. B. their round shape is believed to have been created by flowing water. C. the hematite would have been destroyed if water had ever been present on Mars. D. hematite on the Earth is most commonly produced by biological activity.
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In a binary star system with components of unequal masses, A. the larger Roche lobe surrounds the more massive star. B. the larger Roche lobe surrounds the less massive star. C. the Roche lobes are always equal in size whatever the stellar masses. D. only the more massive star has a Roche lobe.
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In a post-main-sequence star with about 1 solar mass whose core is shrinking, what physical process will set a definite limit on further compression of the gas in the core by the force of gravity? A. quantum mechanical behavior of the free electrons, which prevents their crowding together and generates an outward degeneracy pressure B. increase in temperature and hence gas pressure as a result of the release of gravitational energy C. increase in radiation pressure from the γ rays released by thermonuclear fusion of hydrogen nuclei as the gas is compressed D. convection, which carries fresh hydrogen fuel into the core
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In formulating a model for the structure of the universe on the basis of his general theory of relativity, Einstein introduced a "cosmological constant" to correct the theoretical model for what he thought was an incorrect prediction about the universe. How did he think that this cosmological constant would manifest itself? A. as a form of energy, which, if applied on its own, would make the universe expand—a form of antigravity B. as extra "gravity" that would hold the universe against continuous expansion C. as a large number of "white holes" that would contribute matter to an expanding universe to maintain constant density, as required by the cosmological principle; a continuous creation universe D. as a gradual reduction in the energy of photons, causing their wavelength to increase with increased distance traveled, creating an appearance that more distant objects are more redshifted
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In measuring distances to remote galaxies, what is the fundamental plane? A. Relationship among the size of the galaxy, the motions of stars within it, and the distribution of brightness in the galaxy B. The "equatorial" plane, defined by the dark dust band seen in edge-on spiral galaxies C. Plane defined by masers near the visible edge of the galaxy, which are approaching or receding from the Earth, and masers crossing the line of sight near the middle of the galaxy D. Relationship among the tightness of winding of the spiral arms, the size of the central bulge, and the brightness of the brightest H II regions in the galaxy
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In the early 1900s we thought the Sun was at the center of a universe of stars because A. we didn't know interstellar dust obscured most of the structure of the Milky Way. B. stellar motions increase the farther you are from the sun. C. 21-cm radio measurements indicated it. D. mankind naturally should occupy the center of the universe.
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In the entire lifetime of a very low-mass star, how many kinds of thermonuclear reactions occur? A. two: hydrogen fusion and helium fusion B. one: hydrogen fusion to produce helium C. three: hydrogen, helium, and carbon fusion D. many: hydrogen, helium, carbon, oxygen, and heavier element fusion to make even heavier nuclei
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In the famous Miller-Urey experiment, Stanley Miller and Harold Urey showed that, in conditions that they believed were similar to those on the early Earth, A. simple molecules would combine to form complex organic compounds. B. complex organic compounds would combine to form primitive living cells. C. modern living cells are able to survive. D. complex organic compounds extracted from certain primitive meteorites would combine to form cell-like structures.
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In the meteorite ALH 84001, recovered from Antarctica and traced to an origin on Mars, three of the following, indicating the possibility of life on that planet, have been found. Which is the exception? A. enclosed pockets of carbon dioxide (CO2) and methane (CH4), which were most probably produced by life forms B. elongated tube-like structures resembling fossilized microorganisms C. magnetite and sulfide compounds found together in carbonates, a sign of bacterial action D. organic molecules similar to those produced on the Earth by microorganisms
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In the present stage of the Sun's lifetime, it is converting hydrogen into helium in its core. The total lifetime of this stage, from when the Sun first formed until it exhausts the supply of hydrogen in its core, is calculated to be A. approximately 10 billion (1010) years. B. almost 200 billion (2 × 1011) years. C. approximately 5 million (5 × 106) years. D. slightly more than 10,000 (104) years.
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In what way did dark energy affect the evolution of the universe? A. Dark energy causes the universal expansion to accelerate. After about 6 billion years, the accelerating expansion prevented major new structures from forming. B. Dark energy causes the universal expansion to accelerate. After about 6 billion years, the accelerating expansion increased the rate of fragmentation, causing major new structures to form. C. Dark energy heats the universe, preventing small density fluctuations from contracting gravitationally and therefore decreasing the rate of star formation. D. Dark energy cools the universe, allowing smaller density fluctuations to contract gravitationally and therefore increasing the rate of star formation.
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In what way does the appearance of a star change as it evolves beyond its main-sequence phase? A. The star increases in luminosity but cools as its outer layers expand. B. The star's luminosity and temperature both increase as it shrinks following its main-sequence phase. C. Both the luminosity and temperature of the star decrease as hydrogen fusion ceases in its core. D. The star's luminosity decreases as hydrogen fusion ceases in the core, and its temperature increases as the outer layers expand..
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In what way does the formation of structure in the universe differ if the dark matter is cold or if it is hot? A. With cold dark matter, star-forming regions form first, and they merge to become galaxies, then clusters of galaxies, then superclusters; whereas with hot dark matter, supercluster-sized regions form first, and then they fragment into clusters and into galaxies. B. With hot dark matter, star-forming regions form first, and they merge to become galaxies, then clusters of galaxies, then superclusters; whereas with cold dark matter, supercluster-sized regions form first, and then they fragment into clusters and into galaxies. C. With cold dark matter, the first stars are very massive, live short lives, and quickly eject heavy elements in supernova explosions; whereas with hot dark matter, the first stars are low-mass, live long lives, and do not eject significant heavy elements for billions of years. D. With hot dark matter, the first stars are very massive, live short lives, and quickly eject heavy elements in supernova explosions; whereas with cold dark matter, the first stars are low-mass, live long lives, and do not eject significant heavy elements for billions of years.
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Inhabitants of a planet close to the center of our Galaxy would see a night sky that is A. densely covered with stars that light the landscape more brightly than a hundred full moons. B. similar to our own sky, with a few bright stars and a general scattering of faint stars emitting too little light to see clearly at night. C. completely devoid of stars because any that might have existed have been swallowed by the supermassive black hole. D. blindingly bright, flooding the landscape with more light than a thousand Suns.
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Molecular clouds in our Galaxy are located A. in the spiral arms and can be used to trace the spiral structure of our galaxy. B. uniformly throughout the disk and can be used to measure the rotation speed of the Galaxy at different distances from the galactic center. C. in the halo and the central bulge because they are material left over from the formation of the Galaxy. D. in two oppositely directed jets perpendicular to the disk, ejected by the supermassive black hole at the galactic center.
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Most of the light from a spiral galaxy comes from the central bulge, so it might seem reasonable to suppose that most of the mass of the galaxy resides in the central bulge. If this were correct, how would we expect the rotation speed to behave in the galaxy's disk and spiral arms? A. The rotation speed should decrease smoothly with increasing distance from the central bulge according to Kepler's Laws. B. The rotation speed should increase smoothly with increasing distance from the central bulge. C. The rotation speed should decrease rapidly to zero just outside the central bulge because the disk has such a low mass compared to the bulge. D. The rotation speed should remain essentially constant with increasing distance from the central bulge because the bulge is an extended mass, not a point mass.
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NASA's Kepler Mission, launched in 2008, is searching for Earthlike planets by using the technique of detecting A. periodic dimming of stars caused by transits of Earth-sized planets. B. "wobbles" of stars as Earth-sized planets orbit around them. C. Doppler shifts of stars as Earth-sized planets orbit around them. D. Earth-sized planets visible close to solar-type stars.
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Now that NASA is no longer allowed to support the radio searches for extraterrestrial intelligence, what is the current status of these searches? A. SETI (the Search for Extraterrestrial Intelligence) is being supported by private individuals and foundations and nongovernmental funding, and some universities are funding their own searches. B. Amateur astronomers have formed a network of backyard radio telescopes to continue the search. C. Searches are now done at X-ray wavelengths, for which funding is available. D. All projects are on hold.
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One example of evidence supporting the general theory of relativity is that A. light beams bend near massive objects like the Sun. B. clocks have been measured going slower near massive objects like the Sun. C. gravitational waves are measured by Earth detectors. D. all of Einstein's other theories have been proved correct.
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One of the characteristics of main-sequence stars is A. their energy source is nuclear fusion. B. they expand rather than contract. C. they are not in hydrostatic equilibrium. D. they rotate without turbulence.
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Organic molecules have been shown to exist in several locations in outer space. In which of the following locations have these molecules not been found? A. surface of Mars B. primitive meteorites C. giant molecular clouds in interstellar space D. comets
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Pulsating X-ray sources, first detected in 1971, are caused by A. mass transfer from a companion star onto the magnetic poles of a rotating neutron star, producing hot spots of very intense X-ray emission. B. periodic passage of a neutron star through the dense atmosphere of a companion star as it follows an elliptical orbit, producing intense bursts of X rays as it does so. C. periodic build-up of matter from a companion star onto the surface of a neutron star until the threshold for thermonuclear reactions is reached, whereupon copious amounts of X rays are produced. D. precession of an accretion disk around a hot neutron star, causing a peak in the X-ray intensity whenever the accretion disk is tilted toward the Earth.
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Recent astronomical discoveries suggest that quasars are not stars, but instead A. very luminous objects located at the centers of distant galaxies in birth. B. high-redshift objects associated with low-redshift galaxies. C. very remote galaxies whose brightness has been amplified by gravitational lensing by nearer galaxies or galaxy clusters. D. isolated, supermassive black holes—not part of a galaxy.
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Scientists have recently been able to estimate the degree of "flatness" of the universe, which determines whether we live in an open or a closed universe, by measuring the A. typical sizes of brighter structures in the cosmic microwave background. B. "lensing" or the bending of light from distant galaxies. C. ratio of the average density of matter to that of radiation energy in the universe as a whole. D. hemispheric asymmetry in the temperature of the cosmic microwave background .
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Seyfert galaxies are a type of active galaxy classified as A. spiral galaxies with nuclei that resemble low-energy quasars. B. elliptical galaxies with nuclei that resemble quasars. C. spiral galaxies whose arms arise from a bar across the center of the galaxy. D. the fuzz seen around many quasars.
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Since nothing, not even light, can escape from a black hole, how has the existence of black holes been established? A. by observation of a black hole's gravitational effect on a visible companion in a binary star system B. by the existence of a very dark area in the sky, from which nothing is being emitted C. by the extreme gravitational redshift of light emitted by a close companion star D. by observation of gravitational waves emitted as a black hole rotates
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Solar flares occur only A. in the regions above sunspots. B. along the solar equator, where the magnetic fields are the most intense. C. at the solar poles, where magnetic fields are twisted by solar rotation. D. in coronal holes.
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Starburst galaxies within clusters of galaxies are seen to be extremely bright in the visible light of many newborn stars and in infrared light of warm dust. These galaxies are probably direct evidence of A. collisions between two galaxies, creating shock waves in the interstellar gas and dust that trigger prolific star formation. B. the Big Bang, since these very distant and hence very old galaxies are allowing us to look back at star formation at the beginning of the universe. C. a supermassive black hole at the centers of these galaxies that compresses gas and dust clouds and leads to intense star formation. D. self-propagating star formation, in which radiation pressure from newly formed stars compresses gas and dust and induces more star formation.
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Stars on the main sequence have masses in the range of A. 0.1 to 60 solar masses. B. only 1 to 20 solar masses. C. only 10-2 to 106 solar masses. D. only 0.2 to 8 solar masses.
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Sunspots appear dark because, compared with the photosphere around them, they A. are much cooler. B. contain less hydrogen. C. are less dense and so allow us to see deeper regions of the Sun. D. have weaker magnetic fields.
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T Tauri stars are A. pre-main-sequence stars. B. main-sequence stars that are ejecting matter into space. C. stars that have completed their main-sequence life and are slowly expanding to become red giants. D. protostars that are not massive enough to ever begin hydrogen fusion in their cores.
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The WMAP satellite measured very small fluctuations in the temperature of the cosmic background radiation. What is believed to be the significance of these fluctuations? A. They are the density fluctuations (the "clumping") that produced the superclusters and other immense objects of our present universe. B. They are the supermassive black holes around which all present galaxies formed. C. They are the source of the dark energy that is causing the universal expansion to accelerate. D. They are remnants of nonphysical fluctuations that occurred before the Planck time.
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In terms of black holes what is a wormhole?
A direct connection from a black hole to another part of spacetime
The cosmic microwave background radiation was first detected A. accidentally using a ground-based communications antenna. B. accidentally using a satellite that was launched to monitor above-ground nuclear explosions. C. using a satellite that was launched to test predictions by cosmologists that we should be bathed in a sea of radiation from the early universe. D. using a microwave antenna on the roof of a building at Princeton University.
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The debate between Heber Curtis and Harlow Shapley in 1920 addressed the question of whether A. spiral "nebulae" are objects within the Milky Way Galaxy or are objects similar to our Galaxy at vast distances from us. B. the Sun is at the center of the Milky Way Galaxy or in orbit at thousands of light-years from the center. C. the universe is static in its overall structure or expanding with galaxies moving away from us in all directions. D. galaxies form by much larger objects fragmenting into galaxies or smaller objects coalescing into galaxies.
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The density parameter, Σ0, is the A. ratio of the average density of the universe to the critical density, equal to 1 for a flat universe. B. radius of curvature of the universe as determined by the average density, equal to infinity for a flat universe. C. cosmological constant of Einstein's equations, equal to zero for a static universe. D. ratio of the density in a region of higher temperature fluctuation to the mean background density, equal to 1 in a precisely flat universe.
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The diameter of a typical neutron star is similar to that of A. an average city (20-30 km). B. Earth (10,000-15,000 km). C. Jupiter (100,000-200,000 km). D. the Moon (3000-4000 km).
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The diameter of a white dwarf is A. similar to that of the Earth. B. similar to that of Los Angeles. C. similar to that of the Sun. D. about two to three times that of Jupiter.
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The fundamental characteristic that makes a main-sequence star different from all other stars is that A. hydrogen is being converted to helium in the core of the star. B. they are all stars of low mass. C. helium is being converted to carbon in the core of the star. D. they are all surrounded and hidden from sight by clouds of gas and dust.
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The granules we see under excellent observing conditions on the visible surface of the Sun are A. the tops of columns of rising and falling gas in the layer below the photosphere. B. cooler, darker regions where the Sun's magnetic field is particularly intense. C. columns of gas rising through the Sun's chromosphere. D. waves created by oscillations in the solar interior, with periods of between 5 and 20 minutes.
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The heat that keeps Europa's subsurface ocean from freezing is provided by A. tidal flexing by Jupiter and its other satellites. B. radioactivity in its rocky core. C. solar radiation and an active greenhouse effect. D. biological decay of primitive organisms.
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The instability strip is where A. evolving stars pulsate. B. protostars enter into a free-fall collapse. C. evolving stars blow up into red giants. D. red giant stars lose their outer envelopes, creating planetary nebulae.
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The internal structure of the Sun, in order from the center to the surface, is A. energy-generating core, radiative region, convective region. photosphere. B. energy-generating core, photosphere, convective region, radiative region. C. convective core, chemically-reacting region, radiative region. D. Chromosphere, energy-generating core, convective region.
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The isotropy problem and the flatness problem were both solved by the theory that A. just after the Big Bang the universe suddenly increased in size by a factor of 1050. B. the energy of the background radiation was smoothed by interaction with particles after recombination. C. the Big Bang was an extremely isotropic explosion of space and time. D. there was a preexisting continuum of space into which the Big Bang expanded.
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The key discovery about Cepheid variable stars that led in the 1920s to the resolution of the question of whether spiral "nebulae" (like the Andromeda galaxy) were separate and distant galaxies or part of our Galaxy was the A. direct relationship between their pulsation period and their absolute magnitude, which could be subtracted from the star's apparent magnitude to determine the distance to a "nebula" containing that star. B. Doppler shift in spectra of these extremely bright stars, which showed that they and the "nebulae" in which they resided were moving very rapidly away from us and hence were separate from our Galaxy. C. realization that the variability was caused by the stars moving in and out of dense clouds of dust and gas, indicating that the "nebulae" were part of our Galaxy. D. discovery that Cepheids are fainter in galaxies with higher redshifts, showing that recession speed increases with increasing distance from the Earth.
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The key piece of evidence showing that the expansion of the universe is accelerating is that the A. most distant Type Ia supernovae are fainter than they would be if the expansion were not accelerating. B. most distant quasars are fainter than they would be if the expansion were not accelerating. C. cosmological redshift of light from the most distant quasars is greater than it would be if the expansion were not accelerating. D. most distant gravitational lenses are weaker than they would be if the expansion were not accelerating.
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The known laws of physics describe the universe only after the end of the first A. 10-43 second. B. 10-35 second. C. 3 minutes. D. 380,000 years.
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The mass of a star can be most accurately determined A. by its gravitational effect on a companion star. B. from its luminosity, since luminosity is related directly to mass for all types of stars. C. by an effect upon the star's spectrum known as the so-called gravitational red shift. D. by plotting the star on a Hertzsprung-Russell diagram.
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The mass of the black hole candidate near the center of the galaxy M82 was estimated from the A. luminosity of X rays emitted by matter falling into the black hole. B. orbital radius and orbital speed of matter around the black hole. C. amount of matter ejected from the accretion disk in the form of opposing jets. D. pulsation period of the black hole.
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The mechanism that results in very high rotation rates for certain pulsars is probably A. mass exchange with a binary companion. B. collapse of the neutron star, similar to the way that a skater increases rotation in a spin. C. mass loss from the neutron star, the remainder spinning faster as a result. D. the merger of a pair of neutron stars to form a single object.
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The most important reason why globular clusters are useful for finding the speed of the Sun in its orbit around the Galaxy is that globular clusters A. orbit very slowly around the Galaxy, so they provide a "stationary" frame of reference to which the Sun's motion may be compared. B. are large and bright, so they can be seen through the obscuring dust in the galactic disk. C. are distributed uniformly around the Galaxy, so they provide a well-defined grid of measured locations around the Galaxy. D. on average rotate around the Galaxy at the same speed as the Sun, so they provide a frame of reference that is "stationary" relative to the Sun.
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The nuclei of active galaxies like Seyfert galaxies and radio galaxies differ from quasars in that they A. are less energetic than quasars. B. are all located in spiral galaxies, whereas quasars are all located in ellipticals. C. do not have jets of material extending away from the nucleus. D. are all located in elliptical galaxies, whereas quasars are all located in spirals.
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The principle of equivalence states that A. uniform acceleration is indistinguishable from being at rest in a uniform gravitational field. B. matter and energy are equivalent . C. the laws of physics are the same for all unaccelerated observers, regardless of their motion. D. if object A exerts a force on object B, then object B exerts a force on object A that is equal in magnitude and opposite in direction.
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The pyrolitic release experiments on the Viking Landers on Mars were based on the idea that A. during photosynthesis, organisms take in carbon from the atmosphere. B. during respiration, organisms release carbon into the atmosphere. C. during metabolism, organisms consume nutrients and release gases into the atmosphere. D. only a living organism can negotiate a maze and release the reward at the end.
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The region of the Hertzsprung-Russell diagram occupied by stars that pulsate with periods between a few days and a few weeks A. extends from above the middle of the main sequence toward high-luminosity, low-temperature regions. Look at the diagram. B. extends approximately parallel to and well below the main sequence in the region of low luminosity and high temperature. C. extends over a wide range of luminosities at an approximately constant and very cool temperature. D. is confined to a small area just above the middle of the main sequence.
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The source of the Sun's energy is A. thermonuclear fusion reactions in which lower-mass nuclei combine to form a higher-mass nucleus. B. fission reactions in which a heavier nucleus splits to form two lighter nuclei. C. chemical reaction in which hydrogen burns to form water. D. gravitational contraction that compresses and heats the Sun's interior.
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The source of the steady solar wind, part of which streams past the Earth at about 400 km/s, is A. coronal holes, regions of the corona with a lower temperature than the rest of the corona. B. solar flares, highly energetic outbursts that occur near sunspots. C. prominences, bright arches of gas that occasionally erupt upward. D. granulation, where hot, convecting gas from the solar interior rises into the photosphere.
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The speed at which spiral galaxies rotate is often remarkably constant with increasing distance from the center of the galaxy; that is, the galaxy's rotation curve is remarkably flat. What is the significance? A. These galaxies must contain a much greater amount of "dark matter" than visible matter, thereby keeping the rotation speed higher than the amount of visible matter would indicate B. The stars in these galaxies, like planets orbiting the Sun in our own solar system, move primarily under the gravitational pull of a large mass at the center of the system. C. The stars in these galaxies influence each other gravitationally in such a way that the galaxy seems to rotate like a solid body (for example, like a solid, rotating disk). D. Most of the mass of these galaxies is located in the disk; relatively little mass is located in the central bulge.
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The spiral arm structure of the Milky Way Galaxy is best found by mapping out the locations of A. OB associations. What are these? B. RR Lyrae variable stars. C. Cepheid variable stars. D. the normal stars, as there are few stars between the arms.
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The strongest evidence that there is a supermassive black hole at the center of our neighboring galaxy, the Andromeda Galaxy (M31), is that A. the orbital speeds of stars 50 light-years from the center require a central mass of tens of millions of solar masses to hold them in orbit. B. the Hubble Space Telescope has detected a bright, pointlike nucleus less than 1 parsec in size at the center of the galaxy. C. there is a bright jet of material extending for 6000 light-years from the nucleus of the galaxy. D. Intense X-ray and gamma-ray emission is observed from the nucleus, which varies on a timescale of hours or days.
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The term superluminal motion refers to the motion of A. material at speeds that appear faster than light. B. galaxies having redshifts z > 1. C. arcs of light created by gravitational lensing of background quasars. D. relativistic electrons in the magnetic fields of galactic jets.
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The universe described in the membrane or M-theory of cosmology is A. open. B. closed. C. oscillatory. D. negatively curved.
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There are about a billion times as many photons as atoms in the present universe. Why, then, is the present universe said to be "matter-dominated"? A. It's not a count of number of photons versus number of atoms—it's the equivalence of the energy of the mass versus the energy of the photons: The energy of most of the photons is so low that there is much more mass as matter than as radiation. B. Photons have no rest mass, so the mass density of the universe is made up entirely of matter. C. Although the photons carry a lot of energy, their momentum is negligible compared to that of matter. D. Most of the photons do not interact with matter, so the universe is dominated by interactions between material objects such as atoms, planets, and galaxies.
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What is the force that keeps a neutron star from collapsing to a black hole under its intense self-gravitational field? A. neutron degeneracy pressure, the quantum-mechanical effect in which no two neutrons with the same properties can occupy the same space B. intense nuclear repulsion between neutrons, felt only when the neutrons are very closely packed since the nuclear force is very short-ranged C. very high temperature and velocity of the neutrons, which create a thermal gas pressure to oppose gravity D. outward centrifugal force created by the very rapid spin rate of the neutron star
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open cluster
A loose association of young stars in the disk of our Galaxy; a galactic cluster.
To account for one particular and fundamental observation in the present universe, a brief period of very rapid expansion (the Inflationary Epoch) is now postulated in the model of its evolution. What is this observation and why does it lead to the need for expansion? A. The temperature of the cosmic background radiation is remarkably uniform across the whole observable universe, which requires that all parts of the visible universe had to be in very close mutual contact before being suddenly carried far apart. B. Galaxies and clusters of galaxies are separated by vast distances, which can be accounted for only if the universe underwent a very rapid expansion at some stage of its evolution. C. The redshift of the radiation produced at 1012 K in the Big Bang, from the very short-wavelength photons to the present microwave background wavelengths, required a very rapid expansion of the universe at some stage. D. The small amount of helium in the universe requires a rapid expansion and cooling of the Big Bang to rapidly bring the temperature of the universe below that needed for thermonuclear fusion.
A
Two stars orbit each other with a large separation between them compared to the stars' radii, but they are sufficiently far away from Earth that they cannot be resolved as separate stars. Furthermore, their orbital plane is inclined at 45° to the direction to Earth from the star system. What observation shows us that there are two stars orbiting each other? A. periodic shifting of spectral lines B. periodic decreases in overall light intensity of the star system C. detection of slight positional change in the brightest region of the star system D. periodic changes in color as the stars move toward and away from the Earth
A
Type Ia supernovae are important for establishing distances to very distant objects in the universe. What property of these supernovae allows them to be used this way? A. Their peak brightness is related to how rapidly they fade from maximum light. B. All Type Ia supernovae have the same peak brightness. C. Their peak brightness is related to the strength of the absorption lines in their spectra. D. Their peak brightness is related to the spectral class of their progenitor star.
A
We do not see many nearby supernova remnants because A. interstellar dust blocks our view into the Milky Way. B. they simply are not common. C. local orbital effects from nearby stars quickly break up the gas. D. they don't give off light.
A
We observe a burst of gamma rays from only some (not all) Type Ic supernovae, because the gamma rays are produced by A. a narrow jet of matter, and we see a gamma-ray burst only if the jet points at Earth. B. a short-lived accretion disk, and not all Type Ic supernovae produce an accretion disk. C. the collapse of the core to form a black hole, and if the core is rotating then it cannot collapse. D. the explosion of the outer layers of the star, but if the progenitor star lost too much mass then these layers are absent.
A
What do we know about evaporation of matter from black holes? A. The lesser the mass of the black hole, the faster it evaporates. B. The greater the mass of the black hole, the faster it evaporates. C. Black holes do not evaporate because nothing can ever leave a black hole. D. Only rotating black holes evaporate, as energy escapes through the ergoregion.
A
What evidence do we have that there are strong magnetic fields near the center of the Galaxy? A. strong synchrotron radiation B. strong 21-cm hydrogen radiation C. pinwheel-shaped rings of gas around Sagittarius A* D. bursts of X-ray and gamma-ray radiation
A
What gives rise to the extensive X-ray emission detected from many rich clusters of galaxies? A. hot, intergalactic gas at temperatures of up to 100 million K B. energetic electrons spiraling in intergalactic magnetic fields C. hot O and B stars in the spiral galaxies in the cluster D. collisions between galaxies in the cluster
A
What happened at the end of the Planck time, when the age of the universe was 10-43 seconds? A. Gravity "froze out" as a separate force and was no longer unified with the other three forces. B. The strong nuclear force "froze out" as a separate force and was no longer unified with the other three forces. C. The universe became transparent to radiation, so matter and radiation became decoupled. D. Quarks combined to produce neutrons and protons.
A
What is believed to have been the most important factor that determined whether a protogalaxy in the early universe evolved into a spiral or an elliptical galaxy? A. initial rate of star formation B. mass of the protogalaxy C. rotation speed of the protogalaxy D. ratio of gas to dust
A
What is the behavior of sunspots over one sunspot cycle? A. The first spots appears at around 30° N and S latitude, then first increase and eventually decrease in number while forming closer and closer to the equator, finally dying out near the equator as the next cycle begins near 30° N and S latitude. B. The first spots appear near the equator, then first increase and eventually decrease in number while forming farther and farther from the equator, finally dying out at around 30° N and S latitude as the next cycle begins near the equator. C. The first spots appear near the N and S poles, then first increase and eventually decrease in number while forming closer and closer to the equator, finally dying out near the equator as the next cycle begins near the poles. D. Spots appear randomly over the entire face of the Sun, while gradually increasing and eventually decreasing in number.
A
What is the cosmic light horizon? A. the farthest point from which light can have traveled to the Earth during the interval of time equal to the age of the universe B. the farthest distance light can travel before being completely absorbed by matter in the universe C. the surface around a supermassive black hole within which no light can escape to the outside universe D. the farthest distance to which light can have traveled since the first human campfires
A
What is the deuterium bottleneck? A. Deuterium had to form before helium could form, but deuterium is easily destroyed, thus preventing the formation of helium. B. Deuterium absorbs neutrons efficiently, producing heavier and heavier isotopes of hydrogen instead of elements such as helium. C. Deuterium had to form before helium could form, but deuterium is difficult to create, thus preventing the formation of helium. D. Deuterium reacts to destroy heavier elements, breaking them into hydrogen (protons) again, thus preventing the formation of helium.
A
What is the galaxy content of a rich, regular cluster of galaxies, like the Virgo Cluster? A. mostly elliptical and lenticular galaxies, with relatively few spiral and irregular galaxies B. entirely elliptical galaxies C. mostly spiral and irregular galaxies, with relatively few elliptical and lenticular galaxies D. more-or-less even distribution of spiral, elliptical, irregular and lenticular galaxies
A
What is the main source of energy in the core of a star that has passed the end of its main-sequence lifetime and is making the transition to the giant stage? A. gravitational energy, released by the contraction of the hydrogen-poor but helium-rich gas B. thermonuclear energy, generated by the fusion of helium nuclei into heavier elements C. hydrogen fusion, but at a much slower rate than in the main-sequence phase D. radioactivity from heavy elements such as radium and uranium
A
What is the relationship between grand-design spiral galaxies, with long, well-defined spiral arms, and flocculent spiral galaxies, with chaotic-looking spiral arms? A. None--they are formed by different processes and are not known to evolve from one type to the other. B. Grand-design spirals are younger and evolve into flocculent spirals as the spiral arms are broken up by differential rotation. C. Flocculent spirals are younger and evolve into grand-design spirals as the spiral arms are stretched by differential rotation. D. Flocculent spirals have suffered one or more collisions with other galaxies, whereas grand-design spirals have been undisturbed since they formed.
