Astronomy CH.1-3

The choices below each describe the appearance of an H-R diagram for a different star cluster. Which cluster is the youngest? A)The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants. b)The diagram shows no main-sequence stars at all, but it has numerous supergiants and white dwarfs. c)The diagram shows main-sequence stars of spectral types G, K, and M, along with numerous giants and white dwarfs. d) The diagram shows main-sequence stars of all the spectral types except O and B, along with a few giants and supergiants.

A)The diagram shows main-sequence stars of every spectral type except O, along with a few giants and supergiants.

The lifetime of a star on the main sequence is directly proportional to the amount of mass (fuel) it contains and inversely proportional to the rate at which it uses up that fuel (i.e., to its luminosity). Since this lifetime for the Sun is about 1010 years, we have the following approximate relationship: T = 1010 (M/L) years where T is the lifetime of a main-sequence star, M is its mass measured in terms of the mass of the Sun, and L is its luminosity measured in terms of the Sun's luminosity. What is the approximate main-sequence lifetime of a star with 3 times the mass of the Sun and 90 times its luminosity? A. 0.33x10^9 years B. 0.87x10^9 years C. 10.0x10^9 years D. 0.43x10^9 years E. 0.023x10^9 years

A. 0.33x10^9 years

What is the gravitational effect of a large planet on a star? A. It causes a wobble in the star's motion. B. It causes a Doppler shift in the star's light. C. It causes the star to contract. D. It causes the star to rotate faster.

A. It causes a wobble in the star's motion.

Why is the observation of molecular clouds almost impossible? A. They are shrouded in dust and quickly change. B. They change too slowly to observe in one lifetime. C. They dissociate quickly in the UV light. D. They give off too much visible light.

A. They are shrouded in dust and quickly change.

Why do astronomers think gamma-ray bursts are directed beams? A. Otherwise they would be rarer B. Otherwise they would be invisible C. Otherwise the total energy would be too great D. Otherwise we would see fewer of them E. Otherwise we would not detect their pulsing radiation

C. Otherwise the total energy would be too great

What is the source for the energy a white dwarf radiates? A. Hydrogen shell burning B. Angular momentum C. Residual internal heat D. Gravitational contraction E. Carbon fusion

C. Residual internal heat

How thick is the disk of the Milky Way? A. 100 light-years B. 1000 light-years C. 5000 light-years D. 20,000 light-years E. 35,000 light-years

B. 1000 light-years

How long does it take planets to form? A. Under 1 million years B. 3 to 30 million years C. 13.5 billion years D. Over 3 billion years

B. 3 to 30 million years

What do we call a protostar once almost all of the material has been accreted and it's near its final mass? A. A Herbig-Haro object B. A T Tauri star C. A Cepheid variable D. A brown dwarf

B. A T Tauri star

How far from the galactic center is the Sun? A. About 6,000 ly B. About 26,000 ly C. About 50,000 ly D. About 100,000 ly

B. About 26,000 ly

What causes a type Ia supernova? A. The collapse of a massive star B. Large amounts of material dumped on a white dwarf C. The collapse of a black hole D. Two neutron stars colliding E. The collapse of a neutron degenerate core

B. Large amounts of material dumped on a white dwarf

Which of the following statements about galaxies is true? A. Small galaxies outnumber large galaxies and produce most of the light in the universe. B. Small galaxies outnumber large galaxies but large galaxies produce most of the light in the universe. C. There is an approximately equal number of small and large galaxies in the universe and together they each contribute an equal amount of light. D. Most galaxies in the universe are about the same size as the Milky Way. E. Galaxies come in a wide variety of shapes and sizes but are all very blue in color.

B. Small galaxies outnumber large galaxies but large galaxies produce most of the light in the universe.

All the following statements about known extrasolar planets are true. Which one came as a surprise to scientists who expected other solar systems to be like ours? A. Most of the planets orbit stars that are quite nearby compared to the scale of the entire Milky Way Galaxy. B. Some of the planets orbit their star more closely than Mercury orbits the Sun. C. In some cases, we've found more than one planet orbiting the same star. D. Most of the planets are quite massive—much more like Jupiter than like Earth.

B. Some of the planets orbit their star more closely than Mercury orbits the Sun.

What does the equivalence principle say? A. Gravity is the same thing as the curvature of spacetime. B. The effects of gravity are exactly equivalent to the effects of acceleration. C. You cannot distinguish between motion at constant velocity and weight in a gravitational field. D. The effects of relativity are exactly equivalent to those predicted by Newton's laws of motion. E. All observers must always measure the same (equivalent) weights for moving objects.

B. The effects of gravity are exactly equivalent to the effects of acceleration.

If a very distant galaxy looks blue overall to astronomers, from this they can conclude that A. The galaxy is moving toward us at a great speed B. The galaxy must have a lot of young stars and thus active star formation must still be going in it C. The galaxy must be composed mostly of very old stars D. The galaxy must not be especially massive when compared to most galaxies

B. The galaxy must have a lot of young stars and thus active star formation must still be going in it

Why are older groups of stars easier to see? A. They are brighter than most stars. B. They are no longer shrouded in dust and gas. C. They emit light in the infrared. D. They are closer to the Sun.

B. They are no longer shrouded in dust and gas.

If faster galaxies are farther away, and there is a direct proportion between speed and distance, then A. all galaxies must be avoiding ours. B. all galaxies must have begun moving apart at the same place and time. C. our galaxy must be in the center of the universe.

B. all galaxies must have begun moving apart at the same place and time.

Which type of galaxy is observed to contain mostly older stars? A. spiral B. elliptical C. dwarf elliptical D. irregular E. none of these

B. elliptical

If I want to find a sizeable collection of Population II stars in the Milky Way Galaxy, where would be a good place to look? A. near the Sun B. in a globular cluster high above the Galaxy's disk C. in the outer surface of giant molecular clouds D. in an open cluster, especially one with a lot of dust in and around it

B. in a globular cluster high above the Galaxy's disk

According to our modern "bottom-up" model of the formation of large structures in the universe, the structures that formed first were about the mass of a: A. star B. large globular cluster or a small galaxy C. giant elliptical galaxy D. supercluster of galaxies E. an ice-cold mug of root beer

B. large globular cluster or a small galaxy

What observations about disks of dusty material around young stars suggest that planets may be forming in such disks? A. the disks give off x-rays and gamma-rays characteristic of small planets B. the disks show lanes that are empty of dust within them C. the disks show evidence of very strong winds coming from the star D. the disks are making the stars "wiggle"—move back and forth across the sky—in a way that can be observed even with small telescopes

