Astronomy Final Study Set
Listed following are several stars found in the disk and halo of the Milky Way Galaxy. Assume that both the blue and yellow disk stars are members of the same open cluster. Rank the stars based on the abundance of elements heavier than carbon that you would expect to find in each of the stars, from highest to lowest. If you expect two (or more) stars to have approximately the same abundance, rank them as equal by dragging one on top of the other(s).
(1 of 2 Tied; overlap) Yellow main-sequence star in open cluster in disk& hot, blue main-sequence star in open cluster in disk (Tied 1 of 2 overlapping)Red main-sequence star in globular cluster M13& Red main-sequence star in globular cluster M13
The Big Bang theory is supported by two major lines of evidence that alternative models have not successfully explained. What are they?
(1) the theory predicts the existence of and the specific characteristics of the observed cosmic microwave background; (2) the theory correctly predicts the observed overall chemical composition of the universe.
What kind of measurement does not tell us the mass of a cluster of galaxies, or give us evidence for dark matter?
(Measuring) total mass (of the cluster's stars)
What best explains why a higher-mass cluster of galaxies causes light from a distant galaxy to bend more than a lower-mass cluster of galaxies?
(The) stronger gravity (of a larger cluster curves space itself by a greater amount, and light follows the curvature of space.)
Rotating Black Holes can have accretion disks. Magnetic field lins connect the black holes with the disk. What, if anything, can be transferred between the rotating black hole and its accretion disk?
*Particles and energy can be transferred, but only from the disk to the black hole, never from the hole to the disk
How do rotating black holes DIFFER from nonrotating black holes?
*Rotating black holes have a region juts outside the event horizon in which nothing can be at rest
What is a Cepheid variable star?
*a high mass star that pulsates regularly in brightness
One of the conclusions from the mass-luminosity relationship is that
*bright main sequence stars are more massive than faint main sequence stars
The X-rays from pulsating X-ray sources are believed to arise from
*hot spots at the magnetic poles of a neutron star, caused by matter from a companion star traveling down the neutron star's magnetic field.
The Sun's location in our galaxy is
*in the disk of the galaxy, inside a spiral arm or segment of a spiral arm
In some binary star systems, such as Algol, the less massive star is a red giant and the more massive star is on the main sequence. This is evidence that
*mass transfer has occurred from one star to another
One difficulty with the density wave theory is that
*there is no mechanism proposed to provide the energy output necessary to sustain the density wave
When did particle era end?
0.001 seconds.
Era of nucleosynthesis.
0.001s fusion produced helium from protons (H nuclei). Protons annihilated all antiprotons.
The mass of the supermassive black hole thought to power a typical active galactic nucleus would be around _________.
1 billion solar masses
About what percentage of the mass of a molecular cloud is in the form of dust?
1%
In our location in the Milky Way, the galactic disk is only about ________ ly thick
1,000
Astronomers now believe that most of any galaxy's mass lies beyond the portions of the galaxy that we can see.
1. Yes, because the orbital velocity of gas and stars remains fairly constant as we look farther from the galactic center, even beyond where most stars are found. 4. Yes, because the mass‐to‐light ratio of galaxies is much greater than the value for the Sun.
What are the 3 kinds of galaxies?
1. spiral 2. irregular 3. elliptical
If Euclid is right, then Omega is
1.0
Suppose that you measure a galaxy's redshift, and from the redshift you determine that its recession velocity is 30,000 () kilometers per second. According to Hubble's law, approximately how far away is the galaxy?
1.4 billion light-years
The image sequence zooms in on the center of the Milky Way Galaxy. Consider the first image in the sequence, which is the image that is zoomed-out as far as possible. Approximately what fraction of the Milky Way's total diameter is spanned by this image?
1/200
Hubble time is expressed as
1/H (13 Billion years?)
How many years ago did most quasars became inactive? 5 billion 10 million 13 billion 10 billion Quasars are still active.
10 billion
Energy radiated from a typical quasar requires that its black hole accrete about...
10 solar masses a year
What is the average rate of star formation in our Galaxy? 1 star every year Star formation has ceased to occur in our Galaxy. 1 star every 10 years 10 stars every year 50 stars every year
10 stars every year
How long after the Big Bang was the Planck time, before which our current theories are completely unable to describe conditions in the universe?
10 to power of (exponent) second
If an astronomical source of electromagnetic radiation is observed to flicker, with intensity changes in as short a time as 1/30 second, how large is the emitting region?
10,000 km, a little smaller than Earth
Central black holes can be very efficient for converting the mass-energy of infalling matter to thermal energy in the accretion disk. Roughly what percentage of the mass-energy can be converted to other forms of energy as matter falls into a black hole?
10-40%
Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately
100 billion
Based on the number of galaxies visible in the hubble deep field image, the estimated number of galaxies in the universe is about?
100 billion
How many galaxies are there in the observable universe?
100 billion
Between us and the Galactic Center, the Milky Way has a mass of
100 billion suns
According to our definition, we have been a technological civilization for about...
100 years
How big is the visible disk of our Milky Way galaxy, its diameter from edge to edge?
100,000 light years
to date, physicists have incestigated the behavior of matter and energy at temperatures as high as those that existed in the universe as far back as ______ after the big bang
10^-10 seconds
How long after the Big Bang was the Planck time, before which our current theories are completely unable to describe conditions in the universe?
10^-43 seconds
According to the turn off points of the oldest globular clusters, they formed about...
12 billion years ago
in our best current theory, the first quasars formed about...
13 billion years ago
To determine the mass of the central object, we must apply Newton's version of Kepler's third law, which requires knowing the orbital period and average orbital distance (semimajor axis) for at least one star. Let's consider the star with the smallest orbit, which is represented by red and pink dots. What is the approximate orbital period of this star?
13 yr
How much time has elapsed since the creation of the Universe, according to the Big Bang Theory?
13.798 Billion Years
Current estimates place the age of the universe at about _________.
14 billion years
What is the current best estimate of the age of the universe?
14 billion years old
How long is it from the time the star is born in that distant galaxy until the time we see the supernova resulting from its death?
190 million years
An astronomer studying the spectrum of a distant galaxy finds that its recessional velocity is 14,000 km/s. What is the distance to the galaxy? Take Hubble's constant to be 73 km/s/ Mpc. (24)
192 Mpc
The "aspect ratio" of thickness to width of the galactic disk is about
1:100
When did the era of the galaxies begin?
1B years after the BB.
According to the Big Bang Theory, how many forces -and which ones- operated in the universe during the GUT era?
2 forces: gravity and a single force that later became the strong, weak, and electromagnetic forces
Elements heavier than hydrogen and helium constitute about _________ of the mass of the interstellar medium.
2%
How long between the evolution of single versus multicellular organisms?
2.5 billion years
A billion solar mass black hole would still have a radius of only...
20 AU
The ratio of bulge mass to black hole mass is roughly...
200 to 1
The spiral-arm structure of the Milky Way galaxy has been measured and evaluated most effectively by observations of
21-cm radiation from interstellar hydrogen and the positions of young stars.
galactic year is the time for our solar system to orbit the galaxy; it is about...
225 million years
Based on inventoried matter in the universe, including dark matter known to exist in galaxies and clusters, the actual density of the universe is what fraction of the critical density?
25%
What is the overall density of the world today?
25% of critical density.
What fraction of the universe is Helium? Hydrogen?
25%, 73%
How long would it take to travel to the star, Alpha Centauri, at a rate of 10 astronomical units per year
27,616.7885 years
Hubble's constant is about 22 km/s/million light-years, implying an age of about 14 billion years for the universe. If Hubble's constant were 11 km/s/million light-years, the age of the universe would be about _______.
28 billion years
Suppose that a particular galaxy is 400 million parsecs from Earth. What is the recessional velocity of this galaxy? Take Hubble's constant to be 73 km/s/Mpc.(24)
29,200 km/s
How many properties of the matter inside a black hole can be measured from outside the black hole?
3
A cepheid variable star with a luminosity 1000 times that of the sun has a pulsation period of roughly
3 Days
If we represent the Milky Way Galaxy as the size of a grapefruit (10-cm diameter), the distance to the Andromeda Galaxy would be about
3 meters.
approximately how long did the era of nucleosynthesis last?
3 minutes
Based on current understanding, the minimum mass of a black hole that forms during a massive star supernova is roughly _________.
3 solar masses
in the critical density universe now proposed, the ratio of dark energy to matter is about...
3 to 1
The speed of light is about
3 x 105 km/s
How many stars are in the observable universe?
3 x 10^22
about how hot was the Big Bang when matter and energy "decoupled"?
3,000 K
Astronomer A claims that the Hubble constant is 84 km/s/Mpc, whereas astronomer B claims that it is 63 km/s/Mpc. The age of the universe calculated by astronomer A would be(26)
3/4 of that calculated by astronomer B.
Over what distance does the Cepheid variable technique work? The faintest objects which can be photographed through the best telescopes have apparent magnitudes of about m = 30. Consider a bright Cepheid with an absolute magnitude of M = -2.4. At what distance could it just be seen?
30 Mpc (108 pc)
How many stars are in the Milky Way galaxy?
300 billion
Recall that Hubble's law is written v = H0d, where v is the recession velocity of a galaxy located a distance d away from us, and H0 is Hubble's constant. Suppose H0 = 65 km/s/Mpc. How fast would a galaxy located 500 megaparsecs distant be receding from us?
32,500 km/s
How far into space have radio transmissions from the earth gone? Marconi invented the radio in 1895.
35,400,000 km
How old are cosmic microwave backgrounds?
380,000 years
Era of the atoms.
380,000 years The era of the atoms lasted until all stars and galaxies began to form.
When did the universe become transparent to light?
380,000 years after the Big Bang
What is the temperature of the universe as a whole today?
3K
What percentage of the universe is made up of normal matter, dark matter, and dark energy?
4% normal matter, 25% dark matter, 71% dark energy
Based on observations of the cosmic microwave background, the overall composition of the universe is _________.
4% ordinary (baryonic) matter, 23% non-ordinary (nonbaryonic) dark matter, 73% dark energy
Based on the results from the WMAP satellite, the overall composition of the universe is _________.
4% ordinary (baryonic) matter, 23% nonbaryonic dark matter, 73% dark energy
As of now, the supernova has already occurred in that galaxy. How long ago did it occur?
40 million years
According to Hubble's Law, a galaxy with a velocity of 25,000km/s will be
400 million parsecs away
Photons from the microwave background have not interacted with matter since the universe was how old?
400,000 years old
What would be the wavelength of maximum emission of interstellar dust grains at a temperature of 65 K? (See Wien's law, Section 5-4)
45 μm
The spectrum of the quasar PKS 2000-330 contains the UV Lyman Lα line (λ0 =121.567 nm) which has been shifted into the visible region of the spectrum by a cosmological redshift of z = 3.773. What is the redshift, Δλ0, of this radiation in nanometers?(25)
458.5 nm
How long would it take to send a radio message to the Andromeda galaxy and receive a reply?
5 million years
When did the era of nucleosythesis end?
5 minutes.
Era of nuclei.
5 minutes. A plasma of free electrons and H and He nuclei filled the universe leading to a 75%-25% mix of H, He.
Some of the oldest living organisms on earth are Bristlecone Pine Trees in the White Mountains of California. What is the age of the oldest of these trees?
5,062 years old
The dark halo is now believed to extend at least
50 Kila-parsecs
Matter belonging to the Galaxy can be traced out to ________ from the center.
50 kpc
What is a typical mass-to-light ratio for the inner region of a spiral galaxy, in units of solar masses per solar luminosity?
6
How long from now will it be before we receive the light from the supernova event? Assuming 100 Million ly away, star is now 30 million years old, total lifetime of 90 Million years
60 million years
Considering luminosity and longevity, which of these would be the most likely candidate for seeking extraterrestrial intelligence?
61 Cygni (a K type main sequence star)
at the end of the first 15 minutes, the mass ratio of H/He was about...
75/25
From the Sun, the distance to the Galactic Center is about
8 killa-parsecs
Approximately how far is the Sun from the center of our galaxy?
8 kpc
From the Sun, the distance to the Galactic Center is about
8,000 pc
Look again at the orbit of the star with the smallest orbit, represented by red and pink dots. By comparing the orbit to the scale bar shown on the diagram, you can estimate that this orbit has a semimajor axis of about _____.
800 AU
What is the estimated percentage of dark matter in the universe? 1 percent 90 percent 99.9 percent 10 percent
90 percent
What fraction of the Milky Way Galaxy is dark matter?
90%
If a galaxy's overall mass-to-light ratio is 100 solar masses per solar luminosity, and its stars account for only 5 solar masses per solar luminosity, how much of the galaxy's mass must be dark matter?
95 percent
What object do we think lies in the very center of the Milky Way Galaxy?
A 4 million solar mass black hole
What was "The Great Debate"?
A debate over the size and extent of the Universe and the nature of spiral nebula.
Hubble's constant has been determined to be 72 km/s/Mpc. Given that value, which of the following statements is true?
A galaxy at 100 Mpc from us will appear to be traveling about 7200 km/s
Rank the Milky Way Galaxy locations based on their distance from the center of the Milky Way Galaxy, from farthest to closest.
A globular cluster in the outskirts of the halo, a cloud of gas and dust in the outskirts of the disk, our solar system, and the edge of the central bulge
Which of these galaxies would you most likely find at the center of a large cluster of galaxies?
A large elliptical galaxy/
What was the GUT force?
A merger of strong, weak, and electromagnetic forces.
What is the rotation curve of a spiral galaxy?
A plot of rotation speed vs. distance from the center
What is believed to be the origin of starburst galaxies?(24)
A recent collision with another galaxy has triggered a wave of star formation.
Which model of the universe gives the youngest age for its present size?
A recollapsing universe
What is Einstein's cosmological constant?
A repulsive force that counteracts gravity and was introduced to allow for a static universe
Which of statement below about black holes is not true?
A spaceship passing near a 10 solar mass black hole is much more likely to be destroyed than a spaceship passing at the same distance from the center of a 10 solar mass main-sequence star.
What is a Cepheid variable?
A type of very luminous star that makes an excellent standard candle
The last image in the sequence shows two arrows pointing to the precise location of Sgr A*, yet the image shows nothing located at that position. Based on your study of the entire sequence, which of the following types of image would most likely allow us to see something at this location?
A very high-resolution radio image.
Why do astronomers hypothesize that a massive black hole lies at the center of M 87?
A very small region at the center of M 87 releases an enormous amount of energy.
Which kind of object is the best standard candle for measuring distances to extremely distant galaxies?
A white dwarf supernovae
According to available physical and biological evidence, when did multicellular organisms first appear on Earth?
About 1 billion years ago
According to current cosmological theory, how old is the observable Universe?
About 14 billion years
How far is it from the Sun to the center of the Milky Way?
About 28,000 light years
According to fossil evidence how far back in time did life on Earth exist?
About 3.5 billion years or more
What was the temperature of the universe during the instant of the Big Bang?
Above 10^32.
Imagine a photon of light travelling the different paths in the Milky Way described in the following list. Rank the paths based on how much time the photon takes to complete each journey, from longest to shortest.
Across the diameter of the galactic halo, across the diameter of the galactic disk, from the sun to the center of the galaxy, across the diameter of the central bulge, through the disk from top to bottom
The most active galactic nuclei are usually found at large distances from us; relatively few nearby galaxies have active galactic nuclei. What does this imply?
Active galactic nuclei tend to become less active as they age.
Name things that have each of these elements?
Air
Who predicted gravitational lensing?
Albert Einstein
Imagine that when we looked out into the universe we found that the light from all galaxies was blueshifted (rather than redshifted) and that the light from the most distant galaxies was blueshifted by the greatest amount. Which statement best describes what we would conclude about the motions of galaxies in this case?
All are moving toward Earth, with distant galaxies moving faster than nearby galaxies.
Particle era.
All forces now distinct.Elementary particles filled with universe, then quarks combined to make protons and antiprotons. The electroweak force is split into electromagnetic and weak forces.
Which one of the following conclusions can you draw about the expansion of the Universe from the drawing shown?
All galaxies appear to move away from each other during the expansion of the Universe.
As a star's evolution approaches the Type II supernova, we find... A.) helium to carbon fusion takes at least 100 million K to start. B.) the heavier the element, the higher the temperature to fuse it. C.) photo disintegration of iron nuclei begins at 10 billion K to ignite the supernova. D.) the heavier the element, the less time it takes to make it. E.) All of the above
All of the above
Which of the following are candidates for dark matter?
All of the above Brown dwarfs Jupiter-size objects WIMPs Faint red stars
What were the first biologically important molecules produced in the Miller-Urey experiments? Amino acids DNA Genetic bases Proteins
Amino acids
What is the major difference between an elliptical galaxy and a spiral galaxy?
An elliptical galaxy lacks a disk component
In astronomy, what do we mean by a standard candle?
An object for which we can determine the true luminosity
What fraction of the mass of our galaxy appears to be in the form of dark matter, which we cannot see but can detect through its gravitational influence?
As much as 90 percent of the matter in the universe is invisible. Detecting this dark matter will help astronomers better comprehend the universe's destiny from Scientific American, by Vera Rubin
As you learned in Part E, galaxy M82 has unusually active star formation. Why do astronomers think that this is a "burst" of star formation, rather than thinking that this galaxy always has such a high rate of star formation?
At its current rate of star formation, the galaxy would use up all its dust and gas in just a few hundred million years.
Why do virtually all the galaxies in the universe appear to be moving away from our own?
Because expansion causes all galaxies to move away from nearly all others.
Why do scientists say that evolution is a "theory"?
Because it explains a great deal about life and is supported by an enormous body of evidence
Why should it not be surprising that some galaxies contain little more than 25% helium, but it would be very surprising if some galaxies contained less.
Because the Big Bang fused 25% of normal matter in the universe into helium and stellar nucleosynthesis can increase, but not decrease, this amount.
Why does the rotation curve for the solar system show speeds that become slower with increasing distance from the Sun?
Because the Sun contains most of the mass of the solar system
What is the best explanation for why the sky is dark?
Because the universe is not infinite in space
Why is the cosmic microwave background a microwave?
Because visible light has since been stretched by the expansion of the universe.
Why is dark matter is inferred to exist?
Because we can observe its gravitational influence on visible matter
What is the significance of the Planck time?
Before it, conditions were so extreme that our current understanding of physics is insufficient to predict what might have occurred.
In principle, if we could see all the way to the cosmological horizon we could see the Big Bang taking place. However, our view is blocked for times prior to about 380,000 years after the Big Bang. Why?
Before that time, the gas in the universe was dense and ionized and therefore did not allow light to travel freely.
Why cant we see past the cosmological horizon?
Beyond the cosmological horizon we would be looking back to a time before the universe began
What can't we see past the cosmological horizon?
Beyond the cosmological horizon, we would be looking back to a time before the universe was born
What is the spectral distribution of cosmic microwave background radiation?
Black Body
A proposed explanation for gamma-ray bursters is coalescence of a neutron star binary. hypernova-making black holes and bi-polar jets. collisions between two white dwarfs. Both A and B are possible. All three are possible.
Both A and B are possible
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.
When another spaceship is moving by you (at constant velocity), you will measure the spaceship to be shorter than its rest length, while passengers on that ship will measure your length to be shorter. Imagine that you and the passengers on the other ship are arguing (by radio) about who really is the one that has become shorter. To settle the argument, you agree to meet up on Mars and put the two spaceships next to each other to see which one is really shorter. What will you find when you meet up on Mars? Your spaceship really is shorter than the other one. Both spaceships are the same length. The other spaceship really is shorter than yours.