A
What mechanism, more than any other, affects the evolution of a star that is a member of a close binary system? A. transfer of matter to or from its companion star to change the masses of both stars B. radiant heat from its companion star, raising the temperature of its surface C. tidal distortion, which changes the overall shape of the star D. gravitational stirring, which mixes hydrogen into the star's core
A
What physical mechanism produces the very rapid rotation rate of a neutron star in the center of a supernova explosion? A. A slowly rotating mass rapidly implodes into a much smaller volume, and the conservation of angular momentum results in high rotation speed. B. The off-center explosion of the supernova creates a reaction force that spins up the neutron star, like the reaction force from a cannonball pushing back on the cannon. C. Intense radiation pressure on the imploding stellar core from the supernova explosion spins this core up to high rotation speeds as a consequence of the conservation of energy. D. The intense magnetic field of the neutron star transfers angular momentum inward from the expanding supernova debris to the neutron star, giving it a very high rate of spin.
A
When did the first stars begin to form? A. about 20 million years after the universe became transparent, at the era of recombination B. about 6 seconds after gravitation froze out as a separate force C. about 2,000 years after the universe evolved from being radiation-dominated to being matter-dominated D. about 3 hours after matter and antimatter finished annihilating, leaving the universe composed only of matter
A
When nutrients containing water were added to soil samples on the Mars Viking Lander, what happened to lead scientists into concluding initially that their life-seeking experiments had succeeded in detecting life on our neighboring planet? A. rapid release of gases, caused by unstable chemicals on the surface of Mars B. growth of branched, plant-like structures, caused by crystal growth in inert chemicals C. motion of microscopic components that looked like moving life forms, caused by the water boiling in the low atmospheric pressure of Mars D. sudden disappearance of the water, caused by the extreme dryness of the Martian soil
A
When the first stars (Population III stars) formed, what were they like, compared to the stars with which we are familiar today? A. generally much more massive, up to 1,000 solar masses, and much hotter and more luminous, and deficient in elements heavier than helium B. very similar to today's stars, but lacking elements heavier than helium C. generally much less massive, less than 5 solar masses, and much cooler and less luminous D. We have no idea because none have yet been seen.
A
Where are we? A. nowhere special; just somewhere in an expanding universe B. at the exact center of an expanding universe, as shown by the universal expansion away from us equally in all directions C. somewhere away from the center of an expanding universe, as shown by a higher temperature of the cosmic microwave background radiation in the direction toward which we are traveling and the lower temperature in the opposite direction D. near one edge of an expanding universe, as shown by the Great Wall of Galaxies
A
Which of the following characteristics is expected to be a fundamental property of a black hole and is very important for distinguishing one black hole from another? A. rate of rotation of the black hole B. ratio of protons to neutrons in the singularity within the black hole C. magnetic field of the black hole D. diameter of the singularity within the black hole
A
Which of the following spectral classifications corresponds to the hottest stars? A. O B. B C. F D. G
A
Which of the following spectral classifications corresponds to the stars emitting the most blue light? A. O B. A C. F D. G
A
Which of the following statements correctly describes the significance of the Jeans length for the universe? A. Density fluctuations cannot evolve into permanent objects if their diameter is smaller than the Jeans length. B. Light from a distant object cannot have reached the Earth yet if the object is farther away than the Jeans length. C. The universe cannot inflate if its radius is less than the Jeans length. D. Galaxy superclusters cannot form if their diameter is greater than the Jeans length.
A
Which of the following substances, if detected in the spectrum of an extrasolar planet, are considered most likely to indicate the presence of life on the planet? A. water vapor (H2O), ozone (O3), and carbon dioxide (CO2) B. methane (CH3) and ammonia (NH4) C. hydrogen (H2) and helium (He) D. carbon dioxide (CO2) and argon (Ar)
A
contact binary
A binary star system in which both members fill their Roche lobes.
Which one of the following statements correctly describes the difference between a 3-solar-mass pre-main-sequence star (just after it has formed) and a 3-solar-mass giant star? A. The pre-main-sequence star has a uniform composition of mostly hydrogen, whereas the giant has a hydrogen-rich envelope around a helium-rich core. B. The pre-main-sequence star has hydrogen nuclear reactions only in its core, whereas the giant has hydrogen nuclear reactions in a shell around the core. C. The pre-main-sequence star contains no nuclear energy sources, whereas the giant has hydrogen nuclear reactions occurring in its core. D. The pre-main-sequence star contains no nuclear energy sources, whereas the giant has hydrogen nuclear reactions occurring in a shell around the core.
A
Which sequence properly describes the evolution of a star-forming region? A. giant molecular cloud, young star cluster, H II region B. young star cluster, giant molecular cloud, H II region C. H II region, giant molecular cloud, young star cluster D. giant molecular cloud, H II region, young star cluster
A
Which statement correctly describes the behavior of the strong and weak forces? A. The strong force pulls protons and neutrons together to form nuclei; the weak force acts to separate protons out of neutrons. B. The strong force pulls electrons and nuclei together to form atoms; the weak force pulls protons and neutrons together to form nuclei. C. The strong force acts to change neutrons into protons; the weak force pulls protons and neutrons together to form nuclei. D. The strong force pulls protons and neutrons together to form nuclei; the weak force pulls electrons and nuclei together to form atoms.
A
Which type of observation demonstrates that quasars are relatively small in physical extent? A. rapid fluctuation in brightness, often in times as short as hours B. very small size of their image on Hubble Space Telescope photographs C. very narrow line widths of emission lines in their spectra D. very strong gravitational redshift of the absorption lines in their spectra
A
Which wavelength region of the electromagnetic spectrum is most useful for investigating distant regions in the disk of our Galaxy? A. radio B. optical (visible) C. ultraviolet D. gamma rays
A
Why are elements heavier than iron not able to produce energy through thermonuclear fusion and are therefore unable to sustain the luminous output of a high-mass star late in its life? A. Fusion of elements heavier than iron absorbs energy, rather than producing energy as in the fusion of lighter nuclei. B. No known nuclear reactions occur for nuclei heavier than iron because of the structure and extraordinary stability of these nuclei. C. Nuclei heavier than iron have such a high charge that there is no temperature great enough to force them together. D. After silicon fusion, electron degeneracy prevents further contraction and heating of the core, so the temperature does not become high enough for fusion of elements heavier than iron.
A
Why did the U.S. Congress require NASA to stop supporting radio searches for extraterrestrial intelligence? A. They cost too much money. B. We should not give away our presence. C. No results had yet been achieved. D. The Drake equation predicted too few civilizations to make the search worthwhile.
A
Why does the gravitational force play a more significant role than the electromagnetic force in the universe over very large distances, although the EM force is much stronger? A. Positive electric charges are balanced by negative charges, whereas there is no such balancing of opposites in gravity— there is no "negative" mass and therefore only attractive gravitational force. B. The gravitational force is intrinsically stronger than the electromagnetic force and so dominates it at large distances. C. The electromagnetic force, like the weak and strong nuclear forces, has only a limited range in space. D. Neutrons, a fundamental component of all matter, are electrically neutral but still exert gravitational attraction.
A
Why does the light from the chromosphere appear to be pinkish-red? A. The light from the chromosphere is dominated by photons emitted by a single red spectral line, Hα, in the Balmer series of hydrogen. B. The temperature is lower than in the photosphere, producing a blackbody spectrum with peak wavelength in the infrared. C. M lecules form in this layer, and they scatter red light more efficiently than blue light. D. Strong magnetic fields inhibit the emission of photons of wavelengths shorter than around 600 nm.
A
Why is a main-sequence star of spectral class B3 considered an unlikely place to look for intelligent life? A. Its lifetime is so short that the star would explode in death before intelligent life had time to evolve. B. Its temperature is so low that a planet close enough to the star to be habitable would become tidally locked into synchronous rotation. C. Its temperature is so high that all water on a planet would evaporate and be lost into space. D. Its mass is so small that nuclear reactions could never begin in its core to provide the heat needed to sustain life on a planet.
A
Why is the Darwin Mission being designed to use an infrared telescope rather than an optical telescope? A. Habitable (Earthlike) planets have their maximum emission in the infrared. B. The longer wavelength allows greater angular resolution than does visible light. C. Infrared telescopes are less expensive to launch. D. Stars are brighter in the infrared.
A
Why is the outermost part of our Galaxy considered a poor place to look for habitable planets and life? A. The outer part of the Galaxy is metal-poor, and metals (heavy elements) are the building blocks of planets. B. Planets in the outer part of the Galaxy are unprotected from cosmic radiation from other galaxies. C. It is too cold in the outer part of the Galaxy for life to exist. D. Stars are too close together in the outer part of the Galaxy, and encounters between stars would disrupt planetary systems.
A
What is believed to be the dominant source for elements heavier than iron in the universe (for example, gold, silver, and lead)? A. thermonuclear reactions in the outer layers of massive stars during a supernova explosion as a result of a shock wave passing outward through the star B. thermonuclear reactions in the cores of massive stars during a supernova explosion as a result of compressional heating during core collapse C. silicon fusion reactions in the cores of massive stars during the last stage before a supernova explosion D. thermonuclear reactions during the first three minutes of the Big Bang at the start of the universe, with negligible contributions from any source after that time
A (NOT D)
A teaspoonful of white dwarf material on Earth would weigh
A few tons
ideal gas
A gas in which the pressure is directly proportional to both the density and the temperature of the gas; an idealization of a real gas.
globular cluster
A large spherical cluster of stars, typically found in the outlying regions of a galaxy.
red giant
A large, cool star of high luminosity.
horizontal-branch star
A low-mass, post-helium-flash star on the v-horizontal branch.
red dwarf
A main-sequence star with a mass between about 0.08 M and 0.4 M which has a fully convective interior and which never goes through a red giant stage.
Type II Cepheid
A metal-poor Cepheid variable star.
Type I Cepheid
A metal-rich Cepheid variable star.
The nucleus of an atom
A neutron star is as dense as:
zero-age main-sequence star
A newly formed star that has just arrived on the main sequence.
an expanding gas cloud of ejected outer layers of a red giant.
A planetary nebula is
color-magnitude diagram
A plot of the apparent magnitudes (that is, apparent brightnesses) of stars in a cluster versus their color indices (a measure of their surface temperatures).
Pauli exclusion principle
A principle of quantum mechanics stating that no two electrons can have the same position and momentum.
mass loss
A process by which a star gently loses matter.
The white dwarf
A red giant star orbits around a white dwarf, which slowly accretes material. When they were both on the main sequence, which star was more massive?
instability strip
A region of the H-R diagram occupied by pulsating stars.
Which are the largest galaxies in the Universe?
Giant elliptical galaxies
period-luminosity relation
A relationship between the period and average density of a pulsating star.
What is the famous Virgo cluster of galaxies?
A rich irregular cluster of more than 1000 galaxies
triple alpha process
A sequence of two thermonuclear reactions in which three helium nuclei combine to form one carbon nucleus.
In cosmology what is the "inflationary epoch"?
A short period of extremely rapid expansion when the Universe was very young
Supernova remnant
A spinning neutron star has been observed at the center of a _______________.
In the Hertzsprung-Russell diagram, how does the position of a typical star change while it is at the main-sequence phase of its evolution?
A star does not move on the H-R diagram while it is at this phase of its life.
pulsating variable star
A star that pulsates in size and luminosity.
metal-poor star
A star that, compared to the Sun, is deficient in elements heavier than helium; also called a Population II star.
metal-rich star
A star whose abundance of heavy elements is roughly comparable to that of the Sun; also called a Population I star.
Population II star
A star whose spectrum exhibits comparatively few spectral lines of elements heavier than helium; a metal-poor star.
Population I star
A star whose spectrum exhibits spectral lines of many elements heavier than helium; a metal-rich star.
Which major astronomical event was apparently recorded faithfully by Chinese astronomers in the Sung Dynasty in 1054 A.D.?
A supernova explosion in our Galaxy visible even in daylight
Roche lobe
A teardrop-shaped volume surrounding a star in a binary inside which gases are gravitationally bound to that star.
The Milky Way is an example of which type of galaxy?
Spiral
What proportion of visible stars in the nighttime sky are multiple star systems such as binary stars?
About 50% or 1/2
Neutron stars are 100,000 times denser than a white dwarf
True
Explodes outward as a supernova
After the core of a massive star becomes a neutron star, the rest of the star's matter
Which scientist discovered that the equations he had derived predicted an expanding Universe then modified his equations to eliminate this expansion?
Albert Einstein
Always have at least one magnetic axis pointed towards the earth at some time during their rotation.
All observed pulsars:
If suddenly we find that the distance between Earth and the Sun is not 10 percent larger than we thought it was before, what will change?
All of the above
What happens as a protostar contracts?
All of the above are true
What characteristic Distinguishes a meteorite from a terrestrial Rock? -Meteorites contain rare elements, such as iridium, that terrestrial rocks do not. -A meteorite is usually covered with a dark crust from burning in Earth's atmosphere. -Meteorites have different isotope ratios of particular elements when compared to terrestrial rocks. -A meteorite usually has a high metal content.
All of the above are true.
How are elements heavier than iron made? Why are they rare?
All of the post-iron elements are formed in supernova explosions themselves. So much energy is released during a supernova explosion that the freed energy and copious free neutrons streaming from the collapsing core drive massive fusion reactions, long past the formation of iron. Sure, this absorbs a lot of energy, but there's plenty available once the explosion has begun.
Which of the following does not describe a neutron star?
All of these describe a neutron star
The mass ejected as a shell in the remnant of a supernova explosion of a massive star is what fraction of its pre-explosion mass?
All or almost all (0.96)
Which of the following statements about an open cluster is true?
All stars in the cluster are approximately the same age
Which star in Diagram 13-1 has the greatest surface temperature?
Alnilam
What is the nearest star system to our sun?
Alpha Centauri
Moon's orbit is tilted by 5 degrees
Although the Moon orbits the Earth every 29.5 days, a total eclipse of the Sun does not occur every month because
rocky, ice
An asteroid is a dense ______ object and a comet is a less dense _____ object
What is Eris?
An icy object that orbits in the Kuiper belt and is larger than Pluto
A quasar
An intense radio source is found to coincide with a starlike object whose spectrum contains a pattern of intense emission lines in the visible range that matches that of the Lyman UV hydrogen spectral lines, but is very redshifted. What is this object?
To an astronomer what is a "standard candle"?
Any type of object whose absolute magnitude is known
All globular clusters in our Milky Way are about how old?
Around ten billion years old
When a low mass star firsts runs short of hydrogen in its core, it becomes brighter because
As hydrogen depletes in the core then less fusion can take place at that temperature. If you have less fusion, you have less energy production, so you have less radiative force pushing outward on the rest of the star, so the star must.....
Which of the following is the best answer to the question, "Why does the Sun shine?"
As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
The Space Station and the astronauts are in free fall, both falling with the same acceleration towards the Earth
Astronauts in the International Space Station are seen floating around as if weightless, yet the Space Station is well within the Earth's gravitational field. What is happening?
A 1-solar-mass main-sequence star becomes a young giant when core hydrogen fusion ceases. It becomes a mature giant star when core helium fusion begins. During which stage does it have the largest diameter? A. main sequence B. young giant C. mature giant D. the diameter of a star is determined by its initial mass. As a given star evolves, its diameter remains relatively constant.
B
A head-tail radio source is a A. radio-bright quasar (the head) with a line of fuzz (the tail) extending away from it. B. galaxy (the head) with two radio lobes extending out in the same direction (the tail). C. starlike nucleus (the head) with a jet of radio-bright material extending away from it (the tail). D. line of radio-emitting matter (the tail) extending away from a galaxy to a broad, radio-bright lobe (the head).
B
A planet around another star can probably be detected most easily by A. the light it gives off. B. its gravitational effects. C. looking for stars with large Doppler shifts. D. looking for very massive stars.
B
A star first leaves the main sequence when it starts burning _______ its core. A. helium in a shell around B. helium in C. carbon in a shell around D. hydrogen in
B
A star is observed to move very slowly in a constant direction across the sky at a rate of 0.028 seconds of arc per year. This observed movement is referred to as the star's A. parallax. B. proper motion. C. radial velocity. D. tangential velocity.
B
A typical stellar spectrum (a plot of intensity vs. wavelength) includes a number of deep indentations in which the intensity abruptly falls and then rises. What are these deep indentations? A. emission lines B. absorption lines C. prominences D. solar flares
B
About half of the dark matter halo of the Milky Way Galaxy is believed to be A. weakly interacting massive particles (WIMPs). B. massive compact halo objects (MACHOs). C. dark nebulae. D. neutrinos.
B
According to the Big Bang Model, we cannot see past the A. point where the expansion of space stalls. B. cosmic light horizon defined by the finite age of the universe and the speed of light. C. event horizon, a boundary before which no events had taken place. D. Big Bang location because of the energy that emerged from it.
B
Although emissions from supernova remnants occur at all wavelengths, those most likely to be detected are in which region of the spectrum and why? A. Visible—need to be able to SEE it B. Radio—penetrates and passes through dust whereas light doesn't C. Ultraviolet—blue glow is easier to detect D. X-ray—can pass through anything
B
Among the elements found on the Earth, AGB stars are thought to be the primary source of A. iron, dredged up from the core by convection and ejected into space by helium shell flashes B. carbon, dredged up from the core by convection and expelled into space as grains of soot. C. hydrogen, blown into space by powerful stellar winds. D. gold, formed during collapse and subsequent explosion of the star's core.
B
Among the four fundamental forces in nature, the exchange of the intermediate vector boson describes the A. gravitational force. B. weak force. C. electromagnetic force. D. strong force.
B
Arrange these three types of dwarfs in order of increasing temperature. A. white dwarf, red dwarf, brown dwarf B. brown dwarf, red dwarf, white dwarf C. red dwarf, white dwarf, brown dwarf D. brown dwarf, white dwarf, red dwarf
B
As a 1-solar-mass star expands to become a giant, its surface temperature decreases. What is the main reason? A. Shell hydrogen fusion generates increased amounts of energy (compared with the main-sequence phase), and the radiation of this energy away from the star cools the surface. B. Shell hydrogen fusion generates increased amounts of energy. This generation of energy causes the outer layers of the star to expand, and they cool as they expand. C. The helium flash drains the star of energy, and it cools as a result. D. During this phase, core hydrogen fusion ceases and the entire star cools.
B
As a star evolves off the main sequence, its position on the Hertzsprung-Russell changes toward the A. lower right. B. upper right. C. lower left. D. upper left.
B
As hydrogen fusion proceeds in the core of a 1-solar-mass star, the core shrinks. Why does this happen? A. The temperature increases over time. B. The pressure drops as the number of free particles decreases. C. The outer layers of the star get cooler and collapse, increasing the inward pressure on the core. D. As the core changes from hydrogen to helium, the gravitational attraction increases and pulls the core inward.
B
As stars burn more massive fuels (higher atomic number) like neon and silicon, the time required to exhaust the fuel A. increases. B. decreases. C. stays roughly the same. D. is not yet known.
B
As time goes by, the abundance of metals (elements beyond helium in the periodic table) in our Galaxy A. decreases. B. increases. C. remains the same. D. alternately decreases and increases in cycles.
B
As you move upward and to the right on the H-R Diagram, the stars become A. redder and hotter. B. redder and cooler. C. whiter and hotter. D. whiter and cooler.
B
Astronomers discover a starlike point source of light in the position of an intense and rapidly fluctuating source of radio energy. Further examination reveals highly redshifted emission lines in its visible spectrum. What is this object? A. pulsar B. quasar C. Cepheid variable D. Seyfert galaxy
B
At the center of every black hole is a(n) A. event horizon. B. singularity. C. ergoregion. D. careless Klingon.
B
At what point in its evolution is a 1-solar-mass star when it is a "horizontal branch star"? A. It has just left the main sequence and is progressing toward the helium flash. B. just after the helium flash C. just after the formation of a planetary nebula D. just after the formation of a supernova
B
Based on the numbers of these objects we see at various distances from us, we suspect that A. some radio galaxies evolve into quasars. B. some quasars evolve into radio galaxies. C. some radio galaxies evolve into Seyferts, which evolve into quasars D. quasars, radio galaxies, and Seyferts are all produced independently and have no evolutionary connection with each other.
B
Because black holes emit no light, how can we detect them? Three of the following detection methods are valid. Which method is not valid? A. Matter pulled off a companion star emits a characteristic X-ray spectrum as it falls toward the black hole. B. Companion stars suddenly disappear from view as they plunge into the black hole. C. Black holes can act as gravitational lenses, forming multiple images of objects beyond the hole. D. A star that wobbles in its proper motion can be exhibiting evidence of its orbital motion around an unseen companion.
B
Blazars, also called BL Lac objects, are probably AGN jets A. seen at a 45-degree angle. B. seen coming toward us. C. seen edge-on in the plane of the sky. D. without any accretion disk.
B
During the formation of a 1-solar-mass star like the Sun, what event halts the initial gravitational contraction? A. A supernova explosion occurs. B. Outward pressure when nuclear fusion begins. C. Shock wave when the helium flash occurs. D. The core becomes degenerate.
B
Evidence that there is much more matter than can be seen in the Milky Way Galaxy, thereby indicating the presence of dark matter, comes from the fact that, according to Kepler's Laws, A. stars more distant from the nucleus than the Sun orbit more slowly than expected. B. stars more distant from the nucleus than the Sun orbit more rapidly than expected. C. stars closer to the nucleus than the Sun orbit more rapidly than expected. D. stars closer to the nucleus than the Sun orbit more slowly than expected.
B
Giant molecular clouds are characteristic of spiral galaxies and are A. concentrated toward the outer edge of the galaxy's disk. B. distributed along the spiral arms. C. distributed relatively uniformly throughout the galaxy's disk. D. concentrated toward the center of the galaxy.
B
Horizontal branch stars are A. burning hydrogen in their cores. B. burning helium in their cores. C. burning helium in a shell around the core. D. glowing from gravitational contraction.
B
How do the density and temperature of the parts of the interstellar medium where star formation takes place compare to the density and temperature of the rest of the interstellar medium? Star formation takes place where the interstellar medium is A. densest and hottest. B. densest and coolest. C. least dense and hottest. D. least dense and coolest.
B
How do the spectra of quasars differ from the spectra of normal galaxies? A. Quasar spectra are much brighter than the spectra of normal galaxies. B. Quasar spectra are characterized by greatly redshifted emission lines; the spectra of normal galaxies are characterized by lower-redshift absorption lines. C. Quasar spectra contain lines from unidentified elements. D. Quasar spectra contain broad lines suggesting rapid rotation.
B
How does the galaxy-composition of distant galaxy clusters compare to the composition of nearby galaxy clusters? A. On average, the compositions are the same. B. Distant clusters contain a greater percentage of spirals. C. Distant clusters contain a greater percentage of ellipticals. D. Distant clusters contain only irregular galaxies that have not yet evolved into the mixture of ellipticals and spirals found in nearly clusters.
B
How does the turn-off point on the H-R diagram of a young cluster compare to that for an old cluster? The turn-off point for a young cluster is farther A. up the horizontal branch at redder stars. B. up the main sequence at hotter spectral types. C. down the horizontal branch at dimmer stars. D. down the main sequence at cooler spectral types.
B
How many samples do we have of meteorites which landed on Earth and preliminary analysis indicates they might have come from Mars? A. only one, ALH 84001 B. about a dozen C. several hundred, but most are too small to analyze D. 84,001
B
Hubble's Law says that if galaxy B has twice the redshift of galaxy A, then galaxy B is A. half as distant as galaxy A. B. twice as distant as galaxy A. C. half as hot as galaxy A. D. twice as hot as galaxy A.
B
If higher dimensions exist, it is possible to explain forces as A. energy coming into our universe through these dimensions. B. motion along a straight line through these dimensions. C. arising when structures in these higher dimensions collide. D. arising whenever a higher dimension collapses at a point.
B
In 1845, Lord Rosse put into operation the world's largest telescope, with an aperture of about 72 inches. This telescope was A. a refractor. B. a reflector. C. equipped with a primitive CCD. D. especially designed for photography.
B
In addition to gravity, what type of force holds a neutron star together? A. electron degeneracy pressure B. nuclear force C. magnetic force D. electrical force
B
In an expanding universe, the light of objects that are farther away will be A. more blueshifted B. more redshifted C. neither redshifted nor blueshifted D. more intense
B
In the early universe, the temperature fell steadily as the universe expanded. As the temperature decreased, A. both pair production and annihilation reactions were restricted to particles of smaller and smaller mass. B. pair production reactions were restricted to particles of lower and lower mass, but annihilation reactions were unaffected. C. annihilation reactions were restricted to particles of smaller and smaller mass, but pair production reactions were unaffected. D. neither pair production reactions nor annihilation reactions were affected.
B
In the original solution of Einstein's general relativistic field equations, the cosmological constant represents A. the speed of light. B. an outward pressure. C. the acceleration of gravity at earth's surface. D. the Schwarzschild radius of the universe.
B
In which order does a single star of 1 solar mass progress through the various stages of stellar evolution? A. planetary nebula, main-sequence star, white dwarf, black hole B. protostar, main-sequence star, planetary nebula, white dwarf C. protostar, red giant, supernova, planetary nebula D. protostar, red giant, supernova, black hole
B
Matter came into the universe A. when the energy of the Big Bang created particles from the E = mc2 relation. B. when space inflated so fast that particle-antiparticle pairs could not annihilate each other to leave only energy. C. at the era of decoupling of radiation and matter. D. at the moment of the Big Bang.
B
Measurement of the period of a Cepheid variable star enables astronomers to determine its absolute magnitude; and this, when combined with a measurement of its apparent magnitude, can be used to determine the star's distance from Earth. What further measurement is necessary to ensure that this distance determination is accurate? A. surface temperature of the star B. metal content of the star, to identify the variable as a Population I or Population II variable C. position of the star in our Galaxy D. brightness of the star's companion star to allow for its contribution to the apparent brightness
B
The physical state of the interior of a neutron star is believed to be A. superfluid but not superconducting. B. both superfluid and superconducting. C. superconducting but not superfluid. D. normal fluid.
B
Measurements indicate that a certain star has a dim absolute magnitude (1000 times fainter than the Sun) and yet it is very hot and blue. Therefore, the star must be A. very far away. B. very small. C. very close. D. impossible! Blue stars are all very hot and therefore bright.
B
Most of the stars we see are main-sequence stars, and only about 1% of stars are giants. This tells us that A. giants are generally dimmer than main-sequence stars. B. the main-sequence stage of stellar evolution is about a hundred times longer than the giant stage. C. only about one star in a hundred ever becomes a giant. D. stars evolve from the main sequence to the giant branch.
B
Observationally, how can we identify T Tauri stars? A. Their spectra display absorption lines of atoms normally found deep in the core. B. Their spectra display emission lines and large Doppler blueshifts. C. Their spectra show regular Doppler shift cycles and blueshifts, indicating pulsation of the surface. D. Their spectra are dominated by the infrared radiation characteristic of the Kelvin-Helmholtz contraction.
B
Olbers's paradox was resolved because the universe is A. in an unchanging steady state. B. not infinitely old and is expanding. C. not infinite in extent and is static. D. too big.
B
One important event in the evolution of a 1-solar-mass protostar is the ionization of the outer layers. This stage is important because A. once atoms are ionized, they are able to undergo nuclear reactions. B. radiation can travel relatively freely through ionized gas. C. convection is the most efficient energy transport mechanism through ionized material. D. this makes the outer layers opaque, thus trapping the energy from the core and raising the temperature.
B
Organic molecules can arise A. only in oxygen-rich environments. B. from nonbiological processes in space. C. only in the absence of strong radiation fields. D. only in the presence of a sufficiently strong gravitational field.
B
Over a period of a million years, what is our estimate for the number of stars that form that are similar enough to the Sun to possibly harbor life? A. 103 a thousand B. 106 a million C. 109 a billion D. 1012 a trillion
B
Pulsar periods experience sudden glitches when A. superconducting protons in the core cause the crust to slow down suddenly. B. superfluid neutrons in the core cause the crust to speed up suddenly. C. superfluid neutrons in the core cause the crust to slow down suddenly. D. superconducting protons in the core cause the crust to speed up suddenly.
B
Shock waves from supernovae can trigger star birth. What evidence is there that the formation of the Sun may have begun with this process? A. a layer in the Earth's crust containing the rare element iridium B. meteorites which contain unusual atomic nuclei which are created only in stellar explosions C. a nearby cloud of debris whose expansion rate suggests that it was formed by an explosion 4.6 billion years ago D. a scattered group of stars of the same age as the Sun that share the Sun's motion in the galaxy
B
Some protostars, when they evolve onto the main sequence, use radiation to carry energy outward from the core to some region midway through the star. Convection then carries the energy outward to the surface. Which protostars use this energy transport scheme? In which category is the Sun? A. the lowest-mass, with masses less than about 0.4 solar masses B. intermediate, from about 0.4 solar masses up to about 4 solar masses C. the highest-mass, greater than 4 solar masses D. all three mass ranges of protostar
B
Spiral arms are places where stars A. congregate near massive gas clouds. B. slow down as they orbit about the Galaxy. Why? C. shine brightest because of a lack of obscuring dust. D. speed up in their motions, attracted by density enhancements.
B
Studying sound waves in the early universe tells us A. nothing! Sound cannot travel through empty space! B. densities of matter and energy. C. the era of galaxy formation. D. the era of star formation.
B
Sunspots are created by A. solar flares blasting material out into space. B. twisted magnetic field lines poking above the photosphere. C. chromospheric heating. D. convective cells rising from beneath the photosphere.
B
Superluminal (faster-than-light) sources arise when A. material ejected from an accretion disk travels faster than light. B. jets are beaming nearly toward us causing an illusion of motion faster than light. C. curved spacetime near massive galaxies bends or "lenses" light from distant objects. D. light from some part of the jet has not yet had time to reach us.