B. the disks show lanes that are empty of dust within them

Before you can use Hubble's Law to get the distance to a galaxy, what observation must you make of that galaxy? A. you must find a Cepheid variable star in the galaxy B. you must take a spectrum of the galaxy and measure the redshift C. you must measure how strongly the galaxy emits radio waves at a wavelength of 21 centimeters D. you must find a Type Ia supernova that is exploding in that galaxy E. all you need to do is look at the galaxy through any telescope

B. you must take a spectrum of the galaxy and measure the redshift

What is the typical lifetime for a pulsar? A. 10 billion years B. 12 billion years C. 10 million years D. 10 billion years E. 1 billion years

C. 10 million years

The color of this galaxy indicates that A. It has both young and old stars in it B. It has a young stellar population C. It has an old stellar population D. It is still forming its stellar population E. It is impossible to infer anything about the stellar population from this image

C. It has an old stellar population

What happens to the ratio of heavier elements in each generation of stars? A. Fewer heavier elements are present in each generation. B. Heavy elements end up in planets and don't affect stars. C. More heavier elements are present in each generation. D. Heavy elements break down in supernovae.

C. More heavier elements are present in each generation.

Suppose we observe a source of X-rays that varies substantially in brightness over a period of a few days. What can we conclude? A. The X-ray source is a quasar. B. The X-ray source contains a black hole with an accretion disk. C. The X-ray source is no more than a few light-days in diameter. D. The X-ray source must have a strong, rapidly varying magnetic field.

C. The X-ray source is no more than a few light-days in diameter.

What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure? A. The core contracts and becomes a white dwarf. B. The core contracts and becomes a ball of neutrons. C. The core contracts and becomes a black hole. D. The star explodes violently, leaving nothing behind. E. Gravity is not able to overcome neutron degeneracy pressure.

C. The core contracts and becomes a black hole.

William Herschel thought that the Sun and Earth were roughly at the center of the great grouping of stars we call the Milky Way. Today we know this is not the case. What was a key reason that Herschel did not realize our true position in the Milky Way? A, He did not have a telescope, and most stars are too far away to see without a telescope B. His telescope was only able to show him objects inside the solar system, and not objects in the Galaxy C. The dust that extends throughout the disk of the Galaxy only allowed Herschel to see the small part of the Milky Way that surrounds us D. Herschel shared with ancient people the firm religious belief that we must be the center of everything

C. The dust that extends throughout the disk of the Galaxy only allowed Herschel to see the small part of the Milky Way that surrounds us

How did star formation likely proceed in the protogalactic cloud that formed the Milky Way? A. The protogalactic cloud gradually formed stars, starting from the outer edges of the spiral arms and working inward. B. The stars that formed first eventually settled into a galactic disk, circling the center of the galaxy. C. The stars that formed first could orbit the center of the galaxy in any direction at any inclination. D. The protogalactic cloud gradually formed stars, starting from the center of the galaxy working outwards.

C. The stars that formed first could orbit the center of the galaxy in any direction at any inclination.

By examining rich clusters of galaxies, such as the Coma cluster, astronomers have discovered that spiral galaxies A. grow to be very large and bright at the centers of these clusters B. turn out to be most of the galaxies in such clusters, and many are found throughout each cluster C. are found mostly in the outer regions of such clusters, not in the middle D. are all tilted exactly the same way in such cluster; all their disks are fully aligned

C. are found mostly in the outer regions of such clusters, not in the middle

In 1959, Pound and Rebka did an experiment to test the prediction of Einstein's theory of general relativity about the relationship between the pace of time and the strength of gravity. When two identical atomic clocks, one on the ground floor and one on the top floor, were compared, A. the clocks ran at exactly the same pace in both locations B. the clock on the top floor ran a tiny bit slower C. the clock on the ground floor ran a tiny bit slower D. the clock on the top floor became a little bit lighter

C. the clock on the ground floor ran a tiny bit slower

In the first direct detection of gravitational waves by LIGO in 2015, the waves came from: A. the collapse of a nearby star into a white dwarf B. a supernova explosion in a nearby galaxy C. the merger of two black holes D. the rapid motion of three hot Jupiter planets around a nearby star E. the dashed hopes of all the people in the U.S. who want their government to work well for them

C. the merger of two black holes

What leads astronomers to conclude that the proto-galactic cloud (the cloud from which our Galaxy formed) was roughly spherical? A. all black holes have spherical event horizons B. the shape of the disk and spiral arm of the Milky Way Galaxy is spherical, so the original cloud must have been too. C. the oldest stars in the Galaxy (Population II stars, globular clusters) form a spherical halo around the Galaxy; they outline the original shape of the cloud that gave the Galaxy birth D. since the Big Bang made everything was spherical, all structures in the universe must also be spherical

C. the oldest stars in the Galaxy (Population II stars, globular clusters) form a spherical halo around the Galaxy; they outline the original shape of the cloud that gave the Galaxy birth

What does the equivalent of an H-R diagram for galaxies, plotting luminosity versus color, show? A. galaxies fill the diagram showing that there is no correlation between luminosity and color. B. a continuum from faint, blue galaxies to bright, red galaxies C. two clumps, one blue with relatively low luminosity, one red with relatively high luminosity, and a valley in between with few galaxies. D. a continuum from faint, red galaxies to bright, blue galaxies. E. A main sequence, just as for stars

C. two clumps, one blue with relatively low luminosity, one red with relatively high luminosity, and a valley in between with few galaxies.

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 A. 100 million. B. 1 billion. C. 10 billion. D. 100 billion. E. 1 trillion.

D. 100 billion.

How much mass does the entire Milky Way have? A. About 100 billion solar masses B. About 200 billion solar masses C. About 300 billion solar masses D. About 2 trillion solar masses

D. About 2 trillion solar masses

Where do long-duration gamma-ray bursts come from? A. The galactic core B. Nearby stars C. Globular clusters D. Distant galaxies

D. Distant galaxies

What do we know about the amount of heavy elements in globular clusters? A. It is half the amount in other clusters. B. It is twice the amount in other clusters. C. It is the same as the amount in other clusters. D. It is 1-10% of the amount in younger clusters.