Both spaceships are the same length
Which statement is true about ages and masses of spiral and elliptical galaxies?
Both types are about the same age, but spirals vary less in mass
How much did the universe cool?
By 1 second old, the universe was 10^10 K.
How is the energy that powers radio galaxies, quasars, and other active galactic nuclei produced?
By gravity, which converts potential energy being shot out as jets by a central black hole kinetic energy, which is then converted to thermal energy by collisions among the particles of matter.
How do we calibrate Hubble's Law?
By measuring the distances to many distant galaxies with a standard candle technique
In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?
By observing individual Cepheid variable stars in Andromeda and applying the period-luminosity relation.
When was the hydrogen nuclei in our universe created?
By the time our universe was about 3 minutes old
In stars, helium can sometimes be fused into carbon and heavier elements (in their final stages of life). Why didn't the same fusion processes produce carbon and heavier elements in the early universe?
By the time stable helium nuclei had formed, the temperature and density had already dropped too low for helium fusion to occur.
The satellite that found the ripples in the cosmic background that led to galaxies is
COBE
Which of the following is most like the rotation of stars in the disk of the Milky Way?
Cars moving at a constant speed on a circular race track
The nearest lobe radio galaxy to our Milky Way is
Centaurus A
The largest individual galaxies in the universe are known as what ____?
Central dominant galaxies
The period luminosity relation is crucial in finding distances with
Cepheid Variables
Which technique is the most useful for measuring the distance to a galaxy located 10 million light-years away?
Cepheids
Why are Cepheid variables important?
Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as "standard candles" for distance measurements.
How does a gravitational field affect the passage of time?
Clocks in a gravitational field run slower than clocks outside the field
In what model will the universe stop expanding
Closed Universe
What kind of universe would collapse on itself
Closed Universe
Which of the following statements about large-scale structure is probably not true?
Clusters and superclusters appear to be randomly scattered about the universe, like dots sprinkled randomly on a wall.
What is the main way that we determine the mass distribution of a spiral galaxy?
Constructing its rotation curve, which we make by looking for Doppler shifts in the 21-cm emission from atomic hydrogen in its disk.
Observations of the ___________ provide a way to test the Big Bang Theory.
Cosmic microwave background
What determines whether the universe is opened or closed?
Critical energy density
Some people wish that we lived in a recollapsing universe that would eventually stop expanding and start contracting. For this to be the case, which of the following would have to be true (based on current understanding)?
Dark energy does not exist and there is much more dark matter than we are aware of to date.
Which of the following best sums up current scientific thinking about the nature of dark energy?
Dark energy probably exists, but we have little (if any) idea what it is.
BLANK is inferred to exist because we can observe its gravitational influence on visible matter
Dark matter
The shape of our Galaxy's rotation curve implies the existence of
Dark matter
Which of the following statements best summarizes what studies of the masses of individual galaxies and of clusters of galaxies have told us about dark matter?
Dark matter is the dominant form of mass in both clusters and in individual galaxies
Which of the following statements about degeneracy pressure is not true?
Degeneracy pressure can arise only from interactions among electrons.
The circular but relatively flat portion of the galaxy is the________.
Disk
Which of the following statements about the disk of the Milky Way is false?
Disk stars are all younger than 5 billion years.
What is the Hubble flow?(24)
Distant galaxies are all moving away from us, with speed increasing with increasing distance.
Interstellar dust obscures our view of distant regions of space at optical wavelengths. Which of the following statements is true concerning this dust obscuration?
Distant regions are severely obscured only in the plane of the galaxy
Dr. Smith believes that the Hubble constant is H0 = 70 km/s/Mpc. Dr. Jones believes it is H0 = 50 km/s/Mpc. Which statement below automatically follows?
Dr. Smith believes that the universe is younger than Dr. Jones believes
According to the Big Bang theory, why do we live in a universe that is made of almost entirely of matter rather than antimatter?
During the first 0.001 second after the Big Bang, particles and antiparticles were made in almost but not perfectly equal numbers. Everything annihilated except the very slight excess of matter particles.
When were protons formed?
During the particle era
Why are infrared and radio telescopes the instruments of choice for studying the galactic center?
Dust in the plane of the Milky Way obscures observations at other wavelengths.
A spherical galaxy, like M 87, which looks like a monster globular cluster, is type...
E0
The flattest of ellipticals are class
E7
Why are fossils of early life on Earth more rare than fossils of plants and animals from the past few hundred million years?
Early organisms lacked skeletons and other hard structures that are most likely to be fossilized.
What is our modern worldview about the universe?
Earth is NOT at the center of the solar system, the sun is just an average star in a collection of 100 billion stars that we call the milky way, and the milky way is just one of billions and billions of galaxies in the universe?
Imagine that the Sun could be turned into a black hole without changing its mass. How would Earth's orbit change? Earth's orbit would change from elliptical to unbound. Earth's orbit would move farther from the Sun. Earth would be sucked into the black hole. Earth's orbit would not change.
Earth's orbit would not change.
The astronomer who orginally classified galaxies into Spiral, Elliptical, and Irregular
Edwin Hubble
Who developed our current galaxy classification scheme?
Edwin Hubble
Which force causes an electron to orbit around a proton?
Electromagnetic
Which of the following best describes why a white dwarf cannot have a mass greater than the 1.4-solar-mass limit?
Electron degeneracy pressure depends on the speeds of electrons, which approach the speed of light as a white dwarf's mass approaches the 1.4-solar-mass limit.
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.
Which of the following types of galaxies has experienced no significant star formation during the last 10 billion years?
Elliptical
Which type of galaxy exhibits the largest range of sizes and masses?
Elliptical
In Hubble's classification, which type of galaxy has no stellar disk, no gas, and no dust?
Elliptical (E0)
Astronomers suspect that a galaxy's type can be affected both by the conditions in the protogalactic cloud from which it forms ("initial conditions") and by later interactions with other galaxies. Each item below describes either a condition in a protogalactic cloud or a later interaction. Match these items to the galaxy type you would expect to form as a result.
Elliptical Galaxy protogalactic cloud has high density, stars form rapidly as the protogalactic cloud shrinks, protogalactic cloud rotates very slowly, a galaxy collision strips away gas Spiral galaxy protogalactic cloud has high angular momentum, most protogalactic gas settles into a disk
Which of the following statements about types of galaxies is not true?
Elliptical galaxies are bluer and contain more dust than spiral galaxies.
What evidence supports the theory that elliptical galaxies come from denser clouds?
Elliptical galaxies at high redshifts lack young, blue stars.
It is more difficult to determine the total amount of dark matter in an elliptical galaxy than in a spiral galaxy. Why?
Elliptical galaxies lack the atomic hydrogen gas that we use to determine orbital speeds at great distances from the centers of spiral galaxies.
Although we know less about dark matter in elliptical galaxies than we do in spiral galaxies, what does current evidence suggest?
Elliptical galaxies probably contain a similar proportion of their mass in the form of dark matter as do spiral galaxies
Addition to Mars, which jovian moon shows promise of life, with a surface not that different from the Arctic ocean?
Europa
Why are there no nearby (and thus "young") quasars?(25)
Eventually, most of the accretion disk falls into the black hole and the "central engine" runs out of fuel.
Why is the era of nucleosynthesis so important in determining the chemical composition of the universe?
Except for the small amount of matter produced later by stars, the chemical composition of the universe is the same now as at the end of the era of nucleosynthesis.
What kind of variable stars would be classified as a RR Lyrae?
F giant with a period of 14 hours
How is the cosmic microwave backward now compared to when it was first released?
Fainter and has most of its photons at longer wavelengths
True or False: All heavy elements are made during supernova events.
False
True or False: Collisions between galaxies are rare and have little or no effect on the stars and interstellar gas in the galaxies involved
False
True or False: Compared to the spirals, elliptical galaxies tend to be more dusty.
False
True or False: Current measurements of the density of the universe support the prediction of the theory of inflation that the universe should be flat.
False
True or False: Dark matter is purely hypothetical, because we have no way of detecting its presence.
False
True or False: Globular clusters trace out the large-scale structure of the Galactic disk.
False
True or False: If they exist, MACHOs are expected to be found only in the disk of the Milky Way, whereas WIMPs would be found only in the halo.
False
True or False: If we learn that the universe is a recollapsing universe, it will mean that the universe is presently contracting, rather than expanding as generally believed.
False
True or False: In the cosmological principle, we can easily test cosmic homogeneity with the red shift surveys, but isotropy cannot be so tested.
False
True or False: Individual galaxies generally have higher mass-to-light ratios than clusters of galaxies.
False
True or False: Irregulars typically have very few blue stars.
False
True or False: Like our solar system, the whole Milky Way is about five billion years old
False
True or False: Most Galaxies are spirals like the Milky Way
False
True or False: Most elliptical galaxies contain only young stars.
False
True or False: Most galaxies are spirals like the Milky Way.
False
True or False: Most of the current star formation in the Milky Way occurs in the bulge.
False
True or False: On average, elliptical galaxies are richer star forming regions than spirals.
False
True or False: One possible ingredient of dark matter is known as WIMPs, or weakly interacting massive particles. WIMPs probably are made of protons and neutrons.
False
True or False: Population I stars came billions of years before Population II stars
False
True or False: Population I stars came billions of years before Population II stars.
False
True or False: Quasars radiate most of their energy as radio emission.
False
True or False: The Big Bang predicts that one in four atoms in the universe is helium.
False
True or False: The Galactic halo contains about as much gas and dust as the Galactic disk
False
True or False: The Galactic halo contains as much gas and dust as the disk.
False
True or False: The Planck era is another name for the present period of time in the universe.
False
True or False: The bright blue stars of Orion's Belt are Population I, while our Yellow Sun is population II
False
True or False: The fact that the sky is dark at night shows that the observable universe must be infinite in all directions.
False
True or False: The only possible geometry of an accelerating universe is open
False
True or False: The theory that inflation occurred in the early universe is incompatible with the theory of relativity.
False
True or False: The visible parts of galaxies contribute about one-tenth of the critical density of the universe.
False
Why does faster rotation tend to lead to a spiral galaxy, rather than an elliptical galaxy?
Faster rotation leads to collisions among gas particles that cause the gas to settle into a spinning disk, rather than a more spread out cloud.
What kind of universe represents the critical point were the universe never collapses on itself
Flat Universe
The Viking lander experiments that chemically searched for life on Mars could not have detected which of the following? Seeds Living organisms Fossils Spores
Fossils
Electroweak era.
GUT splits, there are three forces: gravity, strong, electroweak. Elementary particles appeared spontaneously from energy but also transformed rapidly back into energy.
The collective activity of many supernovae events in a relatively small galaxy can create ____?
Galactic winds
What does the universe look like on very large scales?
Galaxies appear to be distributed in chains and sheets that surround great voids
What is the criterion for a group of galaxies to be considered a cluster?
Galaxies in a cluster are bound together by their mutual gravitational pull.
Which of the following statements about rich clusters of galaxies (those with thousands of galaxies) is not true?
Galaxies in the central regions are predominantly spirals, while elliptical galaxies roam the outskirts.
Why should galaxy collisions have been more common in the past than they are today?
Galaxies were closer together in the past because the universe was smaller.
Spectral lines from Galaxy B are redshifted from their rest wavelengths twice as much as the spectral lines from Galaxy A. According to Hubble's law, what can you say about their approximate relative distances?
Galaxy B is twice as far as Galaxy A
Spectral lines from Galaxy B are twice as redshifted as spectral lines from galaxy A. What can you say about their distances?
Galaxy B is twice as far as galaxy A
Which of the following is not a strong argument for the theory that some large elliptical galaxies formed as the result of galaxy collisions?
Galaxy collisions are common and most galaxies in the universe are elliptical
The observed relationship between the masses of central black holes and the bulge masses of galaxies implies that:
Galaxy formation and supermassive black hole formation must be related somehow.
A galaxy cannot have a disk if it does not have what?
Gas
Key differences between the disk and the halo?
Gas and dust are abundant in the disk but not in the halo. Disk stars come in a broad range of masses and colors, while halo stars are mostly of low mass and red. Clusters of young stars are found only in the disk. Stars in the disk all orbit in the same direction and nearly the same plane, while halo stars have more randomly oriented orbits.
What do we mean when we say that the rotation curve for a spiral galaxy is "flat"?
Gas clouds orbiting far from the galactic center have approximately the same orbital speed as gas clouds located further inward.
Which of the following statements is not an assumption used in models of galaxy formation?
Gas contracted to form the disks of galaxies before any stars were born.
If you could watch a time-lapse movie of the interstellar medium over hundreds of millions of years, what would you see?
Gas that is often moving at high speed, particularly after one or more supernovae, and constantly changing form between molecular clouds, atomic hydrogen, and hot, ionized bubbles and superbubbles.
Name a place where anti-protons are made today
Geneva, Switzerland at the CERN. Machine called the Large Hadron Collider
A tightly packed group of a few hundred thousand very old stars is a _________.
Globular cluster
Many millisecond pulsars lie within
Globular clusters
predicts that the strong, weak, and electromagnetic forces should become indistinguishable at high temperatures
Grand Unified Theory
Assuming that the bright core of M 87 is powered by a supermassive black hole, which of the following best describes the source of energy that makes the core appear so bright?
Gravitational potential energy is converted to thermal energy as matter from the surrounding gas disk spirals into the central black hole.
Which force causes galaxies in the Coma Cluster to orbit?
Gravity
What is the effect of dark matter on the formation of the structure of galaxies and clusters of galaxies?
Gravity of dark matter is what caused protogalactic clouds to contract early in time
Name the four forces of nature
Gravity, Electromagnetic, the Strong Force, the Weak Force
What are the main constituents of giant molecular clouds, the birthplace of stars?
H and He
Which of the following molecules is the most abundant in molecular clouds?
H2
The first portion of the galaxy to form was the __________.
Halo
Which of the following statements about halo stars is false?
Halo stars are made entirely of hydrogen and helium with no heavy elements
Harlow Shapley determined the position of the Sun in the galaxy by measuring the distances to 93 globular clusters of stars. How did Shapley obtain the distances to these very distant clusters?
He measured the apparent brightness and pulsation periods of RR Lyrae stars in the clusters
What was produced in nucleosynthesis era?
Helium, lithium, deuterium.
Which type of star is common in the spiral arms of our Galaxy, and found almost nowhere else?
High-mass O and B stars
What do the laws of thermal radiation tell us about objects and their wavelength?
Hotter objects emit light with shorter wavelengths (higher energy)
In the present theory of the Big Bang in the universe, what significant event occurred at about 380,000 years after the start of the Big Bang?(26)
How does the measured mass density of matter in the universe, including the hypothesized dark matter, compare to the critical density required to just close the universe?
What is currently the best way to estimate the age of the universe?
Hubble's Constant
Quasars usually have their distances measured by what technique?
Hubble's Law
What discovery ended "The Great Debate"?
Hubble's calculation of the distance to Andromeda using Cepheid variable stars.
Name the first 8 elements? How many protons in each nucleus?
Hydrogen 1, Helium 2, Lithium 3, Beryllium 4, Boron 5, Carbon 6, Nitrogen 7, Oxygen 8
Which of the following gives the two main assumptions of theoretical models of galaxy evolution?
Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others.
What is the critical density of matter needed to cause the universe to eventually collapse?
If it is greater than the square of the Hubble Constant
What evidence tells us that quasars are the centers of distant galaxies?
Images and spectra show quasars to be embedded at the centers of distant galaxies.
Which statement concerning black hole masses and Schwarzschild radii is not true?
In a binary system with a black hole, the Schwarzschild radius depends on the distance from the black hole to the companion star.
In what sense are the quasars "quasi-stellar"?
In short time exposures, their images looked stellar
a dramatic expansion of the universe thought to have occured when the universe was only a tiny fraction of a second old
Inflation
How does the idea of inflation account for the existence of the "seeds" of density from which galaxies and other large structures formed?
Inflation would have caused random, microscopic quantum fluctuations to grow so large in size that they became the seeds of structure.
Telescopes designed to study the earliest stages in galactic lives should be optimized for observations in ______.
Infrared light
Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei or powered by accretion disks around massive black holes?
Infrared observations show that many stars are forming near the centers of active galaxies
The sequence of photos in the Interactive Figure consists of infrared and radio images. Why doesn't the sequence include any visible-light images?
Interstellar dust in the galactic disk prevents us from seeing the galactic center with visible light.
Large and small Magellanic Clouds fall into Hubble's Class
Irr I
According to observations, what type of galaxy was much more common when the universe was 2 billion years old than it is today?
Irregular galaxies.
When we say that a cluster of galaxies is acting as a gravitational lens, what do we mean?
It bends or distorts the light coming from galaxies located behind it.
What is the likely final fate of a star that has a mass of 15 solar masses after completing its nuclear fusion burning phases?
It collapses and becomes a black hole.
What is the distinguishing characteristic of what we call ordinary or baryonic matter?
It consists of atoms or ions with nuclei made from protons and neutrons
Which of the following is not an observed characteristic of the cosmic microwave background?
It contains prominent spectral lines of hydrogen, the primary chemical ingredient of the universe.
How do we explain Hubble's constant?
It describes the expansion rate of the universe, with higher values meaning more rapid expansion
Based on what you have learned, which of the following best describes the meaning of Hubble's constant ( )?
It describes the expansion rate of the universe, with higher values meaning more rapid expansion.
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.
Why do we call dark matter "dark"?
It emits no or very little radiation of any wavelength.
Why do we call dark matter "dark"?
It emits no radiation that we have been able to detect.
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.
What do we mean when we say that a particle is a weakly interacting particle?
It interacts only through the weak force and the force of gravity.
Which of the following best summarizes what we mean by dark energy?
It is a name given to whatever is causing the expansion of the universe to accelerate with time.
What is actually happening to the expansion of the universe?
It is accelerating
Which of the following statements is not true of the object known as Sgr A* in the center of our Galaxy?
It is by far the brightest source of visible light lying in the direction of the galactic center.
Is the universe hotter or cooler since the Big Bang?
It is cooler
Which of the following best describes the milky way among the local group of galaxies?
It is one of the two largest galaxies
Which of the following best describes the status of the Milky Way in our Local Group of galaxies?
It is one of the two largest galaxies in the group.
Most nearby stars move relative to the Sun at speeds below about 30 km/s. Suppose you observe a nearby star that is moving much faster than this (say 300 km/s). Which of the following is a likely explanation for its high speed?
It is probably a halo star that is currently passing through the disk.
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 do we mean by the star-gas-star cycle?
It is the continuous recycling of gas in the galactic disk between stars and the interstellar medium
Which of the following best describes natural selection?
It is the idea that organisms with genetic traits that improve their ability to reproduce are more likely to pass those traits on to future generations.
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.
Which of the following statements about the cosmic background radiation is not true?
It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
Which statement about the cosmic microwave background is not true?
It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
How does the interstellar medium affect our view of most of the galaxy?
It prevents us from seeing most of the galactic disk with visible and ultraviolet light
The present universe seems to require a "cosmological constant" equivalent to that introduced into general relativity by Einstein when his theory would not explain the expected static universe. What is the effect on the evolution of the present universe of the "new" cosmological constant?(26)
It produces a pressure to oppose the mutual gravitational pull of all the matter in the universe, accelerating its expansion.
How would you expect a star that formed recently in the disk of the galaxy to differ from one that formed early in the history of the disk?
