Astronomy 100 Exam 3
What is the order of the regions of the sun?
1. Core 2. Radiative Zone 3. Convective Zone 4. Photosphere 5. Chromosphere 6. Corona 7. Solar Wind
Put the following stellar remnants in order of increasing mass. Black Hole White Dwarf Neutron Star
1. White dwarf 2. Neutron star 3. Black hole
The apparent magnitude of a star is m = 14.72 and its absolute magnitude is M = 4.57, how far away (in light years) is it?
3,493 Lys (d= 10 * 10^(1/5)(m-M+5))
The hottest region in the Sun's atmosphere is the _____.
Corona
The apparent brightness of a star that is 8.0 ly away from Earth is 0.240 W/m2. What would be the apparent brightness of an identical star that is 12 ly away? a. 0.107 W/m2 b. 0.160 W/m2 c. 0.360 W/m2 d. 0.540 W/m2
a. 0.107 W/m2 ([L/4πd^2]=apparent brightness)
If a star has a mass of 3.0 solar masses, about how long will it live? a. 1/9 of a solar lifetime b. 1/3 of a solar lifetime c. the same as the Sun, about 10 billion years d. 3 solar lifetimes e. 9 solar lifetimes
a. 1/9 of a solar lifetime (1/mass^2)
A star has an apparent magnitude of +4.5 and an absolute magnitude of -1.8. How far away is it? a. 182 pc b. 315 pc c. 450 pc d. 900 pc
a. 182 pc ( d=10^[(1/5)m-M+5])
The Pleiades is a very young cluster. What would you expect its overall color to be when observed from the Earth? a. Blue b. Yellow/white c. Red d. Invisible because it emits only infrared light
a. Blue
How is the sunspot cycle directly relevant to us here on Earth? a. Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment. b. The sunspot cycle strongly influences Earth's weather. c. Solar activity produced during the sunspot cycle affects compass needles that we use on Earth. d. The brightening and darkening of the Sun that occurs during the sunspot cycle affects plant photosynthesis here on Earth.
a. Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
As a protostar moves downward and to the left on a typical HR diagram, what is happening to its properties? a. It is contracting, growing hotter and less luminous. b. It is contracting, growing cooler and less luminous. c. It is contracting, growing hotter and more luminous. d. It is expanding, growing hotter and more luminous.
a. It is contracting, growing hotter and less luminous.
What event happens at the end of the protostar stage of a star's life? a. Nuclear fusion begins, generating energy and increasing internal pressure. b. It explodes, forming a supernova remnant. c. It begins a long period of contraction in which gravitational energy is converted into heat. d. Gas is spun off from its equator, forming planets.
a. Nuclear fusion begins, generating energy and increasing internal pressure.
All main-sequence stars of spectral type G have approximately the same mass. a. TRUE b. FALSE
a. TRUE
All stars in hydrostatic equilibrium that fuse hydrogen in their cores appear along a single line in a Hertzsprung-Russell diagram. a. TRUE b. FALSE
a. TRUE
Brown dwarfs, white dwarfs, and neutrons stars are all kept from collapsing by degeneracy pressure. a. TRUE b. FALSE
a. TRUE
In any star cluster, stars with lower masses greatly outnumber those with higher masses. a. TRUE b. FALSE
a. TRUE
Our Sun will end its life in a planetary nebula and become a white dwarf. a. TRUE b. FALSE
a. TRUE
The Sun rotates more quickly at the equator than at the poles. a. TRUE b. FALSE
a. TRUE
The corona and chromosphere are hotter than the photosphere. a. TRUE b. FALSE
a. TRUE
if the distance between us and a star is doubled, its apparent brightness will decrease by a factor of four. a. TRUE b. FALSE
a. TRUE
What is gravitational (or hydrostatic) equilibrium in the Sun? a. The balance between the outward push of internal gas pressure and the inward pull of gravity. b. The balance between the magnetic field pushing inward and the gravitational pressure outward in the Sun. c. The balance between the rate at which fusion produces energy in the core and the rate at which the Sun's surface radiates energy. d. The balance between the magnetic field pushing against the rotation of the Sun.
a. The balance between the outward push of internal gas pressure and the inward pull of gravity.