D. It is 1-10% of the amount in younger clusters.

What can happen when a white dwarf steals material from a partner in a binary system? A. It forms a planetary nebula. B. It grows into a white giant. C. It collapses and becomes a neutron star. D. It quickly burns the hydrogen, causing a nova. E. It shrinks and becomes a black dwarf

D. It quickly burns the hydrogen, causing a nova.

What does the fact that the oldest stars in the galactic disk are the same age as the youngest stars in the halo indicate? A. That they formed in different galaxies and then merged B. That the galaxy was primarily first-generation stars C. That the stars migrated after they formed D. That the galactic collapse must have been rapid

D. That the galactic collapse must have been rapid

As a cluster of stars begins to age, which type of star in the cluster will move off the main sequence of the H-R diagram first? A. All the stars in a cluster are born at the same time, so they will all move off the main sequence at the same time, as they evolve B. G type stars, like our Sun C. M type stars, which are the coolest D. The O and B type stars

D. The O and B type stars

How did SN 1987A demonstrate that new elements are made in supernova explosions? A. Spectra of the supernova light revealed elements that have never been found on Earth or the stars B. The neutrinos observed from the supernova could only be produced through radioactive decay of heavy elements C. A pulsar with new elements in it was found using radio telescopes in England D. The light output was kept at high levels by the energy released from radioactive elements that decay very quickly; these must have been made by the supernova

D. The light output was kept at high levels by the energy released from radioactive elements that decay very quickly; these must have been made by the supernova

Where do heavier elements like iron and gold come from? A. They were created inside molecular clouds. B. The were created in the Big Bang. C. They were created inside planets. D. They were created inside more massive stars.

D. They were created inside more massive stars.

As a star becomes a giant, its outer layers are expanding. Where does the energy for expanding these layers come from? A. from the fusion of helium into carbon in the core. B. from the long-term fusion of hydrogen into helium in the core. C. from an explosion in the core. D. from the fusion of hydrogen into helium in a shell around the core.

D. from the fusion of hydrogen into helium in a shell around the core.

Calculations show that gravity begins to overcome thermal pressure in clouds that are A. less massive than the Sun. B. more massive than the Sun. C. more massive than ten times the Sun. D. more massive than a hundred times the Sun. E. more massive than a thousand times the Sun.

D. more massive than a hundred times the Sun.

Which of the following is evidence that the formation process of our Galaxy may have included collisions with smaller neighbor galaxies? A. the presence of millions of new stars, recently formed from clouds of gas and dust B. the existence of supernova remnants, such as the Crab Nebula, in the Galaxy's disk C. the observation that globular clusters are arranged in a spherical "halo" around the Galaxy D. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo

D. the observation of long moving streams of stars that continue to orbit through our Galaxy's halo

The "great voids" that astronomers studying galaxies are finding are: A. regions where a number of black holes have cleared out space in the center of a galaxy B. empty regions between the spiral arms of the Milky Way Galaxy C. huge regions inside spiral galaxies, where the powerful radiation from a very hot star has cleared out the local interstellar material D. very large regions of intergalactic space, where relatively few galaxies or galaxy clusters can be found

D. very large regions of intergalactic space, where relatively few galaxies or galaxy clusters can be found

What has happened to the number of quasars over time? A. It has steadily decreased. B. It has steadily increased. C. It has remained fairly constant. D. It peaked over 7 billion years ago. E. It peaked when the universe was ~2 billion years old.

E. It peaked when the universe was ~2 billion years old.

What type of radiation does material entering an event horizon emit? A. Radio B. None, because no radiation can come from anywhere near a black hole. C. Ultraviolet D. Infrared E. X-ray

E. X-ray

How do we know what goes on under the surface of the Sun? A. We have X-ray images from satellites of the interior of the Sun. B. Astronomers create mathematical models that use the laws of physics, the Sun's observed composition and mass, and computers to predict internal conditions. C. We have sent probes below the surface of the Sun. D. By measuring Doppler shifts, we observe vibrations of the Sun's surface that are created deep within the Sun. E. both B and D

E. both B and D

In the far future, a starship becomes trapped inside the event horizon of a black hole. Although the crew discovers that their ship cannot get out, they at least want to send a message to other ships in the area to stay away from the danger zone. If they send out a message in the form of a radio wave, what will be its fate? A. the message will emerge from the event horizon with a huge gravitational redshift B. although the radio wave will emerge from the event horizon, all the information in the message will be garbled C. the radio wave will become a gamma ray by the time it emerges from the event horizon D. the radio wave will only emerge from the event horizon if it is moving in the direction of the magnetic north and south pole of the star that formed the black hole E. the message will never emerge from the event horizon

E. the message will never emerge from the event horizon

If you have a 100-watt light bulb, how much energy does it use each minute? a)6,000 joules b)6,000 watts c)600 joules d)600 watts e)100 joules

a) 6,000 joules

Suppose that, for some unknown reason, the core of the Sun suddenly became hotter. Which of the following best describes what would happen? Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and turn the Sun into a giant star. a) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal. b) Higher temperature would cause the rate of fusion to fall, decreasing the internal pressure and causing the core to collapse until the rate of fusion returned to normal. c) The higher temperature would not affect the fusion rate but would cause the core to expand and cool until the temperature returned to normal, with the core at a new, slightly larger size.

a) Higher temperature would cause the rate of nuclear fusion to rise, which would increase the internal pressure, causing the core to expand and cool until the fusion rate returned to normal.

In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot thanks to gravitational contraction. What was the major drawback of this idea? a) It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth. b) It predicted that the Sun would shrink noticeably as we watched it, and the Sun appears to be stable in size. c) It is physically impossible to generate heat simply by making a star shrink in size. d) It predicted that Earth would also shrink, which would make it impossible to have stable geology on our planet. e) It was proposed before Einstein's theory of general relativity and was therefore incorrect.

a) It predicted that the Sun could last only about 25 million years, which is far less than the age of Earth.