It should have a higher fraction of elements heavier than hydrogen and helium.
What effect does a spiral density wave have on the material it encounters?
It slows the material down, causing it to compress and heat up, assisting gravity in forming stars.
Why did the particle era end?
It was no longer hot enough to spontaneously create protons and antiprotons.
How did oxygen (O2) get into Earth's atmosphere?
It was released by life through the process of photosynthesis.
What is the likely fate of our Milky Way within about the next 6-8 billion years?(24)
It will collide with the Andromeda Galaxy, triggering new star birth in gas and dust clouds.
Suppose that we suddenly discovered that all these years we'd been wrong about the distance from Earth to the Sun, and it is actually 10% greater than we'd thought. How would that affect our estimate of the distance to the Andromeda Galaxy?
It would mean the distance to the Andromeda Galaxy is also 10% greater than we thought.
Which of the following places is not generally considered a potential home for life in our solar system?
Jupiter's atmosphere
What temperature has the Big Bang cooled to by now?
Just over 2.7K
Pre-galactic blobs had masses similar to...
Large Magellanic clouds
What fraction of the mass needed to halt expansion is known to exist in the form of visible mass in the universe?
Less than 1 %
During the history of the universe, what event occurred 380,000 years after the Big Bang?
Light began to travel freely through the universe
During the history of the universe, what important event occurred about 380,000 years after the Big Bang
Light began to travel freely through the universe.
an object the size of earth located in the halo of our galaxy would be an example of the form of dark matter known as _____
MACHOS
the formed meteorite with carbonate rocks and possible microfossils came from...
Mars
Most important property in how a star will evolve and die?
Mass
A nova includes...
Mass transfer into a white dwarf in a binary system
What is not a main source of evidence for the existence of dark matter?
Massive blue stars
Astronomers have concluded that Sgr A* is actually a very small but extremely massive object, which is presumed to be a massive black hole. What additional observations or measurements (not shown in this sequence) must have been made for astronomers to reach this conclusion?
Measurements of the orbital speeds and distances of gas clouds and stars around Sgr A*.
Which of the following methods used to determine the mass of a cluster does not depend on Newtons's laws of gravity?
Measuring the amount of distortion caused by a gravitational lens
Which of the following is NOT one of the three main strategies used to measure the masses of galaxy clusters?
Measuring the temperatures of stars in the halos of the galaxies
Which of the following best sums up current scientific thinking about the nature of dark matter?
Most dark matter probably consists of weakly interacting particles of a type that we have not yet identified.
During the history of the universe, what important event occurred about 0.001 seconds after the Big Bang?
Most matter in the early universe was annihilated by antimatter
What important event occurred about 0.001 seconds after the Big Bang?
Most matter in the early universe was annihilated by antimatter
What conclusions can be drawn about the nature of the galaxy cluster's mass? (more than one)
Most of the cluster's mass cannot be seen as visible matter, The mass of the dark matter accounts for more of the gravitational force within the cluster than does the mass of the visible matter.
Which of the following statements comparing halo stars to our Sun is not true?
Most stars in the halo have either died or are in their final stages of life, while the Sun is only in about the middle of its lifetime.
do all galaxies obey hubbles law perfectly?
NO. Besides this recessional velocity due to the expansion of the Universe, galaxies have their own motions due to mutual gravitational attraction. Some galaxies are even merging like the pair below.
Most of the energy of the supernova is carried outward via a flood of...
Neutrinos
Why can't the dark matter in galaxies be made of neutrinos?
Neutrinos travel at extremely high speeds and can escape a galaxy's gravitational pull.
some examples of which type of dying star exhibit rapid pulses that were originally suspected to be communications from extraterrestrials?
Neutron Star
Which law is used in the calculation of the combined galaxy masses of a binary galaxy system? Hubble's law Wien's law Newton's form of Kepler's third law Newton's first law
Newton's form of Kepler's third law
Does Hubble's law work well for galaxies within the local group? Why or why not?
No because galaxies in the local group are gravitationally bound together
Does Hubble's law work well for galaxies in the Local Group? Why or why not?
No, because galaxies in the Local Group are gravitationally bound together
Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?
No, because it is not orbited by another star.
Is space expanding within clusters of galaxies?
No, because their gravity is strong enough to hold them together even while the universe as a whole expands.
A cluster of galaxies is held together by the mutual gravitational attraction of all the stars in the cluster's galaxies.
No, the amount of mass in a cluster's stars is much lower than the amount needed to hold the cluster together.
Do astronomers expect to find planets around binary stars that are stable enough for life to develop? Why? No. Planets won't form at all in binary systems. No. Planets may form in binary systems, but their orbits won't be stable. Yes. It is possible for a planet stable enough for life to develop to form a stable orbit in a binary system. No. Planets may form stable orbits in binary systems, but the conditions on them won't be conducive to developing life.
No. Planets may form stable orbits in binary systems, but the conditions on them won't be conducive to developing life.
Are there equal amounts of matter and anti-matter on earth today?
No. There is way more matter
Imagine that our Sun were magically and suddenly replaced by a black hole of the same mass (1 solar mass). What would happen to Earth in its orbit?
Nothing - Earth's orbit would remain the same.
If the Andromeda Galaxy collided with the Milky Way, what would most likely happen to Earth?
Nothing.
Galactic Disks appear blue because of
O and B blue giants are much brighter than G, K, or M dwarfs
how do observations of distant galaxies help us learn about galaxy evolution?
Observations at different distances show galazies of different ages and therefore different stages of evolution.
What is the primary form of evidence that has led astronomers to conclude that the expansion of the universe is accelerating?
Observations of white dwarf supernovae
Dark energy has been hypothesized to exist in order to explain what?
Observations suggesting that the expansion of the universe is accelerating
BLANK forces us to think about why the sky is dark at night.
Olbar's Paradox
forces us to think about why the sky is dark at night
Olbers paradox
The darkness of the night sky in an infinite universe is addressed in
Olbers's paradox
Is an older era larger or smaller than a new era?
Older eras are smaller
Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case?
Only Mercury would be in the Sun's habitable zone.
Did the Big Bang produces elements heavier than helium?
Only trace amounts of lithium
Stars in the outermost regions of the Milky Way Galaxy
Orbit faster than astronomers would expect on the basis of the Galactic mass we can see.
The flat part of the Milky Way's rotation curve tells us that stars in the outskirts of the galaxy do what?
Orbit the galactic center just as fast as stars closer to the center
Which best described the best possible scenario for the formation of our Galaxy?
Our Galaxy began as a number of "dwarf galaxies," which merged under the influence of gravity to form our Galaxy
If there is no dark matter in the Milky Way Galaxy, what is the best alternative explanation for the observations?
Our understanding of gravity is not correct for galaxy-size scales.
Why do we find a larger percentage of spiral galaxies in distant clusters compared to nearby clusters?(24)
Over time, galactic collisions and mergers have destroyed many of the spiral arms which give spirals their distinctive appearance.
According to current science, why didn't oxygen begin to accumulate in the atmosphere for more than a billion years after life appeared on the Earth?
Oxygen was removed from the atmosphere by chemical reactions with surface rocks as quickly as it was released by life.
If the circumference of the earth were increasing, which city would be moving away from Oxford the most rapidly?
Paris, France
What direct evidence do we have that the weak and electromagnetic forces were once unified as a single electroweak force?
Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory.
What was the effect of the intense heat of the Big Bang in the first FEW SECONDS?
Particle creation and annihilation - energy turned from matter to energy freely by antimatter pairs.
the first probe carrying mankind's message to alien civilizations was...
Pioneer 10
List the 7 eras of formation after the Big Bang.
Planck era, GUT, electroweak, particle era, era of nucleosynthesis, era of nuclei, era of atoms, era of the galaxies.
Which of the following statements cannot be tested by science today?
Prior to the Planck time, our universe sprouted from another universe.
Which particle has the largest mass? Smallest Mass? a. Photon b. Electron c. Proton
Proton, Photon (massless)
Which of the following particles are baryons?
Protons
About 25% of hydrogen produced in the Big Bang was urned into helium. Why wasn't more of the hydrogen fused into Helium?
Protons outnumbered neutrons 7 to 1. After the era of nucleosynthesis the predicted hydrogen-to-helium mass ratio is 12 to 4 (75% to 25%)
Each Voyager spacecraft carries a "postcard" designed to be understandable to any aliens that might someday encounter it. On the "postcard," scientists pinpointed the location of Earth by triangulating it between pulsars. Why did the scientists choose pulsars rather than some other type of star?
Pulsars are easy to identify by their almost perfectly steady periods of pulsation.
Which statement about pulsars is not thought to be true?
Pulsars can form only in close binary systems.
Why do we think tiny quantum ripples should have been present in the very early universe?
Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle.
Which of the following is NOT a way that we detect the existence of dark matter?
Quasar accretion dynamics
The most luminous objects in the universe are ____?
Quasars
Which of the following is not true of quasars?
Quasars are powered by the intense production of large numbers of stars that can only be sustained for a relatively short time
For finding the distances to globular clusters, Harlow Shapley used
RR Lyrae variables
Location of the galactic center was first found by Harlow Shapley using
RR lyrae variables in globular clusters
BLANK are often characterized by sources of immense energy located hundreds of thousands of light years away on either side of their centers.
Radio galaxies
Which of the following has spent the longest time traveling in space before reaching the earth today?
Radio signals from a quasar
Is it easier to send a radio transmission or a spaceship to a nearby star?
Radio transmission
Why does rapid star formation tend to lead to an elliptical galaxy, rather than a spiral galaxy?
Rapid star formation means that there may not be enough gas left to make a disk
what formed when the universe became transparent to light?
Recombination: The First light of the Universe. AKA Cosmic Microwave Background Radiation
Which of the following observations is not a piece of evidence supporting the Big Bang theory.
Relative motions of galaxies in the Local Group.
Why are collisions between galaxies more likely than collisions between stars within a galaxy?
Relative to their sizes, galaxies are closer together than stars.
The BLANK of spiral galaxies provide strong evidence for the existence of dark matter.
Rotational curves
Which type of galaxy has a stellar disk, but without gas and dust?
S0 (Spiral Galaxy)
An intermediary wound barred spiral galaxy would, in Hubble's system, be...
SBb
Hubble's classification, which type of galaxy has a small bulge and loose, widely spread, poorly defined spiral pattern
Sc
Which of the following is not one of Hubble's types of galaxies?
Seyfert spirals
Observationally, the biggest difference between quasars and other active galaxies such as Seyferts and radio galaxies appears to be that (25)
Seyferts and radio galaxies are less powerful than quasars.
How are planets in orbit around nearby stars detected?
Shift in spectrum, change in position in the sky, bending of light from background stars by the gravitational field of intervening stars
Why do we expect WIMPs to be distributed throughout galactic halos, rather then settled into a disk?
Since they do not interact with the electromagnetic force, they do not feel friction or drag and hence do not contract with the rest of the protogalactic cloud
What is an important starting assumption in most models for galaxy formation?
Some regions in the universe start out denser than others.
Which of the following is an important starting assumption in models of galaxy formation?
Some regions in the universe start out denser than others.
Why are the absorption lines of elliptical galaxies wide?
Some stars in them are going away from us, some toward us, so we get red and blueshifts -which make lines wider
According to general relativity, why does the Earth orbit the Sun?
Space around the Sun is curved and the Earth follow this curved space
What important event occurred earliest in the history of the universe
Space time rapidly expanded during a brief period of inflation
What was the first important event to occur in the history of the universe?
Spacetime rapidly expanded during a brief period of inflation
Which of the following important events occurred earliest in the history of the universe? Light began to travel freely through the universe. Spacetime rapidly expanded during a brief period of inflation. Spacetime expansion increased the average distance between galaxies. The first massive supernovae explosions occurred.
Spacetime rapidly expanded during a brief period of inflation
Imagine that the Sun gained mass without changing its radius. How would the structure of spacetime change at the distance of Earth's orbit? The structure of spacetime would stay the same. Spacetime would become more curved at Earth's orbit. Spacetime would become flatter (less curved) at Earth's orbit. A black hole would engulf the Earth.
Spacetime would become more curved at Earth's orbit.
A galaxy containing substantial amounts of dark matter will
Spin faster
Most of the observable galaxies are of the type represented by picture
Spiral
Our milky way galaxy is a ___________.
Spiral Galaxy
You see a spiral galaxy with a large central bulge and tightly wrapped arms. It would be a...
Spiral galaxy (Sa)
What are Type I supernovae used for?
Standard candles for determining distances to other galaxies
Which galaxies have the highest star formation rate?
Starburst galaxies
Study all of the individual images and the Multi image that combines all of them. Which of the following statements provides the best interpretation of what we see in the Multi image?
Stars in the central region of this galaxy are exploding as supernovae, generating a galactic wind of hot gas and warm dust gains.
Which of the following statements correctly summarize key differences between the disk and the halo?
Stars in the disk all orbit in the same direction and nearly the same plane, while halo stars have more randomly oriented orbits. Gas and dust are abundant in the disk but not in the halo. Clusters of young stars are found only in the disk. Disk stars come in a broad range of masses and colors, while halo stars are mostly of low mass and red.
Which statement concerning the orbital motions of stars in spiral galaxies is most correct?
Stars in the disk orbit the center in mainly the same direction, while stars in the bulge can orbit in any direction and orientation.
How do we know that there is much more mass in the halo of our galaxy than in the disk?
Stars in the outskirts of the Milky Way orbit the galaxy at much higher speeds than we would expect if all the mass were concentrated in the disk.
If we could watch spiral arms from a telescope situated above the Milky Way over 500 million years, what would we see happen?
Stars will move through the spiral arms, bunching up closer as they pass through. Young hot stars will form and die within the arms before having a chance to move out.
Which force prevents all the positively charged protons in an iron nucleus from tearing it apart?
Strong
What binds nuclei together?
Strong force.
What is a likely candidate for the majority of the dark matter in galaxies?
Subatomic particles that we have not yet detected
Why do we believe that starburst galaxies represent a temporary stage in galaxy evolution?
Such galaxies produce so much light that they would have consumed all their gas long ago if they had always been forming stars at this high rate.
You observe the peak brightnesses of two white dwarf supernovae. Supernova A is only ¼ as bright as Supernova B. What can you say about their relative distances?
Supernova A is twice as far away as Supernova B.
Which of the following is not true about differences between novae and supernovae?
Supernovae eject gas into space but novae do not.
What is the best way to determine a galaxy's redshift?
Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory
Suppose a scientist holds a press conference at which he claims 10% of the matter in the Milky Way is in the form of dust grains. Does his claim seem reasonable? Why or why not?
The 10% figure is too high because there are not enough heavy elements to make that much dust.
In structure, our milky way is most similar to
The Andromeda Galaxy
What is the origin of most helium found in our solar system today?
The Big Bang
What is the relationship between neutron stars and the Chandrasekhar Limit?
The Chandrasekhar Limit applies only to systems stabilized by degenerate electrons. Neutron stars are stabilized by the pressure of the neutron degeneracy.
Clicker Question: We take a spectrum of a galaxy that is 10 Mly away from us. We measure its redshift, z, and compute the recession velocity: v = c z. In agreement with Hubble's law, we find it is 220 km/s. An alien in this distant galaxy takes a spectrum of the Milky Way. What does he observe?
The MW will appear moving away from the alien's galaxy with a speed of 220 km/sec, because the expansion of the universe looks the same from the vantage point of any galaxy
If all the "dark matter" in the Universe were to be, somehow, instantaneously removed, which of the following would not happen?
The Solar System would fly apart
Observe a source of X rays that varies substantially in brightness over a period of a few days. What can we conclude
The X-ray source is no more than a few light-days in diameter.
How does an accretion disk around a neutron star differ from an accretion disk around a white dwarf?
The accretion disk around a neutron star is much hotter and emits higher-energy radiation.
Based on current evidence, how does the actual average density of matter in the universe compare to the critical density?
The actual density, even with dark matter included, is less than about a third of the critical density.
What do we mean by the critical density of the universe?
The average density the universe would need in order for its gravity to ultimately win out over the current rate of expansion (if it weren't accelerating)
Why does the Big Bang theory predict that the cosmic background radiation should have a perfect thermal radiation spectrum?
The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe.
The cosmic microwave background radiation is not uniform over the sky—it is slightly hotter toward the constellation Leo and slightly cooler in the opposite direction, toward Aquarius. Why?(26)
The background radiation really is uniform; the observed difference is due to Earth's motion through the universe
What was the significance of the end of the era of nucleosynthesis, when the universe was about 5 minutes old?
The basic chemical composition of the universe had been determined.
What are the slight fluctuations seen in maps of the cosmic background radiation?
The beginning of the formation of galaxies and clusters of galaxies
The third image in the interactive photo (with the most detailed view of the galactic center) is labeled "gas disk." Which of the following best describes what we are seeing in this photo?
The black hole is located deep within the bright central region, and around this region we see gas that is orbiting the central black hole.
A clock is moving across your line of sight with its face turned toward you. Each of the following statement about this clock, as seen by you, is true except one. Which statement is incorrect?
The clock will appear thinner, front to back, than it would if it were at rest
A clock is moving across your line of sight with its face turned toward you. Each of the following statement about this clock, as seen by you, is true
The clock will run slow compared to a clock in your hand, The clock will appear shorter than it would if it were at rest, The clock will appear more dense than it would if it were at rest
What happens when a particle of matter meets its corresponding antiparticle of antimatter?
The combined mass of the two particles is completely transformed into energy (photons).
Evidence that the cosmic background radiation really is the remnant of a Big Bang comes from predicting characteristics of remnant radiation from the Big Bang and comparing these predictions with observations. Four of the five statements below are real. Which one is fictitious?
The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does.
What condition is necessary for the universe to be unbounded (infinite in extent)?(26)
The density of the universe must be equal to or less than some critical value.
Which of the following is NOT evidence in favor of the Big Bang theory?
The detection of supermassive black holes in the centers of most galaxies
How does the diameter of the disk of Milky Way Galaxy compare to its thickness?
The diameter is about 100 times as great as the thickness.
The Big Bang Theory seems to explain how elements were formed during the first few minutes after the Big Bang. Which hypothetical observation below would call our current theory into question?
The discovery of a galaxy with a helium abundance of only 10% by mass
What did the existence of cosmic microwave background indicate?
The end era of the nuclei in which electrons were stable and integrated into atoms, and no longer blocked light.
Where do the photons in the cosmic background radiation originate?
The end of the era of nuclei
Gamma ray bursters are great distances from us, yet we receive tremendous amounts of energy from them. What accounts for this?
The energy is released along jets rather than uniformly in all directions. If Earth is in the path of one of these jets we see a gamma ray burster.
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 home town?
The entire Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star.
Which of the following statements about gamma ray bursts is not true?
The events responsible for gamma ray bursts apparently produce only gamma rays, and no other light that we can hope to detect.
What is chemical evolution? The evolution of biologically important chemicals from nonbiological chemicals The process by which certain chemicals move through the environment, changing as they do so The evolution of the minerals of the land and material in the sea and air The process by which exposure to chemicals mutates or evolves life-forms on Earth
The evolution of biologically important chemicals from nonbiological chemicals
What are two main pieces of evidence for the Big Bang?
The existence of cosmic microwave background predicted to be emitted from the end era of the nuclei and the percentage of hydrogen and helium.
Which of the following is not evidence for dark matter?