B
Supernovae of types Ib and Ic appear to have lost most of their outer layers prior to core collapse. How can a massive star lose its outer layers prior to core collapse? A. They can be lost during the planetary nebula phase. B. They can be siphoned off by a binary companion. C. They can be lost through convection during the asymptotic branch phase. D. A massive star can supernova more than once. The first time it does so it loses its outer layers.
B
Suppose a typical interstellar cloud contains 1 million (106) solar masses of gas and dust. About how many solar masses of helium does it contain? A. 480,000 solar masses B. 250,000 solar masses C. 740,000 solar masses D. 1,000 solar masses
B
Suppose you are in a spaceship traveling at 99% of the speed of light past a long, narrow space station. Your direction of travel is parallel to the length of the station. If you measure lengths of objects on the station and also how time is passing on the station, what results will you get? A. Lengths will appear shorter, and time will appear to pass more rapidly. B. Lengths will appear shorter, and time will appear to pass more slowly. C. Lengths will appear longer, and time will appear to pass more rapidly. D. Lengths will appear longer, and time will appear to pass more slowly.
B
THe supermassive object at the center of our Galaxy has been shown to be smaller than the diameter of the orbit of Mars. On what observation is this measurement based? A. direct photography by the Hubble Space Telescope B. short timescale of X-ray variability C. very long baseline interferometry of the accretion disk around the black hole D. occultations of the galactic center by our Moon
B
The space between stars has been found to contain A. only particles of dust. B. atoms and molecules of gas and grains of dust. C. a perfect vacuum. D. only atoms and molecules of gas.
B
The "isotropy problem," one of the major problems in present-day cosmology, refers to the fact that two points in space separated by a distance farther than light can have traveled in the lifetime of the universe have exactly the same A. mix of chemical elements, as if they have originated from the same material. B. temperature, as if they had been in contact earlier in history. C. density of neutrinos, indicating that these regions have had time to redistribute these highly penetrating particles. D. curvature of space, indicating that the gravitational force can reach farther than electromagnetic radiation.
B
The Sun will eventually become an AGB star. What will the Sun's mass be (in solar masses) at the end of this phase, as a result of mass-loss to space? A. between 0.2 and 0.4 B. 0.6 C. almost 1.0, because mass loss is negligible for low-mass stars like the Sun D. less than 0.1
B
The apparent magnitude of Kapteyn's Star is +8.8, and that of the star Ross 154 is +10.4. Using only this information, we know for sure that Kapteyn's star is A. fainter than Ross 154. B. brighter than Ross 154. C. closer than Ross 154. D. more distant than Ross 154.
B
The blue glow surrounding the central rotating neutron star in the Crab Nebula is caused by A. light scattered from dust particles ejected from the neutron star's crust. B. synchrotron radiation from electrons spiraling in intense magnetic fields. C. blackbody radiation from this very hot gas. D. intensely blueshifted light from atoms being ejected violently from the neutron star.
B
The color of a particular star appears to be bluer than that of the Sun. Which of the following conclusions is the most likely? A. The spectral class of the star is K or M. B. The star's temperature is higher than that of the Sun. C. The star is moving very rapidly toward the Sun. D. Dust and gas between the star and Earth has absorbed or scattered much of the red light of the star.
B
The cosmic microwave background is A. a sea of radiation produced by cosmic ray particles striking the Earth's upper atmosphere. B. left-over radiation from the Big Bang itself, greatly redshifted by the expansion of the universe. C. the combined radiation from all stars and nebulae in the universe. D. thermal noise produced by quantum energy fluctuations in the vacuum of space.
B
The cosmic neutrino background has an effective temperature of about 2 K, whereas the cosmic photon background (the cosmic microwave background) temperature is about 3 K. Why is the neutrino background cooler? A. Neutrinos interact less with matter than do photons and have not exchanged energy with the matter in the universe as much as have the photons. B. The photon background received extra energy from electron-positron annihilation; there was no similar reaction for neutrinos. C. The neutrinos decoupled from the rest of matter later than the photons did, when the universe was cooler. D. Neutrinos have a rest mass and therefore travel at a slower speed than do photons (which travel at the speed of light). This slower speed is equivalent to a lower temperature.
B
The density-wave model suggests that the spiral arms of our Galaxy A. are permanent, stable features that have been in the same place relative to each other since the origin of the Galaxy. B. are the result of a shock wave moving around the Galaxy. C. were thrown out of the core of the Galaxy by a violet eruption in the distant past. D. are collapsing in toward the core of the Galaxy.
B
The diameter of the X-ray source Cygnus X-1 has been measured to be about 3,000 km. How was this value determined? A. from the time required for the edge of the Moon to cover the X-ray source during a lunar occultation of Cygnus X-1 B. from the length of time it takes the intensity of the flickering X-rays to change from maximum to minimum C. using long-baseline radio interferometry D. from the duration of eclipses of Cygnus X-1 by its companion star
B
The energy source for an active galaxy A. extends throughout the entire galaxy. B. is located in the galaxy's center. C. is located in the galaxy's center, except for radio galaxies, in which it is located in the radio lobes. D. is not a fixed point but moves about within the galaxy.
B
The evolution of stars is understood from modeling them using the laws of physics. In models, stars evolve in accordance with the competing forces of A. pressure and thermodynamics. B. gas pressure and gravity. C. pressure and nuclear fusion. D. gravity and kinetic energy.
B
The expansion of the universe A. was initially accelerating but is now decelerating. B. was initially decelerating but is now accelerating. C. has been accelerating ever since the Big Bang. D. has been decelerating ever since the Big Bang.
B
The fundamental plane technique is used to determine distances to elliptical galaxies. According to this technique, the elliptical's size can be determined from a knowledge of how its brightness is distributed across its surface and also A. its rotation rate. B. the average motion of its stars. C. the amount of gas and dust it contains. D. the rate of supernova eruptions within it.
B
The helium flash occurs at the A. beginning of core helium uclear reactions in a high-mass star. B. beginning of core helium nuclear reactions in a low-mass star. C. end of core helium nuclear reactions in a high-mass star. D. end of core helium nuclear reactions in a low-mass star.
B
The hydrogen-fusion stage (the main-sequence lifetime) in the life of a 25-solar-mass star is 7 million years. In contrast, how long does the silicon-fusion stage of this star last? A. second B. one day C. one year D. 600 years
B
The largest galaxies in size and greatest in mass in our observable universe are _________ galaxies. A. lenticular B. elliptical C. spiral D. barred spiral
B
The method used to find the distances to the very farthest galaxies is A. trigonometric parallax. B. Type Ia supernovae peak brightnesses. C. RR Lyrae and Cepheid variables. D. spectroscopic parallax.
B
The original "seeds" from which the galaxies grew were A. acoustic (sound) waves B. density fluctuations. C. particle-antiparticle pairs. D. primordial black holes.
B
The outer limb of the Sun is darker than the center because A. we see in to deeper, hotter levels at the limb. B. we see higher, cooler levels at the limb. C. the fusion process is weaker at the limb. D. the photosphere is not as thick at the edge.
B
The spectrum of a Population II star is characterized by A. strong metal lines. B. weak metal lines. C. weak metal lines and strong helium lines. D. weak hydrogen lines, regardless of the strength of the metal lines.
B
The thickness-to-diameter ratio of the disk of our Milky Way Galaxy that contains the spiral arms is about A. 1 ( a sphere!). B. 1/80. C. 1/3.25. D. 1/1000 ("paper thin").
B
Three of the following are factors in the Drake equation. Which is the exception? A. rate at which solar-type stars form in the galaxy B. rate at which solar-type stars die C. fraction of planets that are Earth-like D. lifetime of an advanced civilization
B
Thus far, searches for life on Mars have found A. no evidence in favor of it. B. some disputed possible evidence for ancient microorganisms. C. some tentative evidence for microorganisms in the soil. D. structures built by ancient Martians that resemble faces.
B
To use the method of spectroscopic parallax to determine the distance to a star, we need to first know the star's A. luminosity class and luminosity. B. spectral type and apparent magnitude C. parallax angle and spectral type. D. mass and luminosity.
B
Using the Drake equation and the estimates of its various factors developed in the text, what is our estimate for the number of civilizations in the galaxy with which we might communicate? A. 0 B. 10 C. 1000 D. 1,000,000
B
We know that a globular cluster is old by A. counting the number of stars in the cluster. B. noting the higher population of giant stars on the H-R diagram for the cluster. C. measuring the density (number of stars per unit volume) for the cluster. D. measuring the average apparent magnitudes of the RR-Lyrae variable stars in the cluster.
B
We know that some higher-mass asymptotic branch stars, also called carbon stars, are not completely stable because A. they will eventually become Type II supernovae and explode. B. carbon from the core is convected (dredged up) all the way to the surface. C. these stars send out regular pulses of radiation at short (millisecond) intervals. D. bipolar jets can be detected carrying enormous amounts of energy away from these stars.
B
We observe the cosmic microwave background to be almost completely isotropic. What do we infer from this observation? A. The Milky Way galaxy must be near the center of the universe. B. The matter in the early universe from which this radiation had its last scattering must have been very smoothly distributed. C. The Jeans length in the space between the galaxy clusters is extremely short. D. The matter in the early universe must have been predominantly charged rather than neutral.
B
What are the names of the satellite galaxies which orbit the Milky Way Galaxy? A. Pandora and Prometheus B. the Large and Small Magellanic Clouds C. the Oort Cloud and the Kuiper Belt D. S1 and S2
B
What causes the difference in magnetic field strength between a magnetar and an ordinary pulsar? A. Magnetars have magnetic fields while ordinary pulsars do not. B. Magnetars spin much faster than ordinary pulsars. C. The interior of a magnetar is molten, giving it a strong magnetic field, while an ordinary pulsar has a solid interior. D. Magnetars have a much longer active life than does an ordinary pulsar.
B
What discovery allowed astronomers to rule out any other possibility for the nature of pulsars except that they must be neutron stars? A. planets orbiting a pulsar B. observations of the Crab Pulsar, at the center of the Crab Nebula C. binary pulsar (two pulsars orbiting around each other) D. Some pulsars were moving away from their place of origin at great speeds.
B
What proportion of quasars emits intense radio radiation in addition to their shorter wavelength spectra? A. less than 1% B. 10% C. 60% D. 100%
B
What would happen to Earth in its orbit if the Sun were to be replaced by a black hole of 1 solar mass on the stroke of midnight tonight? A. The Earth would plunge into the black hole before dawn. B. nothing C. The Earth would begin to spiral inward under the gravitational force of the black hole. D. The Earth would begin to move in a straight line at a tangent to its previous orbit.
B
When a T Tauri star loses mass, we often see this as A. thermal pulses ejecting shells of material. B. a bipolar outflow. Look at the diagram C. a burster. D. a nova.
B
When material transfers from a companion star to a white dwarf, we see it as a(n) A. supernova. B. nova. C. X-ray burster. D. gamma-ray burster.
B
When we measure the narrow emission lines of hydrogen at the 21-cm wavelength along some line of sight through the galactic disk, we are able to determine the distances to and map the locations of different radiation-emitting neutral hydrogen clouds because A. the gas clouds that are farther away have a greater delay in the arrival time of the 21-cm radiation. B. clouds at different distances have different Doppler shifts because of the different rotational speeds of the galaxy at different radii. C. the clouds that are farther away have smaller angular sizes. D. the emission is stronger from clouds that are closer.
B
Where would you expect to find a newly formed O or B star? A. inside an H II region that is inside a giant molecular cloud that is inside a dark nebula B. inside an H II region that is inside a dark nebula that is in a giant molecular cloud C. inside a dark nebula that is inside an H II region D. inside a dark nebula that is inside an H II region that is inside a giant molecular cloud
B
Where would you look to find Population II stars? A. in open clusters B. in globular clusters C. in the immediate solar neighborhood D. among the fifty brightest stars in the sky
B
Which of the following extraterrestrial locations do astronomers suspect might harbor primitive life forms? A. Io B. Europa C. Callisto D. Triton
B
Which of the following is an example of hot dark matter? A. black holes B. neutrinos C. WIMPs D. gamma rays
B
Which of the following is not a characteristic of quasars? A. They have broad emission lines. B. They are less common in the early universe than they are today. C. They are at enormous distances from Earth. D. They often give off strong radio radiation.
B
Which of the following statements correctly describes the "law of cosmic censorship"? A. Black holes cannot have magnetic fields. B. Singularities are always hidden behind event horizons (i.e.: There are no naked singulatities.). C. We can never know both the mass and electric charge of a black hole with unlimited precision: the more precisely we know one, the less precisely we know the other. D. Only three properties of a black hole can be measured from the outside world: its mass, its electric charge, and its angular momentum.
B
Which one of the following properties is not a measured characteristic of a black hole? A. mass B. magnetic field C. electric charge D. angular momentum
B
Which part of the Milky Way contains the largest percentage of Population II stars? A. nucleus B. halo C. disk D. bulge
B
While the outer layers of a massive star are exploding outwards during a supernova, the core of the star has reached a density of about A. 104 kg/m3, the density at the center of Earth. B. 1017 kg/m3, the density of an atomic nucleus. C. 109 kg/m3, the density of electron-degenerate matter. D. 103 kg/m3, the density of iron.
B
Who first discovered evidence that the Sun is not at or even close to the center of our Galaxy? A. Henrietta Leavitt B. Harlow Shapley C. William Herschel D. Edwin Hubble
B
Why do horizontal branch stars radiate more energy in the blue? A. These are massive supergiants whose cores send out so much energy that the outer layers are heated until they radiate predominantly in the short wavelength end of the spectrum. B. After the helium flash in these low-mass stars, energy is generated by both core helium fusion and shell hydrogen fusion. The outer layers are heated as they contract and begin to radiate in the short-wavelength end of the spectrum. C. After the helium flash in these low-mass stars, energy is generated by both core helium fusion and shell hydrogen fusion. The outer layers are heated as they expand and begin to radiate in the short-wavelength end of the spectrum. D. Horizontal branch stars are moving toward us rapidly enough that their spectra are Doppler shifted toward short wavelengths.
B
Why does the collapsar model (which seems to explain long-duration gamma-ray bursters) not explain short-duration gamma-ray bursters? A. Gamma-ray bursters are distributed along the plane of our Galaxy and thus must have a galactic origin. B. The jets that produce the gamma rays in the collapsar model last ten times longer than the short-duration gamma-ray bursters. C. Short-duration gamma-ray bursters have far too much energy to be explained by the collapsar model. D. Unlike long-duration gamma-ray bursts, which have a nonthermal spectrum, short-duration gamma-ray bursts have thermal spectra and thus must have a different explanation.
B
Recently, we have designed monitoring programs which can detect which of these for an extrasolar planet? A. individual beings B. oceans and continents C. layers in the atmosphere D. orbiting natural satellites
B & C
The stars a Cygni and B (weird b) Cyngni are the constellation Cygnus. Which statement is true?
B cyngni appears brigther
Which of these stars would be the hottest?
B0
How does the number of barred spirals in the Universe compare to the number of ordinary spirals?
Barred spirals outnumber ordinary spirals.
If double radio sources quasars and blazars are considered to be the same basic object why do they appear to us to have very different and distinct properties?
Because we are viewing them at different angles to the line of the double jets emitted from their cores
Vega is an AØ V star with a surface temperature of about 10 000 degrees. Use Figures 19-13 and 19-21 in your text to estimate the mass of Vega.
Between 1.5 and 2.0 solar masses
The luminosities and temperatures of stars in a cluster are plotted on a Hertzsprung-Russell diagram. Most of the stars appear on the main sequence, but none are seen on the upper part of this sequence and a few stars appear in the red-giant phase. How old is this cluster?
Between 30 and 100 million years. Yes. This cluster is intermediate in age. Section 19-4
How far is the nearest star beyond the Sun?
Between one and two parsecs away
____ are small dark nebulae about 1 light-year in diameter that contain 10 to 1,000 solar masses.
Bok globules
Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore
Both stars have the same luminosity, but the apparent brightness of Star B is four times that of Star A.
____ are star-like objects that contain less than 0.08 solar masses and will never raise their core temperatures high enough that the proton-proton chain can begin. Other minor fusion reactions do occur in these objects. They fall in a gap between the low-mass M dwarf stars and the massive planets in which nuclear fusion never occurs.
Brown dwarfs
How is the mass of the Galaxy estimated?
By applying Newton's extension of Kepler's laws to the motion of the Sun and other stars
How did astronomers discover the relationship between spectral type and mass for main-sequence stars?
By measuring the masses and spectral types of main-sequence stars in binary systems.
How is a luminosity class assigned to a star?
By studying the absorption line width in the spectrum of the star.
A barred spiral galaxy is a(n) A. spiral galaxy which, because of the gravitational influence of a neighboring galaxy, is unable to continue, or is "barred" from, rotating in a normal manner. B. spiral galaxy that has lost all its interstellar gas and dust and now just shows a central bulge crossed by a straight, featureless disk. C. galaxy with a straight bar of stars passing through its nucleus and spiral arms extending from the ends of the bar. D. edge-on galaxy with a very dense dust lane in its plane that blocks light from the spiral arms and disk.
C
A difficulty in attributing the energy source of the Sun to anything but nuclear reactions is A. a lack of alternate ideas. B. a lack of other reasonable sources of fuel. C. that reliance on other sources of energy requires the Sun to be unreasonably young. D. that other sources of energy do not work in the vacuum of space.
C
A particular galaxy is observed to have a recessional velocity (away from the Earth) of 300,000 km/s. According to Hubble's law, what is the distance to this galaxy? Assume the Hubble Constant to be 70 km/s/Mpc. A. 4.3 Mpc B. 21 Mpc C. 4300 Mpc D. 21,000,000 Mpc
C
A rotation curve is a plot of the rotational velocity of the stars and other objects in a galaxy as a function of their distance away from the center. Predictions for rotation curves for spiral galaxies suggest that the curve should decline beyond the galactic bulge. Actual measurements, however, show that the rotation curve is flat beyond the bulge. What does this deviation from prediction tell us about spiral galaxies? A. They are not rotating as rapidly as we had believed. B. The spiral arms move around as rigid objects. C. There is a great deal of unseen mass surrounding the visible galaxy. D. The centers of spiral galaxies contain supermassive black holes.
C
A single pulsar (not a member of a binary system) is observed to be rotating at the rapid rate of 20 times per second. What does this tell us about the pulsar? A. It will soon collapse to form a black hole. B. It has a mass greater than four solar masses. C. It is a young pulsar. D. It is an old pulsar.
C
According to Hubble's Law, if a very distant galaxy B is three times farther away from our Galaxy as another galaxy A, then galaxy B is receding from us ___ Galaxy A. A. nine times as fast as B. one-ninth as fast as C. three times as fast as D. one-third as fast as
C
According to the unified model for active galactic nuclei, what would be observed when viewing a galaxy with a supermassive black hole and an accretion disk but no jets? A. Nothing could be seen since the jets provide the only radiation from such a galaxy. B. The galaxy would look like a normal galaxy, not an active galaxy. C. A radio-quiet galaxy would be observed. D. A blazar with a featureless spectrum would be observed.
C
All stars in a star cluster formed at approximately the same time. How does this affect the appearance of the Hertzsprung-Russell diagram of a young star cluster? A. All the stars arrive on the main sequence at the same time, so a young cluster provides a clear picture of what the main sequence looks like. B. Stars that form at the same time reach the main sequence at the same point in the H-R diagram, so a cluster never shows a recognizable main-sequence band. C. More-massive stars are hotter and therefore evolve faster, so the higher-mass stars are on the main sequence while the lower-mass stars are pre-main-sequence (above the main sequence). D. Less massive stars are cooler and therefore evolve faster, so the lower-mass stars are on the main sequence while the higher-mass stars are still approaching (above) the main sequence.
C
An alpha (α) particle is A. the nucleus of a heavy hydrogen atom. B. a high-energy photon (electromagnetic radiation). C. the nucleus of a h lium atom. D. a high-speed electron released from an atomic nucleus.
C
An astronomer makes a direct measurement of the brightness of a star in the nighttime sky. What the astronomer has measured is the star's A. distance. B. luminosity. C. apparent magnitude. D. absolute magnitude.
C
An astronomer who wants to measure the sizes and masses of stars will get the most information by studying A. single-line spectroscopic binary stars. B. stars in open clusters, for which a Hertzsprung-Russell diagram can be plotted. C. eclipsing spectroscopic binary stars. D. bright single stars, since companion stars interfere with the measurement.
C
An atom of helium now residing in Earth's atmosphere could have been formed A. only during the initial, hot part of the expansion of the universe. B. only by nuclear reactions within stars after the early expansion of the universe. C. by either of the two processes in a and b. D. by neither of the two processes in a and b.
C
An observer on a planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at...
C
As strange as it sounds, black holes can evaporate because A. they radiate X rays back into space. B. they lose material through "white hole" exit points. C. of pair production near the event horizon. D. gravitational "boosting" of objects near them takes some of their energy away.
C
As you watch an object fall toward the event horizon of a black hole, you will observe three of the following. Which observation would not be possible? A. The object will become elongated in the directions toward and away from the black hole. B. The object will become narrower in the directions perpendicular to its motion. C. The object will appear to speed up continually until it finally disappears inside the event horizon. D. The color of the object will appear to shift to longer and longer wavelengths.
C
Capella is a giant star in the constellation Auriga (just above Orion). If you watch it for six months it is possible to measure its parallax angle, which is 0.079 seconds of arc. Also near Orion is Aldebaran, in Taurus. Its parallax angle is 0.05 arcseconds. Regulus is a main-sequence star in Leo. Its parallax angle is 0.041 arcseconds. Which of these stars is farthest away? A. Capella B. Aldebaran C. Regulus D. It cannot be determined from this information alone.
C
Does the Milky Way belong to a galaxy cluster? A. yes, to a binary system consisting of the Milky Way and the Andromeda galaxy B. yes, to a rich cluster, the Virgo Cluster C. yes, to a poor cluster, the Local Group D. No. It is a single, isolated galaxy.
C
Galaxy collisions often cause A. spectacular supernova explosions. B. spectacular explosions between colliding stars. C. a burst of star formation in one or both galaxies. D. galaxies to completely disintegrate.
C
How long after the Big Bang did quarks combine to form neutrons and protons? A. 1-2 billion years B. 3 minutes C. 10-6 second D. the Planck time, 10-43 second
C
Hubble classified the galaxies he saw into A. small, medium, and large galaxies. B. dwarf, main-sequence, and giant galaxies. C. elliptical, spiral, and barred spiral galaxies. D. approaching, receding, and static galaxies.
C
If Hubble's constant, H0, were 50 km/s/Mpc, the universe would be approximately _____ billion years old. A. 9.18 B. 13.4 C. 19.6 D. 26.2
C
If I want to know both the size and mass of a star, I will most likely be able to calculate this information if the star is a member of a(n) A. optical double. B. spectroscopic binary. C. eclipsing binary. D. globular cluster.
C
If a 5-solar-mass black hole has a radius to its event horizon of 15 km, what will be the radius of the event horizon of a 50-solar-mass black hole? A. 1.5 km because the greater mass will cause a greater condensation of space B. zero because a black hole of more than about 20 solar masses will collapse to a singularity C. 150 km, occupying much more space. D. the same radius because all black holes have the same size.
C
If space is hyperbolic, then initially parallel light beams would subsequently A. always converge. B. always remain parallel. C. always diverge. D. either converge or diverge, depending on the curvature of space.
C
If the lighthouse model for pulsars is correct, A. it violates the conservation of energy. B. we should observe many more pulsars than we do. C. there should be many pulsars we do not detect as pulsars. D. pulsations of radiation should be produced only if the magnetic axis is aligned with the rotation axis.
C
If the universe is closed, then parallel lines A. will remain parallel no matter how far they extend. B. will diverge from each other as they extend into space. C. will eventually intersect as they extend into space. D. are undefined.
C
If you were able to view the entire Milky Way Galaxy through a filter that passed only far infrared wavelengths, what would you see? A. billions of points of light representing the far infrared emissions of the stars B. relatively few points of light representing the far infrared emissions of newly formed stars C. a bright glow from the dust in the galactic plane D. almost nothing since the galaxy emits almost no far infrared radiation
C
In 1976, the Viking Landers were the first spacecraft to land on Mars and also the first to search for life there. Their search A. discovered life on Mars. B. ruled out any possibility of life on Mars. C. found ambiguous evidence concerning life on Mars. D. was conducted over a large part of the Martian surface.
C
In February 2000, astronomers announced the discovery of a quasar in the constellation Cetus, the Whale, that has a redshift z = 5.82. During the time the light from this quasar was traveling to the Earth, how much larger did the universe become? A. 4.82 times larger B. 5.82 times larger C. 6.82 times larger D. The answer depends on the value used for the Hubble constant, H0.
C
In which of the following locations is star formation most likely to be taking place? A. reflection nebulae B. proplyds C. giant molecular clouds D. emission nebulae (H II regions)
C
Interstellar reddening causes more-distant stars to look redder. What physical process produces this reddening? A. Blue light is preferentially absorbed by atoms and molecules of gas in interstellar space. B. Photons gradually lose energy in passing through interstellar gas, and lower-energy photons have longer wavelengths (redder light). C. Blue light is scattered out of the beam of starlight by grains of dust in interstellar space. D. Red light from stars close to the nebula is scattered towards the observer by grains of dust in interstellar space.
C
Jets of material ejected from the centers of galaxies are evidence that A. black holes have exit points called "white holes" where captured material is ejected. B. there are no black holes at the centers of these galaxies. If black holes existed there the material would not be able to escape along the jets. C. black holes with masses more than 106 times that of the Sun are there. D. black holes evaporate with time.
C
Main-sequence stars in the upper-left corner of the Hertzsprung-Russell diagram are A. red. B. less luminous that the Sun. C. more massive that the Sun. D. over a hundred times larger than the Sun.
C
Normally, when we compress a gas, the temperature increases. But for the density fluctuations in the early universe, we associate denser regions with lower temperature. Why? A. The early universe was composed of a plasma that had properties very different from those of a normal gas. B. Because we are dealing with degenerate matter, the normal relationship between pressure and temperature does not apply. C. The denser regions contain more mass and thus cause a larger gravitational redshift of photons emerging from it. The lower temperatures refer to the spectrum (color) of the emerging photons rather than to the temperature of the material itself. D. So much X-ray radiation is emitted from the hot gas associated with these density concentrations that it has a cooling effect.
C
Of the following methods, which is the most accurate for measuring the age of a star cluster? A. measuring the amount of gas and dust in the cluster B. counting the number of stars still remaining in the cluster, as stars slowly "evaporate" from it into the rest of the galaxy C. determining the turn-off point on the main sequence in the Hertzsprung- Russell diagram of the cluster D. observing the strength of the metal lines in the spectra of the stars in the cluster
C
Older, metal-poor stars in our Milky Way are found predominantly A. near the very active galactic center, very close to the black hole. B. in globular clusters. C. in the halo and in the central bulge. D. in the spiral arms.
C
Planetary nebulae were given this name because they A. have spectra rich in methane and ammonia, similar to the gas giants in our solar system. B. are debris left over from planets that were destroyed when the star expanded to become an asymptotic giant branch (AGB) star. C. are often small and round, and looked like planets when first discovered using the small telescopes of the nineteenth century. D. are debris left over from the formation of the star, from which planets are expected to coalesce.
C
Protostars __________ mass as they evolve. A. lose B. gain C. both gain and lose D. neither gain nor lose
C
Quasars lie at the centers of what kind of active galaxies? A. ellipticals only B. spirals only C. both ellipticals and spirals D. irregulars only
C
RR-Lyrae variable stars proved to be the key to Harlow Shapley's 1917 determination of the shape and size of the Milky Way Galaxy because they are A. the only variable stars bright enough to be seen across the galaxy. B. the only variable stars with luminosities that can be determined from their periods. C. routinely found in globular clusters. D. routinely found in open clusters and their distances can be measured.
C
Radio galaxies are probably quasars A. seen face-on to the accretion disk. B. seen at an angle around 45° to the accretion disk. C. with jets that are beaming into the plane of the sky. D. that are just starting up.
C
Stars on the main sequence have masses in the range of __________ solar masses. A. 10-2-106 B. 0.2-8 C. 0.1-60 D. 1-20
C
Studies of binary stars have taught us that A. the more massive star tends to orbit in the shorter time. B. the less massive star tends to orbit in the shorter time. C. more massive stars tend to be more luminous. D. less massive stars tend to be bluer.
C
Suppose a galaxy is observed in which the globular clusters appear blue. What might be the significance? A. There is no special significance since globular clusters, in our own Galaxy and others, are normally blue. B. These globulars must have orbits that take them well out into cold intergalactic space, since these clusters are at particularly low temperatures. C. These globulars must have been created recently in an encounter with another galaxy. D. The globulars of this galaxy are moving toward us at high speeds.
C
Suppose the recessional velocity of a distant galaxy is half the speed of light. How would the values of redshift z compare if calculated using the non-relativistic equation and using the relativistic equation? A. They are equal. B. The z value computed nonrelativistically is greater. C. The z value computed relativistically is greater. D. The nonrelativistic value of z is imaginary for a velocity this large.
C
The Black Widow pulsar is significant because it provides evidence that A. binary pulsars (two neutron stars orbiting each other) can destroy each other. B. a pulsar can destroy itself through mass ejection from its poles. C. pulsars can destroy their companion stars. D. pulsars can be destroyed by their companion stars.