A spectral type B white dwarf has the same surface temperature as a spectral type B main sequence star. a. True b. False
a. True
Elements heavier than carbon are only produced in high mass stars. a. True b. False
a. True
In any star cluster, stars with lower masses greatly outnumber those with higher masses. a. True b. False
a. True
Neutron stars have very strong magnetic fields. a. True b. False
a. True
Sunspots are cooler areas on the visible surface of the Sun. a. True b. False
a. True
Under what conditions does electron degeneracy occur? a. When electrons become crowded too closely together. b. When ultraviolet light from hot, young O and B stars ionizes the interstellar medium. c. When electrons and positrons annihilate, releasing energy. d. When thermonuclear reactions release more electrons than protons.
a. When electrons become crowded too closely together.
As time progresses, the pulse rate for most solitary pulsars is... a. decreasing, because rotational energy is being used to generate the pulses. b. remaining constant due to conservation of angular momentum. c. varying periodically as the neutron star expands and contracts. d. increasing, because the neutron star slowly contracts.
a. decreasing, because rotational energy is being used to generate the pulses.
Which of the following hypothetical observations would contradict our theories about the formation and evolution of white dwarfs? a. discovery of a white dwarf with a mass 1.8 times that of the Sun (1.8M) b. discovery of a white dwarf with a surface temperature of 6000 K c. discovery of a white dwarf at the center of a planetary nebula d. discovery of a white dwarf with a main-sequence companion star that has mass 1.8M
a. discovery of a white dwarf with a mass 1.8 times that of the Sun (1.8M)
Which has a greater mass? a. four protons b. two neutrons and two protons in a helium nucleus c. neither; (a) and (b) each have exactly the same mass.
a. four protons
Stellar winds can do each of the following EXCEPT a. generate an intense interstellar magnetic field b. clear away the cocoon of gas that surrounds a forming star, revealing the protostar within it c. compress cold gas and set off the formation of other new stars d. shape dusty nebulae into elongated pillars
a. generate an intense interstellar magnetic field
Which of the following phenomena on the Sun is NOT a source of particles that travel out into the solar system? a. granules b. eruptive prominences c. coronal holes d. flares
a. granules
If Star A is closer to Earth than Star B, then Star A's parallax angle ________. a. is larger than that of Star B b. is smaller than that of Star B c. oscillates at a faster rate than that of Star B d. is negative but Star B's parallax angle is positive
a. is larger than that of Star B
A star's evolutionary track is... a. its change of position on the H-R diagram over time. b. its motion through the dark dense cloud in which it was born. c. its orbit about the galactic center. d. the line on the H-R diagram that marks the main sequence.
a. its change of position on the H-R diagram over time.
A white dwarf star is... a. not producing energy, but is slowly cooling. b. producing energy by the release of gravitational energy. c. producing energy by chemical reactions on the surface of the star. d. producing energy through fusion.
a. not producing energy, but is slowly cooling.
What keeps the Sun's outer layers from continuing to fall inward in a gravitational collapse? a. outward pressure due to super-heated gas b. the strong force between protons c. electromagnetic repulsion between protons d. neutrinos produced by nuclear fusion drag the gas outward.
a. outward pressure due to super-heated gas
Solar energy leaves the core of the Sun in the form of _____. a. photons b. rising hot gas c. sound waves d. volcanic eruptions
a. photons
Sunspots are dark because... a. they are cool relative to the gas around them. b. they contain 10 times more iron than the surrounding regions. c. nuclear reactions occur in them at a slower rate than in the surrounding gas. d. they are clouds in the cool corona that block our view of the solar surface. e. absorption lines are clustered together there.
a. they are cool relative to the gas around them.