The expansion of the universe
Evidence from distant supernovae (as well as from studies of the cosmic microwave background) suggests that the universe is doing something that goes against what nearly all astronomers expected just a decade ago. What is this phenomenon, which is variously attributed to things called dark energy, the cosmological constant, or quintessence?
The expansion of the universe seems to be getting even faster.
Hubble's constant is related to the age of the universe, but the precise relationship depends on the way in which the expansion rate changes with time. For a given value of Hubble's constant today (such as 24 km/s/Mly), the age of the universe is oldest if what is true?
The expansion rate has been increasing with time (an accelerating universe).
Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why?
The expected lifetime of a massive star is too short to allow for the evolution of complex life
Interactions among galaxies also are thought to influence a galaxy's type in at least some cases. Which of the following does not support the idea that interactions can shape galaxies?
The fact that more distant galaxies have larger redshifts.
Which of the following phenomena are NOT thought to be results of collisions or other interactions between galaxies?
The fact that spiral galaxies have both disk and halo components
We can study how galaxies evolve because ______.
The farther away we look, the further back in time we see
Which statement below correctly describes the relationship between expansion rate and age for the universe?
The faster the rate of expansion, the younger the age of the universe.
Imagine that it turns out that dark matter (not dark energy) is made up of an unstable form of matter that decays into photons or other forms of energy about 50 billion years from now. Based on current understanding, how would that affect the universe at that time?
The galaxies in clusters would begin to fly apart.
What did astronomers expect might cause the expansion of the universe to slow down?
The gravitational pull of all the matter in it
Hubble's Law states that
The greater the distance to a galaxy, the greater the galaxy's redshift.
Which is the oldest component of the Galaxy?
The halo
Which of the following is NOT a difference between the disk and the halo of the Galaxy?
The halo population stars are primarily red in color, and there are no red stars in the disk.
Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy?
The higher gas density forms stars more efficiently so all the gas is converted into stars before a disk can form.
What are the typical features seen in quasar absorption lines of intergalactic clouds?
The hydrogen line is wider and lines from heavy elements are weaker at higher redshifts
When we use an analogy that represents the expanding universe with the surface of an expanding balloon, what does the inside of the balloon represent?
The inside of the balloon does not represent any part of our universe.
Which of the following phenomena is probably NOT related to the presence of a supermassive black hole?
The large sizes of central dominant galaxies
What law of nature explains why the galaxy began to rotate rapidly as it shrunk in size?
The law of conservation of angular momentum.
Why don't we expect to find life on planets orbiting high-mass stars?
The lifetime of a high-mass star is too short.
As currently understood, what happens to the density of matter and the density of dark energy as the universe expands?(26)
The matter density decreases, but the density of dark energy remains constant.
How does the measured mass density of matter in the universe, including the hypothesized dark matter, compare to the critical density required to just close the universe?(26)
The measured density is between 0.2 and 0.4 of the critical density.
Recent measurements of the expansion rate of the universe is doing something astronomers did not expect. What is that?
The measurements show that the expansion is accelerating, rather than slowing under the influence of gravity
Some recent but still preliminary measurements of the expansion rate of the universe suggest a problem with our standard idea about how the universe should be expanding. What is the problem?
The measurements show that the expansion may actually be accelerating, rather than slowing under the influence of gravity.
Why wasn't the intracluster medium in galaxy clusters discovered until the 1960s?
The medium emits X-rays, which are blocked by the Earth's atmosphere and require X-ray satellites in space in order to be observed
What is Hubble's law?
The more distant a galaxy is from us, the higher its apparent recessional velocity.
What does Hubble's law tell us?
The more distant a galaxy, the faster it is moving away from us.
All of the following observations are real.Which one does NOT support the theory that active galactic nuclei are powered by accretion disks around massive black holes?
The most luminous active galactic nuclei have huge redshifts.
Using the method of standard candles, we can, in principal, find the distance to a campfire if we know.
The number of logs used
Which characteristic is not generally true of a starburst galaxy?
The observed features of the starburst are thought to be caused by the presence of a supermassive black hole in the galaxy's center.
If the era is older, is it hotter or cooler than a newer era?
The older the era, the hotter it is
Based on observations, which of the following statements about stars in the Milky Way Galaxy is generally true?
The older the star, the lower its abundance of heavy elements
Given that the universe is about 14 billion years old, which of the following statements is logically valid?
The oldest galaxies we see at great distances are younger then the oldest galaxies we see nearby.
Suppose that we look at a photograph of many galaxies. Assuming that all galaxies formed about the same time, which galaxy in the picture do we see when it was the youngest?
The one that is the most distant to us as given by its redshift
Why do we believe 90 percent of the mass of the Milky Way is in the form of dark matter?
The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo.
What evidence suggests that most of the mass of the Milky Way is in the form of dark matter?
The orbital speeds of stars far from the galactic center are surprisingly high.
Spiral galaxy rotation curves are generally fairly flat out to large distances. Suppose that spiral galaxies did notcontain dark matter. How would their rotation curves be different?
The orbital speeds would fall off sharply with increasing distance from the galactic center.
What is the best evidence for an extremely massive black hole in the center of the Milky Way?
The orbits of stars in the center of the galaxy indicate that the presence of 3 to 4 million solar mass object in a region no larger than our Solar System.
What do astronomers mean by the large-scale structure of the universe?
The overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe
What two properties of a Cepheid variable are directly related to one another?
The period between its peaks of brightness and its luminosity
What causes cosmological redshift of photons that reach us from distant galaxies?(26)
The photons have traveled across space that has been expanding and their wavelengths have expanded with it, becoming redder.
Which statement about accretion disks is not true?
The primary factor determining whether a white dwarf has an accretion disk is the white dwarf's mass.
What is the "stellar habitable zone"? The range in temperatures of a star around which a terrestrial planet with Earth's mass and density is expected to form.
The range of distances from a star in which an Earth-like planet could sustain liquid water.
The infrared image of M82 shows a whitish-blue region running down the center, along with a much larger red region. What is emitting the light that is shown in red and what is emitting the light that is shown in whitish-blue?
The red is emission from warm dust grains; the whitish-blue is emission from stars.
What is Cosmic Microwave Background Radiation
The remnant radiation from the Big Bang, which we detect using radio telescopes sensitive to microwaves.
What effect is thought to be due to the presence of dark matter around spiral galaxies?
The rotation rates of spiral galaxies and orbital interactions among galaxies within clusters suggest the presence of extra mass around them
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?(24)
The rotation speed should decrease smoothly with increasing distance from the center, following a Keplerian curve.
What did a major discovery made by Harlow Shapley using RR Lyrae stars and globular clusters establish?
The size of the Galaxy and the Sun's position in it
Which of the following models best explains why our galaxy has spiral arms?
The spiral arms are a wave of star formation caused by wave of density propagating outward through the disk of the galaxy.
Inflation.
The splitting of the GUT forces into electroweak forces which led to the rapid expansion of the universe.
Which of the following best compares the motion of stars in the halo to the motion of the stars in the disk of the Galaxy?
The stars in the halo move in randomly-oriented orbits, while the disk stars generally stay confined to moving in the disk.
How did star formation likely proceed in the protogalactic cloud that formed the Milky Way?
The stars that formed first could orbit the center of the galaxy in any direction at any inclination.
What two observations allow us to calculate the galaxy's mass?
The suns orbital velocity and its distance from the Galactic Center
Why does the temperature of the gas between galaxies in galaxy clusters tell us about the mass of the cluster?
The temperature tells us the average speeds of the gas particles, which are held in the cluster by gravity, so we can use these speeds to determine the cluster mass.
What is a Grand Unified Theory?
The theory that predicts the merger of electroweak and strong forces converts into a single strong force by which the Big Bang was immediately governed.
How should we expect the Milky Way's interstellar medium to be different in 50 billion years than it is today?
The total amount of gas will be much less than it is today.
What does inflation help explain?
The uniformity of the cosmic microwave background and the origin of galaxies
Which of the following statements correctly summarizes the events in the early universe according to the Big Bang theory?
The universe began with the forces unified. During the first fraction of a second, the forces separated and there was a brief but important episode of inflation. Subatomic particles of both matter and antimatter then began to appear from the energy present in the universe. Most of the particles annihilated to make photons, but some became protons, neutrons, electrons, and neutrinos. The protons and neutrons underwent some fusion during the first three minutes, thereby determining the basic chemical composition of the universe.
Why did the era of nuclei end when the universe was about 300,000 years old?
The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form.
Which of the following is not consistent with observations of the cosmic microwave background?
The universe is at least 20 billion years old
What can we imply from Hubble's Law?
The universe is expanding.
The idea of inflation makes one clear prediction that, until the discovery of an accelerating expansion, seemed to contradict the available observations. What is this prediction?
The universe should be geometrically "flat" (in the four dimensions of spacetime).
Why can nothing be seen from the beginning of the Big Bang?
The universe was not transparent to light.
What is the meaning of a "closed" universe?
The universe will someday stop expanding and begin collapsing inward
Suppose that a white dwarf is gaining mass through accretion in a binary system. What happens if the mass someday reaches the 1.4 solar mass limit?
The white dwarf will explode completely as a white dwarf supernova.
Suppose we observe a source of x-rays that varies substantially in brightness over a period of a few days. What can we conclude?
The x-ray source is no more than a few light days in diameter
Why isn't space expanding within systems such as our solar system or the Milky Way?
Their gravity is strong enough to hold them together against the expansion of the universe
When we see that a spectral line of galaxy is broadened, that is , spanning a range of wavelengths we conclude that gas
There are different Doppler shifts among the individual stars in the galaxy
How do we know that spheroidal stars are older, on average, than disk stars?
There are no blue spheroidal stars
Now zoom through the image sequence, looking carefully at each image. Which of the following are reasonable conclusions?
There are strong magnetic fields in the central region of the galaxy. Gas orbits the radio source called Sgr A*. Stars near the galactic center are much closer together than stars around our Sun.
Why do astronomers consider very long-wavelength, low-frequency radio waves not to be a good range to search for an extraterrestrial signal?
There are too many natural galactic sources that cause noise at these wavelengths.
Although most astronomers assume dark matter really exists, there is at least one other possible explanation for the phenomena attributed to dark matter. What is it?
There could be something wrong or incomplete with our understanding of how gravity operates on galaxy-size scales.
You've now found that the central object has a mass of about 3 million solar masses but is no more than about 70 in diameter—which means it cannot be much larger than the size of our planetary system. Why do these facts lead astronomers to conclude that the central object is a black hole?
There is no known way to pack so much mass into such a small volume without it collapsing into a black hole.
Why does the central bulge of a spiral galaxy appear red when compared to the color of the spiral arms? (24)
There is no star formation there, and the star population is dominated by old, long lived, low-mass red stars.
What do the (fast) speeds of stars in elliptical galaxies tell us?
There must be a lot of dark matter whose gravity can be felt but which isn't seen
Which of the following statements best explains what we mean when we say that the electroweak and strong forces "froze out" at 10-38 second after the Big Bang?
These two forces first became distinct at this time.
The idea of dark matter arose to explain gravitational effects observed in galaxies and clusters of galaxies. However, studies of the early universe (especially the cosmic microwave background and of chemical abundances) also tell us something about dark matter. What do they tell us?
They add further support to the idea that dark matter really exists and is made of non-ordinary (nonbaryonic) matter, such as WIMPs
How do disk stars orbit the center of the galaxy?
They all orbit in roughly the same plane and in the same direction.
What happens when matter and anti-matter meet?
They annihilate each other totally, transforming all their mass-energy back into photon energy. In order to conserve both energy and momentum, an annihilation reaction must produce two photons instead of just one.
If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?
They are far more technologically advanced than we are.
All of the following are true. Which of these gives evidence that quasars were more common in the early stages of the universe?
They are more common at very great distances.
By looking at the graph, what can we say about the galaxies that have the lowest speeds?
They are moving away from Earth and are closer to Earth than galaxies with high speeds
What is true about galaxies that are measured from earth with high speeds?
They are moving away from Earth and are farther from Earth than galaxies with lower speeds.
what can we say about the galaxies measured from earth at low speeds?
They are moving away from earth and are closer to earth than galaxies with high speeds.
What are X-ray bursters?
They are neutron stars on which accreted matter builds up, then explodes in a violent nuclear explosion.
Some MACHOs emit radiation. Why are they considered dark matter?
They are not as bright as a normal star and are not visible across great distances of space
Which of the following features is not a feature of central dominant galaxies?
They are often spiral galaxies
Given that white dwarf supernovae are such good standard candles, why don't we use them to measure the distance to all galaxies?
They are rare events, so we have observed them in only a tiny fraction of all galaxies.
Why are the ionization nebulae so bright?
They are regions where gas is ionized by hot, young stars
The irregular classification is in some ways a method of dealing with galaxies that are clearly not elliptical or spiral in shape. Select the properties associated with irregular galaxies.
They are typically smaller than spiral galaxies, they exhibit vigorous star-forming activity, some show evidence for prior collision or close encounter with another galaxy.
What happens when a proton collides with an antiproton?
They convert into two photons
Consider again the civilization described in the previous question. (They live on a planet orbiting 10 AU from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole surrounded by an accretion disk.) Through a bizarre (and scientifically unexplainable) fluctuation in the space-time continuum, a copy of a book from that civilization arrives on your desk; it is entitled Iguoonos: How We Evolved. In the first chapter, you learn that these beings evolved from organisms that lived 5 billion years ago. Which of the following statements should you expect to find as you continue to read this book?
They evolved on a different planet in a different star system, and moved to their current location.
Which of the following statements describes the orbits of stars within most elliptical galaxies?
They have random orbits in three dimensions.
What do we mean when we say that particles such as neutrinos or WIMPs are weakly interacting?
They interact with other matter via the weak force but do not interact with the electromagnetic force and hence cannot emit light.
Which of the following cannot be true of the very first stars formed in the Universe?
They may have had rocky planets around them.
What do halo stars do differently disk stars?
They orbit the galactic center with many different inclinations, while disk stars all orbit in nearly the same plane
What do we mean when we say that particles such as neutrinos or WIMPs are weakly interacting?
They respond to the weak force but not to the electromagnetic force, which means they cannot emit light.
If WIMPs really exist and make up most of the dark matter in galaxies, which of the following is not one of their characteristics?
They travel at speeds close to the speed of light.
Imagine that radar had never been invented and that we instead had to rely on a less reliable method of measuring distances in our solar system. If that method led us to underestimate the Earth-Sun distance by 10%, how would it affect other measurements in the distance chain?
They would all be off by the same 10%.
What can we conclude about this galaxy from the fact that there are so many supernovae occurring?
This galaxy contains an unusually large number of young stars.
A radio galaxy whose lobes are swept back as if forming a tail, what dose this probably indicate
This is evidence for intergalactic matter.
What might cause liquid water oceans beneath the ice crust of Jupiter's moon Europa?
Tides or currents.. we don't know
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
True or False: Active galaxies can emit thousands of times more energy than our own galaxy
True
True or False: Approximately 90 percent of the mass of the Milky Way is located in the halo of the galaxy in the form of dark matter.
True
True or False: By definition, our Sun has a mass-to-light ratio of 1 solar mass per solar luminosity.
True
True or False: Cepheid Variable can be used to determine the distances the nearest galaxies
True
True or False: Dark Matter has not been observed at any electromagnetic wavelength
True
True or False: Deuterium abundance suggests that normal matter makes up only 3-4% of the critical density.
True
True or False: GUT theories predict that protons will eventually decay, causing all solid objects in the universe to fall apart if the universe keeps expanding forever.
True
True or False: Herschel believed the Milky Way was a disk of stars, while Shapely found the extended halo more like a ball
True
True or False: Herschel's attempt to map the Milky Way by counting stars led to an inaccurate estimate of the Galaxy's size because he was unaware of absorption by interstellar dust.
True
True or False: If inflation really occurred, then our observable universe is only a tiny portion of the entire universe born in the Big Bang.
True
True or False: If the universe is accelerating, it will expand forever.
True
True or False: In our vicinity, the galactic disk is about 100 times wider than it is thick.
True
True or False: Irr II galaxies may be the result of a collision, or close encounter, of two normal galaxies.
True
True or False: Irregular galaxies, although small, have large star-forming (HII) regions and much ongoing star formation for their size.
True
True or False: It appears that nearly three times as much dark energy exists in the universe than normal and dark matter combined
True
True or False: It would be very unlikely to find a massive, young star out in the halo
True
True or False: M31 in Andromeda is a bigger version of our Galaxy, and the largest member of the Local Group.
True
True or False: Observations of the cosmic background radiation from the COBE satellite revealed tiny variations in its temperature from one place to another (corresponding to a few millionths of a degree Kelvin).
True
True or False: On the largest scales, galaxies in the universe appear to be arranged on huge sheets surrounding nearly empty voids.
True
True or False: Recent measurements of the cosmic microwave background confirm white-dwarf supernovae observations of an accelerating universe.
True
True or False: Shapley found the globulars were strongly concentrated toward Sagittarius
True
True or False: Some of the static "snow" (random noise) you see on an antenna‐fed TV (uses an antenna instead of satellite or cable) when it is not tuned to a broadcasting channel, is left over radiation from the Big Bang.
True
True or False: Spiral galaxies have more gas, dust, and younger stars than elliptical galaxies do.
True
True or False: Stars and Gas in the Galactic disk move in roughly circular orbits around the Galactic Center.
True
True or False: Stars and gas in the Galactic disk move in roughly circular orbits around the Galactic center.
True
True or False: Stars within an emission nebula, such as M42, are considered Population I stars
True
True or False: The Galactic halo contains only old stars.
True
True or False: The Globular star clusters are the most obvious examples of population II around us
True
True or False: The background hiss that Bell Labs detected was the best observational evidence for the Big Bang.
True
True or False: The density wave theory attempts to explain why the spiral arm structure persist over a long time
True
True or False: The fact that the sky is dark at night shows that the observable universe cannot extend forever.
True
True or False: The larger the value of Hubble's constant, the more rapid the expansion of the universe and hence the younger the universe.
True
True or False: The most likely explanation of the high-speed motion of stars and gas near the Galactic center is that stars and gas are orbiting a supermassive black hole
True
True or False: The most likely explanation of the high-speed motion of stars and gas near the Galactic center is that the stars and gas are orbiting a supermassive black hole.
True
True or False: The observed composition of ordinary matter in the universe is roughly 75 percent hydrogen and 25 percent helium closely matches theoretical predictions based on the Big Bang model.
True
True or False: The orbit of the Solar System around the Galaxy is similar to that of a planet, almost circular and in the galactic plane.
True
True or False: Type I supernovae can be used to determine distances to galaxies.
True
True or False: Unlike spirals, elliptical galaxies do not contain a flattened disk.
True
True or False: X-ray bursters are similar to novae, except the collapsed star is a neutron star, not a white dwarf.
True
True or False:Deuterium abundance suggests that normal matter makes up only 3-4% of the critical density.
True
True or False:The density wave theory attempts to explain why the spiral arm structure persist over a long time
True
GUT era.
Two forces are thought to operate during the Gut era: gravity and GUT force.
Which of these standard candles has been used to determine distances to the most distant galaxies?
Type I supernovae
The latest studies from ________ led to the discovery of "dark energy."
Type I supernovae at very large red shifts
Of the following distance measurement techniques, which one can be used to find the farthest distances?(24)
Type Ia supernova apparent brightness measurement
If the universe is homogeneous and isotropic, Hubbles Law implies
Universal Expansion
How does gravitational lensing tell us about the mass of a galaxy cluster?