C
The Chandrasekhar limit refers to the maximum possible A. mass of a red supergiant, equal to about 80 solar masses. B. size of a low-mass star, equal to 5.0 solar masses. C. mass of a white dwarf, equal to 1.4 solar masses. D. mass of a neutron star, equal to 3.0 solar masses.
C
The Hubble expansion provides an explanation for Olbers's paradox because it says that A. the universe is finite in size. B. the universe is infinite in size. C. the universe is finite in age. D. starlight is redshifted so much that we can no longer detect it.
C
The Hubble tuning fork diagram arranges galaxy types from E0 ellipticals at one end to Sc and SBc spirals at the other end. What characteristic of galaxies is being plotted in this diagram? A. size B. evolutionary sequence C. amount of rotation D. number of spiral arms
C
The Tully-Fisher relation indicates that the width (Doppler broadening) of the 21-centimeter line in the spectrum of a spiral galaxy is proportional to the galaxy's A. age. B. distance. C. absolute magnitude. D. apparent magnitude.
C
The X-ray source Cygnus X-1 bears what characteristics indicating it is a black hole? A. binary system consisting of a stellar-mass black hole and a neutron star. B. solitary stellar-mass black hole formed by the coalescence of two neutron stars C. binary system consisting of an 8-solar-mass black hole and a normal B-type supergiant. D. supermassive black hole near the center of our Galaxy.
C
The amount of mass lying inside the orbit of the Sun in our Galaxy is approximately ____ solar masses. A. 260,000 B. 2.6 million C. 90 billion D. 600 billion
C
The amount of matter in the Milky Way that is dark matter is A. 10%. B. 50%. C. 90%. D. 99%.
C
The cosmic microwave background radiation is virtually identical no matter where we look in space. This indicates that A. the universe has to have a flat geometry. B. the universe has to be at least 14 billion light-years across. C. just after the Big Bang the now-distant parts had to be close together. D. the Big Bang had to be extremely hot.
C
The escape speed at the surface of a neutron star, the speed a projectile would need to have in order to escape from the neutron star, is _____ the speed of light. A. greater than. Therefore, matter cannot leave the surface of a neutron star. B. 1/10 C. 1/2 D. 9/10
C
The evolution of a protostar generally involves A. collapse caused by radiation pressure. B. expansion caused by gravity. C. collapse caused by gravity. D. expansion caused by nuclear reactions.
C
The galaxy NGC 4261 has jets of material streaming out from its core in opposite directions and also a disk of material in rapid rotation about its core. This rotating disk is significant because A. it shows that the core of NGC 4261 went through a nova phase at least once. B. it shows that the black hole in the core of NGC 4261 is newly formed and is now dissipating the gas and dust clouds that surrounded its creation. C. application of Kepler's third law to this disk allows us to calculate the mass of the central core. D. it is the first direct observation of an accretion disk.
C
The gravitational redshift is produced by the A. inability of light or matter to escape from inside the event horizon of a black hole. B. emission of gravitational waves by an accelerating mass. C. slowing down of time in a gravitational field. D. Doppler shift when gravitating objects make other objects fall toward them and thus away from the observer.
C
The lifetimes of stars are A. infinite. We have no evidence that any star has ever ceased to exist. B. finite because stars are all ultimately destroyed when they are swept into black holes. C. finite because stars contain only a limited amount of fuel that they cannot renew when it has been used up. D. finite because stars process the gas and dust in the envelope around them, and when this envelope has been consumed out to a certain distance from the star, it is extinguished.
C
The mass of a nonrotating black hole is A. uniformly distributed on a spherical shell that has a radius equal to the Schwarzschild radius. B. uniformly distributed inside a spherical shell that has a radius equal to the Schwarzschild radius. C. all concentrated in a singularity at the center. D. mostly contained in jets erupting from each pole.
C
The most important parameter of a star that governs its lifetime is its A. surface temperature. B. chemical composition. C. mass. What is the relation between mass and lifetime? D. location in the galaxy.
C
The most stable nucleus, which cannot produce any nuclear reactions that emit energy (i.e.: are exothermic), is A. B. C. D.
C
The only difference between double radio sources, quasars, and blazars, in terms of appearance, may be A. their distance from Earth. Double radio sources are close enough to be resolved, quasars are sufficiently close to show some structure, and blazars always appear as point sources because of their extreme distance. B. the mass of their central black holes. Double radio sources have the lowest mass black holes, quasars the highest, and blazers in between. C. the angle between the line of sight and the line of the two oppositely directed jets of matter in the source. D. their age. Blazars are the youngest, showing no spectral line emission, quasars are of intermediate age, and double radio sources are the oldest, the result of the dying out of the central source of the system.
C
The process that removes energy from the core of a high-mass star, triggering core collapse and supernova explosion, is A. photodisintegration. B. heavy element fusion. C. neutrinos escaping. D. runaway hydrostatic pulsations.
C
The search for extraterrestrial intelligence has used mostly radio telescopes (rather than optical or other types) to try to detect signals. Why this wavelength band? A. Optical telescopes are all being used for other research and are not available for SETI. B. Radio wavelengths travel fastest through vacuum, and thus we can receive signals from sources farther away. C. Longer wavelengths can travel farther through interstellar dust without appreciable scattering and degradation. D. Radio was the first long-distance electromagnetic communication system developed on Earth, so other civilizations might develop it first also.
C
The stars that evolve most rapidly are those with A. low mass. B. low temperature. C. high mass. D. high temperature.
C
The summary of the nuclear reactions in the 3-step dominant nuclear process in the core of a 1-solar-mass main-sequence star is What is the source of the energy released in this reaction? A. The energy is released in the gravitational collapse of the core. B. The outer layers of the star expand. As they expand, they release energy. C. is less massive than four hydrogen nuclei. The excess mass is converted into energy. D. Stored chemical energy is released as hydrogen atoms combine to form helium molecules.
C
The universe described in the membrane or M-theory of cosmology is A. open. B. closed. C. oscillatory. D. negatively curved.
C
The upper limit for the mass of a neutron star (greatest mass it can have without collapsing onto itself) is calculated to be ____ solar masses. A. 0.8 B. 1.4 C. 3 D. 8
C
Two stars are the same distance away from us and have the same surface temperature but different radii. What can you determine about their apparent magnitudes? A. They have the same apparent magnitudes. B. The larger star has the larger apparent magnitude. C. The larger star has the smaller apparent magnitude. D. Nothing can be determined about the relative apparent magnitudes from this information.
C
Using infrared satellites, we can A. pinpoint places on planets where radio waves originate. B. look for living forms on Mars by the heat they radiate. C. identify stars with Earth-like planets for follow-up studies. D. better search for evidence of UFOs.
C
We can find a star's distance by inferring its absolute magnitude from its position on an H-R diagram after measuring its A. mass and color index. B. mass and luminosity class. C. spectral type and luminosity class. D. absolute magnitude and apparent magnitude.
C
We have observed evidence that a mass about equal to that of Mercury recently fell into the black hole at the center of the Galaxy. What is our evidence? A. The mass of this black hole, as measured by the orbital characteristics of the stars circling it, was seen to increase by this amount. B. A Mercury-sized object was observed orbiting the black hole, and it is no longer observed. C. Gravitational waves of the right intensity to represent this much mass were detected coming from the galactic center. D. A number of nebulae in the vicinity of the galactic center were seen to brighten suddenly as though illuminated by an intense burst of X rays.
C
What are RR Lyrae stars? A. pre-main-sequence stars that vary rapidly and eject jets of material along each polar axis B. yellow giants and supergiants that pulsate with periods that are closely related to their luminosities C. metal-poor variable stars that are undergoing core helium fusion and pulsate with periods of less than one day D. giant stars that pulsate with periods of several months to several years
C
What are a similarity and a difference between a Type Ib supernova and a Type Ia supernova? A. Both are massive stars exploding, but Type Ib has strong hydrogen lines in its spectrum whereas in Type Ia these lines are absent. B. Both are massive stars exploding, but Type Ib lacks hydrogen lines in its spectrum whereas in Type Ia these lines are strong. C. Both types lack hydrogen lines in their spectra, but Type Ib is a massive star exploding and Type Ia is a white dwarf exploding. D. Both types lack hydrogen lines in their spectra, but Type Ib is a white dwarf exploding and Type Ia is a massive star exploding.
C
What are the dominant nuclear reactions in an asymptotic giant branch (AGB) star, and where do they occur? A. helium reactions, in the star's core B. hydrogen reactions, in a shell outside the core. C. helium reactions, in a shell outside the core D. carbon reactions, in the star's core.
C
What fraction of the mass of a rich cluster of galaxies is in a form that we can see (that emits or reflects light or other electromagnetic radiation)? A. between 50% and 70% B. almost 100% C. about 10% D. less than 1%
C
What happened to the first generation of stars, the Population III stars? A. They have ceased active nuclear reactions but still constitute much of the dark matter we detect. B. They left behind a large number of massive black holes. C. They exploded and sent their heavy elements into space to enrich the raw material for the next generation of stars. D. They lived their short lives entirely before the end of the cosmic fireball, so it is not possible to see back to the time of their demise.
C
What is the difference between a MACHO and a WIMP? What do the letters stand for? A. Both are smaller than an atom, but a MACHO is charged and a WIMP is uncharged. B. A MACHO is supermassive (millions of solar masses), and a WIMP is smaller than an atom. C. A MACHO is planet-sized or larger, and a WIMP is smaller than an atom. D. A MACHO is smaller than an atom, and a WIMP is comet- or planetesimal-sized.
C
What is the difference between a pulsar and a neutron star? A. Most neutron stars are stationary. If they rotate they are called pulsars. B. Pulsars are neutron stars that oscillate in and out radially, emitting radiation as they do so. C. Neutron stars rotate rapidly and send out beams of radio waves. If these beams sweep across Earth, we detect radio-wave pulses, and the object is called a pulsar. D. Neutron stars are called pulsars when they have binary companions from which they can siphon material. This act results in the emission of radiation.
C
What is the main difference in the energy-transport mechanism between a 1-solar-mass main-sequence star and one of less than 0.4 solar mass? A. Temperatures are too low in the less massive star to allow convection. B. Stars of less than 0.4 solar masses have so little nuclear fuel that transport by neither convection nor radiation can occur C. The lower-mass star convects throughout its whole volume rather than just in its outer layers. D. Stars of less than 0.4 solar masses transport energy by radiative transfer throughout their entire volume
C
What kind of star is an RR-Lyrae variable star? A. white dwarf star B. main-sequence star C. horizontal branch star D. carbon star
C
When material transfers from a companion star to a neutron star we see it as a(n) A. supernova. B. nova. C. X-ray burster. D. gamma-ray burster.
C
When their absolute magnitude and spectral class are plotted in a Hertzsprung-Russell Diagram, star X is found to be to the lower left of star Y. From this we know that star X is __________ than star Y. A. cooler, more energetic, and larger B. hotter, more energetic, and larger C. hotter, less energetic, and smaller D. cooler, less energetic, and smaller
C
Which chemical element is the building block of life because it is best suited for making the wide variety of combinations of structural patterns necessary for the complex organic molecules in biological systems? A. water B. silicon C. carbon D. nitrogen
C
Which group represents stars that are extremely bright and emit most of their radiation as ultraviolet light? H/R Diagram
C
Which group represents the most common type of stars? (H/R DIAGRAM)
C
1.4 M
Chandrasekhar worked out a mass limit above which stars would undergo an evolution different than solar type stars. That limit is:
Which of the following descriptions of stars in the Sun's neighborhood is correct? A. The hottest stars in our sky are the brightest. B. The parallax increases with increasing distance from the Earth. C. The stars that appear to move most as the Earth orbits the Sun are the closest. D. The brightest stars in our sky are the stars nearest to the Earth.
C
Which of the following is not a type of gas or dust cloud found in space? A. H II region B. dark nebula C. light nebula D. reflection nebula
C
Which of the following is not believed to result from collisions between galaxies? A. hot X-ray-emitting gas in clusters of galaxies B. prolific star formation C. black holes created by colliding stars D. spiral arms
C
Which of the following mechanisms does not lead to star formation? A. compression of part of a giant molecular cloud by stellar winds from hot O and B stars B. compression of giant molecular clouds as they pass through spiral arms C. collapse of a hot, massive H II region under the influence of its own gravity D. collapse of a cold, dense cloud of gas and dust under the influence of its own gravity
C
Which of the following objects is not the final stage in the life of a star? A. neutron star B. white dwarf C. asymptotic giant branch star D. black hole
C
Which of the following sequences of stellar classification types shows stars in order of decreasing surface temperature? A. B8, A7, A3, G5 B. G5, A7, A3, B8 C. B8, A3, A7, G5 D. G5, A3, A7, B8
C
Which one of the following features is most likely to occur in a universe created with cold dark matter than in one with hot dark matter? A. cluster-sized structures in the gas distribution that then collapses into galaxies and stars B. small-sized voids surrounded by thicker strings of galaxies C. small structures like stars that sweep together into galaxies and clusters D. quasars immediately after the Big Bang
C
Which one of the following statements is not evidence that supports the Big Bang Model for the formation of the universe? A. Clusters of galaxies are all going away from us. B. The sky gets dark at night (resolution of Olbers's Paradox). C. Elliptical galaxies appear to be about the same size. D. There is a microwave background radiation seen wherever we look.
C
Why do nuclear fusion reactions, like those in the Sun, take place only at high temperatures? A. The high temperatures are a result of the energy released in the reactions. They are not actually needed to produce the reactions. B. The high temperatures are needed to ionize the atoms (to strip them of their electrons) so that the bare nuclei can interact. C. All nuclei are positive, and high temperatures—and the high velocities that go with them—are necessary to force these repulsive nuclei together. D. To undergo fusion reactions, a nucleus must separate into its constituent particles (neutrons and protons), and this happens only at high temperatures.
C
Why would we expect that a solar system with at least one Jupiter-mass planet would have a better chance of developing an intelligent civilization than a solar system without? A. A Jupiter-mass planet would absorb much of the hydrogen and helium in the solar nebula, leaving the heavier elements concentrated to form terrestrial planets. B. A Jupiter-mass planet might be expected to have satellites like Europa on which tidal friction produces enough heat to keep water liquid. C. The gravity of a massive planet would keep many asteroids and comets out of the inner solar system and prevent collisions with terrestrial planets. D. We believe that solar systems form to certain basic patterns, so the existence of a Jupiter-mass planet would suggest that an Earth-mass planet is also likely.
C
What are the products of helium burning in a star?
carbon and oxygen
Evidence for black holes includes A. novas and X-ray bursters. B. vast surveys that successfully look for nothing. C. plotting their positions on H-R diagrams, which shows that their mass is huge. D. X-ray and synchrotron (nonthermal) radiation coming from compact sources.
D
Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?
Calculate the star's luminosity if we know its distance, or calculate its distance if we know its luminosity
A white dwarf is composed of
carbon and oxygen nuclei and degenerate electrons.
Which of the following elements was not created as a result of Big Bang nucleosynthesis?
Carbon
What are the main byproducts of helium nuclear "burning" in red giant stars?
Carbon and oxygen nuclei
Which type of meteorite has been found to contain large organic molecules that make up the building blocks of life and provide strong evidence for their extraterrestrial production?
Carbonaceous chondrite
What are the stars in the upper part of the instability strip called?
Cepheid variables
How does a gravitational field affect the passage of time?
Clocks in a gravitational field run slower than clocks outside the field.
How are galaxies spread throughout the universe?
Clusters of galaxies exist that are themselves often clustered into superclusters. Clusters and superclusters appear to be distributed on surfaces surrounding empty regions of space.
Which of the following statements about comets and asteroids is true?
Comets are balls of ice and dust
3, 2, 1
Consider three black holes with different masses: #1 has a mass equal to that of the Earth, #2 has 10 Solar Masses, and #3 has one Million Solar Masses. Rank them in order of INCREASING average density (defined as total mass enclosed divided by volume inside their event horizons):
What physical process begins to heat the core of an intermediate-mass star after the hydrogen "fuel" is depleted and thermonuclear fusion has stopped in that core?
Contraction of the core and release of gravitational energy. Yes. As nuclear fusion ceases, gravity will shrink the core, thereby heating it so that helium "burning" can begin. Section 19-2
7. from inside out, which is in the correct order for the structure of the sun?
Core, Radiation Zone, Convection Zone
How is the sunspot cycle directly relevant to us here on earth?
Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
Evidence indicates that the main elements formed in the Big Bang were A. carbon, oxygen, and nitrogen. B. hydrogen, helium, and carbon. C. hydrogen, carbon, and nitrogen. D. Hydrogen and helium
D
A black hole is so named because A. the gravitational field at the surface is so strong that the wavelengths of the radiation it emits are Doppler shifted into the long-wavelength portions of the spectrum, and none of its emitted radiation is emitted in the visible. B. it emits no visible light because it is so cold and the atomic motion necessary for light emission is not present. C. its spectrum has the same shape as that of a laboratory blackbody but for very low temperatures (with peak wavelengths outside the visible range). D. its powerful gravitational field results in an escape speed greater than the speed of light.
D
A distant galaxy has a redshift z = 2. A volume of empty space between clusters of galaxies that was 1 (Mpc)3 when the light we now observe was emitted from this galaxy will have what volume today? A. 1/27 (Mpc)3 B. 1 (Mpc)3 C. 8 (Mpc)3 D. 27 (Mpc)3
D
A magnetar is a A. neutron star viewed almost exactly pole-on, so its beams of radiation never point at Earth. B. white dwarf highly convoluted magnetic fields and frequent flares. C. millisecond pulsar undergoing mass transfer from a close companion star. D. pulsar with an exceptionally strong magnetic field.
D
A neutron star is believed to have three of the following characteristics. Which characteristic does it not have? A. atmosphere B. crust C. superfluid layer D. fusion core
D
A primordial black hole is any black hole A. at the center of a galaxy. B. having a mass similar to those of stars (less than about 100 solar masses). C. that is alone in space (not part of a binary system). D. created during the formation of the universe.
D
A proplyd is a A. knot of hot gas where a jet from a T Tauri star collides with an interstellar cloud. B. protostar hidden inside a dense cloud of dust. C. small, cold cloud of gas and dust seen in silhouette against a bright H II region. D. protoplanetary disk around a young star.
D
A quasar's distance from the Sun is determined from its redshift to be 1000 Mpc (326 billion LY). How many years ago did this radiation leave the quasar? A. 3.26 million B. 326 million C. 3.26 billion D. 326 billion
D
A semidetached binary is a binary star system in which A. both stars fill their Roche lobes, but they have not yet expanded further to create a common envelope. B. the two stars are so far apart that the gravitational pull of any other star passing nearby would disrupt the system. C. the two stars share a common envelope. D. one star fills its Roche lobe. What is the Roche lobe?
D
According to Einstein, Earth orbits the Sun because A. of the actions of gravity, operating at a distance. B. time slows down near massive objects. C. space inside the Earth's orbit contracts as the Earth moves through it. D. it is following the path of curved spacetime generated by the sun.
D
Aggregates of gas and dust from which stars form can be found in space. Dust affects starlight by causing it to appear A. Doppler shifted to the red. B. Doppler shifted to the blue. C. dimmer and bluer. D. dimmer and redder.
D
As it evolves off the main sequence, the mass of a Sun-like star A. increases as it becomes a giant and then decreases when it becomes a white dwarf. B. decreases as it goes through its giant stage and then increases sharply as it enters the asymptotic branch. C. increases through all stagesof its evolution. D. decreases through all stages of its evolution.
D
Cepheid variables are A. white dwarf stars. B. stars at an early stage of evolution. C. members of binary systems in which one star periodically eclipses the other. D. stars that pulsate regularly in size, brightness, and temperature.
D
Compared to Population I stars, Population II stars have A. less mass, lower ages, thick surrounding gas and dust. B. more planets, dusty rings, greater reddening of emitted light. C. less hydrogen, more lithium, more carbon. D. fewer metals, greater ages, no surrounding gas or dust.
D
Compared to the oldest quasars, the quasars that have formed in the past 1 billion years are A. brighter. B. dimmer. C. radio-loud. D. absent! There are no nearby (young) quasars.
D
During which of the following evolutionary stages does a 1-solar-luminosity star lose the most mass? A. main sequence B. red giant C. horizontal branch D. asymptotic branch
D
Edwin Hubble determined that the Andromeda Galaxy was a star system in its own right outside the Milky Way by detecting and measuring ___ in the Andromeda Galaxy. A. OB associations. B. globular clusters. C. molecular clouds. D. Cepheid variables.
D
Figure 20-3 in Freedman and Kaufmann, Universe, 8th ed., shows an H-R diagram for the globular cluster M55. The diagram shows stars on the main sequence, the giant branch, the horizontal branch, and the asymptotic branch. Which of these regions contains the oldest stars? A. giant branch B. horizontal branch C. asymptotic branch D. All these stars would be about the same age.
D
Galaxies are found A. in a perfectly smooth distribution everywhere. B. mainly in the northern portion of the sky. C. in greater densities at higher redshifts. D. inside clusters within superclusters surrounding empty volumes called voids.
D
Giant elliptical galaxies, often found near the centers of rich clusters of galaxies, are believed to have formed A. as we see them and have remained that way ever since. B. by the merger of several normal elliptical and spiral galaxies in the dense cluster core, early in the life of the cluster. C. by gradual accretion of intracluster gas and dust over the lifetime of the galaxy cluster. D. by devouring many smaller galaxies over the lifetime of the cluster.
D
How long after the Big Bang did gravity separate out from the Superforce as an independent force? A. 300,000 years B. 3 minutes C. 10-6 second D. the Planck time, 10-43 second
D
If we were to observe a spaceship falling toward the event horizon of a black hole, we would see it A. suddenly disappear. B. circle a few times and then be ejected back into space. C. shatter as it hits the event horizon. D. get pulled apart into a line of material, then disappear over the edge.
D
In a Hertzsprung-Russell Diagram with absolute magnitude plotted vertically and temperature plotted horizontally, a particular star is found to be evolving slowly to the right at constant absolute magnitude. From this information, we know with certainty that the star is becoming A. only larger because temperature has no effect. B. only cooler because size has no effect. C. both smaller and cooler to keep the output the same. D. both larger and cooler to cancel each other's effects.
D
In a massive, main-sequence star (more than about 4 solar masses), the A. deep interior is radiative because of the large temperature differences, and the outer layers are convective because the gas is relatively opaque. B. entire star is convective because the temperature is too low to ionize the gas. C. entire star is radiative because the temperature is so high that all the gas in the star is ionized. D. deep interior is convective because of the large temperature differences, and the outer layers are radiative because of the low density of the gas.
D
In a rotating black hole, the ergoregion is the region A. inside the event horizon where it is impossible to remain at rest. B. inside the ring-shaped singularity. C. from which no energy, not even light, can escape. D. outside the event horizon where it is impossible to remain at rest.
D
In a β (beta) Lyrae binary star system, the more massive star is the less-luminous of the two. Why? A. The more massive star is still hidden in the dust clouds from which it formed. B. The more massive star is a black hole, from w ich light cannot escape. C. The Roche lobe of the more massive star is filled with material from the less massive star. D. The more massive star is hidden by an accretion disk of material from the less massive star.
D
In order of decreasing strength, the four physical forces of nature inside an atomic nucleus (over distances of less than about 10-15 m) are A. gravitational, electromagnetic, strong nuclear, and weak nuclear forces. B. strong nuclear, weak nuclear, electromagnetic, and gravitational forces. C. electromagnetic, strong nuclear, gravitational, and weak nuclear forces. D. strong nuclear, electromagnetic, weak nuclear, and gravitational forces.
D
Iron is a very useful element that is made into many common items such as nails, saw blades, and automobiles. Where has most of the iron on the Earth come from? A. core-collapse supernovae B. ejection of planetary nebulae by asymptotic giant branch (AGB) stars C. exploding neutron stars D. white dwarf supernovae
D
Jets of material being ejected from a central source characterize three of the following objects. Which object is the exception? A. quasars B. Seyfert galaxies C. radio galaxies D. supernova remnants
D
MACHOs of about half the mass of the Sun A. have been shown to not exist. B. make up at least 90% of the mass of the dark matter halo of our galaxy. C. make up less than 1/5 of the mass of the dark matter halo of our galaxy. D. make up about half of the mass of the dark matter halo of our galaxy.
D
Main-sequence red dwarfs evolve much more slowly than 1-solar-mass stars. Which one of the following statements does not describe aspects of the explanation for this difference? A. Red dwarfs convect through their entire volumes and therefore have a relatively large supply of fuel. B. Red dwarfs are less massive and therefore have lower core temperatures. C. Red dwarfs are less massive and therefore have lower core pressures. D. Red dwarfs do not use the proton-proton cycle, but rather a different nuclear reaction sequence; and this sequence produces energy at a slower rate.
D
Mars and Europa are good places to search for life because they have A. favorable orbits. B. traces of oxygen vapor on their surfaces. C. reasonably warm climates. D. liquid water.
D
Microwave radiation from carbon monoxide (CO) molecules at 2.6 mm wavelength is caused by a(n) A. change in the rate at which the molecules vibrate. B. "spin-flip" transitions, in which an electron flips its direction of spin relative to the plane of the molecule. C. electrons in the molecules jumping to lower-energy orbits. D. change in the molecules' rotation rate.
D
Most stars are members of multiple star systems, but the Sun is not. How could a lone star, like the Sun, form? A. The Sun can have formed only from the collapse of a very small dark nebula. B. The Sun probably formed in the collision of two small red dwarfs. C. We believe that all stars form singly, far removed from other stars. Multiple star systems are formed only long afterwards in chance encounters, which the Sun has apparently not had. D. The Sun was probably formed with companions within a stellar association that gradually dispersed over time.
D
Neutral hydrogen gas (H I) in galaxies is detected by its A. Balmer emission lines. B. blackbody emission at infrared wavelengths. C. Lyman emission in the ultraviolet. D. emission of radio waves of 21 cm wavelength.
D
OB associations are A. ionized hydrogen clouds. B. open clusters of stars formed or associated with an older population as well. C. pre-main-sequence stars surrounded by dust. D. groups of young stars whose population is dominated by high-mass stars.
D
Olbers's paradox arises when we attempt to answer this question: A. "Why is the universe isotropic?" B. "What caused the Big Bang?" C. "Why is the universe flat?" D. "Why is the sky dark at night?"
D
One characteristic that differs among nuclei of active galaxies is the width of their spectral lines. What causes a spectral line to be wide? A. Gas at low pressure emits wide spectral lines. When the pressure increases, the lines narrow. B. Broad spectral lines tend to be produced as part of the thermal spectrum, while narrow lines are associated with the nonthermal spectrum. C. Heavier elements (metals) tend to produce wide spectral lines, while lighter elements tend to produce narrow spectral lines. D. Rapid motion of the sources of radiation broadens the spectral lines because of the Doppler shift.
D
One property of the solar corona is that A. its density increases with distance from the Sun. B. solar wind currents in it reverse near the chromosphere. C. it disappears every eleven years. D. its temperature is higher than the temperature of the chromosphere.
D
Pulsars slow their rotation rate as they radiate away A. electron beams. B. both electron and positron beams. C. blue thermal radiation. D. synchrotron radiation.
D
Recent measurements indicate that the universe is A. flat and expanding slower with time. B. open and expanding slower with time. C. closed and expanding faster with time. D. flat and expanding faster with time.
D
SN 1987A in the Large Magellanic Cloud) actually brightened for 85 days as it exploded because A. the explosive energy worked its way to the stellar surface. B. ejected material collided with surrounding nebulae. C. fusion processes continued to release energy. D. radioactive isotopes decayed.
D
Since 1995, astronomers have discovered over 500 extrasolar planets orbiting hundreds of stars. What probability do these observations suggest that a given planetary system will contain at least one earth-like planet orbiting in the star's habitable zone? A. one in ten B. one in a thousand C. one in a million D. We do not have enough observations yet to formulate a statistically meaningful answer.
D
Suppose that, when observed at rest, a particular type of subatomic particle decays in a time of 485 microseconds. If you observe a beam of such particles, all traveling at 0.92 of the speed of light, what would you observe their lifetime to be? A. 190 microseconds B. 137 microseconds C. 74 microseconds D. 1238 microseconds
D
Synchrotron radiation is emitted whenever A. charged particles are ejected in straight lines through a dense gas such as the outer atmosphere of a star. B. electrons recombine with atomic nuclei, dropping through energy levels to produce specific, or synchronous, wavelengths of light. C. electrons and positrons are created in pairs (the pair production process). D. charged particles such as electrons are forced to move along curved paths through a magnetic field.
D
The "ash" of helium fusion is A. beryllium. B. oxygen. C. carbon. D. both oxygen and carbon.
D
The Local Bubble is a region relatively near the Sun, several hundred parsecs across, with a very low density but a very high temperature. What do we believe to be the origin of the Local Bubble? A. It is the original location of the collapse that created the solar nebula. B. It is simply a space between two spiral arms. C. Hot, newly formed stars in an OB association have emitted intense ultraviolet radiation, carving out this cavity in the interstellar medium. D. It is the result of a supernova explosion.
D
The Martian meteorite ALH 84001 contained carbonate grains with very pure crystals of iron sulfide and magnetite. Why was this finding significant and exciting? A. These chemicals were bound together with water, demonstrating that the meteorite formed during the "wet" period on Mars. B. These two chemicals are found together only in certain deposits on Mars, thus demonstrating the Martian origin of the meteorites. C. The iron sulfite-magnetite combination acts like radioactive decay in that the ratio of the two quantities can be used to calculate the age since formation. D. These two chemicals are rarely found together except when they are produced by certain types of bacteria.