On a Hertzsprung-Russell diagram, where would you find stars that are cool and luminous? a. upper right b. lower right c. upper left d. lower left e. upper middle
a. upper right
Star A has a +3.0 apparent magnitude. If star B appears 100 times brighter than star A, what is its apparent magnitude? a. −2.0 b. +5.5 c. +7.5 d. +8.0
a. −2.0 (every change of +5 magnitude corresponds to a change of 100 times in brightness)
You measure the parallax angle for a star to be 0.5 arcseconds. The distance to this star is a. 0.5 parsec. b. 2 parsec c. 5 light-years. d. 5 parsecs.
b. 2 parsec (1/0.5)
A binary star consists of two identical stars orbiting each other. If the semimajor axis of the orbit is 4 AU and orbit period is 4 years, how massive is each star? a. 4 solar masses b. 2 solar masses c. 1 solar mass d. 0.50 solar masses
b. 2 solar masses ( 2m[4^2]=4^3)
What is a protostar? a. A star that has used up the fuel in its core and is in the process of dying. b. A hot, dense cloud of gas that is collapsing to form a star. c. A cool, dense cloud of gas. d. A star that is currently fusing hydrogen into helium in its core.
b. A hot, dense cloud of gas that is collapsing to form a star.
Horizontal-branch stars, which have a range of temperatures and luminosities between 50 and 100 times that of the Sun, are in what stage of their lives? a. Core hydrogen burning b. Core helium burning c. Hydrogen shell burning with a degenerate helium core d. Gravitational contraction before the start of core hydrogen burning
b. Core helium burning
Gravitational equilibrium means that the surface and the core of the Sun are at the same pressure. a. TRUE b. FALSE
b. FALSE (Gravitational force causes the surface and the core of the sun to be at very different pressure)
A pulsar is a white dwarf that has an oscillating luminosity. a. TRUE b. FALSE
b. FALSE (Pulsar is a neutron star that is rapid)
Two stars have the same luminosity. Star X is spectral type F, while Star Y is spectral type K. Star X must be larger in radius than Star Y. a. TRUE b. FALSE
b. FALSE (Star X has a smaller radius than Star Y)
Energy from the core of the Sun first travels slowly through a convection zone and then much faster through the outer radiation zone. a. TRUE b. FALSE
b. FALSE (Travels slower through outer radiation zone than through a convection zone)
It is impossible for a star to have a negative apparent magnitude. a. TRUE b. FALSE
b. FALSE (Uncommmon)
The helium fusion process works by fusing two helium nuclei into one beryllium nucleus. a. TRUE b. FALSE
b. FALSE (fusing 3 helium into 1 carbon nucleus)
Protostars tend to form in interstellar clouds of higher density and higher temperature than other regions of space. a. TRUE b. FALSE
b. FALSE (lower temperature)
Protostars smaller than 0.08M will form K-type main sequence stars. a. TRUE b. FALSE
b. FALSE (they will form brown dwarfs)
A protostar is in gravitational (hydrostatic) equilibrium. a. True b. False
b. False
High mass stars have much longer lifetimes because of the large amount of fuel (hydrogen) available to them. a. True b. False
b. False
How will a high mass star (10 solar masses) end its life? a. It will become a white dwarf. b. It will explode. c. It will become a protostar. d. After leaving the main sequence it will slowly cool and become very dim.
b. It will explode.