Using Einstein's general theory of relativity, we can calculate the cluster's mass from the precise way in which it distorts the light of galaxies behind it.
What are peculiar velocities?
Velocities of distant objects that are not caused by the expansion of the universe
Who discovered dark matter through study of the flat rotation curves of spiral galaxies?
Vera Rubin
The best evidence for the existence of supermassive black holes is:
Very high orbital velocities in a very compact region.
In what sense are viruses on the border between material that we consider living and that we consider nonliving?
Viruses cannot reproduce on their own but must make use of the genetic machinery of the cells they invade to multiply
BLANK are defined as subatomic particles that have more mass than neutrions but do not interact with light
WIMPS
Quasar spectra often show many absorption lines that all appear to be due to the same electron transition (such as level 1 to level 2 in hydrogen) but that fall at different wavelengths in the spectrum. Why do we think this is the case?
We are seeing absorption lines from clouds of gas that lie between us and the quasar, and therefore each cloud has a different redshift
Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation?
We can learn the distance to the galaxy
If we observe a Cepheid variable in a distance galaxy with a period of about 10 days. What can we determine?
We can learn the distance to the galaxy.
How do we learn about what is going on in the center of our own galaxy (the Milky Way)?
We cannot see the galactic center with visible or ultraviolet light, but radio and X rays from the center can be detected.
What is the primary way in which we determine the mass distribution of a spiral galaxy?
We construct its rotation curve by measuring Doppler shifts from gas clouds at different distances from the galaxy's center.
Suppose an elliptical galaxy is so far away that we cannot see even its brightest stars individually. Which of the following techniques might allow us to measure its distance?
We could use a white dwarf supernova as a standard candle.
Suppose an elliptical galaxy is so far away we can't see even its brightest stars individually. How can we measure its distance?
We could use white dwarf supernovae
How do we know that galaxy clusters contain a lot of mass in the form of hot gas that fills spaces between individual galaxies?
We detect this gas with X-ray telescopes.
The rare Earth hypothesis" holds that Earth-like planets will prove to be quite rare. Which of the following statements best sums up the current status of the debate over this hypothesis?
We do not have enough data to settle the debate, because counterarguments can be made for each argument suggesting Earth-like planets may be rare.
What is the primary practical difficulty that limits the use of Hubble's law for measuring distances?
We do not know Hubble's constant very accurately yet
What is the general meaning of the cosmological principle?(26)
We do not occupy a special location in space, because the universe is the same everywhere, on average.
Why can't current theories describe what happened during the Planck era?
We do not yet have a theory that links quantum mechanics and general relativity.
What might be causing the universe to accelerate?
We don't know- but we call it "dark energy"
Which of the following best sums up current scientific thinking about the nature of dark matter?
We have been able to rule out the possibility that most dark matter is made of a known form of matter, meaning that it must be made of some as-yet-undiscovered type of particle.
What evidence tells us that at least some dark matter consists of objects that astronomers call MACHOs (massive compact halo objects)?
We have detected gravitational lensing of distant objects that appears to be caused by compact but unseen objects in the halo of our galaxy.
Which of the following is not key evidence in support of the idea that all life today shares a common ancestor?
We have identified fossils of the first life forms that ever existed on Earth.
Which of the following statements best describes the current state of understanding regarding the apparent acceleration of the expansion of the universe?
We have moderately strong evidence that the acceleration is real, but essentially no idea what is causing it.
Why do we use Hubble's law to estimate the distances of most distant galaxies, rather than using white dwarf supernovae in all cases?
We have not observed white dwarf supernovae in most galaxies.
What evidence do we have that the object in question 9 exists in the center of our galaxy?
We infer its existence by mapping the orbits of stars near the center of the galaxy with high resolution imaging.
Which of the following best describes the predominant scientific view of the origin of life on Earth?
We may never know precisely how life arose, but current evidence suggests that life probably can arise naturally under the conditions that prevailed on the early Earth.
How do we determine the amount of dark matter in elliptical galaxies?
We measure the speeds of stars at different radii from the galactic center and determine how much mass is interior to the orbit.
What evidence suggests that the Milky Way contains dark matter?
We observe clouds of atomic hydrogen far from the galactic center orbiting the galaxy at unexpectedly high speeds, higher speeds than they would have if they felt only the gravitational attraction from objects that we can see.
What exactly is dark energy?
We really don't know, but since it's not a form of matter, we use "dark energy" as the all-purpose explanation for the observed acceleration of the expansion of the universe.
What observational evidence supports the galactic fountain model (which describes how gas cycles between the disk of the galaxy and regions high above the disk)?
We see hot gas high above the region of the disk near our solar system, along with cool gas that appears to be raining down from the halo.
How do we know that there are intergalactic clouds between a distant quasar and us?
We see hydrogen absorption lines at redshifts smaller than that of the quasar.
What evidence suggests that small galaxies in our Local Group have undergone two or more starbursts in the past?
We see small galaxies in which many stars have one age and many others have another age that is billions of years old.
How do we determine the conditions that existed in the very early universe?
We work backward from current conditions to calculate what temperatures and densities must have been when the observable universe was much smaller in size.
Suppose that Cepheids did not exist and there were no other standard candle technique that worked at the same distances. Which statement would be true?
We would not be able to measure the distances of distant galaxies
Suppose that Cepheids did not exist and there were no other standard candle technique that worked at the same distances. Which statement would be true?
We would still be able to measure the distances of distant galaxies using white dwarf supernovae, but we would not be able to use Hubble's law.
Which force is involved in the radioactive decay of a neutron?
Weak
What question does the Drake equation attempt to answer?
What is the number of technological civilizations in the Galaxy?
Why didn't elements heavier than helium form in the first minutes of creation?
When He-4 was formed, the expansion cooled the cosmos below 100 million K
The major evidence for the idea that the expansion of the universe is accelerating comes from the observations of what?
White dwarf supernoave
Why are white dwarf supernovae more useful than massive star supernovae for measuring cosmic distances?
White dwarf supernovae all have roughly the same true peak luminosity, while massive supernovae come in a wide range of peak luminosities.
What is the evidence for an accelerating universe?
White‐dwarf supernovae are slightly dimmer than expected for a coasting universe.
Olbers's paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question?
Why is the sky dark at night?
The first attempt to map the Galaxy via star counts was done by
William Herschel in the late 18th century
A telescope searching for newly formed stars would make the most discoveries if it were pointed
Within a spiral arm.
Where are large dust clouds predominately located in the galaxy M51?
Within or on the edges of the spiral arms
Where are the ionization nebulae predominately located in the galaxy M51?
Within or on the edges of the spiral arms of the galaxy
Consider again the civilization described in the previous question. (They live on a planet orbiting 10 AU from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole surrounded by an accretion disk.) One foolhardy day, a daring individual in their space force (let's call him Major Tom) decides to become the first of his species 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 to start the process of killing him first)?
X rays from the accretion disk
The most successful model for explaining nuclear activity in galaxies involves a supermassive black hole that is gravitationally accreting matter from its surroundings. According to this model, different regions of the active galactic nucleus produce different types of radiation. Referring to the figure, match the region with the type of radiation being emitted. (Accretion Disk) - infrared, none, x-ray, radio
X-ray
What is the dominant radiation that we see from the intergalactic matter in rich clusters of galaxies?(24)
X-rays from very hot gas
Can the 3 degrees K background radiation be observed to be coming from all directions?
Yes
Based on the observational evidence, is it possible that dark matter doesn't really exist?
Yes(, but only if there is something wrong with our current understanding of how gravity should work on large scales.)
Is there a limit on how fast a rocket ship can travel?
Yes, cannot reach the speed of light
Although the universe today appears to be made mostly of matter and not antimatter, the Big Bang theory suggests that the very early universe had nearly equal amounts of matter and antimatter.
Yes, the Big Bang theory predicts that high temperatures in the early universe generated matter‐antimatter pairs, and the amounts of each were therefore virtually equal.
The flat rotation curves of spiral galaxies tell us that they contain a lot of dark matter. Do they tell us anything about where the dark matter is located within the galaxy?
Yes, they tell us that dark matter is spread throughout the galaxy, with most located at large distances from the galactic center.
The theory of inflation suggests that the structure of the universe may have originated as tiny quantum fluctuations.
Yes, tiny quantum fluctuations were stretched to enormous sizes by inflation and became large enough to grow into galaxies and galaxy clusters.
You are feeling like spaghetti. Although normally only about 2 meters tall, you are not about 25 meters long. (How fortunate, if painful, that the being has arranged for your body to become elastic enough so that it is not ripped apart under these conditions) As you look up over your head, you see things moving pretty quickly in the universe-but that lasts only for a brief instant, and then all contact with the universe is lost. Where are you?
You are crossing the event horizon of a black hole
At last you are in a place where the heat and high density are no longer bothering you. However although the density is very low, the gas around you is extremely high in temperature. in fact, the temperature is so high that it is emitting lost of X rays, which are creating cancer-causing mutations in your body at a rapid rate. Well at least the view is great! there are no stars anywhere within about 10,000 light-years of you, but at slightly greater distances your sky is brightened by many beautiful, star-filled structures, some with majestic spiral shapes. Where are you?
You are in intergalactic space within a rich cluster of thousands of galaxies
You are in a place that is extremely hot and dense, making you feel quite sweaty and claustrophobic. You cant see far because your surroundings are opaque to light. Around you, nuclear fusion is converting carbon into oxygen and other elements. Where are you?
You are in the center of a massive star near the end of it's life.
You find yourself in a place that looks (except for your own presence) perfectly symmetrical. There is no way to distinguish one place from another, and all forces are one. With this perfect symmetry, there is no obvious way to define the flow of time. Where are you?
You are in the early universe before the Planck time.
You are once again in a hot, dense place. You are surrounded by protons and neutrons, some rapidly fusion into helium. You notice that your surroundings are cooling (good, because its really hot!) and rapidly dropping the density. Within about 3 minutes, the fusion reactions stop. Where are you?
You are in the early universe during the era of nucleosynthesis.
It sure is bright everywhere; you've been able to travel around a bit, and its clear that you are not in a star. Yet it is as bright as looking directly at the Sun. In your extensive travels through your current surroundings, you cannot find a single neutral atom anywhere, nor can you find a nucleus besides hydrogen or helium. and, while it is hot (a few thousand degrees Kelvin), it is nowhere near the temperature needed for nuclear fusion. Where are you?
You are in the universe during the first 300,000 years
Talk abotu cold, dark, and empty! As far as you look around you, there seems to be nothing at all. Even the nearest electron is light-years away. And no matter how far you travel, you can find no solid matter, not even a single proton. You do however detect a few strong gravitational fields-probably due to black holes- at enormous distances away from you. Where are you?
You are in the universe when it is over about 10^110 years old
At last, someplace fairly comfortable. Very weak gravity is holding you to the surface of the small object on which you sit. Your object is apparently moving away form a star, perhaps once that it orbits with a period of thousands of years. Around you geysers are spouting gas into space. Look back along the objects orbit you see particles of dust that the geysers apparently blew off the object when it was nearer to the star that it is now leaving behind. You conclude that the geysers were recently much more active but are now settling down into a quiescent state that may last for millennia. You also seen realize that you are closer to home than you have been in all the previous journeys. Perhaps if you can somehow find a small rocket, a heat shield, and a good parachute, you can escape and head home for your final exam. Where are you?
You are on comet Hale-Bopp, circa MAy 1997
You are on the surface of an object, and you have a fairly clear view out into space. It might be very nice, except for one major drawback: You are very squashed. Also, light you observe from distant objects in apparently slightly blue shifted (compared to what it normally look like). The surface of the object is composed primarily of carbon and oxygen, and the horizon distance is about the same as that on Earth. By observing the stellar background for a few weeks, you realize that there are several planets orbiting your object. Where are you?
You are on the surface of a white dwarf
According to our modern understanding, what is a nova?
Your Answer: an explosion on the surface of a white dwarf in a close binary system It occurs when fresh hydrogen from the accretion disk piles up on the surface
What kind of object do we think lies in the center of the Milky Way Galaxy?
a 3 to 4 million solar mass black hole
Which of these does not exist? -a million solar mass black hole -a 6 solar mass black hole -a 6.8 solar mass neutron star -a 1.0 solar mass white dwarf -a 0.06 solar mass brown dwarf
a 6.8 solar mass neutron star
Good evidence for an original big bang, which "created" our universe, comes from(26)
a background "glow" of microwaves, with blackbody temperature of about 3 K26
The Milky Way in which the Sun resides is an example of which type of galaxy?(24)
a barred spiral galaxy
photon
a boson which is the particle of electromagnetic radiation (light). The photon is also the carrier particle of the electromagnetic force.
acceleration
a change of velocity with respect to time
fermion
a class of elementary particles whose spin is a half-integer multiple of a fundamental quantized value. Fermions make up matter. The best-known fermions are protons, neutrons, electrons, and neutrinos. Fermions obey the exclusion principle.
boson
a class of elementary particles whose spin is an integer multiple of a fundamental quantized value. The major function of bosons is to mediate the fundamental forces. The best-know boson is the photon.
In active galaxies, their central engines may be temporarily fed by
a close encounter with a neighbor galaxy
What do we mean by a protogalactic cloud?
a cloud of hydrogen and helium that contracts to become a galaxy
What is the Local Group?(24)
a cluster of about 40 galaxies of which the Milky Way is a member
supercluster
a cluster of galaxy clusters.
What is an ionization nebula?
a colorful cloud of gas that glows because it is heated by light from nearby hot stars
Which of the following types of protogalactic clouds is most likely to form an elliptical galaxy?
a dense cloud with very little angular momentum
What is an accretion disk?
a disk of hot gas swirling rapidly around a white dwarf, neutron star, or black hole
what is the current temperature of the universe?
a few K
What is the current temperature of the universe?
a few degrees
The RR Lyrae stars all have periods of
a few hours
What is the average distance between adjacent galaxies in a galactic cluster? A few million parsecs A few hundred parsecs A few parsecs A few hundred thousand parsecs A few billion parsecs
a few hundred thousand parsecs
what is the earliest time in the universe that we can directly observe?
a few hundred thousand years after the Big Bang
About how many galaxies are within 30 mega parsecs of the sun
a few thousand
Suppose a collision strips gas out of a spiral galaxy. Why would this tend to change the spiral galaxy into an elliptical galaxy?
a galaxy cannot have a disk if it does not have gas.
Hubble's law
a galaxy's recession is proportional to its distance v=cz=Hod 22 km/s/mly distance is in mega light year- 10^6 light years
What is a central dominant galaxy
a giant elliptical galaxy at the center of a dense cluster?
Listed following are several locations in the Milky Way Galaxy. Rank these locations based on their distance from the center of the Milky Way Galaxy, from farthest to closest. - the edge of the central bulge, a cloud of gas and dust in the outskirts of the disk, our solar system, a globular cluster int he outskirts of the halo
a globular cluster in the outskirts of the halo, a cloud of gas and dust in the outskirts of the disk, our solar system, the edge of the central bulge
What is a rotation curve?
a graph showing how orbital velocity depends on distance from the center for a spiral galaxy
galaxy cluster
a group of galaxies that are mutually gravitationally bound.
As we look at larger and larger scales the universe we find
a larger and larger percentage of the matter is dark
A standard candles is ______________.
a light source of known luminosity
What is main-sequence fitting?
a method for determining the distance to a star cluster by assuming that its main sequence should line up with the main sequence on a standard H-R diagram
Three terrestrial-sized planets in orbits of a fraction of an AU have been found near Supernova 1987A. a magnetar. Cygnus X-1. a millisecond pulsar. a white dwarf.
a millisecond pulsar
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
Which of the following best describes what we mean by a habitable world?
a planet or moon that could support life, if any life happened to be on it
The distinguishing feature of a starburst galaxy is _________.
a rate of star formation that may be 100 or more times greater than that in the Milky Way
nuclear reaction
a reaction that occurs in and may change the nucleus of at least one atom. Examples include radioactivity, fission, and fusion.
blueshift
a shift in the frequency of a photon toward higher energy
redshift
a shift in the frequency of a photon toward lower energy
A typical neutron star is more massive than our Sun and about the size (radius) of _________.
a small asteroid (10 km in diameter)
What is Sgr A?
a source of bright radio emission in the center of our galaxy
One possible explanation for a galaxy's type invokes the angular momentum of the protogalactic cloud from which it formed. Suppose a galaxy forms from a protogalactic cloud with a lot of angular momentum. Assuming its type has not changed due to other interactions, we'd expect this galaxy to be _________.
a spiral galaxy
What do we mean by inflation?
a sudden and extremely rapid expansion of the universe that occurred in a tiny fraction of a second during the universe's first second of existence
What do we mean by inflation?
a sudden and extremely rapid expansion of the universe that occurrred in a tiny fraction of a second during the universe's first second of existence
What do we mean by inflation?
a sudden expansion of the universe after the strong force froze out from the GUT force
What is a superbubble?
a very low-density region of interstellar space, formed by the merger of several bubbles.
What is a shock wave?
a wave of pressure that moves faster than the speed of sound
Which of these particles was most common immediately after the big bang and on earth today? a. electron b. positron c. anti-proton d. all 3 found about equally
a. because b and c aren't on earth today naturally
The maximum mass of a white dwarf is _________.
about 1.4 times the mass of our Sun
If an object doubles it luminosity in 10 hours, how large can the emitting source of light be?
about 10 light hours across
the average density of a neutron star approaches...
about 10^14 kg/m^-3
If you had something the size of a sugar cube that was made of neutron star matter, it would weigh _________.
about as much as a large mountain
In the Milky Way Galaxy, our sun is located
about halfway out from the center
How many more stars does a starburst galaxy form, in one year, than the Milky Way?
about one hundred
Which is the correct description of the sun's location within the milky way?
above the disc, about 1/3 of the galactic radius from the center
The observational fact about a Cepheid variable star that leads to a measurement of its distance from Earth is that its period of variation is directly related to its(24)
absolute magnitude or luminosity.
Intergalactic hydrogen clouds are easiest to study by looking at ______.
absorption lines in quasar spectra
A(n) BLANK consists of hot, swirling gas captured by a white dwarf (or neutron star or black hole) from a binary companion star
accretion disk
Rank the following steps that lead to a Type I supernova event in order of when they occur from first to last. -white dwarf at Chandrasekhar limit, accretion disk with growing white dwarf, carbon fusion begins throughout, detonation
accretion disk with growing white dwarf, white dwarf at Chandrasekhar limit, carbon fusion begins throughout, detonation
The unusually bright centers found in some galaxies are called _________.
active galactic nuclei
Einstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will _________.
age less than people who stay behind on Earth
Which types of galaxies have a clearly defined spheroidal component?
all but irregulars
Because of the general expansion of space, all distant galaxies appear to be moving away from us, with speeds that increase with distance from our galaxy. An observer in one of these distant galaxies would apparently see(26)
all galaxies moving away from her, the more distant galaxies moving faster
Because of the expansion of space, we see all distant galaxies moving away from us, with more distant galaxies moving faster. An observer in one of these distant galaxies would see(24)
all galaxies moving away from the observer, with more distant galaxies moving faster.
what is the ultimate fate of an open universe?
all matter decays to a low-density sea of photons and subatomic particles
What evidence supports the idea that a collision between two spiral galaxies might lead to the creation of a single elliptical galaxy?
all of the above
What kinds of objects lie in the disk of our galaxy?
all of the above
Which of the following is evidence for supermassive black holes in active galaxies?
all of the above
The sky is dark at night because...
all the light from the objects in space hasn't reached us yet
The figures below show several different astronomical objects. Rank the objects based on the amount that spacetime is curved (relative to flat spacetime) at a distance of 10 AU from the center of each of the objects, from least to greatest. If two (or more) cases are equal, show this equality by dragging one figure on top of the other(s). - the sun, black hole mass, red giant mass, white dwarf mass
all the same
The figures below show several different astronomical objects. Rank the objects based on the strength of the gravitational force that would be felt by a spacecraft traveling at a distance of 10 AU from the center of each of the objects, from weakest to strongest. - the sun, black hole mass, red giant mass, white dwarf mass
all the same
Mixing water, methanol, ammonia, and carbon monoxide. The purpose of this experiment was to determine whether...
amino acids could form in the harsh vacuum of outer space
According to current understanding, what is a quasar?
an active galactic nucleus that is particularly bright
What do astronomers believe is the result of a merger between two spiral galaxies?
an elliptical galaxy
Why might inflation have occurred at the end of the GUT era?
an enormous amount of energy was released when the strong force froze out from the GUT force.