D
The Miller-Urey experiment in 1953 successfully created A. a few simple protein strands from organic molecules. B. life in a glass container in the laboratory C. a few bases of the DNA molecule. D. organic molecules in a primitive Earthlike atmosphere.
D
The Sun spends about 1010 years as a main-sequence star. By comparison, how long did the Sun spend as a protostar? Compare this answer to the numbers for lower- and higher-mass stars. A. about 10 times as long, or about 1011 years B. about 1/100,000 as long, or about 105 years C. No time at all. Low-mass stars collapse directly to the main sequence without spending time as protostars. D. about 1/1000 as long, or about 107 years
D
The best explanation for active galactic nuclei is that they are A. primordial black holes that are evaporating. B. clusters of neutron stars with their magnetic fields aligned. C. clusters of black holes with their magnetic fields aligned D. supermassive black holes surrounded by an accretion disk.
D
The center of the expansion of the universe is A. the Milky Way, much to our surprise. B. the cosmic microwave background. C. the Great Attractor. D. nowhere in space--all clusters of galaxies move away from all others, not away from a center
D
The era of inflation came when A. the weak force decoupled from the electromagnetic force. B. all the forces were unified and pushed together. C. the temperature in the universe suddenly increased to 1027 degrees. D. the space in the universe transitioned from a false vacuum to a true vacuum.
D
The evolutionary life of a protostar is a very slow process of A. contraction and cooling of the entire protostar. B. contraction of the core and expansion of the outer layers. C. contraction of the outer layers and prevention of the core from contracting by thermonuclear reactions. D. contraction and heating of the entire protostar.
D
The galaxy distribution map made by the Two-Degree Field Galaxy Redshift Survey resulted in two pie-shaped wedges. Why? A. The telescope used for the survey is so large that its direction could be changed by only two degrees, resulting in this map shape. B. These two wedges represent the only two directions in which galaxies are found. C. The redshift survey went out only to redshift z = 0.25, and all the galaxies within this distance are clustered into these two regions. D. These regions were chosen to avoid the obscuring dust lanes in the plane of the Milky Way.
D
The location of the sun and the solar system in the Milky Way is A. 220 kpc from the center, between spiral arms, orbiting at 1.5 km/sec, in the Sagittarius Arm. B. 220 kpc from the center, in a spur off a spiral arm, orbiting at 1.5 km/sec, in the Vega Arm. C. 8 kpc from the center, between spiral arms, orbiting at 1.5 km/sec, in the Perseus Arm. D. 8 kpc from the center, in a spur off a spiral arm, orbiting at 220 km/sec, between the Sagittarius Arm and Perseus Arm.
D
The positron is the antiparticle of the electron. Three of the following statements describe correctly the relationship between a positron and an electron. Which statement is incorrect? A. The positron and the electron have opposite electric charges. B. A positron and an electron can constitute a virtual pair. C. A positron and an electron can annihilate, leaving only energy. D. The electron has positive mass and the positron has negative mass.
D
The rapid orbital speeds of galaxies inside rich clusters give an indication that A. Newton's laws break down at large distances. B. Kepler's laws break down at large distances. C. galaxies are escaping from their clusters as the universe expands. D. clusters as well as galaxies contain unseen or dark matter.
D
The temperature of the cosmic microwave background is 2.725 K. At what point in the history of the universe did the radiation cool to this temperature? A. 380,000 years after the Big Bang began, when the universe became transparent and radiation was able to travel freely B. 24,000 years after the Big Bang began, when the universe ceased being dominated by radiation C. 10-43 second after the Big Bang began, when the laws of physics first allowed a definite temperature to exist D. It took the entire history of the universe—it took until now (the present day)
D
The visible "lifetime" of a typical planetary nebula is A. very short, about 100 years, since it represents the rapidly expanding shell of an exploding star, or supernova. B. relatively long, about 100 million years, until nuclear reactions cease in the central star's core. C. very long, billions of years, since it is a fixed shell of interstellar matter illuminated by a white dwarf star whose age is this long. D. relatively short, about 50,000 years, after which it fades from view as the gas of the expanding shell moves too far from the exciting central star.
D
Three of the following experiments were to have been performed by the crashed British Beagle 2 Mars lander to search for life on Mars in 2003. Which experiment was the exception? A. heating samples to determine the temperature at which they decompose B. determining what fraction of carbon atoms in a Martian sample contain the isotope 12C and what fraction contain 13C C. determine the presence of methane in the Martian atmosphere D. attempt to grow seeds from earth in the Martian soil and atmosphere
D
Three of the following solar characteristics vary as part of the solar cycle and one does not. Which does not? A. number of sunspots B. locations of sunspots C. intensity of auroras on Earth D. rate of the Sun's rotation
D
To collapse a neutron star, the inward gravitational force would have to overcome neutron degeneracy pressure and A. electron degeneracy pressure. B. gas pressure. C. proton degeneracy. D. neutron-neutron repulsion.
D
To compute the distance to a Cepheid variable star (in comparison to other known Cepheids), the minimum amount of information necessary is A. the period in variation of brightness. B. the star's spectrum. C. the star's average brightness. D. all three quantities.
D
Toward the end of a sunspot cycle, the new spots form A. in the chromosphere. B. near the solar poles. C. at the Sun's middle latitudes. D. near the solar equator.
D
Two galaxy clusters collide. If the dark matter responds only to gravitational forces, we might expect the A. galaxy clusters to merge smoothly with the gas, stars, and dark matter, continuing to form a symmetric distribution as they did before the collision. B. clusters to bounce apart once they begin to overlap. C. overlapping clusters to react violently, disintegrating in intense bursts of X rays and gamma rays. D. dark matter components to pass through each other more easily than the gas, which is affected by fluid resistance. This should result in a relative displacement of the gas from the dark matter.
D
Two observers stand next to two identical clocks, one at rest just above the surface of Earth and the other at rest high above Earth. Which statement correctly describes the clock readings? A. Each observer will see the other's clock to be running slow with respect to the observer's own clock. B. Each observer will see the other's clock to be running fast with respect to the observer's own clock. C. Both observers agree: since the clocks are not moving with respect to each other the clocks run at the same speed and read the same time. D. Both observers agree: the clock near Earth is running slower than the clock high above Earth's surface.
D
Type Ia supernovas are created when A. the core of a high-mass star collapses to form a neutron star. B. the core of a high-mass star collapses to form a black hole. C. a carbon flash in a high-mass star blows the star apart. D. a white dwarf gains too much mass and explodes in a thermonuclear blast.
D
What aspect of Sagittarius A* shows evidence of a massive black hole in the center of our Galaxy? A. It is emitting much 21-cm radiation. B. It has ejected a cloud of low-density dust. C. It is emitting far infrared radiation. D. Rapidly orbiting stars are near it. What is Sagittarius A?
D
What causes the red color of an emission nebula (H II region)? A. Calcium atoms become excited by collisions with other atoms and ions and emit red light as they return to the ground state. B. The gas in the nebula is heated to about 3,000 K by luminous O and B type stars, and it emits light of predominantly longer wavelengths (red). C. The nebula contains dust, which scatters red light more efficiently than blue light. D. Electrons are captured by hydrogen ions, creating neutral hydrogen atoms, and these electrons lose energy by emitting light as they return to the ground state.
D
What event has resulted in enhancement of radiation output in some galaxies to produce very active quasars? A. supernova explosion near the galactic center, resulting in compression and heating of matter there B. gravitational lensing of the central energy source by the dense matter in the surrounding accretion disk C. precession of the accretion disk, allowing more radiation to travel in the direction of the Earth D. collision between galaxies, thereby enhancing the accretion disk of matter that generates energy by falling into the central black hole
D
What is the difference between an open cluster and a stellar association? A. Open clusters typically contain hundreds of stars while stellar associations are composed of hundreds of thousands of stars. B. Open clusters are dominated by hot O and B stars while stellar associations are dominated by red dwarfs. C. Open clusters are very young while stellar associations are very old. D. Open clusters are gravitationally bound, whereas stellar associations are not.
D
What is the significance of the cosmic microwave background radiation discovered by Penzias and Wilson in 1964? A. It was the first radio transmission believed to indicate the presence of extraterrestrial life in the universe. B. It indicated the difference between Type I and Type II Cepheid variable stars. C. It showed a connection between millisecond pulsars and X-ray bursters. D. It is the remnant of the burst of energy released during the Big Bang explosion which began the universe
D
What is the source of the charged particles that are accelerated along a neutron star's magnetic field to produce two oppositely directed beams of radiation? A. matter transferred from a companion star B. electrons and protons from the neutron star's ionized atmosphere C. nuclear fusion reactions in the neutron star's crust D. pair production of electrons and positrons
D
What kind of physics is used to describe the interaction of matter and energy from the beginning of the cosmic singularity to the Planck time? A. classical physics of Newton B. general relativity of Einstein C. quantum physics of Bohr and others D. There is no current physics which can do this.
D
When a protostar first forms from the gravitational collapse of an interstellar cloud, it is usually A. detected by jets of gas that it ejects from its poles. B. easily seen from the Earth because it is large and very bright. C. detected only by the ultraviolet radiation it emits. D. hidden from sight inside a cocoon of dust.
D
When the Sun completes its life on the main sequence 5.4 billion years from now, its position on the H-R diagram will change in the direction toward the A. O and B type main-sequence stars. B. white dwarfs. C. M type main-sequence stars. D. giant region.
D
When the helium in the degenerate core of a low-mass star ignites, the result is the A. supernova. B. nova. C. burster. D. helium flash.
D
Which group represents stars that are cool and dim? (HR DIAGRAM)
D
Which of the following does not occur as an isolated main-sequence star evolves? A. The star loses mass to space. B. The chemical composition of the star changes as nuclear fusion reactions convert lighter elements into heavier elements. C. The star's diameter increases. D. The star gains mass because nuclear fusion reactions convert lighter elements into heavier elements.
D
Which of the following does not promote star formation? A. supernova explosions B. collisions between interstellar clouds C. stellar wind pressure from recently formed stars D. cosmic ray heating of molecular clouds
D
Which of the following main-sequence stars lives the longest? A. O B. F C. G D. M
D
Which of the following phenomena is not produced by the Sun's magnetic field? A. sunspots B. plages C. prominences D. granulation
D
Which one of the following statements correctly describes elliptical galaxies? A. They contain both young, Population I stars and old, Population II stars, with little or no interstellar gas and dust. B. They contain both young, Population I stars and old, Population II stars, and large quantities of interstellar gas and dust. C. They contain young, Population I stars and copious amounts of interstellar gas and dust, but very few old, Population II stars. D. They contain only old, Population II stars, with little or no interstellar gas and dust.
D
You are in a spaceship moving past Earth at a high rate of speed. Three of the following statements describe observations you might make. Which observation would you not make? A. Earth does not look round. B. A clock observed on Earth's surface appears to run slow compared to the clock in your spaceship. C. You are flying parallel to the runway from which you took off some time ago, but now it appears shorter than it was when you were sitting there before you took off. D. People on Earth are signaling you that, indeed, your moving clock appears to be running fast compared to their clocks on Earth.
D
At what stage of its evolutionary life is the Sun?
main-sequence—middle age
As much as 90% of the matter in the universe may be unseen "dark matter." Where is this dark matter?
Dark matter appears to be concentrated in spherical haloes around galaxies but extends several times the radius of visible matter.
Hubble's law describes how two quantities are related to each other. What are these two quantities?
Distance and velocity of recession
Variable stars such as Cepheid variables and RR Lyrae stars are used in what important measurement in astronomy?
Distance measurement
For which objects in the Universe has the Hubble relation been shown to hold experimentally?
Distant galaxies
Which group represents stars of the largest radii?
E
What name is given to a galaxy with a smooth distribution of brightness and a round shape?
E0
The Hubble classification for a galaxy with a circular outline and a smooth distribution of brightness is:
E0.
The Hubble classification for a very flat elliptical galaxy is:
E7.
returns to the red giant branch
Each time a form of nuclear fuel is exhausted in the core of a star, the star
Which statement best describes what was called the solar neutrino problem? Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected. It referred to the fact that neutrinos are extremely difficult to detect. No one understood how it could be possible for neutrinos to be produced in the Sun. Our understanding of fusion in the Sun suggested that neutrinos should be destroyed before they arrive at Earth, yet neutrinos were being detected.
Early experiments designed to detect solar neutrinos found them, but in fewer numbers than had been expected.
Which of the following is closest in size (radius) to a white dwarf?
Earth
the Earth is tilted on its axis by 23.5 degrees
Earth has seasonal changes because:
Suppose our Sun were suddenly replaced by a supergiant star. Which of the following would be true?
Earth would be inside the supergiant.
is partly responsible for the Van Allen radiation belts and the Northern Lights (the Aurora Borealis)
Earth's magnetic field
Parallax would be easier to measure if
Earth's orbit was larger.
Who developed the classification system that divides galaxies into spiral, elliptical, and irregular and classifies spirals by the size of their nuclear region and the tightness of winding of their arms?
Edwin Hubble
What is the relationship between a star's mass and its lifetime
Effectively the life time is inversely proportional to the square of the mass.
Being at rest in a gravitational field is equivalent to being in an upwardly accelerated frame of reference in a gravity-free environment.
Einstein's principle of equivalence in his general theory of relativity asserts that
Which of the following statements about electron degeneracy pressure and neutron degeneracy pressure is true?
Electron degeneracy pressure is the main source of pressure in white dwarfs, while neutron degeneracy pressure is the main source of pressure in neutron stars.
In a white dwarf, what is the source of pressure that halts its contraction as it cools?
Electrons packed so closely that they become incompressible
There is little or no interstellar dust or gas in which of the following galaxy types?
Ellipticals
Which of the following types of galaxies contains primarily population II low-mass long lived stars?
Ellipticals
What happens to energy in the convection zone of the Sun?
Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.
Where in the universe did the Big Bang take place?
Everywhere in the universe
The intricate patterns visible in an X-ray image of the Sun generally show
Extremely hot plasma flowing along the magnetic field lines
Of the following astronomical objects or systems which is likely the oldest?
Globular cluster
All massive-star supernovae leave behind black holes as remnants.
False
No space craft has ever visited an asteroid or comet
False
Only A type stars show hydrogen lines in their spectra
False
Planet-sized bodies have been detected around pulsars
False
T/F Although protons repel each other, they will actually bind if they come close enough together.
False
T/F Dark dust clouds are optically invisible, but give off radio energy
False
T/F It is the formation of iron in an evolved giant's core that triggers the Type II supernova event.
False
T/F Light from distant stars must pass through dust arrives bluer than when it left its star
False
T/F Like emission nebula, planetary nebula glow because of stars are causing the gases to ionize when exposed to strong ultraviolet radiation
False
T/F Main sequence stars lie at the top right corner of the H-R diagram
False
T/F Most stars are single stars like our own
False
T/F Our Sun should become a planetary nebular in another five billion years.
False
T/F The solar corona is much cooler than the sun's surface, hence we must wait for a total solar eclipse to glimpse it with the naked eye
False
T/F The sun's structure is uniform throughout its interior, with no evidence of different layers.
False
T/F Type II supernova spectra are poor in hydrogen, as they used it all up before leaving the main sequence
False
What are the characteristics of an open cluster of stars?
Few hundred mainly main sequence
How many fundamental forces are known in science?
Four
The first person to look for signals from extraterrestrial civilizations was:
Frank Drake.
And object that emits flashes of light several times per second or more, with near perfect regularity.
From an observational standpoint, what is a pulsar?
How has the mass of the black hole candidate Cygnus X1 been estimated?
From the periodic wobble it produces in the spectral lines of its normal companion star
Which of the following best explains why the Sun's luminosity gradually rises over billions of years?
Fusion gradually decreases the number of independent particles in the core, allowing gravity to compress and heat the core, which in turn increases the fusion rate and the Sun's luminosity.
Venus orbits the Sun and not the Earth
Galileo's observations that Venus showed all possible phases (new, gibbous and full) helped to prove conclusively:
that Venus orbits the Sun and not the Earth
Galileo's observations that Venus showed all possible phases (new, gibbous and full) helped to prove conclusively:
What mechanism in the vicinity of a star gives us a hint of the presence of a black hole as a companion to the star?
Gas from the star, falling in toward a black hole, is compressed to very high densities and temperatures so that it emits an intense and rapidly fluctuating flux of X rays.
A typical protostar may be several thousand times more luminous than our Sun; where does this energy come from?
Gravatational energy
Of the following forces at work in molecular clouds, which inevitably dominates the clouds' evolution?
Gravity
43. Which star in Table 13-2 has the greatest diameter?
HD 39801
Emission nebulae are also called ____ because they are composed of ionized hydrogen.
HII regions
38. From the data given,, which star in Table 13-1 is the closest to Earth?
HR 2491
39. From the data given,, which star in Table 13-1 has the greatest surface temperature?
HR 4621
Which star in Diagram 13-1 is most like the sun?
HR 5337
Why does it require higher gas temperatures in the core of a star to produce nuclear fusion of helium compared to that required for hydrogen?
Higher collision speeds are needed to overcome the extra electrostatic repulsion between doubly charged He nuclei.
Why do higher mass stars live shorter lives on the main sequence than lower mass stars?
Higher mass stars burn through their nuclear fuel faster.
How is the length of a star's lifetime related to the mass of the star?
Higher mass stars run through their lives faster and have shorter lifetimes.
How is the length of a star's lifetime related to the mass of the star?
Higher-mass stars run through their lives faster and have shorter lifetimes.
Which kinds of stars are the major source of energy for the heating of the dust clouds and the H II emission nebulae within the planes of the Milky Way and other galaxies?
Hot young O and B stars via their UV radiation
The core of the sun is
Hotter and denser than the surface
It has a smaller radius.
How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf?
Why is Cygnus X1 thought to be a black hole?
It is smaller than the Earth but its mass is too large to be a neutron star or white dwarf.
Which elements were created during the Big Bang?
Hydrogen helium lithium and beryllium
The extinction of starlight due to the interstellar medium
I. is the greatest in the ultraviolet. IV. is caused by dust particles.
Red giant stars are
I. more luminous than the sun. II. larger in diameter than the sun. III. cooler than B stars. IV. located above the main sequence stars in the H-R diagram.
they have consumed their fuel which powers the AGN phenomena.
If all galaxies harbor a massive black hole in their nuclei, why aren't they all Active Galactic Nuclei (quasars)?
Which of the following statements A black hole is truly a hole in spacetime, through which we could leave the observable universe. If you fell into a black hole, you would experience time to be running normally as you plunged rapidly across the event horizon. If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls nearer to the black hole. If you watch someone else fall into a black hole, you will never see him or her cross the event horizon. However, he or she will fade from view as the light he or she emits (or reflects) becomes more and more redshifted.about black holes is not true? If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole.
If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole.
What "safety valve" operates in the gas of normal (nondegenerate) stars?
If the stellar gas is suddenly heated, it will expand and cool.
visual wavelengths
If you want to study objects at distances of 50,000 light years, in the direction of Sagittarius in the plane of the Milky Way, which wavelength will not work very well:
What do we mean by the singularity of a black hole?
It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions.
What explanation does general relativity provide for gravity...
In GR, gravity is a result of the curvature of space-time. Unaccelerated objects moving through flat space-time move in straight lines, but in curved space-time they move in curves.
Where in the Hertzsprung-Russell diagram do we find stars that have just finished the "burning" of hydrogen in their cores?
In a band parallel to the zero-age main sequence (ZAMS), extending from the high-luminosity, high-temperature region to the low-luminosity, low-temperature region. Yes. These stars have moved slightly away toward the upper right from their ZAMS positions. Section 19-4
Where would you look for an event horizon?
In a black hole
neutrino
In a collapsing star of high mass, when electrons and protons are squeezed together with enormous force, they turn into a neutron and a
What do we mean by the event horizon of a black hole?
It is the point beyond which neither light nor anything else can escape.
Where in the Universe would you look for a protostar?
In dense dust and gas clouds
How do two unequal-mass stars move around each other in general in a binary system?
In elliptical orbits about a common "center of mass"
Where is the solar system located in our Galaxy?
In the galactic disk
Where are the majority of older metal-poor stars found in our Galaxy?
In the globular clusters in the galactic halo
One might imagine that if energy generation by nuclear fusion were to increase in a star, this would heat the gas, which would in turn increase the rate of nuclear fusion, and so forth in a runaway cycle of increasing temperature. What process acts in a normal main-sequence star to prevent this behavior?
Increased energy generation causes a temperature increase that in turn causes expansion and hence cooling of the gas. This slows down the nuclear fusion. Yes. This normal behavior of the gas is sufficient to act as a "safety valve." Section 19-2
Which range of electromagnetic radiation is useful for observing newborn protostars within their gas and dust nebulae?
Infrared
Which range of wavelengths of electromagnetic radiation is most effective in the study of newborn protostars in their dust clouds and nebulae?
Infrared
The center of our Milky Way galaxy can be observed most easily at which of the following wavelengths?
Infrared and radio radiation
Virtually all the carbon-rich dust in the plane of the galaxy orginated in
Intersteller medium in the plane of the galaxy
How are the Magellanic Clouds the two nearby satellite galaxies of our own Galaxy classified?
Irregular galaxies
Which of the following statements is not true of a globular cluster?
It contains significant amounts of dust and gas surrounding the stars.
What happens to the helium-rich core of a star after the core runs out of hydrogen?
It contracts and heats up.
What happens to the helium-rich core of a star after the core runs out of hydrogen?
It contracts and heats.
What is "special" about the special theory of relativity?
It deals only with objects moving in a straight line at constant speed.
What happens to light passing through even thin clouds of dust?
It dims and reddens the light of all more distant stars.
Why was the Shoemaker-Levy 9 impact so important to astronomers?
It dredged up material that gave us our first direct look at Jupiter's interior composition
What makes us think that the star system Cygnus X-1 contains a black hole?
It emits X rays characteristic of an accretion disk, but the unseen star in the system is too massive to be a neutron star.
What is a supercluster of galaxies?
It is a cluster of galaxy clusters.
17. In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass?
It is converted to energy.
The spectrum of a very distant star shows spectral absorption lines of ionized helium He II and molecular absorption bands from titanium oxide TiO. What would be your conclusion about this star?
It is obviously the spectrum of a binary system two stars close together a hot star and a cooler companion unresolved as separate stars from our distance but contributing separate spectra.
How does the addition of a nonzero cosmological constant affect the expansion of the universe?
It is possible for the density of the universe to be above the critical mass density and still expand forever
A white dwarf is generating its energy from what source?
It no longer generates energy but cools slowly.
In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?
It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
What is Pluto's moon Charon thought to have in common with our own Moon?
It probably formed as a result of a giant impact.
When a star's evolutionary track on the Hertzsprung-Russell diagram carries it into the instability strip, what happens to the star?
It pulsates regularly in brightness.
In what way was the discovery of pulsars initially misinterpreted as evidence of intelligent life elsewhere in the Universe?
It was not thought possible for a "natural" source to produce the rapid and extremely regular radio pulses detected from space.
How does the mass of the protostar impact its future evolution?
It will affect the lifespan of the star as well as many other things.
If space is flat what is the future of the Universe?
It will barely expand forever reaching zero expansion speed after infinite time.
What is the ultimate fate of an isolated pulsar?
It will slow down, the magnetic field will weaken, and it will become invisible.
What would happen to the gravitational force upon the Earth if the Sun were to be replaced by a 1-solar-mass black hole?
It would remain as it is now.
Which of the following conditions will ensure that a star in a binary star system will evolve as if it were a single isolated star?
Its Roche lobe extends well beyond the star's surface. Yes. When this is true, its companion star does not influence it in a major way. Section 19-7
Who discovered the first four pulsars?
Jocelyn Bell Burnell
10,000 times
Keck telescopes have a mirror diameter of 10 meters whereas a simple backyard telescope has a diameter of only 10 cm. The faintest objects seen by the 10-m telescope are _______ dimmer than the faintest objects seen by the 10 cm telescope
If most of the mass of a galaxy is located near the center of the galaxy then in the outer part of this galaxy we would expect the orbital speeds of stars to decrease with increasing distance from the center. This is an example of:
Kepler's third law.
How do Kerr black holes differ from Schwarzschild black holes?
Kerr black holes rotate; Schwarzschild black holes do not.
In the orbital plane of a binary star system, matter can be transferred from one star to the other at the ________ located directly between the two stars is the point where the Roche lobes meet.
Lagrangian points
The combined mass of all the asteroids in the asteroid belt is
Less than half of any terrestrial Planet
At what speed will the neutrino travel if it is shown to have a small mass?
Less than the speed of light c.
How does the gravity of an object affect light?
Light coming to us from a compact massive object, such as a neutron star, will be REDSHIFTED
Around which types of stars are we most likely to find planets supporting our kind of life forms?
Low-mass main sequence stars
The period of variability of a Cepheid variable star which is easily measured is directly related to which stellar parameter thereby providing a reliable method for the measurement of distance to stars?
Luminosity
Which two vital parameters are used to describe the systematics of a group of stars (for example a cluster) in the Hertzsprung-Russell diagram?
Luminosity and surface temperature
Which of the following is the most common type of main-sequence star?
M Star
Which of the following four spectral-luminosity classes would correspond to a red supergiant?
M2 I
Which of the following spectral classification of stars is in correct order of increasing temperature?
MKGFABO
Neutron stars have
Magnetic Fields
A neutron star contains the mass of up to three Suns in a sphere with a diameter approximately the size of
Manhattan
What factor is most important in determining a star's position on the main sequence and subsequent evolution?
Mass
What is not the same for each star in a cluster?
Mass
You observe a star and you want to plot it on an H-R diagram. You will need to measure all of the following, except the star's
Mass
A nova is the result of which explosive situtation?
Mass transfer onto a white dwarf
What prevents the buildup of a core of helium ash in a high-mass main sequence star?
Mixing by convection
Which of the following statements about a globular cluster is true?
Most stars in the cluster are yellow or reddish in color
If we lived on a galaxy one billion light-years from our own, what would we see?
Much the same universe we see today
*As each stage ends, the core shrinks and heats further. *Each successive stage creates an element with a higher atomic number and atomic mass number. *As each stage ends, the reactions that occurred in previous stages continue in shells around the core.
Name statements about various stages of core nuclear burning (hydrogen, helium, carbon, etc.) in a high-mass star
Where did comets that are now in the kuiper belt originally form?
Near the radius at which they orbit today
the careful application of Newton's laws to the motion of other planets.
Neptune was discovered by
Radio waves of 21cm wavelength originate from which component of the interstellar medium?
Neutral atomic hydrogen
What new method has recently provided astronomers with new information about the behavior of stars beneath their surfaces (for example the collapse of the inner core of a star undergoing supernova explosion or the interior of the Sun)?
Neutrino astronomy
measuring the orbital size and orbital period for one of Jupiter's moons.
Newton's form of Kepler's 3rd Law allows the mass of Jupiter to be calculated by
Can a star become a red giant more than once?
No but look up why
How many stars (other than the Sun) have a stellar parallax greater than 1 second of arc?
None
What is the typical age for a globular cluster associated with our Milky Way?
Nothing the turnoff mass in a star cluster allows you to determine its age
A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?
Nova
What occurrence defines the end of the protostar phase of a star's life and the start of the main sequence phase?
Nuclear reactions begin in its core.
Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
How can an O-type star trigger the formation of other stars? Three of the following statements are correct, and one is incorrect. Which is incorrect?
O-type stars are massive. When they form stellar nebulae, as the Sun did, small stars form instead of planets.
From hottest to coolest, the order of the spectral types of stars is
OBAFGKM
Almost half of all known millisecond pulsars are found in what type of object?
Open Clusters
Which of the following statements comparing open and globular star clusters is not true? Stars in open clusters are relatively young while stars in globular clusters are very old. Open clusters are found only in the disk of the galaxy while globular clusters may be found both in the disk and the halo of the galaxy. For both open and globular clusters, we can assume that all the stars in a particular cluster are about the same age. Open and globular clusters each typically contain a few hundred stars
Open and globular clusters each typically contain a few hundred stars
The bright star Rigel is found in the constellation of:
Orion.
Which of the following statements about novae is not true? Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now. A nova involves fusion taking place on the surface of a white dwarf. When a star system undergoes a nova, it brightens considerably, but not as much as a star system undergoing a supernova. A star system that undergoes a nova may have another nova sometime in the future. The word nova means "new star" and originally referred to stars that suddenly appeared in the sky, then disappeared again after a few weeks or months.
Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now
Once per two hundred million years
Our sun goes around the center of the galaxy about:
Which layer of the Sun do we normally see?
Photosphere
A T Tauri star is at what stage of its stellar evolution?
Protostar before main sequence phase
Which statement about pulsars is not thought to be true?
Pulsars can form only in close binary systems.
What does QUASAR (QSO) stand for?
QUASI0STELLAR OBJECT
Which of the following objects does not represent the endpoint of a star's evolutionary life?
Red giant
The Hubble classification for a spiral galaxy with a prominent central bulge and tightly wound spiral arms is:
Sa.
In which constellation in our sky is the center of our Milky Way galaxy located?
Sagittarius
Suppose you put two protons near each other. Because of the electromagnetic force, the two protons will
Repel
You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the
Rotation Rate of the star
The Hubble classification for a galaxy having loosely wound spiral arms originating at the ends of a bar through the central bulge is:
SBc.
To what do the letters SETI refer?
Search for extraterrestrial intelligence
In some cases, a supernova in a binary system may lead to the eventual formation of an accretion disk around the remains of the star that exploded. All of the following statements about such accretion disks are true except
Several examples of flattened accretion disks being "fed" by a large companion star can be seen clearly in photos from the Hubble Space Telescope.