Which of the following stellar spectral types would appear the bluest? a. F b. O c. A d. G e. M
b. O
The luminosity and spectral classification for several stars are listed below. Which star has the smallest size? a. O type star, luminosity = 100 solar units b. O type star, luminosity = 0.001 solar units c. M type star, luminosity = 0.001 solar units d. M type star, luminosity = 100 solar units
b. O type star, luminosity = 0.001 solar units
Which of the following stars would be the least luminous? a. Any spectral type M star b. Spectral type M main sequence star c. Spectral type O supergiant star d. Spectral type M giant star e. Any spectral type O star f. Spectral type O main sequence star
b. Spectral type M main sequence star
Star X has an apparent magnitude of 3, and star Y has an apparent magnitude of 13. How do they compare in observed brightness? a. Star X is 10 times brighter than star Y. b. Star X is 10,000 times brighter than star Y. c. Star Y is 10 times brighter than star X. d. Star Y is 10,000 times brighter than star X
b. Star X is 10,000 times brighter than star Y. (100 * 100)
Why does the core of an old main sequence star collapse? a. The iron core becomes so massive that its gravitational pull causes the collapse. b. The pressure due to fusion energy production is less. c. The outer layers of the star become too massive. d. Hydrostatic equilibrium forces the core into a smaller volume.
b. The pressure due to fusion energy production is less.
Betelgeuse has a very high luminosity (40,000 times as much as our Sun), but its surface is cool (around 3100 K). Which of the following explains this? a. The star has a much smaller surface area than the Sun. b. The star has a much larger surface area than the Sun. c. The star is very close to our Sun. d. The star's hot core emits more light than the cool surface.
b. The star has a much larger surface area than the Sun.
The photosphere of the Sun is... a. a thin pinkish gas with rising spicules. b. a 5800-K layer with convective granules. c. a hot thin gas energized by the magnetic field. d. a dense, hot layer enriched by helium.
b. a 5800-K layer with convective granules.
The physical process that provides the energy to eject a planetary nebula from a star is... a. the transfer of hydrogen-rich material to the surface by a companion star. b. a series of thermal pulses from helium shell fusion. c. a collision with another star. d. the violent explosion of the shell upon core collapse.
b. a series of thermal pulses from helium shell fusion.
What are coronal holes? a. regions in the photosphere where magnetic lines gather, creating cooler areas with much less plasma b. areas of the corona where magnetic field lines project out into space, allowing charged particles to escape and form the solar wind c. areas in the corona that allow us to see through to the photosphere d. tunnels in the outer layers of the Sun that allow photons to escape and form the solar wind
b. areas of the corona where magnetic field lines project out into space, allowing charged particles to escape and form the solar wind
The _____ of the Sun has the greatest density. a. convective zone b. core c. photosphere d. corona
b. core
The evolution of a star is determined primarily by its _____. a. location in the galaxy b. initial mass c. chemical composition d. surface temperature
b. initial mass
As a 1.0-solar-mass protostar moves toward the main sequence, a. its surface temperature and luminosity increase. b. its surface temperature increases and its luminosity decreases. c. its surface temperature and luminosity decrease. d. its surface temperature decreases and its luminosity increases.
b. its surface temperature increases and its luminosity decreases.
On a Hertzsprung-Russell diagram, where would you find main-sequence stars with the least mass? a. upper right b. lower right c. upper left d. middle left e. lower left
b. lower right
Stars like the Sun probably do not form iron cores during their evolution because... a. all the iron is ejected when they become planetary nebulas. b. their cores never get hot enough for them to make iron by nucleosynthesis. c. the iron they make by nucleosynthesis is all fused into uranium. d. their strong magnetic fields keep their iron in their atmospheres. e. they live such a short time that it is impossible for iron to form in their cores.
b. their cores never get hot enough for them to make iron by nucleosynthesis.
You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster? a. 10,000 years b. 4.6 billion years c. 10 billion years d. 100 billion years.
c. 10 billion years
A star of spectral type B with a mass of 10 times the mass of the Sun lives approximately how long on the main sequence? a. 1,000 years b. 10,000 years c. 100 million years d. 1 billion years e. 10 billion years
c. 100 million years
A star has a high luminosity (100 solar luminosities) and a surface temperature of 3500 K. What type of star is it? a. A high mass-main sequence star b. A low mass-main sequence star c. A red giant d. A white dwarf
c. A red giant
Which of the following processes does NOT lead to star formation? a. Compression of a cold interstellar gas-and-dust cloud by the shock wave from a nearby supernova explosion. b. A collision between two cold interstellar clouds. c. Compression of a hot interstellar gas cloud by its own gravity. d. Compression of a cold part of a large interstellar cloud by another part which contains a group of hot, young, massive stars.
c. Compression of a hot interstellar gas cloud by its own gravity.