What is a standard candle?
an object for which we are likely to know the true luminosity
What is the basic definition of a black hole?
an object with gravity so strong that not even light can escape
When a particle of ordinary matter meets its precise opposite particle of antimatter, the result is ____________ with complete conversion of mass into energy.
annihilation
neutrino
any of three species of very weakly interacting lepton with an extremely small mass.
To an astronomer, what is a "standard candle"?(24)
any type of object whose absolute magnitude is known
The distribution of the dark matter in a spiral galaxy is
approximately spherical and about ten times the size of the galaxy halo
Gamma-ray bursts are observed to occur... approximately uniformly over the entire sky. throughout the Milky Way Galaxy. near pulsars. mainly near the Sun.
approximately uniformly over the entire sky
Elliptical Galaxies
are more reddish in color, contain primarily old low-mass stars
If we could see our own galaxy from 2 million light years away, it would appear ____________.
as a flattened disk with a central bulge and spiral arms
A typical white dwarf is _________.
as massive as the Sun but only about as large in size as Earth
If you had something the size of a sugar cube that was made of white dwarf matter, it would weigh _________.
as much as a truck
The expansion of the universe means that(26)
as time goes by, space itself expands carrying the galaxies along with it.
Astronomers observe galaxies and categorize them according to four different kinds of shapes: elliptical, spiral, barred-spiral, and irregular. In addition to shape, each of the four different galaxy types can be described by other common characteristics. Match the following characteristics with their corresponding galaxy type. (Irregular galaxy - Irr) - elongated central structure flattened disk, spiral arms, gas and dust, young stars - central bulge, flattened disk, spiral arms, gas, dust, young stars - round, no disk, very little gas and dust, only old stars - asymmetric, often with gas and dust, and young stars
asymmetric, often with gas and dust, and young stars
At what location in the space around a black hole does the escape velocity become equal to the speed of light?
at the event horizon
The most common form of gas in the disk of the Milky Way Galaxy is _________________.
atomic hydrogen gas
The critical density of the universe is the _______.
average density the universe would need for gravity to someday halt the current expansion ifdark energy did not exist
Assuming conditions are ripe for life and intelligence around the galaxy, what factor limits the number of galactic civilizations?
average survival time of the civilizations
Suppose that Hubble's constant were 20 kilometers per second per million light-years. How fast would we expect a galaxy 100 million light-years away to be moving? (Assume the motion is due only to Hubble's law.)
away from us at 2,000 km/s
detailed measurements of the disk and central bulge region of our galaxy suggest our Milky Way is a...
barred spiral galaxy
Matter made from ordinary items represent what we call ______.
baryonic matter
In order for gravitational lensing of a distant quasar to occur, the galaxy producing the lensing must(24)
be almost perfectly placed on a line between Earth and the quasar.
Collisions between galaxies is thought to
be commonplace
why is thought that quasars probably spend only a fairly short time in their highly luminous place?
because a black hole cannot power a highly luminous quasar for more than a few million years
Why are telescopes sometimes called "time machines"?
because observations of distant objects reveal them as they were in the past
Why does the observable universe have an "edge"?(26)
because we cannot see any farther than the distance that light has traveled over the lifetime of the universe
The Planck era refers to the time period
before the Planck time.
The most likely region of the radio spectrum for communication with other civilizations is in the "water hole." What part of the spectrum is this?
between the radio emissions of hydrogen and OH
Most of the stars in the Local Group are in
big spirals like our galaxy (M31)
Reflection nebula result when gas and dust clouds near a star reflect some of the light in our direction. What color do these nebula usually appear?
blue
Stars orbiting in the ________ near the galaxy's center can have orbits highly inclined to the galactic plane
bulge
How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path?
by applying Newton's version of Kepler's third law to the orbits of the Sun or other nearby stars around the center of the Galaxy
How can astronomers determine the size of an emission region in a very distant and unresolvable source?(25)
by measuring brightness variability, because an object cannot vary more rapidly than the time taken for light to cross the source.
How can we see through the interstellar medium?
by observing in high-energy wavelengths such as X rays and long wavelengths of light such as radio waves.
Essentially all the hydrogen nuclei that will ever exist in our universe was created
by the time the universe was about 3 minutes old
At present, what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out?
by using radio telescopes to search for signals from extraterrestrial civilizations
How do astronomers create three-dimensional maps of the universe?
by using the position on the sky and the redshift to determine a distance along the line of sight
Two rocket ships are traveling past Earth at 90% of the speed of light in opposite directions (i.e., they are approaching each other). One turns on a searchlight beam, which is seen by scientists aboard the second spaceship. What speed do the scientists measure for this light? (c = speed of light in a vacuum)
c
The white dwarf that remains when our Sun dies will be mostly made of ______.
carbon
collisions between galaxies
cause the gas and dust clouds to collide, leading to rapid star formation
Astronomers observe galaxies and categorize them according to four different kinds of shapes: elliptical, spiral, barred-spiral, and irregular. In addition to shape, each of the four different galaxy types can be described by other common characteristics. Match the following characteristics with their corresponding galaxy type. (Spiral Galaxy - S) - elongated central structure flattened disk, spiral arms, gas and dust, young stars - central bulge, flattened disk, spiral arms, gas, dust, young stars - round, no disk, very little gas and dust, only old stars - asymmetric, often with gas and dust, and young stars
central bulge, flattened disk, spiral arms, gas, dust, young stars
For finding the distance to M31, Hubble relied upon...
cepheid variables in its spiral arms
Why does the cepheid "standard candle" have limited usefulness beyond 20 mpc?
cepheids are too faint to be seen beyond that distance, even with HST
Based on star counts, 100 years ago most astronomers thought galaxies were
circular disk, 10 kpc wide, 2 kpc thick
Strong evidence for the existence of dark matter comes from observations of
clusters of galaxies
Astronomers think most galaxy interaction took place at redshifts greater than 1 because...
clusters were more compact
In a closed universe, a beam of light will...
come back to where it originated
the orbits of Population II stars (older stars) have been compared to
comets around the sun
Based on galactic rotation curves and cluster dynamics, we think of dark matter
comprises of over 90% of the entire mass of the universe
Sort the following source properties by whether they might be considered as originating from intelligence or simply be natural phenomena. (probably cosmic) - sequence of pulses varying over time, constant unchanging signal, identical repetitive pulses, random radio fluctuations, single strong visible light burst that fades away over months
constant unchanging signal, identical repetitive pulses, random radio fluctuations, single strong visible light burst that fades away over months
Spiral Galaxies
contain abundant clouds of cool gas and dust, are rare in central regions of galaxy clusters, have significant, ongoing star formation, contain many bright hot stars, have a flattened disk of stars
Synchotron radiation produces a _______ spectrum
continuous non-thermal
Homogeneity and isotropy taken as assumptions regarding the structure and evolution of the universe, are known as...
cosmological principle
Scientists investigation ____ study how the distribution of galaxies changes with time.
cosmology
the universal accelerating force could not be considered...
dark matter
most of the mass of the Milky Way seems to exist in the form of...
dark matter (out in the halo)
examples of nonbaryonic matter
dark matter consisting of weakly interacting subatomic particles and matter that probably makes up the majority of dark matter
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 _________.
dark matter represents much more mass and extends much further from the galactic center than the visible stars of the Milky Way
A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a...
day
In the 1960s, Maarten Schmidt determined that quasars were very distant objects by
determining their redshifts
The scarcity of what isotope is a critical test of the density of the present cosmos?
deuterium
From Earth, the view of the Milky Way is a thin band of stars across the night sky. The part of the Milky Way galaxy that is described here is the...
disk
our sun belongs to the ______ of the milky way galaxy
disk component
The Hubble relation links which two characteristics of distant objects in the universe?(24)
distance and velocity of recession
Cepheid stars are useful to astronomers as indicators of
distance, particularly to stars in our galaxy and to nearby galaxies
Use these four characteristics as a working definition of life to see which generally accepted living and non-living things from the table would be considered alive based on these characteristics.They can react to their environment and can often heal themselves when damaged. They can grow by taking in nourishment from their surroundings and processing it into energy. They can reproduce, passing along some of their own characteristics to their offspring. They have the capacity for genetic change and can therefore evolve from generation to generation and adapt to a changing environment. (for things that exhibit 4 characteristics) - dogs, trees, viruses, rocks, stars
dogs, trees
What is the most important piece of evidence known about Mars that suggests it once had an environment that could be supportive of life? Ice caps Rotation rate Dry river and lake beds Volcanoes
dry river and lake beds
nucleon
either of the two fermionic particles, the proton and the neutron, which form the nuclei of atoms.
the radius of a white dwarf is determined by a balance between the inward force of gravity and the outward push of ________
electron degeneracy pressure
The BLANK is a single force that unifies the electromagnetic and weak forces
electroweak force
a single force that unifies the electromagnetic and weak forces
electroweak force
A galaxy with little cool gas or dust and no evidence of ongoing star formation is most likely a(n)
elliptical
Which galaxy would appear reddest in color?
elliptical
Which type do you commonly find in the center of rich clusters?
elliptical
An BLANK contains hot, ionized gas but very little cool gas or dust
elliptical Galaxy
The greatest variation in size mass and luminosity occurs in
elliptical galaxies
Which of these would be made up of only Population II stars?
elliptical galaxies
The most basic difference between elliptical galaxies and spiral galaxies is that ______.
elliptical galaxies lack anything resembling the disk of a spiral galaxy
Which of the following galaxy types contain little or no interstellar dust or gas?
ellipticals
Which of the following types of galaxies are most spherical in shape?
ellipticals
Which of the following types of galaxies are reddest in color?
ellipticals
Which of the following types of galaxies contains primarily population II, low-mass, long-lived stars?(24)
ellipticals
Astronomers observe galaxies and categorize them according to four different kinds of shapes: elliptical, spiral, barred-spiral, and irregular. In addition to shape, each of the four different galaxy types can be described by other common characteristics. Match the following characteristics with their corresponding galaxy type. (Barred Spiral Galaxy - SB) - elongated central structure flattened disk, spiral arms, gas and dust, young stars - central bulge, flattened disk, spiral arms, gas, dust, young stars - round, no disk, very little gas and dust, only old stars - asymmetric, often with gas and dust, and young stars
elongated central structure flattened disk, spiral arms, gas and dust, young stars
What is the galaxy content of a rich, irregular cluster of galaxies, like the Hercules cluster?(24)
entirely elliptical galaxies
The Sun's habitable zone _________.
extends from some place a little beyond the orbit of Venus to some place near the orbit of Mars
Compared to when the cosmic microwave background was first released, the radiation of the cosmic microwave background today is
fainter and has most of its photons at longer wavelengths
True or False: The Sun's velocity around the Milky Way tells us that most of our galaxy's dark matter lies in the galactic disk near the center of the galaxy.
false
True or False: The collision of two spiral galaxies will likely result in a single giant spiral galaxy.
false
According to Hubble's Law, the greater a galaxy's red shift, the
farther it is from us
High angular momentum leads to faster rotation. Why does faster rotation tend to lead to a spiral galaxy, rather than an elliptical galaxy?
faster rotation leads to collisions among gas particles that cause the gas to settle into a spinning disk, rather than a more spread out cloud.
Economic history is easier to write than the history of the universe. Nevertheless, most cosmologists now think that when the universe was formed
first there was a Big Bang, then inflation (of space) caused recession (of all matter, away from the Big Bang)
From a science quiz that appeared in the weekly magazine The Economist.) Economic history is easier to write than the history of the universe. Nevertheless, most cosmologists now think that when the universe was formed
first there was a Big Bang, then inflation (of space) caused recession (of all matter, away from the Big Bang).
How did large galaxies form? From the collisions and mergers of smaller galaxies From the fragmentation of very large clouds of gas From very large clouds of gas, much like the smaller galaxies By very slowly accreting gas from the surrounding space
from the collisions and mergers of smaller galaxies
Recent evidence suggests that galaxies formed(24)
from the mergers of hundreds of smaller objects.
How do we determine the Milky Way's mass outside the Sun's orbit?
from the orbits of stars and gas clouds orbiting the galactic center at greater distances than the Sun.
The overall distribution of galaxies through space is now found to be(24)
galaxies concentrated on the surfaces of huge open spaces or voids, like soap bubbles.
what happened sometimes after the first five minutes of the big bang?
galaxies formed, stars formed, photons of cosmic microwave background released, and carbon nuclei formed by fusion
every where we look, the universe is filled with
galaxies!
are there more galaxies or stars in the milky way?
galaxies! there are more galaxies than there are stars in the milky way!
what is the main problem with the hubble constant?
galaxy distances are very hard to measure! Different techniques give slightly different answers
When spiral galaxies do collide, the impact is greatest on their...
giant molecular clouds
All the following types of objects are found almost exclusively in the disk (rather than the halo) of the Milky Way EXCEPT
globular clusters
Almost half of all known millisecond pulsars are found in what type of object?
globular clusters
What kinds of objects lie in the halo of our galaxy?
globular clusters
Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?
globular clusters in the halo of the galaxy
which sequence of formation by age is correct, oldest to youngest? - open clusters, emission nebulae, globular clusters
globular clusters, emission nebulae, open clusters
Which is not one of the three major categories of galaxies?
globular galaxies
Which of the following is not one of the three major categories of galaxies?
globular galaxies
A BLANK predicts that the strong, weak, and electromagnetic forces should become indistinguishable at high temperatures
grand unified theory
A photograph of a cluster of galaxies shows distorted images of galaxies that lie behind it at greater distances. This is an example of what astronomers call a
gravitational lens
A massive object can distort the light of more distant objects behind it through the phenomenon that we call
gravitational lensing
the BLANK of spiral galaxies provide strong evidence for the existence of dark matter
gravitational lensing
According to the theory that active galactic nuclei are powered by supermassive black holes, the energy released as light comes from _____.
gravitational potential energy released by matter that is falling toward the black hole
galaxy
gravitationally bound collection of stars, gas, dust, and dark matter typically comprised of a few million to a few 100 billion stars
Over time, the star-gas-star cycle leads the gas in the Milky Way to ____________.
have a greater abundance of heavy elements
Scientists have detected thousands of gamma ray bursts. The evidence suggests that most or all of these bursts _________.
have occurred in distant galaxies
how did Charles Messier contribute to the history of galactic discovery?
he cataloged objects known as Messier objects, which included galaxies, planetary nebulae, star clusters, etc. This happened because he was looking for comets and kept finding fuzzy objects that clearly weren't comets.
Newton reached the conclusion that the universe must consist of an infinite expanse of stars because(26)
he reasoned that a finite number of stars would eventually fall together under their mutual gravity.
Why was Herschel's strategy for mapping out galaxy flawed?
he relied on visual wavelengths, which are obscured by dust
what did the philosopher Kant hypothesize in 1755 about the collections of stars?
he thought they might just exist outside the milky way!
Pulsars show all of the following except...
high temp. fusion reactions
Compared to the central regions of spiral galaxies, we expect elliptical galaxies to have
higher mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals.
The concept that on the grandest of scales, the universe is similar in appearance everywhere is
homogeneity
What did the cosmic microwave background tell cosmologists about the early universe?
horizon problem in that the microwave background is too isotropic
What is a galactic wind?
hot gas erupting into intergalactic space from a large superbubble
If observations had shown that the cosmic microwave background was perfectly smooth (rather than having very slight variations in temperature), then we would have no way to account for _________.
how galaxies came to exist.
Collisions between galaxies typically unfold over a period of _________.
hundreds of millions of years
of the normal elements around us, the Big Bang produced...
hydrogen and helium
What kinds of atomic nuclei formed during the era of nucleosynthesis?
hydrogen and helium and trace amounts of lithium, beryllium, and boron.
The Big Bang formed
hydrogen and helium, but nothing else
According to present understanding, a nova is caused by _________.
hydrogen fusion on the surface of a white dwarf
how does hubbles law allow us to estimate the age of the universe?
if galaxies are currently moving away from each other, it implies that they were closer together in the past -if no forces act to accelerate or decelerate the expansion, then we can trivially compute the time since they were in contact -by this reasoning we infer that roughly 14 bililon years ago, all galaxies were crammed into a tiny volume
why do we expect to see more distant galaxies moving away faster?
if the universe is expanding uniformly, then we expect to see more distant galaxies moving away faster because there is more space between us and them
To calculate the dashed orbits from the stellar positions, astronomers had to assume that __________.
if they observed for many more years, the dots would trace out ellipses
where are the X rays produced that are emitted by quasars and other active galactic nuclei?
in hot gas in an accretion disk around a central black hole.
Which of the following is considered by biologists to be a likely place where life might have first arisen on Earth?
in hot water near undersea volcanoes
Where are most heavy elements made?
in stars and supernovae
Where do we find supermassive black holes?(25)
in the centers of both active and normal galaxies, both nearby and far away
In our galaxy, young metal-rich stars are found
in the disk and spiral arms
The Sun's location in the Milky Way Galaxy is
in the galactic disk, roughly halfway between the center and the outer edge of the disk
Where would you look in our galaxy to find older, metal-poor stars?
in the globular clusters in the galactic halo
Where does most star formation occur in the Milky Way Galaxy?
in the spiral arms
The periods of most pulsars
increase with time
As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________. Select from the choices in the format first blank / second blank.
increases / increases
BLANK was a dramatic expansion of the universe thought to have occurred when the universe was only a tiny fraction of a second old
inflation
The most successful model for explaining nuclear activity in galaxies involves a supermassive black hole that is gravitationally accreting matter from its surroundings. According to this model, different regions of the active galactic nucleus produce different types of radiation. Referring to the figure, match the region with the type of radiation being emitted. (Dusty Donut) - infrared, none, x-ray, radio
infrared
The center of our Milky Way galaxy can be observed most easily at which of the following wavelengths?
infrared and radio radiation
The image of our galaxy in radio emission from CO, mapping the distribution of molecular clouds, is closest to the image of our galaxy in
infrared emission from interstellar dust grains
Region on the HR diagram where pulsating variables occur is called the
instability strip
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 rule out the possibility of a black hole?
intense X-ray bursts
What is the explanation of the low-redshift absorption lines in the spectra of quasars? Slow-moving gases surrounding the quasar High-velocity gas ejected toward us High-velocity gases in the galaxy of which the quasar is a part Intervening gas much closer than the quasar
intervening gas much closer than the quasar
A type II supernova occurs when...
iron builds up in the core
Select the visible-light view of the galaxy M82. Based on its appearance, what type of galaxy is it?
irregular
The Small Magellanic Cloud is of the type represented by picture
irregular
Galaxies that we see as they were 2 billion years after the Big Bang tend to look like __________.
irregular galaxies
The type of galaxy known as an ____ was more common in the universe 10 billion years ago.
irregular galaxy
Recent results from very bright supernovae in very distant galaxies seem to indicate that the expansion of the universe(26)
is accelerating (speeding up).