What is the baseline that astronomers use to measure the parallax (the distance) of the nearest stars? a) the diameter of the Earth's orbit around the Sun b)the diameter of the Earth c)no one can measure parallax for the stars; only for planets in our solar system d)the distance between observatories in Greenwich, England and Washington, DC e) the distance between the Earth and the Moon

a) the diameter of the Earth's orbit around the Sun

Alpha Centauri A lies at a distance of 4.4 light-years and has an apparent brightness in our night sky of 2.7 * 10-8 (watt)/m2. Recall that 1 (light-year) = 9.5 * 1012 (km)= 9.5* 1015 m. Use the inverse square law for light to calculate the luminosity of Alpha Centauri A. a)5.9x10^26 watts b)1.5x10^26 watts c) 4.7x10^25 watts d) 2.7x10^24 watts

a)5.9x10^26 watts

Which of the following persons reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars? a)Annie Jump Cannon b)Williamina Fleming c) Cecilia Payne-Gaposchkin d)Henry Draper e) Edward Pickering

a)Annie Jump Cannon

What do we mean by the event horizon of a black hole? a)It is the boundary within which events in the black hole cannot influence events in the outside universe. b)It is the "bottomless pit" of the black hole. c)It is the place where time begins to slow down as you approach a black hole. d)It is the center of the black hole.

a)It is the boundary within which events in the black hole cannot influence events in the outside universe.

What happens to the surface temperature and luminosity when gravity first assembles a protostar from a collapsing cloud? a)Its surface temperature and luminosity increase. b)Its surface temperature remains the same and its luminosity decreases. c)Its surface temperature and luminosity decrease. d)Its surface temperature decreases and its luminosity increases. e)Its surface temperature and luminosity remain the same.

a)Its surface temperature and luminosity increase.

How do observations of distant galaxies help us learn about galaxy evolution? a)Observations at different distances show galaxies of different ages and therefore different stages of evolution. b)We can observe the birth of galaxies. c)We can observe the evolution of a single galaxy over time. d)We can observe two galaxies merging and what the result is, helping us learn how mergers affect evolution. e)We can see what our galaxy used to look like and therefore theorize about the physical processes that led to its current appearance.

a)Observations at different distances show galaxies of different ages and therefore different stages of evolution.

Why are collisions between galaxies more likely than collisions between stars within a galaxy? a)Relative to their sizes, galaxies are closer together than stars. b)Galaxies are much larger than stars. c)Galaxies travel through space much faster than stars. d)Galaxies have higher redshifts than stars.

a)Relative to their sizes, galaxies are closer together than stars.

Why is the spectral sequence of stars not alphabetical? a)The letters refer to the initials of the original discovers. b)The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered. c)They were chosen to fit a mnemonic. d)Because there is still uncertainty over what generates the energy in stellar cores. e)Because it refers to stellar masses and these were difficult to measure accurately

a)The original alphabetical labeling did not correspond to surface temperature and thus had to be reordered.

Which of the following statements correctly explains why HII regions appear red? a)The red Hα line is the strongest emission line in the visible portion of the hydrogen spectrum. b)HII regions are typically moving away from us, producing a redshift. All other colors emitted by an HII region are scattered away by dust, producing a reddened appearance. c)Stars within HII regions are typically low-mass main sequence stars and evolved giants, both of which have cooler surface temperatures. d)The regions that are found near red giant stars.

a)The red Hα line is the strongest emission line in the visible portion of the hydrogen spectrum.

Suppose a white dwarf is gaining mass because of accretion in a binary system. What happens if the mass someday reaches the 1.4-solar-mass limit? a)The white dwarf undergoes a catastrophic collapse, leading to a type of supernova that is somewhat different from that which occurs in a massive star but is comparable in energy. b)The white dwarf, which is made mostly of carbon, suddenly becomes much hotter in temperature and therefore is able to begin fusing the carbon. This turns the white dwarf back into a star supported against gravity by ordinary pressure. c)The white dwarf immediately collapses into a black hole, disappearing from view. d)A white dwarf can never gain enough mass to reach the limit because a strong stellar wind prevents the material from reaching it in the first place.

a)The white dwarf undergoes a catastrophic collapse, leading to a type of supernova that is somewhat different from that which occurs in a massive star but is comparable in energy.

Which of the following statements correctly explains why molecules like H2, H20, NH3, etc. form inside dark nebulae, rather than filling all of interstellar space? a)These molecules are easily broken up by starlight and can only form where they are protected from such photons. b)There are no elements available outside dark nebulae with which these molecules can form. c)Outside of dark nebulae these molecules quickly form stars and planets rather than remaining as free molecules. d)Outside of dark nebulae these molecules quickly form even larger molecules rather than remaining individualized.

a)These molecules are easily broken up by starlight and can only form where they are protected from such photons.

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? a)We are seeing absorption lines from clouds of gas that lie between us and the quasar, and therefore each cloud has a different redshift. b)Quasars are rotating rapidly, and this rotation produces spectral lines with a wide variety of Doppler shifts. c)The lines fall at different wavelengths because they are produced by different chemical elements. d)No one knows—it remains perhaps the greatest mystery about quasars.

a)We are seeing absorption lines from clouds of gas that lie between us and the quasar, and therefore each cloud has a different redshift.

A few decades ago, there was great controversy among astronomers over the question of quasar distances, with some arguing that quasars are much nearer than application of Hubble's law would seem to imply. Why do nearly all astronomers now agree that quasars really are quite far away? a)We now have images and spectra that show quasars to be embedded at the centers of distant galaxies and within distant galaxy clusters. b)All quasars have large redshifts. c)Now that we can explain bright quasar emission with power due to the presence of supermassive black holes, there is no reason to doubt that quasars are far away. d)No one could think of a way to explain quasar speeds if they are nearby, so we concluded they must be far away.

a)We now have images and spectra that show quasars to be embedded at the centers of distant galaxies and within distant galaxy clusters.

Why do we think the first generation of stars would be different from stars born today? a)Without heavy elements, the clouds could not reach as low a temperature as today and had to be more massive to collapse. b)Without heavy elements, the nuclear reactions at the center of the stars would be very different. c)Without heavy elements, there was no dust in the clouds and they collapsed faster. d)The Universe was much denser when the first stars were born. e)There were no galaxies when the first stars were born.

a)Without heavy elements, the clouds could not reach as low a temperature as today and had to be more massive to collapse.

An astronomer wants to observe a cloud of cold neutral hydrogen, far away from any stars. What would be an instrument that could help in this task? a)a radio telescope, tuned to a wavelength of ~21 cm. b)a large telescope observing visible light, but with a very sensitive CCD detector, deep underground. c)a telescope in space, able to pick up x-rays from space. d)you can't fool me, there is no way to observe clouds of hydrogen that are not near a star.

a)a radio telescope, tuned to a wavelength of ~21 cm.