Why does stellar main-sequence lifetime decrease with increasing stellar mass? a. It doesn't; higher mass stars have more hydrogen available for fusion, and thus have longer lifetimes. b. Strong stellar winds cause higher mass stars to lose mass quickly. c. Higher core temperatures cause fusion to proceed much more rapidly. d. Higher outward pressure prevents the core hydrogen from being replenished by the star's outer layers
c. Higher core temperatures cause fusion to proceed much more rapidly.
Which of the following is the measure of the total amount of energy per second leaving a star? a. Stellar spectral type b. Apparent brightness c. Luminosity d. Apparent magnitude
c. Luminosity
What color is an emission (or ionization) nebula, and why? a. Red, because it is a cool gas. b. Blue, because it is a hot gas. c. Red, because the main emission spectral line of hydrogen is red. d. Blue, because of blue starlight scattered by the cloud.
c. Red, because the main emission spectral line of hydrogen is red.
Which of the following statements about stellar evolution is true? a. All stars evolve at the same rate, controlled by nuclear fusion and core temperature. b. The more massive the original star, the slower the evolution, because there is more material available for thermonuclear fusion. c. The more massive the original star, the faster the evolution. d. The chemical makeup of the original nebula is the major factor in deciding the rate of stellar evolution.
c. The more massive the original star, the faster the evolution.
Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is true? a. The Sun's radius changes during the 11 year cycle, expanding to its largest size when there are the fewest sunspots. b. When sunspots are at a minimum, we observe the largest number of flares and prominences. c. The number of sunspots gets larger and smaller over the course of 11 years. d. Every 11 years sunspots completely cover the Sun, making its surface much darker.
c. The number of sunspots gets larger and smaller over the course of 11 years.
Which of the following statements about the sunspot cycle is NOT true? a. The number of sunspots peaks approximately every 11 years. b. The magnetic polarity of the Sun reverses approximately every 11 years. c. The rate of nuclear fusion in the Sun peaks about every 11 years. d. At solar minimum, the first sunspots form at mid-latitudes on the Sun.
c. The rate of nuclear fusion in the Sun peaks about every 11 years.
While a protostar is forming, it typically becomes hotter and less luminous. Why? a. Warmer objects are always less luminous. b. Because they follow Wien's Law. c. The size of the protostar is decreasing. d. The protostar is running out of fuel.
c. The size of the protostar is decreasing.
How do astronomers know that globular clusters are old? a. There are no white dwarfs in any globular cluster. b. They do not contain any red giant stars. c. There are no massive main sequence stars in globular clusters. d. Their stars have a high abundance of helium.
c. There are no massive main sequence stars in globular clusters
Which of the following is closest in size (radius) to a neutron star? a. Jupiter b. the Earth c. a city d. a football stadium e. a basketball
c. a city
What type of nebula is very dense and blocks most visible light trying to pass through it? a. emission (or ionization) nebula b. reflection nebula c. dark molecular cloud d. supernova remnant e. planetary nebula
c. dark molecular cloud
What is the source of luminosity for protostars that have not yet become hot enough for fusion in their cores? a. fission from concentrated radioactive elements b. light absorbed from nearby stars c. energy released by infalling matter d. shockwaves from nearby supernova explosions
c. energy released by infalling matter
The granulation pattern that astronomers have observed on the surface of the Sun tells us that... a. the Sun's surface is made of a thin solid that cracks easily. b. the Sun expands and contracts with a four-week cycle. c. hot material must be rising from the Sun's hotter interior. d. the Sun is a lot cooler on the inside than on the outside.
c. hot material must be rising from the Sun's hotter interior.