The discovery of the cosmic microwave background was important because
it was was experimental verification of a prediction from the Big Bang theory
Much of the mass of our galaxy appears to be in the form of "dark matter" of unknown composition. At present this matter can be detected only because
its gravitational pull affects orbital motions of matter in the galaxy.
If we say that a galaxy has a lookback time of 1 billion years, we mean that _________.
its light traveled through space for 1 billion years to reach us
A white dwarf can explode when...
its mass exceeds the Chandreskhar limit
so if its more redshifted
its moving away faster
why does the galaxy distribution seem to change along the zero latitude line?
just due to dust in the milky way blocking our view
hubble's law for raisin bread
just like bread rises, galaxies aren't moving IN space... its the space itsself that is expanding
X-rays that come from the vicinity of a black hole actually originate from
just outside the event horizon, on the accretion disk.
What environmental factor works against Mars having any life on its surface? Complete lack of water Its rate of rotation Lack of a magnetic field Carbon dioxide atmosphere
lack of magnetic field
models show that the _________ of the universe is better explained when we include the effects of dark mater along with the effects of luminous matter
large scale structures
What is the Great Wall?
large sheet of galaxies measuring 70 mpc by 100 mpc
galaxies with disks but no evident spiral arms are called?
lenticular galaxies
Matter made out of protons, neutrons, and electrons in the universe accounts for that percent of the total mass of the universe?
less than 4%
Suppose you are on board a spaceship that is passing Earth at 80% the speed of light. You see a clock on Earth tick off five seconds. How much time elapsed on your clock while this was happening?
less than 5 seconds
What is the meaning of the term extremophiles? Planets that orbit either very close to or very far from their parent star Life-forms that have adapted to live in extreme environments Scientists who postulate unorthodox methods for finding extraterrestrial life Scientists who believe there is an infinitesimal, yet nonzero, chance of finding extraterrestrial life
life-forms that have adapted to live in extreme environments
According to the theory that active galactic nuclei are powered by supermassive black holes, the high luminosity of an active galactic nucleus primarily consists of ______.
light emitted by hot gas in an accretion disk that swirls around the black hole
Which of the following is not considered crucial for life to exist on some world?
liquid water
The Milky Way and Andromeda galaxies are among a few dozen galaxies that make up our _______
local group
The 21 centimeter line is one of the most important wavelengths in radio astronomy. That it is a relatively long wavelength is important because
long wavelengths are more likely to pass through clouds of gas and dust
All RR lyrae stars have about the same
luminosity (of about 100 suns)
In a neutron star, the core is.... A.) electrons and protons packed so tightly they are in contact. B.) made of compressed neutrons in contact with each other. C.) primarily iron and silicon. D.) constantly expanding and contracting. E.) no longer rotating.
made of compressed neutrons in contact with each other
Which cosmic distance measurement techniques are considered standard candle techniques?
main-sequence fitting, cepheids, and white dwarf supernovae (distant standards)
Rank these objects based on their diameter, from largest to smallest. (Note that the neutron star and black hole in this example have the same mass to make your comparison easier, but we generally expect black holes to have greater masses than neutron stars.) Jupiter, one-solar-mass white dwarf, main-sequence star of spectral type A, a two-solar-mass neutron star, the event horizon of a two-solar-mass black hole, the moon
main-sequence star of spectral type A, Jupiter, one-solar-mass white dwarf, the moon, a two-solar-mass neutron star, the event horizon of a two-solar-mass black hole
why is the hypothesis that life on Earth came from outer space considered plausible?
many meteorites contain complex organic molecules
Gravitational lensing of distant, faint irregular galaxies may be the key to...
mapping dark matter
Harlow Shapley concluded that the Sun was not in the center of the Milky Way Galaxy by
mapping the distribution of globular clusters in the galaxy
Gravitational lensing occurs when
massive objects bend light beams that are passing nearby.
A(n) BLANK occurs when fusion creates iron in the core of a star
massive star supernova
examples of baryonic matter
matter in brown dwarfs, matter in our bodies, dark matter consisting of jupiter-sized objects in galactic halos, and matter in stars
Which of the following best summarizes what we mean by dark matter?
matter that we have identified from its gravitational effects but that we cannot see in any wavelength of light
Current understanding holds that a galaxy's type (spiral, irregular, or elliptical) ____________.
may either be the result of conditions in the protogalactic cloud that formed it or the result of later interactions with other galaxies
We can always determine the recession velocity of a galaxy (at least in principle) from its redshift. But before we can use Hubble's law, we must first calibrate it by __________.
measuring the distances to many distant galaxies with a standard candle technique
Interstellar dust consists mostly of _____________.
microscopic particles of carbon and silicon
Our entire solar system orbits around the center of the ______ about once every 230 million years
milky way galaxy
Interstellar matter blocks our view of the disk of our galaxy
more at optical wavelengths, less in the infrared, and not at all at radio wavelengths.
Black holes result from stars having initial masses
more than 25 times the mass of the Sun.
The fraction of mass of the universe made up of dark matter is
more than 90%
What is the galaxy content of a rich, regular cluster of galaxies, like the Coma cluster?(24)
mostly ellipticals and S0 galaxies, with relatively few spirals and irregulars
Helium originates from
mostly from the Big Bang with a small contribution from stellar nucleosynthesis.
A head-tail radio galaxy is one that has ______ significantly while ejecting its radio lobes. varied in brightness
moved
The graph shows that galaxies with high speeds as measured from Earth are __________.
moving away from Earth and are farther from Earth than galaxies with lower speeds
While examining the spectrum of a galaxy you find that all the hydrogen lines are shifted to the longest wavelengths. The galaxy is...
moving away from us
if the spectral lines of galaxy A appear MORE REDSHIFTED than galaxy B, we infer that galaxy A must be
moving away from us faster than galaxy B
For distant galaxies their recession velocity...
much greater than any other motion
when the universe was 10 years old, the density of radiation was
much greater than that of matter
Harlow Shapely was correct in arguing the Milky Way was
much larger than previously expected
Harlow Shapley found the Milky Way was
much larger than previously thought
Compared to the average density of matter in the present universe, the equivalent "mass density" of radiation, using Einstein's relation E = mc2 for the photons, is(26)
much less, leading to a matter-dominated universe
Many nearby galaxies may have been
much more active in the past
What is the charge of an antiproton?
negative
Radio waves of 21-cm wavelength originate from which component of the interstellar medium?
neutral atomic hydrogen
Some dark matter may consist of what astronomers call MACHOs (massive compact halo objects). Which of the following would not be considered a type of MACHO if it were found in the halo of the galaxy?
neutrinos
which of these could be considered as "hot dark matter"?
neutrinos
An object more massive than the sun, but roughly the size of a city, is a... A.) white dwarf. B.) brown dwarf. C.) red dwarf. D.) neutron star. E.) supernova remnant.
neutron star
Proposed WIMPS would be massive like ______, but more elusive than __________, however this is not yet proven
neutrons, neutrinos
Have radio transmissions from alien civilizations been detected?
no
If the universe were infinite and static, would we need streetlights at night?
no
do we know the exact value of the hubble constant?
no its been a debate for centuries, but Recent work by the Hubble Space Telescope and the Planck satellite constrain H 0 with an uncertainty of just a few percent!
From Part E you know the mass of the central object. Now consider its size. Based on what you can see in the diagram, you can conclude that the diameter of the central mass is __________.
no more than about 70 AU
was the existence of other galaxies known in the early 20th century?
no, not even then! the milky way WAS considered to be the universe!
The most successful model for explaining nuclear activity in galaxies involves a supermassive black hole that is gravitationally accreting matter from its surroundings. According to this model, different regions of the active galactic nucleus produce different types of radiation. Referring to the figure, match the region with the type of radiation being emitted. (Supermassive black hole) - infrared, none, x-ray, radio
none
A(n) BLANK occurs when hydrogen fusion ignites the surface of a white dwarf in a binary system
nova
To which of these phenomena are X-ray busters most similar? hypernovae novae type II supernovae type I supernovae planetary nebulae
novae
What evidence now exists for a supermassive black hole at the center of our galaxy?
observations of intense inflow of matter toward the center of the galaxy, as seen by light, Doppler-shifted toward the red, emitted by this matter
Evidence that supports the idea that inflation really happened
observations of the cosmic microwave background that indicate a flat geometry for the universe
Neutron stars
often emit radio waves in two narrow beams
Compared with our Sun, most stars in the halo are
old, red, and dim and have fewer heavy elements
A large mass-to-light ratio for a galaxy indicates that
on average, each solar mass of matter in the galaxy emits less light than our Sun
Simplest life forms appeared on Earth when it was how old?
one billion years
isotope
one of the forms in which an element occurs. one isotope differs from another by having a different number of neutrons in its nucleus. the number of protons determines the elemental identity of an atom, but the total number of nucleons affects properties such as radioactivity or stability, the the types of nuclear reactions, if any, in which the isotope will participate, and so forth.
Based on our current understanding of physics, we can understand the conditions that prevailed in the early universe as far back in time as about _________.
one ten-billionth of a second after the Big Bang
Which property is common to spiral galaxies?
ongoing star formation and emission nebula in the arms
what is common to spiral galaxies?
ongoing star formation and emission nebula in the arms
Red and orange stars are found evenly spread throughout the galactic disk, but blue stars are typically found _____________.
only in or near star forming clouds
Robot probes sent to the other planets of the solar system have demonstrated that life as we know it exists on which of the following? On the planet Mars On the moon Europa Only on Earth On the moon Titan Possibly on Jupiter
only on earth
The Schwarzschild radius of a black hole depends on ________.
only the mass of the black hole
in Robert Frost's classic poem, when he ends with "ice will suffice", the universe is...
open
Which two parameters of star motion in the Milky Way are represented by its rotation curve?
orbital speed as a function of star distance from the galactic center
You are one year older each time Earth ______ about the Sun
orbits
What gas might one look for to see if there was life on another planet?
oxygen
antimatter
particles with certain properties opposite to those of matter. each matter particle has a corresponding antiparticle. The antiparticle has exactly the same mass and electric charge as its partner. When a particle combines with its antiparticle both are annihilated and converted into photons.
The history of the universe can be divided into seven major phases. Taken together, these phases make up the cosmic evolutionary scheme—the continuous transformation of matter and energy that has led to the appearance of life and civilization on Earth. Rank the phases in the history of cosmic evolution from earliest to most recent. - stellar, galactic, biological, cultural, chemical, planetary, particulate
particulate, galactic, stellar, planetary, chemical, biological, cultural
leading explanation for the existence of spiral arms are
passages of spiral density waves
In the expansion of the universe, the expansion takes place(26)
primarily in the huge voids between clusters of galaxies: "small" objects like galaxies or Earth do not expand.
The expansion of the universe takes place(24)
primarily in the huge voids between clusters of galaxies: "small" objects like galaxies or Earth do not expand.
An elliptical galaxy contains mostly what kind of stars?(24)
primarily old, metal-poor stars, population II
When we say that the electroweak and strong forces "freeze out" at 10 to power of (exponent) seconds after the Big Bang, we mean that
prior to this time the electroweak and strong forces maintained a single identity, but they possessed separate identities following this time.
Characteristics of a spiral galaxy
protogalactic cloud has high angular momentum, most protogalactic gas settles into a disk
Characteristics of an elliptical galaxy
protogalactic cloud has high density, stars form rapidly as the protogalactic cloud shrinks, protogalactic cloud rotates very slowly, a galaxy collision strips away gas.
Identify which emission properties relate to thermal and synchrotron (nonthermal) radiation (Synchrotron) - radiation peaks at a characteristic frequency, radiation is consistently stronger at lower frequency (longer wavelengths), radiation depends on the temperature of the source, radiation depends on the presence of magnetic fields
radiation is consistently stronger at lower frequency (longer wavelength), radiation depends on the presence of magnetic fields
Identify which emission properties relate to thermal and synchrotron (nonthermal) radiation (Thermal) - radiation peaks at a characteristic frequency, radiation is consistently stronger at lower frequency (longer wavelengths), radiation depends on the temperature of the source, radiation depends on the presence of magnetic fields
radiation peaks at a characteristic frequency, radiation depends on the temperature of the source
The most successful model for explaining nuclear activity in galaxies involves a supermassive black hole that is gravitationally accreting matter from its surroundings. According to this model, different regions of the active galactic nucleus produce different types of radiation. Referring to the figure, match the region with the type of radiation being emitted. (Magnetized Jet) - infrared, none, x-ray, radio
radio
The primary way that we observe the atomic hydrogen that makes up most of the interstellar gas in the Milky Way is with _________.
radio telescopes observing at a wavelength of 21 centimeters
The first stars that formed in the Milky Way now have
random orbits in the halo
Which of the following is not a characteristic of the stars of the disk component of our galaxy?
randomly inclined orbits (true: circular orbits, higher metal abundance, young starts and star formation regions)
High density tends to lead to more rapid star formation in a protogalactic cloud. Why does this rapid star formation tend to lead to an elliptical galaxy, rather than a spiral galaxy?
rapid star formation means that there may not be enough gas left to make a disk
Pulsars are thought to be _________.
rapidly rotating neutron stars
Which type of universe would not expand forever?
recollapsing universe
The figures below show several different astronomical objects. Rank the objects based on the acceleration a spaceship would have as it passed very near the surface (or event horizon) of each object, from smallest to largest. - the sun, black hole mass, red giant mass, white dwarf mass
red giant mass, the sun, white dwarf mass, black hole mass
The figures below show several different astronomical objects. Rank the objects based on the amount that spacetime is curved (relative to flat spacetime) very near the surface (or event horizon) of the objects, from least to greatest. - the sun, black hole mass, red giant mass, white dwarf mass
red giant mass, the sun, white dwarf mass, black hole mass
The figures below show several different astronomical objects. Rank the objects based on the amount that spacetime is curved (relative to flat spacetime) very near the surface (or event horizon) of each of the objects, from least to greatest. - neutron star, main sequence star, red giant, white dwarf, black hole
red giant, main sequence star, white dwarf, neutron star, black hole
The figures below show the same astronomical objects as shown in Part A. Rank the objects based on the amount that each would deflect the path of a photon of light from a very distant galaxy (as viewed from Earth), assuming the photon passes very near the surface (or event horizon) of each object, from smallest to largest. - neutron star, main sequence star, red giant, white dwarf, black hole
red giant, main sequence star, white dwarf, neutron star, black hole
is the spectra of most galaxies blue shifted or redshifted?
redshifted! (moving away from us)
hubble discovered that galaxies farther away have greater ___
redshifts. this redshift was interpreted as a doppler shift, or measure of radial velocity
What is meant by the "habitable zone"?
region around each star where terrestrial planets could have water on their surfaces
Hubbles galaxy classifications diagram (the tuning fork)
relates galaxies according to their shapes but not their evolutionary status
Hubble's galaxy classification diagram (the "turning fork") ____________.
relates galaxies according to their shapes, but not according to any evolutionary status.
Two ways in which the starting conditions in a protogalactic cloud might cause it to become an elliptical (rather than spiral) galaxy are if the cloud begins with either:
relatively little angular momentum or relatively high density
The Crab Nebula is a nearby example of what type of physical phenomenon?
remnant of a supernova explosion
The sun appears to rise and set in our sky because Earth ______ once each day
rotates
Lighthouse model explains
rotating neutron star generates observable beam of light
The Tully-Fisher relation is between the galaxy's luminosity and its....
rotation
Astronomers observe galaxies and categorize them according to four different kinds of shapes: elliptical, spiral, barred-spiral, and irregular. In addition to shape, each of the four different galaxy types can be described by other common characteristics. Match the following characteristics with their corresponding galaxy type. (Elliptical Galaxy - E) - elongated central structure flattened disk, spiral arms, gas and dust, young stars - central bulge, flattened disk, spiral arms, gas, dust, young stars - round, no disk, very little gas and dust, only old stars - asymmetric, often with gas and dust, and young stars
round, no disk, very little gas and dust, only old stars
An astronomer studying a distant cluster of galaxies finds that several of the galaxies are spiral-shaped, with a large nuclear region and tightly wound arms. How should the astronomer classify these galaxies?(24)
sa
Sort the following source properties by whether they might be considered as originating from intelligence or simply be natural phenomena. (possibly extraterrestrial) - sequence of pulses varying over time, constant unchanging signal, identical repetitive pulses, random radio fluctuations, single strong visible light burst that fades away over months
sequence of pulses varying over time
Galaxies sometimes interact at a distance, becoming distorted or changing shapes. Typically, how long does such an encounter take? 10 million years Up to 10,000 years Several hundred million years 3-5 billion years
several hundred million years
Based on DNA studies, it seems that all life on Earth _________.
shares a common ancestor
If you see an object moving past you at 90% of the speed of light, you will measure the length of this object to be
shorter than if it were at rest.
Compared to our own galaxy, elliptical galaxies
show no evidence of ongoing star formation
Curtis was right in arguing the milky way was
similar to spiral nebulae, blocking our view of spiral nebula in the galactic plane
Listed following are several astronomical objects. Rank these objects based on their density, from highest to lowest.
singularity of a black hole, typical neutron star, one solar mass white dwarf, main sequence star
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.
Which adjective does not necessarily describe a known feature of the early universe? (Be sure to consider the universe as a whole, not just the observable universe.)
small
Most galaxies in the local group are...
small ellipticals like the companions to M31 in Andromeda
The more massive a white dwarf, the _________.
smaller its radius
Our ________ is moving toward the star Vega at about 70,000 km/hr
solar system
Redshift of galaxies is correctly interpreted as...
space itself is expanding with time, so the photons are stretched while they travel outside of space
Using the technique of main sequence fitting to determine the distance to a star cluster requires that
spectral types of main sequence stars of many masses in the cluster
In the closed universe model, the geometry of space time in two dimensions resembles the surface of a...
sphere
the globular cluster m13 belongs to the _____ of the milky way galaxy
spheroidal component
the most rapidly "blinking" pulsars are those that... -spin fastest. -are oldest. -are most massive. -are hottest.
spin fastest
Which galaxies are relatively rare in regions of high galaxy density? Irregular Giant elliptical Spiral Elliptical Dwarf elliptical
spiral
A BLANK stands out in a photo of a galaxy because it shines brightly with light from massive young stars and glowing clouds of gas and dust.
spiral arm
most of the new star formation in the Galaxy is found in the...
spiral arms
The Milky Way is an
spiral galaxy
due to the galaxy density and collisions, _______ are in the centres of clusters
spirals
Why is the center of galaxies yellow and the outside blue?
star formation is happening which makes the blue color, it is always blue because when they die they are replaced by another blue star. the red yellow color is the older stars
why do the disks of galaxies contain stars that are more massive and bluer than those found in the bulge?
star formation is still occurring in the disk, but not in the bulge
BLANK have the highest rates of star formation
starburst galaxies
Look again at the visible-light view of M82. What is the source of the white and blue light that dominates the image?
stars
Standard candles," which are important for finding distances to remote galaxies, are (24)
stars and other objects of known intrinsic brightness.