By studying main-sequence turn-off points, astronomers have learned that globular clusters __________. a)are always very old; typically 12 to 13 billion years old b)are always very young; typically just a few million years old c)come in a wide variety of ages, from very young to very old

a)are always very old; typically 12 to 13 billion years old

Cosmic rays are: a)high-speed atomic nuclei, electrons, and positrons b)neutrinos of various types c)fast-moving dust grains d)high-energy electro-magnetic radiation

a)high-speed atomic nuclei, electrons, and positrons

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 a)light emitted by hot gas in an accretion disk that swirls around the black hole. b)intense radiation emitted by the black hole itself. c)the combined light of thousands of young, high-mass stars that orbit the black hole. d)radio waves emitted from radio lobes found on either side of the galaxy we see in visible light.

a)light emitted by hot gas in an accretion disk that swirls around the black hole.

On the life track of one-solar-mass protostar, when does a newly forming star have the greatest luminosity? a)when it is a shrinking protostar with no internal fusion b)when it first becomes a main-sequence star c)when its internal temperature becomes high enough for nuclear fusion d)when its surface temperature is the highest

a)when it is a shrinking protostar with no internal fusion

What happens to energy in the convection zone of the Sun? Energy slowly leaks outward through the diffusion of photons that repeatedly bounce off ions and electrons. a)Energy is produced in the convection zone by nuclear fusion. b) Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma. c) Energy is consumed in the convection zone by the creation of electrons and positrons. d) Energy is conserved so while the gas moves up and down, there is no net transport of energy.

b) Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.

Suppose you measure the parallax angle for a particular star to be 0.1 arcsecond. The distance to this star is a)10 light-years. b)10 parsecs. c)0.1 light-year. d)0.1 parsec. e)impossible to determine.

b)10 parsecs.

You can use the mass-luminosity relation to estimate the mass of a star if you know (or measure) its luminosity. But it's important to bear in mind that this only works for main-sequence stars. The fifth brightest-looking star in the sky is Vega, which has a luminosity of 60 LSun. What is its mass in solar masses? a)1.78 b)2.78 c)3.86 d)7.75 e)4.09

b)2.78

How does the spectrum of a molecule differ from the spectrum of an atom? a)A molecule does not have spectral lines due to electrons changing energy levels. b)A molecule has additional spectral lines due to changes in its rotational and vibrational energies. c)Molecules only have spectral lines at ultraviolet wavelengths. d)Most atoms only have spectral lines at infrared wavelengths. e) An atom has a wider range of spectral lines than molecules.

b)A molecule has additional spectral lines due to changes in its rotational and vibrational energies.

What causes the radio pulses of a pulsar? a)The star vibrates. b)As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse. c)The star undergoes periodic explosions of nuclear fusion that generate radio emission. d)The star's orbiting companion periodically eclipses the radio waves emitted by the main pulsar. e)A black hole near the star absorbs energy and re-emits it as radio waves.

b)As the star spins, beams of radio radiation sweep through space. If one of the beams crosses Earth, we observe a pulse.

What detection can tell us there is a p-p chain nuclear reaction in the core of the Sun? a)Detection of sun light b)Detection of neutrinos from the Sun c)Detection of gamma-ray from the Sun d)Detection of X-ray from the Sun

b)Detection of neutrinos from the Sun

What happens to the visible radiation produced by new stars within a molecular cloud? a)It escapes the cloud completely. b)It is absorbed by dust grains and heats up the cloud. c)It is reflected back onto the protostar, heating it up further. d)The blue light is absorbed and the red light transmitted. It shoots out in bright jets.

b)It is absorbed by dust grains and heats up the cloud.

What happens to the visible radiation produced by new stars within a molecular cloud? a)It escapes the cloud completely. b)It is absorbed by dust grains and heats up the cloud. c)it is reflected back onto the protostar, heating it up further. d)The blue light is absorbed and the red light is transmitted. It shoots out in bright jets.

b)It is absorbed by dust grains and heats up the cloud.

If an astronomer wanted to find some relatively complex molecules in space, what technique should she use? a)Take a spectrum of the visible light coming from our own Sun b)Point a radio telescope into regions in the galaxy where there is a lot of dust c)Use the Hubble Space Telescope to take many visible-light images of faint nebulae d)point a gamma-ray telescope toward the center of the Milky Way Galaxy

b)Point a radio telescope into regions in the galaxy where there is a lot of dust

Why is there an upper limit to the mass of a white dwarf? a)White dwarfs come only from stars smaller than 1.4 solar masses. b)The more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure. c)The more massive the white dwarf, the higher its temperature and hence the greater its degeneracy pressure. At about 1.4 solar masses, the temperature becomes so high that all matter effectively melts, even individual subatomic particles. d)The upper limit to the masses of white dwarfs was determined through observations of white dwarfs, but no one knows why the limit exists. e)Above this mass, the electrons would be pushed together so closely they would turn into neutrons and the star would become a neutron star.

b)The more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure.

Why is it so difficult to take pictures of extrasolar planets? a)Telescopes are too busy with other projects. b)Their light is overwhelmed by the light from their star. c)Extrasolar planets give off light at different wavelengths than planets in our solar system. d)No telescope is powerful enough to detect the faint light from a distant planet.

b)Their light is overwhelmed by the light from their star.

At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter? a)a gas of rapidly moving molecules b)a plasma consisting of positively charged ions and free electrons c)a gas consisting of individual, neutral atoms, but no molecules d)a plasma consisting of rapidly moving, neutral atoms e) none of the above (At these extremely high temperatures, matter cannot exist.)

b)a plasma consisting of positively charged ions and free electrons

Elements heavier than carbon __________. a)were all produced during the Big Bang b)are manufactured in high-mass stars c)are manufactured in low-mass stars

b)are manufactured in high-mass stars

The following questions refer to the sketch below of an H-R diagram for a star cluster. Consider the star to which the arrow points. How is it currently generating energy? a)by gravitational contraction b)by hydrogen shell burning around an inert helium core c)by core hydrogen fusion d)by core helium fusion combined with hydrogen shell burning e)by both hydrogen and helium shell burning around an inert carbon core

b)by hydrogen shell burning around an inert helium core

Astronomers now understand that the dark regions or rifts in parts of our Galaxy that are otherwise crowded with stars are caused by: a)holes in the structure of our Galaxy b)clouds with a considerable amount of dust which blocks the light of the stars behind them c)Starlight being blocked by otherwise invisible planets at the outskirts of our solar system d)the absence of stars in regions that have been cleared out by recent explosions

b)clouds with a considerable amount of dust which blocks the light of the stars behind them

What kind of pressure supports a white dwarf? a)neutron degeneracy pressure b)electron degeneracy pressure c)thermal pressure d)radiation pressure e)all of the above

b)electron degeneracy pressure

Which of the following types of galaxies are most commonly found in large clusters? a)spirals b)ellipticals c)lenticulars d)irregulars

b)ellipticals

elescopes being planned for the study of the earliest stages in galactic life will be optimized for observations in a)visible light. b)infrared light. c)radio waves. d)X rays.

b)infrared light.