Which of the stars in Diagram 13-1 has the largest absolute visual magnitude?
Sirius B
Humans have not sent a spacecraft into the interior of the Sun to confirm any models of the interior. What evidence then do we have to support our current ideas about the solar interior?
Solar Neutrinos
How can we tell that some stars are relatively close to us in the sky?
Some stars appear to move periodically back and forth against the background stars because of the Earth's movement around the Sun.
Where are we?
Somewhere in an expanding universe but not in any special part of it
Each choice below lists a spectral type and luminosity class for a star. Which one is a red supergiant?
Spectral type M2, luminosity class 1
Which of the following terms is given to a pair of stars that we can determine are orbiting each other only by measuring their periodic Doppler shifts?
Spectroscopic Binary
An eclipsing binary has been analyzed and it has been determined that the ratio of the mass of star A to the mass of star B is 6 and the total mass of the two stars is 26 solar masses. What are the masses of star A and star B?
Star A has a mass of 22.3 solar mass and star B has a mass of 3.7 solar masses.
Suppose that two identical stars (having the same total light output or luminosity) are located such that star A is at a distance of 3 pc and star B is at a distance of 15 pc. How will star B appear compared to star A?
Star B will be 1/25 as bright as star A
What characteristic of a star cluster is used to determine its age?
The main sequence turnoff point
What do astronomers mean when they say that the universe is homogeneous?
Stars and galaxies are generally distributed similarly throughout the universe
Which stars always have large positive absolute magnitude?
Stars of low luminosity.
When we see X rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system. Which one would force us to immediately rule out the possibility of a black hole?
Sudden, intense x-ray bursts.
*If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls nearer to the black hole. *If you watch someone else fall into a black hole, you will never see him or her cross the event horizon. However, he or she will fade from view as the light he or she emits (or reflects) becomes more and more redshifted. *A black hole is truly a hole in spacetime, through which we could leave the observable universe. *If you fell into a black hole, you would experience time to be running normally as you plunged rapidly across the event horizon.
Statements about black holes
The initial mass of a protostar generally determines the star's future evolution. But in many cases, what can alter this process?
Stellar evolution is pretty much determined by the mass. So change the mass and the evolution will change... a) A blue and a yellow star form a binary. The blue star is more massive and evolves therefore quicker than the yellow star b) Mr Blue has become a red giant and has swollen. Mass spills over to Miss Yellow. She gains mass which speeds up her evolution in term
Which important stellar parameter can be determined by the study of binary stars?
Stellar mass
Where are elements heavier than iron primarily produced?
Supernovae
Which of the following is responsible for heating the bulk of the very hot intercloud gas?
Supernovae
Earth's orbital period will stay about the same
Suppose a black hole were now put in the center of our solar system (by itself) and suppose it had a mass of 1 solar mass. The Earth is 1AU away from it. What will happen?
You couldn't
Suppose the room in which you are sitting was magically transported far from the Earth, and sent accelerating through the universe at 9.8 m/s2. Assuming your doors and windows are sealed and closed, how could you tell that you'd left the Earth?
The ratio of brightnesses of a star at two different colors blue and visual is a direct measure of what property of the star?
Surface temperature
Observationally, the biggest difference between quasars and other active galaxies, such has and radio galaxies and Seyferts appears to be that
Syeferts and radio galaxies are less powerful than quasars
____ is a form of electromagnetic radiation produced by rapidly moving electrons spiraling through magnetic fields.
Synchrotron radiation
The spectral-luminosity class of the star Spica is B1 V and that of the star Tau Ceti is G8 V. From this information (with luminosity measured in solar luminosities) we know for sure that:
Tau Ceti is cooler and has a lower luminosity than Spica.
What physical property of a star does the spectral type measure?
Temperature
How do massive protostars (4 solar masses) evolve on the H-R diagram?
Temperature increases at approximately constant luminosity.
2. typically a granule in the photosphere is about
Texas 1000
a period in the 1600's when there were no sunspots and a mini ice age in Europe
The 'Maunder Minimum' is
____ is the thermonuclear fusion of hydrogen to form helium operating in the cores of massive stars on the main sequence.
The CNO cycle
main-sequence lifetime
The total time that a star spends fusing hydrogen in its core, and hence the total time that it will spend as a main-sequence star.
be in the same quantum state.
The Pauli exclusion principle, describing the quantum states of particles, stipulates that no two identical particles can have the same
How are elements heavier than iron made? Why are they rare? Will our Sun become a supernova? Why?
The Sun does not have enough mass to become a supernova because its mass is less than the Chandrasekhar mass (approximately 1.4 Suns) and it has no way to gain mass.
Will our Sun become a supernova?
The Sun does not have enough mass to become a supernova because its mass is less than the Chandrasekhar mass (approximately 1.4 Suns) and it has no way to gain mass.
How does the Sun's mass compare to Earth's mass?
The Sun's mass is about 300,000 times the mass of the Earth.
In the 1970s it was discovered that among spiral galaxies the wider the 21cm radio emission line the brighter the galaxy. What name is given to this relation?
The Tully-Fisher relation
What will happen if the Universe is unbounded?
The Universe will expand forever.
An advanced civilization lives on a planet orbiting a close binary star system that consists of a 15MSun red giant and a 10MSun black hole. Assume that the two stars are quite close together, so that an accretion disk surrounds the black hole. The planet on which the civilization lives orbits the binary star at a distance of 10 AU. One foolhardy day, a daring major (let's call him Tom) in the space force decides to become the first of his race to cross the event horizon of the black hole. To add to the drama, he decides to go in wearing only a thin space suit, which offers no shielding against radiation, no cushioning against any forces, and so on. Which of the following is most likely to kill him first (or at least cause significant damage)? (Hint: The key word here is first. Be sure to consider the distances from the black hole at which each of the noted effects is likely to become damaging.)
The Xrays from the Accretion disk
speed of motion of the atoms in the gas
The absolute temperature of a gas is most directly related to the:
What can be said with certainty about a red star and a blue star?
The blue star is hotter than a red star
What does apparent magnitude tell us about a star?
The brightness of a star as it appears in our sky
Most of the energy produced in the Sun is released in the form of visible light from the photosphere. However, some energy is released from the upper layers of the solar atmosphere. Which of the following best describes where other forms of light are released?
The chromosphere is the source of ultraviolet light, and the corona is the source of X rays.
Does a planetary nebula have anything to do with planets? Explain...
The class of objects known as "planetary nebulae" have nothing whatever to do with planets. They were called that back in the days of crude telescopes because their small disk shapes resembled planets and the name has stuck.
What causes the core of a star to contract during the main-sequence phase of the star's life?
The conversion of hydrogen into helium reduces the number of particles in the core.
What happens after hydrogen fusion ceases in the core of a star?
The core contracts and the surface of the star expands outward. Yes. The core contracts because there is no nuclear energy source in it at this time. However, hydrogen fusion begins in a shell around the core, and this causes the layers between it and the surface to expand, pushing the surface outward. Section 19-2
What was the COBE satellite designed to measure?
The cosmic microwave background radiation
What is the most important use of Cepheid variables for astronomers?
The distance to a Cepheid variable can be found very easily.
The Hubble law representing observations of distant objects in the Universe relates which two parameters?
The distance to a distant object and its recession velocity
What is a planetary nebula?
The ejected envelope of a giant star surrounding a stellar core remnant
your latitude
The elevation angle in degrees of the North Pole star above the horizon is equal to
accretion disks around supermassive black holes.
The energy generation mechanism for active galaxies is believed to be
Why does the luminosity of a high-mass star remain nearly constant as the star burns heavy elements in its core, even though it is producing millions of times more energy per second than it did on the main sequence?
The energy is carried off in the form of neutrinos
Which of the following best describes what would happen if a 1.5-solar-mass neutron star, with a diameter of a few kilometers, were suddenly (for unexplained reasons) to appear in your hometown?
The entire mass of Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star.
The end of the life of a red dwarf star is predicted to be a sphere of almost pure helium. But we have not detected any of these. What do we believe is the reason?
The evolution rate for red dwarfs is so slow that none has yet evolved to its end stage.
mass transfer
The flow of gases from one star in a binary system to the other.
When a low-mass star runs out of hydrogen in its core, it gets brighter. Why?
The fusion in the core will briefly stop. Why? Since fusion is the outward force generator, the star will begin to collapse under its own gravity. During this collapse the center of the star will become MUCH hotter and the pressure will also greatly increase in a very short timescale (literally minutes)
Suppose a satellite were placed in orbit around (and very close to) a neutron star. Which theory would you need to use to describe how it moves?
The general theory of relativity
Why does the overall mass of the universe decide its ultimate fate?
The greater the mass of the universe, the more gravitationally bound the universe will be.
How does the diameter of a black hole (meaning the size of the event horizon) depend on the mass inside the black hole?
The greater the mass the greater the diameter.
How does the diameter of a black hole (size of the event horizon) depend on the mass inside the black hole?
The greater the mass, the greater is the diameter.
How does a main-sequence star's lifetime depend on its overall mass?
The higher the star's mass, the shorter its lifetime, because a more massive star "burns" hydrogen fuel much faster than a low-mass star. Yes. The luminosity of a star is highly dependent upon its mass because higher core densities and temperatures lead to much more active nuclear fusion reactions and shorter lifetimes. Section 19-1
How do the stars in a star cluster change with time?
The highest-mass stars evolve the most quickly.
What makes a red giant star so large?
The hydrogen-burning shell is heating the envelope and making it expand.
If you were to look at one kilogram of material taken from the surface of the Sun and 1 kilogram taken from the center, which of the following statements would be true of these two 1 kilogram masses?
The kilogram from the surface would contain more hydrogen than the one from the center
Suppose it were possible to lower a yellow sodium lamp toward the event horizon of a black hole. What would you see while watching from a safe distance?
The light from the lamp would change to orange and then red.
zero-age main sequence
The main sequence of young stars that have just begun to burn hydrogen at their cores.
What characteristic of a star cluster is used to determine its age?
The main sequence turnoff
Which one of the following statements is true about clusters of galaxies?
The mass observed in the galaxies of the cluster is about 10 times too small to hold the cluster together.
Which of the following statements about neutrinos is not true?
The mass of a neutrino is 30 percent of the mass of an electron
What is the relationship between stellar mass and position on the main sequence of the Hertzsprung-Russell diagram?
The more massive the star, the higher up on the main sequence the star will appear.
helium flash
The nearly explosive beginning of helium fusion in the dense core of a red giant star.
a tiny particle that interacts very weakly with matter, with extremely low or zero mass and no charge.
The neutrino is
alpha particle
The nucleus of a helium atom, consisting of two protons and two neutrons.
If you see an object moving past you at 90% of the speed of light, what will its length appear to be?
The object will look shorter than if it were at rest.
What do cosmologists study?
The origin structure and evolution of the Universe
Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes more luminous. How is this possible?
The outer layers expand due to the high rate of fusion in a shell around the dead core
degeneracy
The phenomenon, due to quantum mechanical effects, whereby the pressure exerted by a gas does not depend on its temperature.
inner Lagrangian point
The point between the two stars comprising a binary system where their Roche lobes touch; the point across which mass transfer can occur.
turnoff point
The point on an H-R diagram where the stars in a cluster are leaving the main sequence.
We have seen that electron degeneracy occurs when the carbon core of a white dwarf becomes dense enough. We have also seen that neutron degeneracy occurs when a neutron star becomes dense enough. Why do you suppose we do not find Òproton degeneracyÓ in some density range between these?
The pressure at which the electron degeneracy is overcome (so that the core collapses) is also sufficient to combine electrons and protons to form neutrons. Thus, most protons disappear when the electron degeneracy ends.
degenerate electron (neutron) pressure
The pressure exerted by degenerate electrons (neutrons).
Which statement about accretion disks is not true? The gas in the inner parts of the disk travels faster than the gas in the outer parts of the disk. Accretion disks are made primarily of hydrogen and helium gas. The gas in the inner parts of the disk is hotter than the gas in the outer parts of the disk. The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass.
The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass.
Which of the following statements about the sunspot cycle is not true? The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are only one manifestation of the cycle. The number of sunspots peaks approximately every 11 years. The number of solar flares peaks about every 11 years. The rate of nuclear fusion in the Sun peaks about every 11 years. With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the reverse of the previous peak.
The rate of nuclear fusion in the sun peaks about every 11 years
Most of the light from a galaxy comes from the inner parts. If this means that most of the galaxy's mass is also in the inner region, then how would we expect the galaxy's speed of rotation to behave in its outer region?
The rotation speed should decrease smoothly with increasing distance from the center.
about 1/3 of the originally predicted rate.
The solar neutrino experiment designed by Raymond Davis has detected a rate of solar neutrinos arriving at Earth that is
What is happening in the interior of a star that is on the main sequence on the Hertzsprung-Russell diagram?
The star is generating internal energy by hydrogen fusion.
A star undergoes a core collapse supernova in a binary system. Under what conditions does the star remain intact?
The star that explodes is less massive than the other star
What would happen if mass were continually added to a 2.0 solar mass neutron star?
The star would eventually become a black hole
What are the main general features that make clusters of stars useful to astronomers?
The stars are at the same distance from Earth, were formed at approximately the same time, and were made from same chemical mix.
What is the ultimate fate of an open star cluster?
The stars in it escape one by one until the cluster no longer exists.
What condition MUST hold in the core of a star before helium can begin to fuse to release nuclear energy?
The temperature must reach about 100 million degrees (108 K). Yes. The helium nuclei have electrical charges of +2 and repel one another so they must collide with sufficient energy to fuse together and this requires high temperatures. Section 19-3
Which of the following statements does not correctly describe the Universe at the era of recombination?
The temperature of the Universe was about 3 K.
Dark matter represents much more mass and extends much further from the galactic center than the visible stars of the Milky Way.
The text states that luminous matter in the Milky Way seems to be much like the tip of an iceberg. This refers to the idea that _________.
core helium fusion
The thermonuclear fusion of helium at the center of a star.
helium fusion
The thermonuclear fusion of helium to form carbon and oxygen.
core hydrogen fusion
The thermonuclear fusion of hydrogen at the center of a star.
shell hydrogen fusion
The thermonuclear fusion of hydrogen in a shell surrounding a star's core.
How long does it take an M-type (or O type star?) star to reach the main sequence, compared to a solar-type star?
The time of formation of a star is about 1% of the time it will stay a Main Sequence star. The latter is equal to 10 billion years/M^2.5, where M is the star mass in M_Sun Sun: M=1 M_Sun Main sequence life time: 10 billion years Formation time: 100 million year O-type star: M=20 M_Sun (typical value) Main sequence life time: 6 million years Formation time: 50,000 year
The collision of two similar mass stars will result in coalescence if...
Their relative velocity just before collision is significantly less than their escape velocity
Why does the central bulge of a spiral galaxy appear red when compared to the spiral arms?
There is no star formation there, and the star population is dominated by old, long-lived, low-mass red stars.
Why is it that a planet like the Earth could not form around a Population II star, which has a composition similar to the material formed by the original Big Bang?
There would have been insufficient heavy elements to form the materials of Earth. Yes. The original mix of elements after the Big Bang contained only small amounts of the heavy elements that now make up the Earth (and its inhabitants!). Section 19-5
Why does the core of the Sun contain more helium and less hydrogen than the surface material of the Sun?
Thermonuclear reactions have converted much of the original hydrogen in the core into helium.
Why do sunspots appear dark in pictures of the Sun?
They actually are fairly bright but appear dark compared to the surrounding material
In general, what can be said about Type O and B stars compared to type K and M stars?
They are hotter and younger
What is believed to be the origin of giant elliptical galaxies?
They grew by devouring smaller galaxies.
The 12C and 16O, which now form part of living matter, were part of the cold, dark nebula from which the Sun formed. How did they get there?
They were formed by earlier generations of stars while they were in their horizontal branch phase.
Why are the majority of stars in the sky in the main-sequence phase of their lives?
This is the longest-lasting phase in each star's life.
In the spectral classification of stars strong absorption lines of which of the following atomic or molecular constituents would indicate a very low surface temperature?
TiO
In a neutron star, the protons and electrons are fused together, leaving only neutrons.
True
On the Hertzsprung-Russell diagram in which direction does the position occupied by a star move after hydrogen burning ends in the star's core?
Toward the upper right
5. The vast majority of stars near us would fall to the bottom right on the H-R diagram
True
A hypernova is a gamma ray burster that forms a block hole as well
True
A unique characteristic of type O stars is ionized helium lines in its spectrum
True
Brown dwarfs, white dwarfs, and neutrons stars are all kept from collapsing by degeneracy pressure.
True
Falling stars and shooting stars are simply other names for meteors.
True
If it gains sufficient mass, a white dwarf can become a
Type 1A supernova
What is the brightest "standard candle," and therefore the one that is visible to the greatest distance, found so far?
Type Ia supernovae
The energy required to ionize the hydrogen gas in an emission nebula (H II region) comes from
UV radiation from hot O and B stars.
A low-mass star becomes more luminous while expanding and cooling as it evolves from the main sequence to the giant phase. In which direction will the star's position move on the Hertzsprung-Russell diagram?
Up and to the right. Correct. Cooling moves the star to the right while increased luminosity moves it upward. Section 19-4
On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii?
Upper right
5 AU
Use Kepler's 3rd Law to determine (approximately) the distance from the Sun of a faint object with an orbital period of 11 years
What method is used to determine the distances of very remote galaxies?
Use of their spectral redshifts and the Hubble law
Who first discovered that the majority of galaxies are moving away from the Earth?
V. M. Slipher
0.125
Vega is about 8 parsecs (25 lightyears) from the Sun. What is the expected parallax angle for Vega in seconds of arc? [Hint: p is inversely related to d.]
The star Vega has an absolute magnitude of about 4 and an apparent magnitude of about 0. Based on the definitions of absolute and apparent magnitude, we can conclude that
Vega is nearer than 10 parsecs from Earth.
What evidence now exists for a supermassive black hole at the center of our Galaxy?
Very rapid motion of matter close to the nucleus of the Galaxy requiring a very massive body to hold it in orbit
Which of the following terms is given to a pair of stars that appear to change positions in the sky, indicating that they are orbiting one another?
Visual Binary
Which of the following choices is not a way by which we can study the inside of the Sun?
We can send a space probe into the Sun's photosphere.
What observations characterize solar maximum?
We see many sunspots on the surface of the Sun.
At what point in time does mass transfer begin in a binary star system?
When one star expands and fills its Roche lobe, allowing matter to flow from it to its companion. Yes. Matter that leaks from one star past the inner Lagrangian point, the point between the two stars where the two Roche lobes touch, is more strongly attracted to the other star, and falls onto it. Section 19-7
As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.
What causes the radio pulses of a pulsar?
It is the center of the black hole, a place of inifinite density where the known laws of physics cannot describe the conditions.
What do we mean by the singularity of a black hole?
We wouldn't be here. Our solar system would be lifeless
What if NO process of stellar evolution EVER resulted in ANY mass being lost from stars?
about one rotation per month
What is the average rotation period of the Sun?
x-rays
What is the dominant radiation that we see from the intergalactic gas in rich clusters of galaxies?
Close to circular and in the plane of the Milky Way
What is the motion of the solar system in the Milky Way?
nuclear fission
When a large atomic nucleus breaks into two smaller pieces, this is called
retrograde
When a planet appears to move backwards relative to the stars over the course of many nights, its motion is called _______.
What nuclear fusion mechanism does an isolated white dwarf use to generate energy?
White dwarfs don't generate their own energy.
The famous Curtis-Shapley debate in 1920 concerned which fundamental astronomical question in astronomy?
Whether the spiral "nebulae" were part of the Milky Way galaxy or more distant separate entities
The sudden collapse of an iron core into a compact ball of neutrons.
Which event marks the beginning of a supernova?
Phobos and Deimos
Which object has NO atmosphere of any kind
Kinetic
Which of the following forms of energy is associated with motion
the deflection of starlight around the sun
Which of the following predictions of Einstein's was used to confirm General Relativity?
Distant stars are obscured by dust in interstellar space.
Why are we only ever able to see a small portion of our own galaxy, the Milky Way?
Because the stars never get hot enough inside to fuse heavier nuclei
Why can't stars like our sun fuse elements heavier than carbon and oxygen?
The flatness problem in cosmology asks the question:
Why is temperature of the cosmic background radiation so smooth (isotropic) around the sky?
What is the dominant radiation from the intergalactic matter in rich clusters of galaxies?
X rays from very hot gas
Black holes are best studied in the ____________ band of radiation.
X-ray
One of the recently discovered components of clusters of galaxies that may have some bearing on the dark matter problem is
X-ray measurements of substantial amounts of very hot intergalactic gas in clusters.
Can a white dwarf explode?
Yes, but only if it is in a binary star system.
A spiral galaxy is observed edge-on so that the spiral arms cannot be seen clearly. Is it possible to classify this galaxy using the Hubble classification scheme?
Yes. The tightness of spiral arms is correlated with the size of the nuclear bulge.
Which of the following components of the Galaxy best outline the spiral arms of the Galaxy?
Young O and B stars dust and gas
Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?
Your meteorite is a fragment from the core of a large asteroid that had undergone differentiation and then was shattered by a collision
Which of these does not exist?
a 1.5 solar mass white dwarf
close binary
a binary star whose members are separated by a few stellar diameters
In what type of object would you expect to observe a nova?
a binary system in which a red giant is overflowing its Roche lobe and accretes onto a white dwarf
A cloud fragment too small to form a star becomes
a brown dwarf
One of the consequences of the collision of two galaxies appears to be:
a burst of vigorous star birth.
90%
a census of the thousand stars nearest to the sun would show that what fraction of them is now on the Main-Sequence?
The "Local Group" is:
a cluster of galaxies in which the Milky Way is located.
The Local Group is
a cluster of galaxies in which the Milky Way is located.
A starburst galaxy appears to be a galaxy in which
a collision with another galaxy has produced a burst of star formation.
What is an accretion disk?
a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole
The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about
a few hundred thousand years ago
The light radited from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about
a few hundred thousand years ago
The shape of the cross-section of the Roche lobes around a close binary star system taken through the centers of both stars is:
a figure eight.
The shape of the cross-section of the Roche lobes around a close binary star system, taken through the centers of the stars, is
a figure-eight.
What is a Cepheid variable star?
a high-mass star that pulsates regularly in brightness
According to current evidence, Pluto is best explained as
a large member of the kuiper belt
A white dwarf is:
a low-mass star at the end of its life.
Opacity is
a measure of the resistance to the flow of radiation (photons) through a gas.
What do we mean by a primitive meteorite?
a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago
a series of emission lines, mostly at red wavelength
a neon light contains a thin dilute gas which is hot. The spectrum of the light coming out is
X-ray binaries result from a process similar to that in a
a nova
The difference between a nova and an X-ray burst is that
a nova involves an explosion on the surface of a white dwarf, whereas an X-ray burst involves an explosion on the surface of a neutron star.
When a supernova explosion results from core collapse in a massive star it appears to leave behind...
a rapidly expanding shell of gas and a central neutron star or black hole
What is a pulsar?
a rapidly rotating neutron star
A pulsar is:
a rapidly rotating neutron star emitting beams of radio radiation and in some cases X-rays and visible light.
As a main sequence star exhausts hydrogen in its core, it next becomes
a red giant star.
In reference to black holes, the word "ergosphere" refers to...
a region just outside the event horizon (of a rotating black, where it is impossible for anything to remain at rest)
A degenerate-electron gas like that in the core of a red giant star lacks the "safety valve" of a normal gas. This is because
a rise in temperature does not change the pressure, so the gas does not expand and cool.
A planetary nebula is:
a shell of ejected gases glowing because of ultraviolet light from a dying central star.
The explosion of a supernova typically leaves behind
a shell of hot, expanding gas with a pulsar at the center.
a small particle of interplanetary dust, burning up and glowing as it enters Earth's atmosphere.
a shooting star is:
decrease
a speeding police car approaches you with sirens wailing. As the police car passes you and then speeds away, the frequency of the siren will suddenly:
increasing Luminosity versus Decreasing Temperature
a standard Hertzsprung-Russell diagram. What is plotted along the y-axis and x-axis respectively?
What is a red giant?
a star burning hydrogen into helium in a shell around the core
The "helium flash" is another name for:
a sudden onset of helium fusion reactions in the core of a low-mass red giant star.
The helium flash is another name for
a sudden onset of helium fusion reactions in the core of a low-mass red giant star.
The "central engine" of an active galaxy appears to be:
a supermassive black hole at the center of an accretion disk with jets of material being ejected perpendicular to the disk.
Essentially all the heaviest elements in the galaxy are formed during
a supernova explosion
The inverse of the value of H₀ is
a time
An advanced civilization lives on a planet orbiting a close binary star system that consists of a 15MSun red giant and a 10MSun black hole. Assume that the two stars are quite close together, so that an accretion disk surrounds the black hole. The planet on which the civilization lives orbits the binary star at a distance of 10 AU. If you were to come back to our Solar System in 6 billion years, what might you expect to find?
a white dwarf
Which of the following kinds of stars is most dense?
a white dwarf
A Type I supernova is believed to occur when
a white dwarf exceeds the Chandrasekhar limit.
A nova is almost always associated with
a white dwarf in a close binary system.
What kind of star is most likely to become a white-dwarf supernova?
a white dwarf star with a red giant binary companion
The overall fusion reaction by which the Sun currently produces energy is
a. 4H -> 1 He + energy
What must occur for an object to be considered a main sequence star?
a. Hydrostatic equilibrium b. Nuclear fusion reaction in the core
Stars in a star cluster
a. all have the same age. b. all have the same chemical composition.
A star will experience a helium flash if
a. it is less massive than about 3 solar masses. b. its has become a red giant star. c. its has formed a helium core. d. the material in the core has gradually become degenerate.
We can determine the surface temperature of a star from
a. studying its continuous spectrum. b. studying its line absorption spectrum. c. measuring the star's luminosity.
If we can solve the orbital motion of an eclipsing binary, we can find
a. the mass of each star. b. the diameter of each star.
Protostars are difficult to observe because
a. the protostar stage is very short. b. they are surrounded by cocoons of gas and dust. c. they radiate mainly in the infrared.
How large will the Sun be as a red giant?
about 1 AU radius (out to Earth's orbit)
The typical diameter of a planetary nebula is:
about 1 light year.
the maximum mass of a white dwarf is
about 1.4 times the mass of our Sun
The total time the Sun will spend as a main-sequence star is
about 10 billion years.
At the present time, the fraction of the mass of the Sun's core that is in the form of helium, a bi-product of nuclear fusion, is
about 2/3. Yes. The fusion process has been operating for long enough that helium has built up in the Sun's core. Section 19-1
What is believed to be the maximum mass that a star can have?
about 200 solar masses
12. A maximum in solar activity should next occur
about 2015
When was pluto discovered
about 80 years ago
What will be the diameter of the Sun when core helium burning begins?
about the size of Earth's orbit
motion
absolute Zero on the Kelvin scale of temperature is defined as the point at which all _________ ceases
the laws of conservation of energy and conservation of angular momentum ensure that any rotating, collapsing cloud will end up as a spinning disk
according to the nebular theory of solar system formation, why do all the planets orbit the Sun in the same direction and in nearly the same plane?
increase by a factor of 4.
according to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
A mass is transferred in a normal star in a binary system toward a white dwarf, the material forms a rapidly growing whirlpool of material known as a(n)
accretion disk.
a carbon core surrounded by a helium-burning shell, which is surrounded by a hydrogen-burning shell
after a sun-like star enters its second red giant phase, its internal structure would consist of
Stars in a binary system are useful in studying mass transfers because we know the two stars have the same
age
Important information can be obtained from the HR diagram of a star cluster because all stars in the cluster have approximately the same
age.
Star clusters are important to the study the stellar evolution because stars in a given cluster have the same
age.
The stars in an open cluster are useful for studying the early stages of stellar evolution because all the stars in a cluster have the same
age.
In the interstellar medium, molecules survive only in regions with
all of the above
Meteorites can come from:
all of the above (the moon, comets, cores of asteroids, mars)
A neutron star will be detected from Earth as a pulsar by its regular radio pulses ONLY if the Earth lies...
almost directly in line with the magnetic axis
An eclipsing binary will
also be observed as a spectroscopic binary.
the Moon's orbit is tilted by 5 degrees with respect to the plane of the Earth's orbit around the Sun (the ecliptic).
although the Moon orbits the Earth every 29.5 days, a total eclipse of the Sun does not occur every month because
The first pulsar was discovered by
an English graduate student, Jocelyn Bell, in 1967.
Astronomy with a radio telescope was initiated by:
an amateur astronomer Grote Reber after Jansky detected radio energy from the Galaxy.
Sitting in a 100° F hot tub feels much hotter than standing outside on a 100° F day. This analogy illustrates why
an astronaut would feel cold in 10⁶ K intercloud gas
the mean distance between the earth and the sun
an astronomical unit, or A.U. is defined as
26 protons, 30 neutrons, 26 electrons
an atom of the element iron has an atomic number of 26 and an atomic weight of 56. If it is neutral, how many protons, neutrons, and electrons does it have?
The neutrino is
an elusive subatomic particle, having very little or no mass and difficult to detect.
According to our modern understanding, what is a nova?
an explosion on the surface of a white dwarf in a close binary system
From an observational standpoint, what is a pulsar?
an object that emits flashes of light several times per second or more, with near perfect regularity
Absorption lines due to interstellar gas
are more narrow than the lines from stars because the gas has a lower pressure than stars.