One major feature that distinguishes a sunspot from other regions on the Sun is... a. its faster rotation around the Sun's axis than neighboring regions. b. its greater light emission compared to the photosphere. c. its very powerful magnetic field. d. the coronal hole that hovers above it.
c. its very powerful magnetic field.
Scientists estimate the central temperature of the Sun using... a. probes that measure changes in Earth's atmosphere. b. probes that travel deep into the Sun and transmit the data to Earth. c. mathematical models of the Sun. d. laboratories that create miniature versions of the Sun.
c. mathematical models of the Sun.
Antares is _____ than Barnard's star because it is ______. a. hotter ... larger b. smaller ... more luminous c. more luminous... larger d. more luminous ... hotter
c. more luminous... larger
The process that produces energy inside a white dwarf is... a. the combining of protons and electrons to form neutrons within its core. b. the helium flash - very efficient and rapid helium fusion. c. nonexistent; a white dwarf is slowly cooling off. d. the fusion of carbon atoms into oxygen.
c. nonexistent; a white dwarf is slowly cooling off.
Compared to the composition of the early Sun, the composition of the gas in the core of a red giant star is... a. very different, because thermonuclear fusion has transformed all the H and He into carbon and heavier elements. b. the same, with a high fraction of H compared to He, because these stars were produced from the same initial material. c. significantly different, with a very high fraction of He and almost no H. d. very different, with lots of H but almost no He after thermonuclear fusion.
c. significantly different, with a very high fraction of He and almost no H.
The Sun's chromosphere is best observed with _____ and the corona is best observed with ______.? a. visible light ... visible light. b. visible light ... radio telescopes. c. ultraviolet telescopes ... X-ray telescopes d. infrared telescopes ... ultraviolet telescopes.
c. ultraviolet telescopes ... X-ray telescopes
A star's parallax angle is 0.83 arcseconds. How far away is this star? a. 1.2 light years b. 2.7 light years c. 4.0 parsecs d. 1.2 parsecs
d. 1.2 parsecs (1/parallax angle= distance in parsecs)
If a star has a mass of 0.25 solar masses, about how long will it live? a. 1/16 solar lifetimes b. 1/4 solar lifetime c. 4 solar lifetimes d. 16 solar lifetimes
d. 16 solar lifetimes (1/mass^2)
What features characterize the chromosphere of the Sun? a. Blackbody radiation emitted from a granulated surface with occasional sunspots. b. Dense gaseous zone dominated by the convective transport of energy. c. Very hot gases that extend to great distances from the Sun and emit X-rays. d. A pinkish color and jets of rising gas called spicules.
d. A pinkish color and jets of rising gas called spicules.
What is a brown dwarf? a. A dense clump of gas and dust that blocks light from behind and inside of it. b. A pre-main-sequence star with a mass between 2 and 7 solar masses. c. The slowly cooling core of an exploded star. d. A pre-main-sequence star with a mass less than 0.08 solar masses.
d. A pre-main-sequence star with a mass less than 0.08 solar masses.
The star Sirius has an apparent magnitude of −1.5, whereas the Andromeda galaxy has an apparent magnitude of +3.5. As seen from Earth, how does the apparent brightness of each object compare? a. Andromeda is 100 times brighter than Sirius. b. Andromeda is 5 times brighter than Sirius. c. Andromeda is 2 times brighter than Sirius. d. Andromeda is 100 times fainter than Sirius.
d. Andromeda is 100 times fainter than Sirius.
What makes a red giant star so large? a. The helium-rich core has expanded, pushing the outer layers of the star outward. b. The star has many times more mass than the Sun. c. Centrifugal force from rapid rotation. d. Hydrogen shell fusion is heating the envelope and making it expand.
d. Hydrogen shell fusion is heating the envelope and making it expand.