The following questions refer to the H-R diagram below that shows the life track of a 1-solar-mass star, with various stages labeled with Roman numerals. During which stage does the star have an inert (nonburning) helium core? a)iii b)iv c)vi d)vii e)viii

b)iv

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? a)observations of X-rays from Sgr A* b)measurements of the orbital speeds and distances of the gas clouds and the stars around Sgr A* c)measurements of the precise amounts of radio and infrared emissions coming from Sgr A* d)a count of the total number of stars orbiting Sgr A*

b)measurements of the orbital speeds and distances of the gas clouds and the stars around Sgr A*

The spectral sequence sorts stars according to a)mass. b)surface temperature. c)luminosity. d)core temperature. e)radius.

b)surface temperature.

An astronomical unit is: a)the distance to the nearest star b)the average distance between the Earth and the Sun c)the time it takes for the solar system to turn once on its axis d)the distance covered by light in one year e)the distance between the nearest planet and the Sun

b)the average distance between the Earth and the Sun

As gravity shrunk the protogalactic cloud that gave birth to our galaxy, the first region to take shape was _____. a)the disk b)the halo

b)the halo

What is the average temperature of the surface of the Sun? a)1 million K b) 100,000 K c) 10,000 K d) 6,000 K e) 1,000 K

c) 6,000 K

What is the Sun made of? a) 100 percent hydrogen and helium b) 50 percent hydrogen, 25 percent helium, 25 percent other elements c) 70 percent helium, 28 percent hydrogen, 2 percent other elements d) 98 percent hydrogen, 2 percent helium and other elements

c) 70 percent helium, 28 percent hydrogen, 2 percent other elements

Not all types of stars are equally common. The most common type of stars in the Galaxy from the options below is a)O b)F C) G D) B E) A

c) G

Which spectral-class star is most likely to exhibit strong molecular absorption bands in its spectrum? a)A b)B c) M d)G e)F

c) M

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? a)65 km/s b)65 Mpc/s c)32,500 km/s d)9 km/s e)0.65 times the speed of light

c)32,500 km/s

When an atom absorbs a photon containing energy, any of the following can happen except which? a)The atom becomes excited. b)The atom is ionized. c)An electron moves from an upper energy level to a lower one. d)An electron moves from a lower energy level to an upper one.

c)An electron moves from an upper energy level to a lower one.

What are the dark columns (or "pillars") in this famous photograph from the Hubble Space Telescope? a)Jets of hot gas shot out from young binary star systems. b)Tall interstellar bubbles blown out by supernovae or stellar winds. c)Cold, dense molecular clouds in which stars are forming. d)Warm atomic hydrogen gas, much like most of the gas in the galaxy.

c)Cold, dense molecular clouds in which stars are forming.

Which of the following statements about globular clusters is false? a)Globular clusters contain many thousands of stars. b)Globular cluster stars are more than 12 billion years old. c)Globular cluster ages increase with distance from the Milky Way. d)Globular clusters are distributed spherically around the Milky Way. e)Globular cluster stars are very metal-poor relative to the Sun.

c)Globular cluster ages increase with distance from the Milky Way.

What is interstellar reddening? a)Interstellar dust absorbs more red light than blue light, making stars appear redder than their true color. b)Interstellar dust absorbs more red light than blue light, making stars appear bluer than their true color. c)Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color. d)Interstellar dust absorbs more blue light than red light, making stars appear bluer than their true color. e)The spectral line shift due to a star's motion through the interstellar medium.

c)Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color.

Based on the protostar tracks on the diagram, which statement must be true about the Sun? a)The Sun was much hotter when it was a protostar than it is today. b)The Sun is 30 million years old. c)The Sun was much more luminous when it was a protostar than it is today. d)The Sun was cooler and dimmer when it was a protostar than it is today.

c)The Sun was much more luminous when it was a protostar than it is today.

What evidence suggests that most of the mass of the Milky Way is in the form of dark matter? a)Although dark matter emits no visible light, we have detected its radio emissions. b)Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk. c)The orbital speeds of stars far from the galactic center are surprisingly high. d)Our view of distant galaxies is often obscured by dark blotches, which are presumably made of dark matter.

c)The orbital speeds of stars far from the galactic center are surprisingly high.

Why are Cepheid variables so important for measuring distances in astronomy? a)They all have the same luminosity. b)They all have the same period. c)Their luminosity can be inferred from their period. d)They are close enough to have a detectable parallax. e)They are circumpolar like Polaris, the North Star.

c)Their luminosity can be inferred from their period.

Compared to the star it evolved from, a red giant is a)hotter and brighter. b)hotter and dimmer. c)cooler and brighter. d)cooler and dimmer. e)the same temperature and brightness.

c)cooler and brighter.

In order to understand star clusters, we need to be able to estimate their ages. What technique do scientists use for this? a)radioisotope dating b)counting the planets that have formed around the largest stars c)finding the main-sequence turnoff point of the stars d)calculating orbital parameters using Kepler's Laws e)measuring its parallax

c)finding the main-sequence turnoff point of the stars

The loss of an electron from a neutral helium atom results in a)neutral hydrogen. b)ionized hydrogen. c)ionized helium. d)neutral deuterium. e)ionized deuterium.

c)ionized helium.

According to observations, what type of galaxy was much more common when the universe was 2 billion years old than it is today? a)elliptical galaxies b)spiral galaxies c)irregular galaxies e)We can't say, because we are living at a time when the universe is 14 billion years old, not 2 billion years.

c)irregular galaxies

An astronomer is interested in a galaxy called M31, the nearest galaxy that resembles our Milky Way. It is about 2 million lightyears away. Which technique would be able to give us a distance to this galaxy? a) parallax b)radar reflections c)period-luminosity relation for Cepheid variables d)Kepler's Laws e)you can't fool me: there is no way at present to get a distance to an object so far away

c)period-luminosity relation for Cepheid variables

Everything looks red through a red filter because a)the filter emits red light and absorbs other colors. b)the filter absorbs red light and emits other colors. c)the filter transmits red light and absorbs other colors. d)the filter reflects red light and transmits other colors.

c)the filter transmits red light and absorbs other colors.