Stars on the main sequence with the greatest mass
are spectral type O stars.
A typical solar-type star spends most of its life:
as a main sequence star.
we can determine some of the orbital parameters from the doppler shifts of the spectral lines
assume we have detected a spectroscopic binary in which we can measure the spectrum of just one of the stars. Which of the following is true:
sometimes cross Earth's orbit
asteroid orbits:
The Doppler shift is used to find
astrométriques binaires
the Space Station and the astronauts are in free fall, both falling with the same acceleration towards the Earth.
astronauts in the International Space Station are seen floating around as if weightless, yet the Space Station is well within the Earth's gravitational field. What is happening?
most comets remain in stable orbits beyond Pluto; only a few have their orbits disturbed and come into the inner solar system
astronomers estimate that there may be a trillion comet nuclei orbiting far beyond Pluto's orbit. Why do we not see more comets in our skies?
most comets remain in stable orbits beyond Pluto; only a few have their orbits disturbed and come into the inner solar system.
astronomers estimate that there may be a trillion comet nuclei orbiting far beyond Pluto's orbit. Why do we not see more comets in our skies?
*93 million miles *150 million km *1 AU *8 light-minutes
average distance of the Earth from the Sun is
Galaxies with large bulges and tightly wound arms are classified as A. S0 (lenticular). B. Sa. C. Sb. D. Sc.
b
Why do nuclear fusion reactions only take place in the interior of a star?
b. The temperature is the hottest in the center. c. The density of material is very high in the center.
Convection is important in stars because it
b. mixes the gases of the star. c. transports energy outward in the star.
In order for gravitational lensing of a distant quasar to occur, the galaxy producing the lensing must...
be almost perfectly placed on a line between Earth and the quasar
The Black Widow pulsar is unusual because it appears to
be eating away at its companion star.
In order to have a comet named after you, you have to
be one of the first 3 discoverers who report it to the International Astronomical Union.
Helium flash occurs
because degenerate electrons in the core do not allow the core to expand as it heats up.
The free-fall contraction of a molecular cloud
can be initiated by shock waves from supernovae.
What are the 7 stages in a star's evolution Stages of star include
being born at stage one, then forming protostars at stage two when heat is generated and they start glowing. Stage three is nuclear reactions, then stage four, finally a main sequence star. Stages five through seven see the star growing until it's a red giant. Final stages are eight and nine, when the star becomes a planetary nebula, a white dwarf, then, it dies as a black dwarf.
If light from a distant star passes close to a massive body, the light beam will
bend towards the star due to gravity. Or continue moving in a straight line
An object more massive than the Sun, but roughly the size of ac ity, is a
black hole
Any main sequence star over 25 solar masses will probably retain enough matter in its core after its supernova to make a
black hole
In a hypernova, a very energetic supernova creates a
black hole
What is a primordial black hole?
black hole created during the formation of the universe
In a binary star system an unseen component is found to have a mass of about 8 solar masses. If this were a normal star then it would be visible so it must be a collapsed object. Theoretical considerations tell us that it must be a:
black hole.
The distinctive color of a reflection nebula is:
blue caused by the scattering of light from dust grains.
A reflection nebula is made visible by
blue light, preferentially scattered by tiny dust grains.
The pressure within a neutron star that opposes the inward force of gravity comes from
both degenerate neutron pressure and the repulsive hard core aspect of the nuclear force between neutrons.
Massive stars cannot generate energy through iron fusion because
both fusion or fission of iron nuclei absorb energy.
How is an X-ray burst (in an X-ray binary system) similar to a nova?
both involve explosions on the surface of stellar corpse
On the H-R diagram, the sun lies
bottom right
A cloud fragment too small to collapse into a main sequence star becomes a
brown dwarf
Suppose that an astronomical observatory announces the discovery of an object with about 50 times the mass of Jupiter, a mass too low to become a main sequence star. What name would the observatory apply to this object?
brown dwarf
The helium flash converts helium nuclei into
carbon
How can astronomers determine the size of an emission region in a very distant and unresolvable source?
by measuring brightness variability, because an object cannot vary more rapidly than the time taken for light to cross the source
"Weather" in the interstellar medium is produced
by supernovae and strong winds from luminous stars
Images of emission nebulae, like the Orion Nebula, often show a predominant red color. What is the origin of this red light? A. Visible light is emitted by nearby stars, and the red portion is scattered in our direction by dust particles in the nebula. B. The dust is heated by background stars and begins to glow a dull red color. C. This is the Hα line, the red line in the Balmer spect um of hydrogen gas. D. The hot O and B stars in the vicinity of the nebula emit primarily red light.
c
Two rocket ships are traveling past the Earth at 90% of the speed of light in opposite directions (that is they are approaching each other). One ship turns on a searchlight beam that is seen by scientists aboard the other ship. What speed do the scientists measure for this light? (c = speed of light in a vacuum.)
c
Which group represents stars that are extremely bright and emit most of their radiation as ultraviolet light?
c
A type-II supernova
c. is characterized by a spectrum that shows hydrogen lines. d. occurs when the iron core of a massive star collapses.
What causes the outward gas pressure that balances the inward pull of gravity in a main sequence star?
c. the high temperature of the gas d. the high density of the gas
Halley's comet is named after the English scientist Edmund Halley, because he
calculated its orbit and predicted that it would return in 1758.
Synchrotron radiation is emitted whenever:
charged particles are forced to move along curved paths within a magnetic field.
A star's surface temperature during the horizontal branch phase is determined primarily by its
chemical composition
What is a rich cluster of galaxies?
cluster containing thousands of galaxies
the star has recently left the main sequence and is in the process of becoming a red giant
consider the following star: its core is helium, but the only nuclear energy being generated is coming from a shell of hydrogen burning just outside the core, and the outer layers are expanding. Which of the following statements are true?
If the sun were replaced by a 1-solar-mass black hole, then Earth would...
continue to orbit the black hole in precisely its present orbit
In a very young star cluster, while the most massive stars are swelling up into giants, the least massive stars are
continuing to shine as stable main sequence stars
The spectrum of an ordinary main sequence star is a:
continuum of colors crossed by dark absorption lines caused by absorption by cooler atoms and molecules at the star's surface.
The Hertzsprung-Russell diagram of a globular cluster contains stars along a line called the horizontal branch. These stars are
converting helium to carbon in their cores. Yes. Horizontal branch stars are post-helium-flash stars with a helium-burning core and a hydrogen-burning shell. Section 19-4
Compared to a type A0 star, a type A9 star is
cooler
The spectral class of the Sun is G2 and that of the star Enif is K2. From this information we know with certainty that Enif is:
cooler than the Sun.
As a main sequence star exhausts hydrogen in its core, its surface becomes ___ and its energy output per second (luminosity) becomes ____.
cooler; larger
heliocentric (sun-centered)
copernicus developed the _________ model of the solar system.
Horizontal-branch stars, which have a range of temperatures with luminosities between 50 and 100 times that of the Sun, are in what stage of their lives?
core helium burning
The main energy generation mechanism in main sequence stars is
core hydrogen fusion
the solar wind blows out of
coronal holes
the solar winds blow outward from
coronal holes
Moon has the same angular size as the Sun and its orbit around the Earth periodically brings it between the Earth and the Sun
correct explanation for a total eclipse of the Sun
*Tsunamis killing millions *A large (10-km) crater *Widespread forest fires *Widespread soot and smoke
could be caused by the impact of a 1 kilometer meteorite hitting the Earth
no
could you use very precise Doppler frequency shift measurements to work out the parallax, and thus the distance of a nearby star?
In the 1790s Sir William Herschel tried to measure the Sun's position in our Galaxy by:
counting the density of stars in different directions along the Milky Way.
The pressure within a neutron star that opposes the inward force of gravity comes from...
degenerate neutron pressure and (the repulsive hard core aspect of) the nuclear force between neutrons
White dwarf stars are supported from collapse by:
degenerate-electron pressure.
Stars are born in
dense molecular clouds.
In cosmology the phrase "critical density" refers to the:
density needed to produce precisely flat space.
What mechanism is believed to produce grand-design spiral galaxies?
density waves in the interstellar medium
The age of a cluster can be found by
determining the turnoff point on the main sequence of its HR diagram.
The escape velocity for any object at the event horizon around a black hole is...
equal to the speed of light
If two stars are emitting the same amount of light, the star that is farther will appear
dimmer.
In high-energy physics when two gamma-ray photons meet they can:
disappear creating a particle-antiparticle pair.
Astronomers use galactic redshift as a measure of
distance
If you measure the pulsation period of a Cepheid variable star, you can also determine its
distance
Parallax of a nearby star is used to estimate its:
distance from Earth.
Cepheid variable stars are important because we can find the
distance to the Cepheid star after measuring only its period and apparent magnitude. Correct. Knowing its period, we can use the period-luminosity law to find the Cepheid's absolute magnitude. We can then use its absolute magnitude and its apparent magnitude to find its distance. Section 19-6
The space between stars is now known to contain:
dust and gas both atomic and molecular.
15 degrees
each international time zone is supposed to cover about one hour. Approximately how many degrees of longitude, on average, should each time zone cover?
The escape velocity at the event horizon around a black hole is
equal to the speed of light.
planetesimals, accretion
in the early solar system, objects called ________ grew by _______ of material from the Solar Nebula
returns to the red giant branch
each time a form of nuclear fuel is exhausted in the core of a star, the star
Which type of binary can have their sizes measured directly by photometry?
eclipsing
The cosmic background radiation is the:
electromagnetic remnants of the explosion in which the Universe was born.
15. what natural barrier tries to prevent two protons from combining
electromagnetic repulsion
What kind of pressure supports a white dwarf?
electron degeneracy pressure
The charged particles that emit beams of electromagnetic radiation from a pulsar are believed to be...
electron-positron pairs (created by very strong electric fields near the neutron star's surface)
The helium flash, in which helium fusion increases very rapidly in the core of a star, occurs because
electrons become so crowded together that the overall gas in which they are embedded cannot expand in the normal way to cool this gas as the temperature increases. Yes. Electron degeneracy produces a change in the nature of the gas in the stellar core, and this change results in explosive temperature rise. Section 19-3
Which galaxy type contain little or no interstellar dust and gas?
elliptical
In which category of galaxy do we find the largest galaxies in the universe?
elliptical galaxies
Blazars or BL Lacertae objects are:
elliptical galaxies whose nuclei resemble quasars.
Which type of galaxy contains primarily population II, low-mass, long-lived stars?
ellipticals
The creation of ____ require(s) that a young hot star (T 25,000 K) be relatively nearby.
emission nebulae
Interstellar gas clouds may collapse to form stars if they
encounter a shock wave.
In the proton-proton chain
energy is produced in the form of gamma rays and the velocity of the created nuclei.
*Uniform, circular motion *A car moving at a uniform 25 mph while executing a right turn *Mars in its orbit about the Sun *A cannonball falling from the Tower of Pisa.
examples of acceleration
A Type II supernova is the
explosion of a single massive star after silicon burning has produced a core of iron nuclei.
A Type Ia supernova is the
explosion of a white dwarf in a binary star system after mass has been transferred onto it from its companion.
What is the source of most of the heavy elements on the Earth and in our own bodies?
explosive nucleosynthesis during supernova explosions of massive stars
Due to the dust in the interstellar medium, a distant star will appear to an observer on Earth to be
fainter and cooler than it really is.
All meteorites collected on Earth come from asteroids or comets
false
Gamma ray bursts are all found to be within our galaxy
false
Gravitational equilibrium means that the surface and the core of the Sun are at the same pressure.
false
No visible light can escape a black hole, but things such as gamma rays, X rays, and neutrinos can.
false
Pluto's gravity affects the orbit of Uranus, and this fact was used to discover Pluto.
false
Stars of less than 8 solar masses will not go supernova
false
The "pulse" from a pulsar is due to the rapidly expanding and contracting outer shell of the star
false
The core of the Sun is at a temperature of about 20,000 K.
false
There is no upper limit to the mass of a neutron star
false
In order to understand star clusters, we need to be able to estimate their ages. What technique do scientists use for this?
finding the main-sequence turnoff point of the stars
Why is there a limit on the maximum luminosity an accreting object may emit?
for luminosities above this limit the radiation from the object would blow away the accreting material
more than 2 Earth years.
from Kepler's third law, a hypothetical planet that is twice as far from the Sun as Earth should have a period of
Recent evidence suggests that galaxies formed...
from the mergers of hundreds of smaller objects
If you make a list of the 100 brightest stars in the sky you will find that most of them are
giants and supergiants.
gamma rays, X rays, ultraviolet, visible light, infrared, radio
from the shortest wavelength (highest energy) to the longest wavelength, what is the correct ordering of these regions of the electromagnetic spectrum?
photosynthesis from single-celled organisms
from where did the molecular oxygen in Earth's atmosphere originate
What is a barred spiral galaxy?
galaxy with a bar through the nuclear bulge and the spiral arms starting from the ends of the bar
What is a lenticular (or S0) galaxy?
galaxy with a central bulge and a disk like a spiral galaxy, but with no spiral arms
What is an elliptical galaxy?
galaxy with an elliptical outline and a smooth distribution of brightness but no apparent structure
Which direction do a comet's dust and plasma tails point
generally away from the Sun
In which one of the following locations are clumps of gas most likely to be collapsing to form stars?
giant molecular clouds
X-ray bursters occur in binary star systems. The two types of stars that must be present to make up such an object are A
giant or supergiant star and a neutron star in a mass transfer binary
A(n) ____ is a collection of 105 to 106 stars in a region 10 to 30 pc in diameter. The stars in the collection tend to be more than 109 years old and mostly yellow and red stars.
globular cluster
RR Lyrae variables are likely to be found in:
globular clusters where low-mass stars are undergoing core helium burning.
A Herbig-Haro object is
glowing interstellar gas, heated by a high-velocity jet of matter from an evolving star.
A particular galaxy appears round, with a nuclear region of uniform brightness and an outer region that is broken up into long, curved, well-defined lanes of stars and light gas clouds. How would this galaxy be classified?
grand-design spiral
19. The pattern of hot convective cells rising in the photosphere is called
granulation
the primary source of the sun's energy is
gravitational collapse of the core. (helium coreward)
After the material in the core of a massive star has been converted to iron by thermonuclear reactions further energy can be released to heat the core only by:
gravitational contraction.
The source of a protostar's heat is
gravitational energy, released as the star contracts.
The source of energy for a contracting protostar comes from
gravitational potential energy
As a star begins to form, the initial energy source is from
gravitational potential energy.
Why isnt there a planet where the asteroid belt is located?
gravitational pull of jupiter prevented material from collecting into a planet
The major source of energy in the pre-main-sequence life of the Sun was:
gravitational.
What force(s) are responsible for the collapse of an interstellar cloud?
gravity
When a star depletes its core supply of hydrogen, ___________ dominates in the core and ____________ dominates in the atmosphere.
gravity; pressure
The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is
greater than Schwartzschild's limit of 3 solar masses
The escape velocity for material inside a black hole is
greater than the speed of light.
A radio galaxy is any galaxy that:
has two lobes one on each side of the galaxy which emit synchrotron radiation at radio wavelengths.
Stars within a cluster that are at the turnoff point
have life expectancies that are equal to the age of the cluster.
The "turnoff" point for a star cluster is the point in the H-R diagram occupied by the
highest-mass main-sequence stars in the cluster
Hydrogen shell burning proceeds increasingly faster due to
heat released from the core's contraction
After the helium flash in a low mass star
helium burning begins in the core and hydrogen burning continues in the layers around the core.
white dwarfs
helium burning starts burning in the cores of
In terms of a star's evolutionary life, an asymptotic giant branch (AGB) star is in the
helium shell-burning phase.
For a star of Sun-like mass, what is the last stage of the nuclear fusion?
helium to carbon and oxygen
Degenerate refers to a state of
high density
have higher energy outputs.
high mass stars evolve more quickly than low mass ones because the high mass stars
A Cepheid variable is a:
high-mass giant or supergiant star that pulsates regularly in size and brightness.
Synchrotron radiation is produced by
high-velocity electrons moving through a magnetic field.
In star clusters, the ____ stars are giant stars fusing helium in their cores and then in their shells.
horizontal branch
What two things are needed to create an emission nebulae?
hot stars and interstellar gas, particularly hydrogen
in elliptical orbits, about a common "center of mass"
how do two unequal mass stars move around each other in a binary system?
the Moon's gravity stretches the Earth causing the Earth to bulge both towards and away from the Moon
how does gravity cause tides?
hot gas shoots out from the rocket and, by conservation of momentum, the shuttle moves in the opposite direction
how does the Space Shuttle take off?
we are about 25,000 light years out, in a disk which is about 100,000 light years in diameter
how does the Sun's orbit compare to the overall scale of the Milky Way?
it gradually leaks out through the radiation zone in the form of randomly bouncing photons
how does the enormous amount of energy in the Sun's core get out?
The luminosity of a star depends on
how efficient its fuel is and how fast it burns
3
how many helium nuclei fuse together when making carbon?
A star's evolutionary "track" in the H-R diagram traces out
how the star's luminosity, temperature, and size change with time
Where would you look for a supermassive black hole?
in the center of a galaxy
A pulsar is most probably formed
in the center of a supernova explosion.
In our Galaxy young metal-rich stars are found:
in the disk and spiral arms.
New stars are formed from:
huge cool dust and gas clouds.
Of the elements in your body, the only one not formed in stars is
hydrogen
The gas in a planetary nebula comes from
hydrogen and elements processed in the core of the post-asymptotic giant branch star
Which are the two most abundant elements in the universe?
hydrogen and helium
Which of the following nuclear fuels does a one-solar mass star use over the course of its entire evolution?
hydrogen and helium
In terms of nuclear reactions, what is the next stage of a star's life after the end of hydrogen burning in the core?
hydrogen burning in a thin shell around the core
A main sequence star is distinguished by
hydrogen burning in its core
Through nuclear reactions in their cores, stars on the main sequence convert
hydrogen to helium.
When a star's inward gravity and outward pressure are balanced, the star is said to be
hydrostatic equilibrium
shape determined only by the absolute temperature of the object
ideal thermal radiation spectrum from a dense hot object has a
is one-fourth the original value
if you double the distance between two planets, the force of gravity between them:
an emission line spectrum
if you heat a thin gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces
raising its gravitational potential energy
if you lift a book up onto a table from the ground you are
one of them could be 100 times less powerful, but 10 times closer to the Earth than the other.
if you observe two stars of the same brightness:
dark line
if you were to take an optical spectrum of Moonlight, it would show what kind of spectrum
Supernovae are detected:
in both our Galaxy and others.
Where in the universe would you look for a protostar?
in dense dust and gas clouds
New stars are formed
in huge, cool dust and gas clouds.
regular 5-minute oscillations and fluctuations of the surface
in recent times, one method that has been used successfully to investigate the deep interior of the Sun has been to observe
gradually increasing
in several episodes of Star Trek, the USS Enterprise was put in dangerously low orbits around various planets, which dragged it through their outer atmospheres. As Scotty correctly pointed out, this friction caused the Enterprise's orbit to "decay", and the ship gradually dropped into lower and lower orbits (increasingly close to the planet's surface). Recalling that even the USS Enterprise must obey Kepler's laws, we can deduce that as it drops closer to the planet, its orbital speed must be
Synchrotron radiation is produced
in supernova remnants.
four protons in, one helium nucleus out plus 2 gamma rays (energy), 2 positrons and 2 neutrinos
in the proton-proton chain reaction that provides the nuclear power source for the Sun, what is the net result?
west to east mostly, but occasionally east to west
in which direction does Mars move through the stars?
According to Hubble's Law, as the distance of a galaxy ____________; its _____________ increases.
increases; recessional velocity
A newly formed protostar will radiate primarily at which wavelength
infrared
Which range of electromagnetic radiation is useful for observing new-born protostars within their gas and dust nebulas?
infrared
The evolution of a star depends predominantly upon its:
initial mass.
an ionized gas or plasma
inside a star like the Sun where the temperature of the gas is exceedingly high, collisions between atoms knock away the orbiting electrons to produce:
ionized gas or plasma
inside a star like the Sun where the temperature of the gas is exceedingly high, collisions between atoms knock away the orbiting electrons to produce:
At which of the following locations will Newton's laws of motion be inadequate in describing precisely the motions of objects?
inside the orbit of Mercury
Herbig-Haro objects (bright variable regions within nebulae) are now thought to be the result of:
intense jets of material ejected from a young star hitting parts of the nebula.
The reason why Cepheid variable stars pulsate in size is that
ionization of atoms below the surface traps heat when the star contracts, and this heat gives an extra push as the star expands. Yes. The Cepheid variable acts like the gasoline engine in a car in which the explosion puts extra heat into the gas during compression, and this drives the outward expansion more strongly than just by rebound against gas pressure alone. Section 19-6
An iron core cannot support a star because
iron cannot fuse with other nuclei to produce energy
A sequence of thermonuclear fusion processes inside massive stars can continue to transform the nuclei of elements such as carbon, oxygen, etc. into heavier nuclei and also generate excess energy, up to a limit beyond which no further energy-producing reactions can occur. The element that is produced when this limit is reached is
iron.
The visual pink glow of the Great Nebula in Orion
is an emission nebula of thin gas.
The main-sequence lifetime of a star with half the mass of the Sun
is longer than that of the Sun
In a binary system, the more massive star
is nearest the center of mass.
The stars at the turnoff point in the H-R diagram of the Hyades star cluster have an absolute magnitude of approximately M = +2 while those at the turnoff point in the cluster M41 have M = 0. From this information we can say with certainty that the Hyades cluster:
is older than M41.
The discovery of the peculiar galaxy Cygnus A was a surprise to astronomers because it:
is very faint at visible wavelengths but extremely bright at radio wavelengths.
21-cm radiation is important because
it allows us to study neutral hydrogen in the interstellar medium
As much as 90% of the matter in the universe may be unseen "dark matter." Where is this dark matter?
it appears to be concentrated in spherical halos around galaxies (but extending several times the radius of of visible matter)
A star first reaches the main sequence when
it attains hydrostatic equilibrium.
What happens to the wavelength of light as it travels outward through the gravitational field of a planet, a star, or other massive object?
it increases
this is explained by conservation of angular momentum during the gravitational collapse of the solar nebula
it is hypothesized that the Sun formed with a large flat disk around it. Which statement is true
Dust reddens starlight because
it scatters optical and higher-frequency light
years
it takes light how long to travel from the nearest star to us? (nearest star beyond the sun, that is)
5. When the glimpse the chromosphere at the start and end of totality (what's this?),
its color is red due to ionized hydrogen at lower pressure
As a spaceship's velocity gets closer to the speed of light..
its length will decrease and its clock will run more slowly
When a G2 star leaves the main sequence,
its luminosity increases and its surface temperature decreases
The only physical properties necessary to describe a black hole and its interaction with the rest of the universe completely are...
its mass; its electric charge; its angular momentum (or spin)
A star's evolutionary track is
its movement when plotted on a Hertzsprung-Russell diagram, as it evolves in luminosity and temperature.
Black holes do not possess a magnetic field because
magnetic field is radiated away in the form of gravitational waves during the collapse.
As a white dwarf evolves the direction of its motion on the Herzsprung-Russell diagram is from upper left to lower right which means that:
its size or radius remains constant as it cools and becomes less luminous.
As a white dwarf evolves, the direction of its motion on the Herzsprung-Russell diagram below the main sequence is upper right to lower left, which means that
its size or radius remains constant as it cools and becomes less luminous.
X-rays that come from the vicinity of a black hole actually originate from...
just outside the event horizon (on the accretion disk)
X-rays that come from the vicinity of a black hole actually originate from:
just outside the event horizon on the accretion disk.
X rays that come from the vicinity of a black hole actually originate from
just outside the event horizon, on the accretion disk.
planet travels faster when it is nearer to the Sun and slower when it is farther from the Sun.
kepler's second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that:
What supports galaxies from gravitational collapse?
kinetic energy from the motions of stars
Stars in the upper right part of the Hertzsprung-Russell diagram are always ____ when compared to stars near the middle of the diagram.
larger
If Star A is closer to us than Star B, then Star A's parallax angle is
larger than that of Star B.
When pulsating variable stars are at their brightest, they are also
largest and bluest
A star (no matter what its mass) spends most of its life as a
main sequence star.
Which of the following kinds of stars best obey the mass-luminosity relation?
main sequence stars
The method used by Harlow Shapley in 1917 to estimate the Sun's location in our Galaxy was the measurement of the:
locations of globular clusters around the Galaxy.
The most common types of stars in our galaxy are
low-mass stars
The most common stars are
lower (less luminous) main sequence stars.
ON the H-R diagram, white dwarfs Sirius B and Procyon B lie at
lower left
In an H-R Diagram, stars with the smallest radius are found in the ____ of the diagram.
lower left corner
The ____ of a star is a measure of the total energy radiated by the star in one second.
luminosity
The total amount of power (in watts, for example) that a star radiates into space is called its
luminosity
The H-R diagram is a plot of:
luminosity versus temperature.
The H-R diagram can plot
luminosity, classifications and effective temperatures.
What are the two longest stages in the life of a one solar mass star?
main sequence, white dwarf
The single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar is its
mass
What characteristic of a star primarily determines its location on the main sequence?
mass
Compared to our sun, a typical white dwarf has about the same
mass & a million times high density
Which factor, more than any other, modifies the evolutionary tracks of stars in binary combinations compared to their single star counterparts?
mass exchange between the stars
Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
mass they are formed with
The Algol paradox is explained by considering
mass transfer between the two stars in a binary system.
velocity along the line of sight
measuring the displacement of an emission or absorption line in the spectrum of a star from its expected laboratory wavelength due to the Doppler effect enables us to determine the
What kind of star is our Sun?
metal rich Population I
Hydrogen fusion in the Sun requires a temperature (in Kelvin) of
millions of degrees
Which of the following is NOT evidence of the existence of an interstellar medium?
molecular absorption lines in the spectra of cool stars `
The most common molecule in a molecular cloud is
molecular hydrogen, H2.
A young protostar is ___________ than the sun even though its surface temperature is ___________.
more luminous; cooler
There is a main sequence mass-luminosity relation because
more massive stars support their larger weight by making more energy.
Compared with the spectral lines in the solar spectrum, lines in a supergiant star's spectrum are
more narrow.
In a spherical universe, the sum of the angles in a triangle sum to
more than 180°
What do asteroids and comets have in common?
most are unchanged since their formation in the solar nebula
the maria formed after the heavy bombardment ended.
most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
impacts and gravitational capture during the formation of the solar system
most of the planets and their moons rotate in the same direction and revolve about the Sun in the same direction. How are exceptions explained?
the spectral lines of elements such as iron are usually found to be at slightly different wavelengths than those observed in laboratory spectra. Why
most stars are moving with respect to the earth and this causes spectral lines, including iron, to be Doppler-shifted from their laboratory wavelengths.
light from a dense, hot part of the star passes through a region of cooler, tenuous gas.
most stars have spectra showing dark lines against a bright continuous background of color. According to Kirchoff's laws, this means that
A 10-solar-mass main-sequence star will produce which of the following remnants?
neutron star
Which of the following astronomical objects are most closely associated with pulsars?
neutron stars
Astronomers initially had difficulty identifying the emission lines in quasar spectra at optical wavelengths because:
no one expected violet and ultraviolet spectral lines to be shifted so far toward the red.
The energy generation process inside a white dwarf star is
nonexistent; a white dwarf star is simply cooling by radiating its original heat.
An indestructible robot would feel ____________ as it crossed the event horizon of a black hole
nothing
The heaviest nuclei of all are formed during
nova explosion
The source of energy that keeps the Sun shining today is
nuclear fusion
The core collapse phase at the end of the life of a massive star is triggered when
nuclear fusion has produced a significant amount of iron in its core.
protons
nuclear fusion in the sun occurs between
While on the main sequence a star's primary energy source comes from
nuclear fusion.
The Drake equation attempts to predict the:
number of technologically advanced civilizations in our Galaxy.
The method used by Hubble to determine the distance to the Andromeda galaxy (M31) thereby establishing the concept of separate and individual galaxies throughout the Universe was the:
observation of Cepheid variable stars.
What range in the electromagnetic spectrum was being observed when the first pulsars were discovered?
radio
The triple alpha process
occurs during helium flash.
After a star becomes a red giant, hydrogen fusion
occurs in a shell around the core.
If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because
of global climate effects initiated by dust and smoke that entered the atmosphere after the impact
Which is characteristic of globular star clusters?
old age and hundreds of thousands of stars, less than 30 ly wide
A globular cluster of stars is judged to be
old, because it contains no hot, blue, luminous main-sequence stars. Yes. These are the oldest systems in the universe, containing only highly evolved stars. Section 19-4
3. what two energy transport mechanisms, in order from outside the core to the surface, are found in the sun?
radiative diffusion, then convection.
In the H-R diagram, 90 percent of all stars are
on the main sequence.
december 21
on what day is the noonday Sun lowest in the sky in the Northern Hemisphere
the electron in the ground state of hydrogen does not have a precisely defined 'position'
one consequence of the Uncertainty Principle is that
The collapse of the core of a high-mass star at the end of its life takes about
one second
In a semi-detached binary star system:
one star fills its Roche lobe while the other does not.
21. compared to the underlying photosphere and chromosphere, the coronoa is
one to three million kelvin in temperature
self-gravity for the most massive asteroids was sufficient to pull them to this shape during their early history.
only the few largest asteroids are found to be spherical. Why is this?