Halo Stars (Green)
stars whose orbits can be inclined at any angle, oldest stars, stars with the smallest abundance of heavy elements, globular clusters
Overall, what is our most accurate technique for measuring the distance to a nearby star?
stellar parallax
What is the most accurate way to determine the distance to a nearby star?
stellar parallax
What does cosmological redshift do to light?
stretches its wavelength
The four fundamental forces that operate in the universe today are _________.
strong force, weak force, electromagnetic force, gravity
Quasar spectra are
strongly redshifted
Based on current evidence, what is considered a likely candidate for the majority of the dark matter in galaxies?
subatomic particles (that we have not yet detected)
What are cosmic rays?
subatomic particles that travel close the speed of light
Glitches are occasionally observed by astronomers studying pulsars. What are these glitches?
sudden increases in rotation rate
the energy for all active galactic nuclei is thought to comes from in-fall of matter into _____________
super massive black holes
The interior of a neutron star is believed to consist of
superfluid neutrons and superconducting protons. The interior of a neutron star will consist of a large core of mostly neutrons with a small number of superconducting protons. Again, normally associated with low temperatures, superconducting protons, combined with the high rotation speeds of the neutron star, produce a dynamo effect similar to what creates the Earth's magnetic field. Surrounding the core is a neutron mantle, then a iron-rich crust.
Which method relies on the mass of a dark object revealing its presence...
temporary brightening of a distant star by a gravity lens
We have sent several spacecraft on trajectories that will ultimately take them into interstellar space (Pioneer 10 and 11, Voyager 1 and 2, New Horizons). How long will it take these spacecraft to travel as far as the nearest stars?
tens of thousands of years
in a sentence, what did hubble show?
that the Andromeda galaxy is at a distance of 2.5 million light years and therefore NOT part of the milky way!
force
that which produces an acceleration
What is postulated to have caused a sudden inflation of the early universe?
the "freezing out" of the strong force from the GUT force
Which of the following observatories is most likely to discover a black hole in a binary system?
the Chandra X-Ray Observatory
Suppose you want to observe and study the radiation from gas from inside an interstellar bubble created by a supernova. Which of the following observations will be most useful?
the Chandra X-ray observatory
Radar, the first link in the cosmic distance chain, is used to establish the baseline distance necessary for the second link, parallax. What baseline distance must we know before we can measure parallax?
the Earth-Sun distance
Disk Stars (Yello)
the Sun, youngest Stars, high-mass stars, stars that all orbit in nearly the same plane.
The lookback time of the cosmological horizon is?
the age of the universe
From the 1970s to the present, the accepted value of H has almost doubled, so
the age of the universe is half what we believed
What is meant by "dark energy"?
the agent causing the universal expansion to accelerate
which of the following does not provide strong evidence for the Big Bang theory?
the amount of hydrogen in the universe
To what does the phrase "superluminal motion" refer?(25)
the apparent motion of jets of gas at speeds faster than light
What is Olbers paradox?
the argument that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe.
Astronomers started taking spectra of galaxies in 1914. the spectra of a galaxy is
the average spectrum of 2 stars
Which of the following locations in our universe has been suggested as the site of a supermassive black hole?(23)
the center of our galaxy
A quasar is now thought to be(25)
the central core of an active galaxy.
Doppler effect
the change in frequency of a wave (light, sound, etc.) due to the relative motion of source and receiver.
What are the two key observational facts that led to widespread acceptance of the Big Bang model?
the cosmic background radiation and the high helium content of the universe
Although the entire universe may be much larger than our observable universe, we can see only within our observable universe. The "boundary" of our observable universe is called _________.
the cosmological horizon
The boundary of our observable universe is called?
the cosmological horizon
The 2.7 K Cosmic Microwave Background radiation comes from(26)
the decoupling of radiation and matter in the early universe.
Based on current evidence, a supercluster is most likely to have formed in regions of space where _________.
the density of dark matter was slightly higher than average when the universe was very young
Measuring the amount of deuterium in the universe allows us to set a limit on _________.
the density of ordinary (baryonic) matter the universe
Based on current evidence concerning the amount of deuterium in the universe, we can conclude that
the density of ordinary (byronic) matter is between 1% and 10% of the critical density.
Hubble's law expresses a relationship between __________.
the distance of a galaxy and the speed at which it is moving away from us
Which two parameters representing observations of distant objects in the universe are related in the Hubble law?(26)
the distance to the object and the redshift of its light
A quasar's spectrum is hugely redshifted. What does this large redshift tells us about the quasar?
the distance to the quasar
What do peculiar velocities reveal?
the distribution of dark matter in large-scale structures
Notice that some of the stars on the diagram are represented by a series of dots that are very close together, while others have their dots farther apart. Keeping in mind that all the stellar positions were measured at one-year intervals, which stars are moving the fastest in their orbits during the time period indicated by the dots?
the dots farthest apart
Which forces have physicists shown to be the same force under conditions of very high temperature or energy, as confirmed by experiments in particle accelerators?
the electromagnetic and weak forces
Laboratory experiments conducted with particle accelerators confirm predictions made by the theory that unifies _________.
the electromagnetic and weak forces into the electroweak force
What is the Big Bang?
the event that started the expansion of the universe
Cosmological redshift is the result of ______.
the expansion of the universe
which is not evidence for dark matter?
the expansion of the universe
What is a quasar?
the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
Which of the following observations cannot be explained by the Big Bang theory unless we assume that an episode of inflation occurred?
the fact that the temperature of the cosmic microwave background is almost the same everywhere
the more distant a galaxy is, ____
the faster it is receding
electromagnetic force
the force between charged particles that accounts for electricity and magnetism. One of the four fundamental forces of nature, it is carried by photons and is responsible for all observed macroscopic forces except for gravitational forces.
In the Drake equation (Number of Civilizations = NHP × flife × fciv × fnow), what do we mean by fnow?
the fraction of planets with civilizations at the present time (as opposed to only in the past or future).
weak interaction
the fundamental force that accounts for some particle interactions, such as beta decay, the decay of free neutrons, neutrino interactions, and so forth. Sometimes called the weak force or the weak nuclear force.
strong interaction
the fundamental force that binds quarks into hadrons and holds nucleons together in atomic nuclei. Sometimes called the strong force or the strong nuclear force.
What is the best description of the distribution of the galaxies that lie within about 200 Mpc of Earth?
the galaxies appear to be arranged in a network of filaments, or strings, surrounding large, empty regions of space known as voids
In a photo like the Hubble deep field, we see galaxies in many different stages of their lives. in general, which galaxies are seen in the earliest stages of their lives?
the galaxies that are farthest away
What do we call the bright, sphere-shaped region of stars that occupies the central few thousand light-years of the Milky Way Galaxy?
the galaxy's bulge
What do we mean by the interstellar medium?
the gas and dust that lies in between the stars in the Milky Way galaxy
Which of the following paraphrases Hubble's Law?
the greater the distance to a galaxy, the greater the redshift
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 the diameter
Which part of the galaxy has gas with the hottest average temperature?
the halo
In general, when we compare the mass of a galaxy or cluster of galaxies to the amount of light it emits (that is, when we look at it mass-to-light ratio), we expect that ______.
the higher the amount of mass relative to light (higher mass-to-light ratio), the greater the proportion of dark matter
The key to finding quasar's distances was
the huge red shifts of the hydrogen lines in 3C273
the best answer to both the flatness and horizon problem is...
the inflationary epoch
Starburst galaxies produce most of their light in the wavelength range of
the infrared
Astronomers have found the existence of spiral arms in galaxies difficult to account for because
the inner part of a galaxy rotates in a shorter time than the outer parts, so the arms should have wound up so tightly that they would have disappeared over the lifetime of the galaxy.
Within the boundaries of the constellations Coma and Virgo are found in
the largest nearby superclusters of galaxies
Newton's first law
the law of motion which states that an object in a state of uniform motion will remain in that state unless acted upon by an external force
Newton's third law
the law of motion which states that if A exerts a force on B, then B will exert an equal and oppositely directed force on A. For every action, there is an equal and opposite reaction.
Newton's second law
the law of motion which states that the net applied force on an object produces an acceleration in proportion to the mass: F=ma
I observe a galaxy that is 100 million light-years away: what do i see?
the light from the galaxy as it was 100 million years ago and it is redshifted.
The main reason for the observed slowdown of Crab pulsar is
the loss of rotational energy through the emission of beams of charges particles
What is the Eddington limit for any object?(25)
the luminosity beyond which the outward force due to radiation pressure on matter exceeds the inward force due to gravity
Applying the Newton's version of Kepler's third law (or the orbital velocity law) to the a star orbiting 40,000 light-years from the center of the Milky Way galaxy allows us to determine ______.
the mass of the Milky Way Galaxy that lies within 40,000 light-years of the galactic center
Hubble Space Telescope observations have shown that when the mass of the central black hole is very large, then ________.
the mass of the bulge of the host galaxy is also very large
What is it that keeps localized regions of space, such as things upon Earth, planetary systems, star clusters, and whole galaxies, from participating in the general expansion of the universe?(26)
the mutual gravity between objects in these systems
The fact that the universe is expanding means that space itself is growing within?
the observable universe
which of the following does inflation help to explain?
the origin of the galaxies
When we speak of the large-scale structure of the universe, we mean _________.
the overall arrangement of galaxies, clusters of galaxies, and superclusters in the universe
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions?
the overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form.
What two observable properties of a Cepheid variable are directly related to one another?
the period between its peaks of brightness and its luminosity
Which of the following phenomena is probably not related to the presence of a supermassive black hole?
the presence of globular clusters in the halos of galaxies.
We believe the cosmic singularity which began the universe occurred 13.7 billion years ago. This means that(26)
the present distance (comoving radial distance) to the most distant objects whose light reaches us is more than 13.7 billion light years.
exclusion principle
the property that fermions of the same type that are able to interact with each other cannot simultaneously occupy the same quantum state.
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.
Imagine an advanced civilization living on a planet orbiting at a distance of 10 AU (1.5 billion kilometers) from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole. The black hole is surrounded by an accretion disk. Sometime within the next million years or so, the civilization's planet is likely to be doomed because ________.
the red giant will probably supernova within the next million years
A neutron star is _________.
the remains of a star that died in a massive star supernova (if no black hole was created)
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.
The Tully-Fisher Relationship relies upon broadening of the 21-cm radio line in distant spiral galaxies. What causes this broadening?(24)
the rotation of the galaxy
the cosmological principle
the rules that apply to one part of our universe apply everywhere
Which of the following processes slowed the collapse of protogalactic clouds?
the shock waves from the exploding supernovae of the earliest stars
What is blackbody radiation?
the spectrum of radiation produced by an opaque object that depends only on the object's temperature
What would happen if mass is added to a 1.4 solar mass white dwarf? -The star would erupt as a carbon detonation (type I) supernova. -The star's radius would increase. -The star would immediately collapse into a black hole. -The core would collapse as a type II supernova. -The star would explode as a nova.
the star would erupt as a carbon detonation (type I) supernova
cosmology
the study of the structure and evolution of the universe as a whole (many consider it the oldest science)
what happened within the first five minutes of the big bang?
the temperature fell to 10^15 K, inflation occured, strong force and electroweak force first became distinct, antielectrons (positrons) as common as electrons.
luminosity
the total power output of an object in the form of light. (Sometimes extended to include the output of all forms of radiated energy.)
The degree of "flatness" of the universe, which determines whether we live in an open or a closed universe, has been determined recently by measuring(26)
the typical size of the "hot spots" in the structure of the cosmic microwave background.
What does Hubble Law imply about the universe?
the universe had a beginning and has expanded since, giving it a finite age
the hubble constant gives the rate at which
the universe is expanding
If the density of the universe is greater than the critical density, this means that...
the universe is expanding at a rate less than the escape speed of the universe
Because almost all galaxies show redshifted spectra, we know that
the universe is expanding.
what are implications of the cosmological principle?
the universe is homogenous and isotropic, and we do not inhabit a special place in the universe homogenous: same when viewed from any position isotropic: same in any direction
the best explanation for why the night sky is dark
the universe is not infinite in space
If Omega is less than 1 then
the universe will expand forever
Rank the following items according to their size (diameter) from left to right, from largest to smallest. - our solar system, milky way galaxy, the sun, jupiter, local group, the universe, the local supercluster, earth
the universe, local supercluster, local group, the milky way galaxy, our solar system, the sun, jupiter, earth
The possible presence of a supermassive black hole at the center of our galaxy has been deduced from
the very high orbital speed of stars close to the galactic center.
gravity
the weakest of the four fundamental forces; that force which creates the mutual attraction of masses.
What use are 21 cm radio waves to galactic astronomers?
their doppler shifts allow us to map the motions of the hydrogen in the galaxy
Which effect has been useful (and successful) in the search for and identification of black holes in the universe?
their gravitational influence on nearby matter, particularly companion stars
Why do we feel type O and B stars are poor candidates for extraterrestrial life?
their lifetime is too short
some quasars show absorption spectra with a smaller redshift than their emission spectra, this indicates that...
there is cooler gas between us and the quasar
What is unusual about the results of mass determinations of clusters of galaxies?
there is much more mass than can be accounted for by the visible galaxies
why are super massive galaxies often found at the cores of rich galaxy clusters?
they are the result of many galactic mergers; one galaxy growing at the expense of others
The very small detected irregularities in the uniformity of the cosmic microwave background are considered to be very important in the study of the evolution of our universe because(26)
they are thought to have led to the development of the present concentrations of matter and energy in superclusters of galaxies
why does light from distant galaxies appear fuzzy and diffuse? how does this affect us?
they are too far away for us to resolve individual stars, so even with good telescopes galaxies are difficult to observe
Why do some quasars have red shifts greater than 1?
they are very distant, with relativistic red shifts that take into account dilation of space-time, as Einstein predicted
What happened to the quarks that existed freely during the particle era?
they combined in groups to make protons, neutrons, and their antiparticles
Spiral arms appear bright because ____________.
they contain more hot young stars than other parts of the disk
What is the defining characteristic of starburst galaxies?
they have a large number of young stars
Quasars were at cosmological distance that appeared like ordinary faint stars meant that
they must be producing such large quantities of energy that even fusion could not explain
Looking for an Earth-size planet around a nearby star (besides the Sun) is like looking for a pinhead located _________.
thousands of kilometers away
How are rotation curves of spiral galaxies determined beyond radii where starlight can be detected?
through observations of the 21 cm line of atomic hydrogen
Sound waves in space
travel much faster than sound on Earth but have such low density that they are inaudible
True or False: A protogalactic cloud with slow star formation is more likely to form a spiral galaxy than an elliptical galaxy.
true
True or False: Galaxy mergers take hundreds of millions of years to complete.
true
True or False: Most of the current star formation in the Milky Way occurs in spiral arms.
true
True or False: Observations of quasar absorption lines show that intergalactic clouds were more common in the past.
true
True or False: Observing the galaxy at radio wavelengths allows us to see beyond the dust in the disk of the galaxy that obscures our view.
true
True or False: Open clusters and young stars are generally found only in the disk of the galaxy and not in the halo.
true
True or False: Some galaxies in the Local Group stopped forming stars for several billion years but then started again
true
Suppose that galaxy B is twicw as far from Earth as galaxy A. Hubbles law predicts that galaxy B will be moving away from earth with approximatley _____.
twice the velocity of galaxy A.
What are the Magellanic Clouds?
two small galaxies that orbit the Milky Way Galaxy
How many forces operated in the universe during the GUT era?
two, gravity and the GUT force
Critical evidence for cosmic acceleration in 1998 came from two teams of astronomers, both observing...
type I supernovae
Rank these objects based on their mass, from largest to smallest. main-sequence star of spectral type M, a one solar mass white dwarf, typical black hole (formed in a supernova), typical neutron star, Jupiter, the Moon
typical black hole (formed in a supernova), typical neutron star, a one solar mass white dwarf, main-sequence star of spectral type M, Jupiter, the Moon
what kind of properties do irregular galaxies have?
typically smaller than spiral galaxies, exhibit vigorous star-forming activity, some show evidence for prior collision or close encounter with another galaxy.
A GUT (grand unified theory) refers to theories that
unify the strong force and the electromagnetic and weak forces.
A "GUT" (grand unified theory) refers to theories that ________.
unify the strong force with the electromagnetic and weak forces
On average, galaxies are getting farther apart with time, which is why we say our ________ is expanding
universe
What method is used to determine the distances of very remote galaxies? (24)
use of their spectral redshifts and the Hubble law
What is the most accurate way to determine the distance to a very distant irregular galaxy?
using a white-dwarf supernova as a standard candle
A star in the instability strip of the HR diagram would
vary in temperature and radius
What two quantities did Edwin Hubble plot against each other to discover the expansion of the Universe?
velocity and distance
Most stars in the Milky Way's halo are _________.
very old
If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be
very small
For which of these forms of life is it hardest to apply present criteria for life, based on its behaviour when isolated?
virus
Use these four characteristics as a working definition of life to see which generally accepted living and non-living things from the table would be considered alive based on these characteristics.They can react to their environment and can often heal themselves when damaged. They can grow by taking in nourishment from their surroundings and processing it into energy. They can reproduce, passing along some of their own characteristics to their offspring. They have the capacity for genetic change and can therefore evolve from generation to generation and adapt to a changing environment. (for things that don't exhibit 4 characteristics) - dogs, trees, viruses, rocks, stars
viruses, rocks, stars
When the ultraviolet light from hot stars in very distant galaxies finally reaches us, it arrives at Earth in the form of?
visible light
By measuring Hubble constant at very large distances (early times) (early times)
we can determine if the expansion rate of the universe has been changing
Using the technique of main-sequence fitting to determine the distance to a star cluster requires that _____.
we have telescopes powerful enough to allow us to identify the spectral types of main-sequence stars of many masses in the cluster
Suppose cepheids did not exist and there were no other standard candle technique that worked at the same distances. Which statement would be true?
we would not be able to measure the distances of distant galaxies.
The fastest pulsars, called millisecond pulsars, have periods of about 1/1000 second. The reason they pulse so much faster than (for example) the Crab and Vela pulsars is that they
were spun up by mass transferred on to them from a companion in a binary star system.
A white dwarf is _________.
what most stars become when they die
Where does an object on an elliptical orbit experience the greatest acceleration?
where spacetime has the most curvature
in the 1800s, we didn't have accurate distances to the milky way stars or to galaxies, so a big debate was
whether spiral nebulae were in the milky way or not
A(n) white dwarf in a close binary system will explode as a supernova if it gains enough mass to exceed the _________
white dwarf limit (1.4 solar masses)
A(n) BLANK can occur only in a binary system, and all such events are thought to have the same luminosity
white dwarf supernova
Which is the correct sequence for the following end-points of stellar evolution, in order of increasing maximum mass?
white dwarf, neutron star, black hole
Intracluster gas has been observed in what region of the spectrum? X-ray Radio Infrared Visible Ultraviolet
x-ray
Which of the following is an example of baryonic matter?
you
Which of the following components best outline the spiral arms of the galaxy?
young O and B stars, dust and gas
The age of the universe is related to the slope of the graph of Hubble's law, and current data put the age of the universe at about 14 billion years. Suppose that future observations showed that the slope of Hubble's law on the graph is actually steeper than that shown. In that case, the age of the universe would be _________ than 14 billion years because the universe is expanding ______ than current data suggest. (Each choice gives words to fill in the two blanks, separated by a slash.)
younger / more rapidly