You are observing a binary star system and obtain a series of spectra of the light from the two stars. In this spectrum, most of the absorption lines shift back and forth as expected from the Doppler Effect. A few lines, however, do not shift at all, but remain at the same wavelength. How can we explain the behavior of the non-shifting lines? a)there is a planet orbiting the stars in the system. b)there are huge clouds of dust just behind this star system from our perspective. c)the lines comes from interstellar matter between us and the star, not from the stars themselves d)there is a star in the system which is not moving at all. It is just sitting there.

c)the lines comes from interstellar matter between us and the star, not from the stars themselves

Which event marks the beginning of a supernova? a)the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun b)the sudden outpouring of X rays from a newly formed accretion disk c)the sudden collapse of an iron core into a compact ball of neutrons d)the beginning of neon burning in an extremely massive star e)the expansion of a low-mass star into a red giant

c)the sudden collapse of an iron core into a compact ball of neutrons

Which of these elements had to be made in a supernova explosion? a)calcium b)oxygen c)uranium d)helium

c)uranium

Which is closest to the temperature of the core of the Sun? a)10,000 K b)100,000 K c)1 million K d) 10 million K e) 100 million K

d) 10 million K

Which of the five lettered positions (A - E) on the HR diagram shown corresponds to a star with the smallest radius? a) A b) B c) C d) D e) E

d) D

In what way do observations of Mercury support Einstein's general theory of relativity? a)We can see that Mercury lies deeper in the spacetime bowl that surrounds the Sun than does Earth. b)Einstein was able to explain the fact that Mercury orbits the Sun exactly twice for every three rotations, and Newton's theory of gravity cannot account for this. c)Einstein discovered that time runs slower on Mercury than on Earth, as his theory predicted. d) Mercury's orbit slowly precesses in a way that matches the prediction of general relativity but disagrees with the prediction based on Newton's universal law of gravitation.

d) Mercury's orbit slowly precesses in a way that matches the prediction of general relativity but disagrees with the prediction based on Newton's universal law of gravitation.

Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.) a)The red star is more massive than the blue star. b)The blue star is more massive than the red star. c)The blue star is farther away than the red star. d) The blue star has a hotter surface temperature than the red star. e) The red star has a hotter surface temperature than the blue star.

d) The blue star has a hotter surface temperature than the red star.

From the center outward, which of the following lists the "layers" of the Sun in the correct order? a) core, radiation zone, convection zone, corona, chromosphere, photosphere b)core, corona, radiation zone, convection zone, photosphere, chromosphere c) core, convection zone, radiation zone, corona, chromosphere, photosphere d)core, radiation zone, convection zone, photosphere, chromosphere, corona

d) core, radiation zone, convection zone, photosphere, chromosphere, corona

What is the diameter of the disk of the Milky Way? a)100 light-years b)1,000 light-years c)10,000 light-years d)100,000 light-years e)1,000,000 light-years

d)100,000 light-years

How long does the protostellar stage last for a star like our Sun? a)1 million years b)3 million years c)10 million years d)30 million years e)100 million years

d)30 million years

If two objects are the same size but one object is 3 times hotter than the other object, the hotter object emits a)3 times more energy. b)9 times more energy. c)12 times more energy. d)81 times more energy. e)none of the above

d)81 times more energy.

Which of the following statements about brown dwarf is not true. a)The masses of brown dwarfs is between 0.01xMSun and 0.083xMSun. b)Brown dwarfs produced energy for a brief of time by means of nuclear reactions involving deuterium, but do not involve hydrogen fusion. c)Brown dwarfs have masses between 13xMJupiter and 80xMJupiter. d)Brown dwarfs are extremely faint and cool, and they emit mostly in visible light.

d)Brown dwarfs are extremely faint and cool, and they emit mostly in visible light.

The visual apparent magnitudes of Antares, Bernard's star, Canopus, Proxima Centauri, and Vega are 1.06, 9.51, -0.72, 11.05, and 0.03, respectively. The list of stars from the brightest to the faintest is .................. a)Antares, Bernard's star, Canopus, Proxima Centauri, and Vega b)Canopus, Antares, Proxima Centauri, Bernard's star, and Vega c)Vega, Proxima Centauri, Canopus, Bernard's star, and Antar d)Canopus, Vega, Antares, Bernard's star, and Proxima Centauri

d)Canopus, Vega, Antares, Bernard's star, and Proxima Centauri

Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen burning, second-stage helium burning, etc.) in a massive star is not true? a)Each successive stage of fusion requires higher temperatures than the previous stages. b)As each stage ends, the core shrinks further. c)Each successive stage creates an element with a higher atomic weight. d)Each successive stage lasts for approximately the same amount of time.

d)Each successive stage lasts for approximately the same amount of time.

The method astronomers commonly used to measure the mass of a star is a)Measure the spectrum and determine the star's spectral type. b)Measure the Doppler shift of the lines in the spectrum. c)Figure out the lines in the spectrum and see what elements they correspond too. d)In binary stars, measure periods, separations, and radial velocities.

d)In binary stars, measure periods, separations, and radial velocities.

What is the ultimate fate of an isolated pulsar? a)It will spin ever faster, becoming a millisecond pulsar. b)As gravity overwhelms the neutron degeneracy pressure, it will explode as a supernova. c)As gravity overwhelms the neutron degeneracy pressure, it will become a white dwarf. d)It will slow down, the magnetic field will weaken, and it will become invisible. e)The neutron degeneracy pressure will eventually overwhelm gravity and the pulsar will slowly evaporate.

d)It will slow down, the magnetic field will weaken, and it will become invisible.

What kind of star is most likely to become a white-dwarf supernova? a)an O star b)a star like our Sun c)a binary M star d)a white dwarf star with a red giant binary companion e)a pulsar

d)a white dwarf star with a red giant binary companion

The following questions refer to the sketch below of an H-R diagram for a star cluster. Based on its main-sequence turnoff point, the age of this cluster is a)less than 1 billion years. b)about 1 billion years. c)about 2 billion years. d)about 10 billion years. e)more than 15 billion years.

d)about 10 billion years.