A Cepheid star varies in luminosity because
only the outer envelope of the star pulsates
A(n) ____ is a collection of 100 to 1000 stars in a region about 25 pc in diameter. The stars in the collection are typically quite young.
open cluster
Most pulsars are observed only as
radio Sources
Dust appears dark in ___________ wavelengths and bright in ___________ wavelengths.
optical; infrared
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto
order of the planets, outward from the Sun is
little changed on its surface appearance over the last billion years
our moon is
A main-sequence star is in hydrostatic equilibrium because of the balance between the inward pressure of gravity on each layer of gas and the
outward pressure of gases heated by the thermonuclear fusion of hydrogen. Yes. Energy from thermonuclear fusion heats the gas, the pressure of which opposes the inward gravity. Section 19-1
indirect evidence based on the Doppler effect in the star's spectrum
over 150 other planetary systems in which there are at least one giant Jupiter-like planet in orbit around a Sun-like star have been discovered by:
A typical shooting star in a meteor shower is caused by a ________ entering Earth's atmosphere.
pea-size particle from a comet
10. visibile sunspots lie in the granulation in the
photosphere
In the context of black holes, a singularity is a(n)
place where a nonzero mass occupies zero volume.
Which of the following stars are metal-poor?
population II stars
To determine the orbital period of a visual binary, we must measure
position on the sky.
the slow conical motion (like a spinning top) that the Earth's rotation axis makes over 26,000 years
precession is
The entire process of star formation is really just an evolving balance between
pressure and gravity
As a white dwarf cools its radius will not change because
pressure does not depend on temperature for a white dwarf because the electrons are degenerate.
In degenerate matter
pressure does not depend on temperature.
Molecular clouds are best observed at ___________ wavelengths.
radio
*Helium *Deuterium *Positron *Neutrino
produced at some step during the proton-proton fusion reactions.
*Helium *Deuterium *Positron *Neutrino
produced during the proton-proton reaction
A planetary nebula
produces an emission spectrum.
8. A loop of gas following the magnetic field lines between sunspots poles is
prominence
The Hubble Space Telescope has photographed disks of gas and dust around young, low-mass stars in the Orion Nebula. It is thought that planets may form from the material in disks such as these. What name has been given to these disks?
proplyds
RR Lyrae stars are
pulsating stars that vary regularly, all with periods of less than one day.
In modern particle physics the proton and the neutron are now thought to be composed of more fundamental particles called:
quarks.
A spectroscopic binary shows periodic variations in its
radial velocity.
Most searches of space for evidence of intelligent life concentrate on radio wavelengths because:
radio energy is least affected by dust and gas in the interstellar medium.
at the speed of light, 3 × 108 m/s
radio waves travel through space at what speed?
Pulsars are thought to be
rapidly rotating neutron stars
earth year being a non-integer number of Earth days
reason for the leap years
*Waves *Photons. *Electric and magnetic fields vibrating perpendicular to the direction of motion *Quantized packets of energy.
reasonable ways of describing light
Warm ionized gas will appear ___________ when imaged in the optical portion of the spectrum.
red
The predominant color of an emission nebula is:
red from the Balmer Hα line.
What is the next stage in a star's life after the main-sequence phase?
red giant
An asymptotic giant branch (AGB) star is a:
red supergiant.
What would you expect to be the overall color of a globular cluster of stars?
red, because of the older population of stars in the cluster
The predominant color of an emission nebula is
red, from the hydrogen Balmer Ha line.
The primary evidence for the expanding universe concept is the
redshift of light from distant galaxies, which increases with distance of the galaxy from Earth.
In the context of black holes, the word ergosphere names the
region just outside the event horizon of a rotating black hole where it is impossible for anything to remain at rest.
Interstellar clouds are
regions where hydrogen tends to be denser than the surrounding gas
Visible pulses are seen to accompany radio pulses only from neutron stars, which are
relatively young, like the Crab or Vela pulsars.
If the distance between us and a star is doubled, with everything else remaining the same, the luminosity
remains the same, but the apparent brightness is decreased by a factor of four.
The Crab Nebula is a nearby example of what type of physical phenomenon?
remnant of a supernova explosion
If the theory that novae occur in close binary systems is correct, then novae should
repeat after some interval.
Most meteorites are
rocky and primitive.
A solar mass star will evolve off the main sequence when it
runs out of hydrogen
What mechanism is believed to produce flocculent spiral galaxies?
self-propagating star formation, where star formation occurs in bursts
red giant, orbit of Mercury, Sun, Jupiter, Earth
sequence is ranked in order of largest to smallest radius
The Pauli exclusion principle
sets a limit to the crowding of electrons into any given small volume of space.
Compared to Cepheid variable stars, RR Lyrae stars have
shorter oscillation periods and are intrinsically fainter. Yes. RR Lyrae stars have periods of about half a day and are fainter than Cepheids. Section 19-6
14. suppose a large flare is detected optically. How long until radio interference arrives?
simultaneously
In the Hubble classification scheme for spiral galaxies, the tightness of the winding of the spiral arms appears to be related directly to the
size of the central bulge of the galaxy.
The lowest mass that a protostar can have and still become a star (i.e., start thermonuclear reactions in its core) is
slightly less than 1/10 of a solar mass.
According to Einstein's general theory of relativity, a clock that ticks at a regular rate far from a source of gravity will appear to tick...
slower (the closer it comes to the source of gravity)
As time progresses, the pulse rate for most solitary pulsars is
slowing down, because rotational energy is being used to generate the pulses.
According to the Hubble classification scheme, an Sc galaxy has a(n)
small central bulge and loosely wound spiral arms.
One star in a binary will almost always become a red giant before the other because
small differences in main sequence masses yield large differences in main sequence ages
the Sun's magnetic field
solar flares, sunspots and prominences are all directly related to
the high temperature of the cornonoa is responsible for the
solar wind
aurorae
solar wind particles can be captured by the earth's magnetosphere. When these particles spiral down along the magnetic field into the atmosphere, they are responsible for
such luminous stars are extremely rare, and thus any small neighborhood of the Galaxy is unlikely to contain one of them
some supergiant stars give off more than 50,000 times the energy output of the sun. Why are there no such stars among those stars closest to the sun?
Galaxies move away from us in all directions because
space is expanding
Hawking radiation exists from black holes because
space itself has physical properties
The chemical makeup of a star's surface is usually determined by:
spectroscopy of the light emitted by the star.
If the fate of the universe were determined solely by the total mass of the universe (luminous and dark), astronomers would predict that we live in a universe that will
stop expanding and eventually copllapse
When distances were carefully measured from Earth to globular clusters above and below the Milky Way plane (where our view of them is not obscured by interstellar dust and gas) their distribution was found to be:
spherically symmetric about a point in the constellation Sagittarius and concentrated in that direction.
Most stars in our part of the Galaxy are formed in associations of thousands of stars across a
spiral arm of the Galaxy
What is photodisintegration?
splitting apart of atomic nuclei by high-energy gamma rays
*Red giant *Planetary nebula *White dwarf
stages the sun will definitely go through as it gets older
During the T-Tauri phase of a protostar, it on an H-R diagram, a protostar would be come a
star
"Standard candles," which are important for finding distances to remote galaxies, are
stars and other objects of known intrinsic brightness.
The T Tauri phase of a protostar is characterized by
strong spectral emission lines.
masses
stars that lie in different places on the main sequence differ from each other mainly by having different:
Cepheid stars are
stars that pulsate in brightness, size, and temperature.
a black hole
stars with main sequence masses of more than 30 solar masses will most likely end up as
they produced the iron nuclei in our bloodstream
statement is true of supernova explosions?
*A circle is considered to be a special type of ellipse. *The semimajor axis of an ellipse is half the length of the longest line that you can draw across an ellipse. *An ellipse with a large eccentricity looks much more elongated (stretched out) than an ellipse with a small eccentricity. *The Earth's orbit is not described by an ellipse
statements about an ellipse
*many of the ones discovered are larger than Jupiter *hundreds have been discovered by careful Doppler measurements of stars *many have been discovered by the eclipses of starlight they produce *it is not unusual for other stars to have at least one (or more) planets
statements about exoplanets:
*They can be produced by pulsating white dwarfs *They can be found in the centers of supernova remnants *They cannot be detected with radio telescopes *They are neutron stars which can spin 30 times per second
statements about pulsars?
*It starts with the implosion of the iron core of a massive star *It can produce a neutron star *It can produce heavy elements such as uranium *It produces most of its energy in neutrinos
statements about supernovas
The study of stars in clusters has helped astronomers to understand:
stellar evolution the development of stars with time.
The fraction of the mass of a red giant that is ejected as a shell in a planetary nebula is:
substantial up to 40% or more.
Glitches are occasionally observed by astronomers studying pulsars. What are these glitches?
sudden increases in rotation rate
The interior of a neutron star is believed to consist of...
superfluid neutrons and superconducting protons
The interior of a neutron star is believed to consist of
superfluid neutrons and superconducting protons.
What are thought to be some possible causes of triggering the contraction of an interstellar cloud?
supernova
The Crab nebula is
supernova remnant.
250 K, which is well below freezing.
suppose Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be
it is composed of a 50/50 mixture of rock and ice
suppose a new solar system object is found, and a NASA satellite flies close enough to measure its mass. It is about 3/4 the size of Ganymede and turns out to have a density about twice that of water. Based on these facts, you could best conclude that:
we live on the edge of the Milky Way
suppose the Milky Way were a band of light that only extended halfway around the sky (i.e. in a semicircle). You could conclude:
your weight will go down. You're in fine shape
suppose you are making a trip to the moon. You weigh 120 pounds on earth and your lunar module is designed to carry precisely this amount (weight), plus the gear and fuel, and no more (or it will collapse). When you land on the moon, what happens to your weight and will you be in trouble or not? (The moon's mass is 0.012 Me; Rmoon = .5 Re if you need them)
both will hit the ground at the same time
suppose you drop a 10-pound weight and a 5-pound weight on the Moon, both from the same height at the same time. What will happen?
your weight would be less than your weight on Earth, but your mass would be the same as it is on Earth.
suppose you lived on the Moon. Which of the following would be true? (weight and mass)
the circumference around the Equator is larger, because Jupiter rotates so rapidly
suppose you measure Jupiter's circumference first around its Equator, and then perpendicular to that (i.e. over its poles). You find that:
trojan 1 formed about ten billion years ago
suppose you measure the temperatures of all the main sequence stars in two star clusters, Bruin 1 and Trojan 1. The hottest main sequence star in Bruin 1 is about 20,000 degrees Centigrade, while the hottest main sequence star in Trojan 1 is about 6,000 degrees C. Does the above information tell you anything about the age of Trojan 1?
trojan 1 is much older than Bruin 1
suppose you measure the temperatures of all the main sequence stars in two star clusters, Bruin 1 and Trojan 1. The hottest main sequence star in Bruin 1 is about 20,000 degrees Centigrade, while the hottest main sequence star in Trojan 1 is about 6,000 degrees C. What does this tell you about the clusters?
the stars would appear to rotate around a DIFFERENT point in the constellations
suppose you were at the North Pole 10,000 years in the future. Would you notice any changes from being there today?
The spectral type of a star is most directly related to (and defines uniquely) its:
surface temperature.
An electron moving in a magnetic field in space is forced to follow a spiral pattern. As it does so it will emit:
synchrotron radiation mostly radio waves.
The main sequence lifetime of a star is given by the equation
t = M/L
A Hayashi track on an H-R diagram is a path of approximately constant
temperature
What physical property of a star does the spectral type measure?
temperature
When helium fusion begins in the core of the star, the situation quickly gets out of control because electron degeneracy pressure does not respond to changes in
temperature
A star's luminosity depends only on the star's
temperature and diameter.
The hydrogen in the outer layers of the Sun cannot undergo fusion because the
temperature in the outer layers is too low to allow the hydrogen nuclei to come close enough together to undergo fusion.
6000 °C
temperature of the Sun's surface is roughly
The more efficient CNO cycle of hydrogen fusion can take place in high-mass stars because of the greater ___________ in their cores.
temperatures
The H-R diagram of a young star cluster shows
that low mass stars have not yet reached the main sequence yet.
The diameter of a typical neutron star of 1 solar mass is predicted to be approximately:
that of an average city about 30 km.
velocity of the particles that make up the gas
the absolute temperature of a gas is most directly related to its
A white dwarf star is about the same size as
the Earth.
A white dwarf star is about the same size as:
the Earth.
temperature drops low enough for hydrogen compounds like water, ammonia and methane to freeze out
the Frost Line is an imaginary boundary in the early solar nebula beyond which
every hypothesis must be testable against observations or experiments
the Scientific Method is highly regarded as the best system for the development of new knowledge because:
10 billion
the Sun is consuming its core mass by nuclear burning. At the rate it is emitting energy the Sun's total lifetime will be _______ years
the outward push of pressure from the hot core balances the inward pull of gravity
the Sun is said to be in gravitational equilibrium which means that
the mass of 4 protons is 0.7% larger than the mass of 1 Helium nucleus
the Sun shines because
absorption
the Sun's rainbow-like spectrum contains many faint dark lines. This is an example of which kind of spectrum
stellar Parallax
the ancient Greeks rejected the idea that Earth goes around the Sun in part because the could not detect
The proper motion of a star is:
the angle through which the star moves across our sky against the background stars each year.
Luminosity, distance
the apparent brightness of a star in the night sky can be determined from its _______ and its _______.
the rotation of the Earth on its axis from west to east
the apparent daily motion of the Sun and stars across the sky from east to west is a result of:
Absolute visual magnitude is
the apparent magnitude of a star observed from a distance of 10 pc.
What does the phrase "superluminal motion" refer to?
the apparent motion of jets of gas at speeds faster than light
ecliptic
the apparent path of the Sun among the constellations over the course of one whole year is called the
A planetary nebula is
the atmosphere of a red giant star slowly expanding away from the star's core to form a shell of gas.
A low-mass main sequence star's climb up the red giant branch is halted by
the beginning of helium fusion in the core
the point at which the two objects would balance if they were somehow connected.
the center of mass of a binary star system is
A quasar is now thought to be
the central core of an active galaxy
A quasar is now thought to be:
the central core of an active galaxy.
The majority of the elements heavier than hydrogen and helium in the Universe are believed to have originated in:
the central cores of stars.
The majority of the elements heavier than hydrogen and helium in the universe are believed to have originated in
the central cores of stars.
The very strong magnetic field of a neutron star is created by...
the collapse of a star (which significantly intensifies the original weak magnetic field of the star)
The very strong magnetic field of a neutron star is created by
the collapse of a star, which significantly intensifies the original weak magnetic field of the star.
As material accretes onto a black hole energy is released. Where does this energy come from?
the conversion of gravitational energy to kinetic energy
Electron degeneracy, a result of the Pauli exclusion principle that prevents electrons from becoming crowded together beyond a certain limit, is important in
the core of a low-mass star just before the start of core helium burning.
In the language of general relativity, what we usually call "gravitational force" is described in terms of
the curvature of spacetime.
The theory that the collapse of a massive star's iron core produces neutrinos was supported by
the detection of neutrinos from the supernova of 1987.
distance
the determination of stellar parallax is important because it allows the direct determination of
neutron
the difference between normal hydrogen and deuterium is an additional
The Hubble law indicates that
the farther superclusters are receding faster than the nearby superclusters.
happened as a by-product of the formation of our sun
the formation of planets
happened as a natural by-product of the formation of our sun.
the formation of planets
Giant and supergiant stars are rare because
the giant or supergiant stage is very short.
When you see the bright flash of a meteor, what are you actually seeing?
the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere
The relationship between mass and luminosity of stars on the main sequence is that:
the greater the stellar mass the larger the luminosity.
What is a Roche lobe?
the imaginary boundary around each star in a close binary system encompassing the mass gravitationally bound to that star
What parameter is now thought to be vital in the evolution of a pregalactic gas cloud into an elliptical rather than spiral galaxy?
the initial rate of star birth
The technique called photometry in stellar astronomy is the measurement of:
the intensity of light from stars through several limited-bandpass filters from which various stellar characteristics such as surface temperature variability and luminosity can be determined.
4. the outward pressure of hot gas in the suns balanced by
the inward gravitational pressure.
In an Algol-type binary star system
the larger star is less massive than the smaller star. Yes. Algol is a semidetached binary in which the star that was originally more massive has expanded and filled its Roche lobe. Mass transfer from it to its companion has then resulted in the companion (the smaller star) becoming the more massive of the two. Section 19-7
the altitude of Polaris
the latitude of a Northern hemisphere observer is approximately equal to:
Absorption lines due to the interstellar medium indicate that some components of the interstellar medium are cold and of a very low density because
the lines are extremely narrow.
ionized helium
the loss of an electron from a neutral helium atom results in
The main reason for the observed slowdown of Crab pulsar is...
the loss of rotational energy (through the emission of beams of charged particles)
What is the Eddington Limit for any object?
the luminosity beyond which the outward force due to radiation pressure on matter exceeds the inward force due to gravity
In which phase of a star's life are thermonuclear reactions converting hydrogen into helium in the core of a star?
the main-sequence phase
measuring the orbital period and distance of one of Jupiter's moons.
the mass of Jupiter can be calculated by
When material expanding away from a star in a binary system reaches the Roche surface
the material is no longer gravitationally bound to the star.
White dwarf stars of different masses have radii or sizes for which
the more massive the star, the smaller it is.
iron
the most stable atomic nucleus is
a tiny particle that interacts very weakly with matter, with extremely low or zero mass and no charge.
the neutrino is:
rises at 6AM and sets at 6PM
the new moon: (rises at ___ and sets at ___)
11 years
the number of sunspots rises and falls with time in a cycle lasting
If you compare two stars,
the one with the smaller absolute magnitude will always have the greater luminosity.
the wavelength of maximum energy emitted
the overall shape of the spectrum of the Sun and stars is roughly that of a thermal blackbody spectrum. What property of this spectral energy curve enables the temperature to be estimated?
The most accurate way to determine the surface temperature of a star is to study
the pattern of absorption lines from various atoms.
In the lighouse model
the period of pulsation slows down due to the drag of the remnant on its field. OR if the beam sweeps across us, we will detect a pulse of radiation.
conservation of angular momentum
the physical principal that best describes why all the planets in the solar system formed in the same plane is:
human eyes are not sensitive to infrared radiation.
the reason we can't see thermal blackbody radiation from people is that:
The age of a cluster of stars can be judged by the:
turnoff point on the main sequence of its H-R diagram.
The event horizon of a black hole is defined as
the radius at which the escape speed equals the speed of light
The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by...
the rapid rotation of a neutron star (that is producing two oppositely directed beams of radiation)
The pulsed nature of the radiation at all wavelengths that is seen to come from a pulsar is produced by
the rapid rotation of a neutron star that is producing two oppositely directed beams of radiation.
Hubble's constant H₀ represents
the rate of expansion of the universe
Relatively rapid fluctuations (within one day) in the electromagnetic output of quasars and blazars is an indication of:
the relatively small size of the emitting regions.
A neutron star is
the remains of a star that died in a massive star supernova (if no black hole was created).
In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?
the rings of Saturn
"The possible presence of a very large amount of unseen (""dark"") matter in the halo of our Galaxy is deduced from:"
the rotation curve of our Galaxy which indicates higher than expected orbital speeds in the outer regions of the Galaxy.
What evidence is there for considerable extra mass within galaxies which does not produce visible light -- the so-called dark matter?
the rotation curves of galaxies (showing orbital speeds of material, remains flat to large distances from the galactic centers, and does not follow a Kepler-type curve)
The broadening of the 21-cm line in distant spiral galaxies is caused by what?
the rotation of the galaxy
If the Sun were to be replaced by a one solar mass black hole, the gravitational pull of the black hole "sun" on Earth would be
the same
the tilt in the Earth's rotation axis with respect to the ecliptic plane
the seasons are primarily caused by
The total mass of a binary system can be calculated from
the semi major axis and period of the orbit.
What is Cerenkov radiation?
the shock wave emitted when recoil positrons move faster than the speed of light in water
The x-Ray source Cygnus X-1 is a black hole candidate located in a binary star system. The X-ray source is believed to occupy a volume smaller than Earth. This size is deduced from...
the short time period of the rapid flickering in its x ray brightness
about 1/3 of the originally predicted rate.
the solar neutrino experiment designed by Raymond Davis has detected a rate of solar neutrinos arriving at Earth that is:
The supernova SN1987A differed from most other supernovae because:
the star was a blue supergiant when it blew up rather than a red supergiant.
is a white dwarf
the surviving central star we see in the center of a "planetary nebula":
blurring caused by turbulence in the earth's atmosphere
the technique known as Adaptive Optics has been developed to remove which problem for ground-based telescopes?
15 million K
the temperature at the center of the Sun is
The smallest mass that a main sequence star can have is about 0.08 solar mass. This is because:
the temperature in a contracting protostar of less than 0.08 solar mass does not get high enough for nuclear reactions to start.
What does the accretion rate onto a massive compact object depend on?
the temperature of the compact object
The lower edge of the Main Sequence band is known as ____ and represents the location in the H-R diagram at which stars begin their lives as main sequence stars.
the zero-age main sequence
The main difference between Cepheid variable stars and RR Lyrae stars is
their masses
the moon's gravitational field creates high tides at both the near and far side of the earth due to the variation in the gravitational force with distance from the moon
there are two high tides a day because
Type Ia supernovae can be used as distance indicators because:
there is a known relation between peak luminosity and the rate of light decline for Type Ia supernovae.
The H-R diagram main sequence of stars has a limit at the lower mass, or energy output end, because
there is a minimum temperature for hydrogen nuclear fusion (the definition of a star).
The Hertzsprung-Russell diagram of a globular cluster does not contain any stars with high luminosity and high temperature on the main sequence because:
these high-mass stars evolved away from the main sequence long ago.
We know that giant stars are larger in diameter than the sun because
they are more luminous but have about the same temperature.
The lowest-mass stars cannot become giants because
they cannot heat their centers hot enough.
What is the common trait of all main-sequence stars?
they generate energy through hydrogen fusion in their cores
Star clusters are important to our study of stars because
they give us a method to test the our theories and models of stellar evolution.
Asymptotic giant branch (AGB) stars lose their atmosphere because
they have a low surface gravity
Light is increasingly redshifted near a black hole because
time is moving increasing ly slower in the observer's frame of reference
Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?
time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted
There are several mechanisms that can trigger star formation in a cold, dark nebula. In each of these the key to star formation is
to compress the gas and dust so that gravitation will overcome the gas pressure.
x-rays
to observe certain wavelengths of electromagnetic radiation, it is necessary to put telescopes in space above the Earth's atmosphere. Which of the following wavelength regions must be observed from space
jump down in energy level.
to produce an emission line, an electron in an atom must
As a spaceship nears an event horizon, a clock on the spaceship will be observed
to run the same as one on Earth.
On the H-R diagram, the bright blue stars that dominate the naked-eye sky lie
top left
On the H-R diagram, red supergiants like Betelgeuse lie
top right
A star's luminosity is the
total amount of light that the star radiates each second.
The luminosity of a star is a unique measure of its:
total energy output.
2. the corona can only be glimpsed from earth during a
totality
Which way does a star of about 1 solar mass evolve, on the Hertzsprung-Russell diagram, at the end of its main-sequence lifetime?
toward higher luminosity and lower temperature—away from the main sequence
The ____ is the nuclear fusion of three helium nuclei to form a carbon nucleus.
triple-alpha process
A neutron star is what remains after a Type II supernova explosion has destroyed the rest of the star
true
An x-ray burster is similar to a nova
true
Both space and time are warped near the strong gravitational fields of neutron stars and black holes
true
More massive white dwarfs are smaller than less massive white dwarfs.
true
Neutron stars are the densest objects that we can observe in the universe.
true
No communication is possible across an event horizon
true
Some stars are cool enough to have molecules in their atmosphere.
true
Special relativity says that c, the speed of light, is the maximum velocity for both matter and energy in our universe
true
Spectral type, surface temperature, and color all describe the same basic characteristic of a star.
true
The escape speed at the event horizon of a bloack hole is c, 300,000 km/sec
true
The pulses from a pulsar are most likely coming from localized areas near the magnetic poles
true
The schwarzchild radius of a black hole is about 3 km per soalr mass; it is amazingly linear over a wide range of masses.
true
The "water hole " a region of the radio spectrum chosen for searches for signals from intelligent life because galactic and Earth-based noise and atmospheric absorption are at a minimum is so named because:
two astronomically important wavelengths the 21-cm line of H and a line from the hydroxyl radical OH are in this region (the letters H and OH signifying water).
two atoms with the same number of protons, but different numbers of neutrons
two isotopes of an element are
An eclipsing binary system is:
two stars that periodically eclipse each other as seen from Earth.
11. as the sun rotates, an individual sunspot can be tracked across its face. From eastern to western limb, this takes about
two weeks
Stars with masses between 0.4 and 4
undergo thermonuclear fusion of hydrogen and helium but never get hot enough to ignite carbon.
On a Hertzsprung-Russell diagram, where would we find red giant stars?
upper right
How can you observationally show (with today's technology) that a member of a spectroscopic binary is a black hole?
use Kepler's third law to show that its mass is greater than 3 solar masses (and constrain its size)
To estimate the central temperature of the Sun, scientists
use computer models to predict interior conditions
What method is used to determine the distance of very remote galaxies?
use of their spectral redshifts and the Hubble Law
The method used in the Urey-Miller experiment:
was to pass an electric arc through a mixture of hydrogen ammonia methane and water and then look for organic compounds.
What are the appropriate units for the Sun's luminosity?
watts
The total mass of the pair of stars in spectroscopic binaries are difficult to estimate because
we can't see the shape or tilt of the orbit.
This is NOT true, the rings are not a single solid sheet.
we know that the rings of Saturn are one solid sheet of ice because
the Main Sequence turn-off point
what property of the H-R diagram for a cluster of stars yields its age?
it is 50% hydrogen and almost 50% helium
what best describes the chemical composition of the CENTER of the Sun TODAY?
very rapid motion of stars close to the nucleus of the galaxy, requiring a very massive body to hold them in orbit.
what evidence now exists for a supermassive black hole at the center of our galaxy?
it was blown away by the strong solar wind of the young Sun
what happened to the remaining gas in the Solar Nebula?
the gaseous core expands, cools slightly, and the energy generation rate drops back to compensate
what happens inside the Sun if a slight rise in the core temperature causes a rapid rise in nuclear energy rate?
they mostly destroy themselves by merging with protons
what happens to electrons at the end of the final evolution of the core of a very massive star
they collide with electrons, producing energy
what happens to the positrons produced by the nuclear reactions in the core of the Sun?
leave the atom completely
what happens when an atom is ionized
it provides our best measurement of the radii of stars
what is especially useful about an eclipsing binary star?
the size of the Earth
what is the approximate size of a White Dwarf star?
the Moon formed from material blasted out of Earth's mantle and crust by the impact of a Mars-size object.
what is the current favored hypothesis for the origin of the Moon?
Jupiter's gravity, or tides, prevented material from coming together to form a planet
what is the currently accepted theory as to why there is an asteroid belt?
tidal Heating
what mechanism is most responsible for generating the internal heat of Io that drives the volcanic activity?
the close packing of electrons creates electron degeneracy pressure
what prevents the White Dwarf from collapsing to a single point due to its own gravity?
his angular momentum must be conserved, so reducing his radius must increase his speed of rotation.
when a spinning ice skater pulls in his arms, he spins faster because
expand
when a star runs out of nuclear fuel in its core, its surface will
emits a photon of a specific frequency.
when an electron in an atom goes from a higher energy level or state to a lower energy level, the atom
When does the Helium Flash occur?
when helium fusion begins in a low mass star
increase by thousands of times.
when the Sun becomes a red giant, its brightness at the Earth will:
helium nuclei begin to fuse to form carbon
when the core of a star reaches a temperature of 100 million degrees, something new happens in the core. What is it?
only in the core
where in the sun does nuclear energy generation occur
in its polar caps and subsurface ground ice
where is most of the water on Mars
earth
which of the terrestrial worlds has the strongest magnetic field?
deuterium
which is an isotope of hydrogen
eclipsing binary
which kind of binary star system produces periodic variations in the total light from the system?
venus
which object has the densest atmosphere
mercury
which object has the most heavily cratered surface
europa
which object is believed to have underground oceans of water
the presence of canals
which of the following does not provide evidence that Mars once had flowing water?
they all have substantial atmospheres.
which of the following is not a characteristic of the inner planets?
x-rays travel through space faster than radio waves
which of the following statements about X rays and radio waves is not true?
as the star is dying, it will lose a considerable part of its mass via a wind
which of the following statements is correct about the life of a star with the same mass as the sun?
at latitude 23 degrees south
you are at the bottom of a deep, vertical well at 12:00 Noon on December 22nd. You look up and see the Sun. Where on Earth could you be?
45,000 years
you discover a rock that contains a naturally occurring radioactive isotope, which is called Heavium. Careful lab measurements show that the stable decay product of Heavium (called Lightium, not produced in any other way), is 7 times more abundant than the Heavium. In other words, of the original Heavium, 7/8 is now Lightium, 1/8 of it remains Heavium. If the half-life of Heavium is 15,000 years, how old is your rock?
H II regions are powered by
young O and B stars
The bright stars at the center of an H II region (emission nebula) are:
young O and B stars.
10 meters
your favorite station is 30 MegaRock FM (in another country). If the 30 in 30 MegaRock stands for 30 MHz, or thirty million cycles per second, how long is the wavelength of its waves?
42. Which star in Table 13-2 has the greatest surface temperature?
δ Cen