What is the fate of an isolated brown dwarf? a. It will become a white dwarf. b. It will become a neutron star. c. It will slowly evaporate to nothing. d. It will remain a brown dwarf forever.
d. It will remain a brown dwarf forever.
The oldest star cluster is the one where the brightest main-sequence stars are a. O stars. b. A stars. c. G stars. d. M stars. e. B stars.
d. M stars.
What process is most likely producing the energy in the Sun? a. Nuclear fission, the breaking up of larger nuclei to create smaller nuclei plus energy. b. Slow release of gravitational energy by material falling inward. c. Chemical energy from the combination of hydrogen and oxygen atoms to form water. d. Nuclear fusion, the combination of small nuclei to create larger nuclei plus energy.
d. Nuclear fusion, the combination of small nuclei to create larger nuclei plus energy.
What do sunspots, solar prominences, and solar flares all have in common? a. They all release about the same amount of energy. b. They are all shaped by the solar wind. c. They all occur only in the Sun's photosphere. d. They are all strongly influenced by magnetic fields on the Sun.
d. They are all strongly influenced by magnetic fields on the Sun.
A planetary nebula is... a. the nebula created by the supernova explosion of a massive star. b. a cloud of gas and dust surrounding newly formed planets from which their moons will eventually form. c. a disk-shaped nebula of dust and gas rotating around a relatively young star, within which planets will eventually form. d. a shell of ejected gases, glowing by fluorescence caused by ultraviolet light from the hot, central white dwarf star.
d. a shell of ejected gases, glowing by fluorescence caused by ultraviolet light from the hot, central white dwarf star.
The energy produced in the central core of the Sun is transported to the surface... a. by convection in the layers just outside the central core and by radiation in the outer layers. b. by convection from just outside the central core all the way to the surface. c. by radiation from just outside the central core all the way to the surface. d. by radiation in the layers just outside the central core and by convection in the outer layers.
d. by radiation in the layers just outside the central core and by convection in the outer layers.
X-ray images of the Sun generally show the _____. a. convective zone b. radiative zone c. chromosphere d. corona
d. corona
The most common element in the Sun is _____. a. helium b. nitrogen c. iron d. hydrogen
d. hydrogen
The spectral type of the Sun is G and the spectral type of the star Antares is K. These facts imply that Antares... a. has a lower luminosity than the Sun. b. is hotter than the Sun. c. has a higher luminosity than the Sun d. is cooler than the Sun.
d. is cooler than the Sun.
Observations of binary stars are used to measure the _____ of a star. a. temperature b. luminosity c. distance d. mass
d. mass
Which of the following is NOT a method astronomers use to determine the physical conditions inside the Sun? a. building mathematical models that use the laws of physics b. detecting solar neutrinos generated in the Sun's core c. measuring Doppler shifts to observe solar vibrations d. observing X-ray images of the solar interior using satellites
d. observing X-ray images of the solar interior using satellites
There are several mechanisms that can trigger star formation in a cold, dark nebula. In each of these the key to star formation is... a. to heat the gas so that gas pressure will overcome gravitation. b. to bathe the cold, dark nebula in ultraviolet radiation and sweep away some of the colder material. c. to subject the dark nebula to an intense magnetic field so that supersonic jets will form. d. to compress the gas and dust so that gravitation will overcome the gas pressure.
d. to compress the gas and dust so that gravitation will overcome the gas pressure.
The heaviest element that is produced in the core of a high mass star is _______.
Iron
The visible surface of the Sun is called the _____.
Photosphere
Large loops of material projected off of the Sun that follow the magnetic field lines of the Sun are called _____.
Prominences
A rapidly rotating neutron star that is periodically beaming light in the direction of the Earth is called a ______.
Pulsar
The explosion of a very massive star at the end of its life is called a ______.
Supernova