Why are neutrinos so difficult to detect? a)because there are so rare b)because they have no mass c)because they move at nearly the speed of light d)because they rarely interact with matter e) because they are so small

d)because they rarely interact with matter

How is the energy that powers radio galaxies, quasars, and other active galactic nuclei produced? a)by nuclear fusion near a central black hole b)by magnetic fields that trap and accelerate charged particles, which then radiate high amounts of energy c)by matter that has been converted to pure energy being shot out as jets by a central black hole d)by gravity, which converts potential energy of matter falling toward a central black hole into kinetic energy, which is then converted to thermal energy by collisions among the particles of matter e)by matter-antimatter annihilation near a central black hole

d)by gravity, which converts potential energy of matter falling toward a central black hole into kinetic energy, which is then converted to thermal energy by collisions among the particles of matter

From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation? a)infrared, visible light, ultraviolet, X rays, gamma rays, radio b)radio, infrared, visible light, ultraviolet, X rays, gamma rays c)visible light, infrared, X rays, ultraviolet, gamma rays, radio d)gamma rays, X rays, ultraviolet, visible light, infrared, radio e)gamma rays, X rays, visible light, ultraviolet, infrared, radio

d)gamma rays, X rays, ultraviolet, visible light, infrared, radio

A star of spectral type G lives approximately how long on the main sequence? a)1,000 years b)10,000 years c)1 million years d)100 million years e)10 billion years

e) 10 billion years

Star A and Star B have different apparent brightnesses, but identical luminosities. If Star A is 20 light-years away from Earth and Star B is 60 light-years away from Earth, by what factor does Star A appear brighter in our sky than Star B? a)1 b)3 c)4 d)6 e)9

e) 9

Why is Supernova 1987A particularly important to astronomers? a)It occurred only a few dozen light-years from Earth. b)It provided the first evidence that supernovae really occur. c)It provided the first evidence that neutron stars really exist. d)It was the first supernova detected in nearly 400 years. e) It was the nearest supernova detected in nearly 400 years.

e) It was the nearest supernova detected in nearly 400 years.

From what you have learned about which kinds of stars produce emission nebulae and which kinds are associated with reflection nebulae, what can you say about the stars in this image? a)They are white dwarfs b)They are all highly evolved giants c)The brightest stars visible are cooler than 10,000 K d)The brightest stars visible are hotter than 25,000 K e) The brightest stars visible are cooler than 25,000 K but hotter than 10,000 K

e) The brightest stars visible are cooler than 25,000 K but hotter than 10,000 K

Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy? a)The higher density of gas has a stronger force of gravity, and therefore the cloud collapses more quickly. b)The force of gravity can pull the material into a more spherical shape. c)The more frequent collisions between particles randomize the particle orbits. d)The thickness of the dense cloud prevents a disk from forming. e) The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form.

e) The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form.

According to general relativity, how is time affected by gravity? a)Time is not affected by gravity. b)Time is affected by gravity, but not in a predictable way. c)Time is stopped by any gravitational field. d)Time runs faster in stronger gravitational fields. e) Time runs slower in stronger gravitational fields.

e) Time runs slower in stronger gravitational fields.

What evidence supports the idea that a collision between two spiral galaxies might lead to the creation of a single elliptical galaxy? a)observations of some elliptical galaxies surrounded by shells of stars that probably formed from stars stripped out of smaller galaxies b)the fact that elliptical galaxies dominate the galaxy populations at the cores of dense clusters of galaxies c)observations of some elliptical galaxies with stars and gas clouds in their cores that orbit differently from the other stars in the galaxy d)observations of giant elliptical galaxies at the center of dense clusters that may have grown by consuming other galaxies e) all of the above

e) all of the above

At the center of the Sun, fusion converts hydrogen into a) hydrogen compounds. b) plasma. c) radiation and elements like carbon and nitrogen. d) radioactive elements like uranium and plutonium. e) helium, energy, and neutrinos.

e) helium, energy, and neutrinos.

Suppose a planet is discovered by the Doppler technique and is then discovered to have transits. In that case, we can determine all the following about the planet except a)its physical size (radius). b)its orbital period. c)its density. d)its precise mass. e) its rotation period.

e) its rotation period.

Which of the following characteristics of stars has the greatest range in values? a)mass b)radius c)core temperature d)surface temperature e)luminosity

e) luminosity

This photo shows an object located in the halo of our Milky Way galaxy. What kind of object is it? a)A "beehive" cluster. b)A supergiant star. c)An open cluster of stars. d)A spiral galaxy. e)A globular cluster of stars.

e)A globular cluster of stars.

The figure hows data from a binary system consisting of two neutron stars (called the Hulse-Taylor binary).Einstein's general theory of relativity predicts that two orbiting neutron stars should radiate gravitational waves. How does the fact that the orbital period is getting shorter support this prediction? a)The figure shows data from a binary system consisting of two neutron stars (called the Hulse-Taylor binary). b)The accumulation of gravitational waves increases the pull of gravity in the binary system, causing the neutron stars to move closer together. c)The gravitational waves add energy to the system, causing the neutron stars to accelerate and orbit faster. d)To compensate for the loss of energy to gravitational waves, the neutron stars must become brighter, and this brightening causes their orbital period to decrease. e)Gravitational waves must carry some energy away from the system, and this loss of energy must cause the orbits to get smaller over time.

e)Gravitational waves must carry some energy away from the system, and this loss of energy must cause the orbits to get smaller over time.

Which of the following cannot be true of the very first stars formed in the Universe? a)They may have all exploded as supernovae by now. b)They may have formed in large clusters. c)They may have formed singly, in isolation. d)Some may still exist in the Milky Way today. e)They may have had rocky planets around them.

e)They may have had rocky planets around them.

How did Henrietta Leavitt "calibrate" her period-luminosity relationship for Cepheid variable stars? In other words, how did she make the general idea into a numerical rule? a)by noting that the period was related to the luminosity in all stars b)because the star closest to us is a Cepheid variable and we know its distance c)by assuming that the Cepheids that appeared the brightest in the sky were closest to us d)by measuring the Doppler shift in the spectral lines of Cepheids as they pulsated e)by finding cepheids in star clusters whose distance was known in another way

e)by finding cepheids in star clusters whose distance was known in another way

After a massive-star supernova, what is left behind? a)always a white dwarf b)always a neutron star c)always a black hole d)either a white dwarf or a neutron star e)either a neutron star or a black hole

e)either a neutron star or a black hole