Exam 4 Chapters 17-20
6) Which of the following statements about degeneracy pressure is not true? A) Degeneracy pressure varies with the temperature of the star. B) Degeneracy pressure can halt gravitational contraction of a star even when no fusion is occurring in the core. C) Degeneracy pressure keeps any protostar less than 0.08 solar mass from becoming a true, hydrogen-fusing star. D) Degeneracy pressure arises out of the ideas of quantum mechanics. E) Degeneracy pressure supports white dwarfs against gravity.
A) Degeneracy pressure varies with the temperature of the star.
26) How does a black hole form from a massive star? A) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole. B) Any star that is more massive than 8 solar masses will undergo a supernova explosion and leave behind a black-hole remnant. C) If enough mass is accreted by a white-dwarf star so that it exceeds the 1.4-solar-mass limit, it will undergo a supernova explosion and leave behind a black-hole remnant. D) If enough mass is accreted by a neutron star, it will undergo a supernova explosion and leave behind a black-hole remnant. E) A black hole forms when two massive main-sequence stars collide.
A) During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy of the core, the core will be compressed until it becomes a black hole.
12) Which of the following is closest in size (radius) to a white dwarf? A) Earth B) a small city C) a football stadium D) a basketball E) the Sun
A) Earth
34) Consider the star to which the arrow points. Which of the following statements about this star is not true? A) It is significantly less massive than the Sun. B) It is larger in radius than the Sun. C) It is brighter than the Sun. D) Its surface temperature is lower than the Sun's. E) Its core temperature is higher than the Sun's.
A) It is significantly less massive than the Sun.
6) What is the ultimate fate of an isolated white dwarf? A) It will cool down and become a cold black dwarf. B) As gravity overwhelms the electron degeneracy pressure, it will explode as a nova. C) As gravity overwhelms the electron degeneracy pressure, it will explode as a supernova. D) As gravity overwhelms the electron degeneracy pressure, it will become a neutron star. E) The electron degeneracy pressure will eventually overwhelm gravity and the white dwarf will slowly evaporate.
A) It will cool down and become a cold black dwarf.
11) What happens when a star exhausts its core hydrogen supply? A) Its core contracts, but its outer layers expand and the star becomes bigger and brighter. B) It contracts, becoming smaller and dimmer. C) It contracts, becoming hotter and brighter. D) It expands, becoming bigger but dimmer. E) Its core contracts, but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness.
A) Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
18) What happens after a helium flash? A) The core quickly heats up and expands. B) The star breaks apart in a violent explosion. C) The core suddenly contracts. D) The core stops fusing helium. E) The star starts to fuse helium in a shell outside the core.
A) The core quickly heats up and expands.
18) Which of the following best describes what would happen if a 1.5-solar-mass neutron star, with a diameter of a few kilometers, were suddenly (for unexplained reasons) to appear in your hometown? A) The entire mass of Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star. B) It would rapidly sink to the center of Earth. C) The combined mass of Earth and the neutron star would cause the neutron star to collapse into a black hole. D) It would crash through Earth, creating a large crater, and exit Earth on the other side. E) It would crash into Earth, throwing vast amounts of dust into the atmosphere which in turn would cool Earth. Such a scenario is probably what caused the extinction of the dinosaurs.
A) The entire mass of Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star.
45) You discover a binary star system in which one member is a15MSun main-sequence star and the other star is a 10MSun giant. How do we believe that a star system such as this might have come to exist? A) The giant must once have been the more massive star but transferred some of its mass to its companion. B) Despite the low odds of finding a system with two such massive stars, there is nothing surprising about the fact that such systems exist. C) The two stars probably were once separate but became a binary when a close encounter allowed their mutual gravity to pull them together. D) The main-sequence star probably is a pulsating variable star and therefore appears to be less massive than it really is. E) Although both stars probably formed from the same clump of gas, the more massive one must have had its birth slowed so that it became a main-sequence star millions of years later than its less massive companion.
A) The giant must once have been the more massive star but transferred some of its mass to its companion.
7) 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.
37) Why are galaxies in the blue cloud blue? A) They contain hot, young stars that signify active star formation. B) They are moving slower than stars in the red cloud. C) They contain lots of dust that cause the bluish color. D) They contain cold, dying stars that are fading to black.
A) They contain hot, young stars that signify active star formation.
41) What does Einstein's general theory of relativity tell us about two co-orbiting white dwarfs? A) They will emit gravitational waves that carry energy and angular momentum away from the system, causing the white dwarfs to gradually spiral inward toward each other and eventually merge. B) They will emit gravitational waves that carry energy and angular momentum toward the system, causing the white dwarfs to gradually spiral away from one another and eventually fly far apart. C) They will emit gravitational waves that carry energy and angular momentum away from the system, causing the white dwarfs to quickly spiral away from one another. D) They will never interact with one another.
A) They will emit gravitational waves that carry energy and angular momentum away from the system, causing the white dwarfs to gradually spiral inward toward each other and eventually merge.
19) What is a carbon star? A) a red giant star whose atmosphere becomes carbon-rich through convection from the core B) a star that fuses carbon in its core C) another name for a white dwarf, a remnant of a star made mainly of carbon D) a star that produces carbon by fusion in its atmosphere E) a star that is made at least 50 percent of carbon
A) a red giant star whose atmosphere becomes carbon-rich through convection from the core
16) What is a superbubble? A) a very low-density region of interstellar space, formed by the merger of several bubbles B) a very high-density region of interstellar space, filled with gas ejected from nearby star systems C) a bubble so large that it fills much of the galactic halo D) the region of space cleared by a powerful supernova E) a cloud of gas that can form a million or more stars
A) a very low-density region of interstellar space, formed by the merger of several bubbles
18) What is a shock front? A) a wave of pressure that moves faster than the speed of sound B) a wave of pressure that moves slightly slower than the speed of sound C) a wave of pressure that moves faster than the speed of light D) a wave of electromagnetic energy that can create electrical shocks E) the wave created when protons slam into electrons
A) a wave of pressure that moves faster than the speed of sound
30) In the end, the remaining core of this star will be left behind as A) a white dwarf made primarily of carbon and oxygen. B) a white dwarf made primarily of silicon and iron. C) a neutron star. D) a black hole. E) a supernova.
A) a white dwarf made primarily of carbon and oxygen.
17) What is a standard candle? A) an object for which we are likely to know the true luminosity B) an object for which we can easily measure the apparent brightness C) a class of objects in astronomy that all have exactly the same luminosity D) any star for which we know the exact apparent brightness E) a long, tapered candle that lights easily
A) an object for which we are likely to know the true luminosity
24) What produces the 21-cm line that we use to map out the Milky Way Galaxy? A) atomic hydrogen B) ionized hydrogen C) molecular hydrogen D) carbon monoxide E) helium
A) atomic hydrogen
9) How can we see through the interstellar medium? A) by observing in high-energy wavelengths such as X-rays and long wavelengths of light such as radio waves B) by observing only the brightest visible sources C) by using only the biggest telescopes D) by using telescopes above the Earth's atmosphere E) We cannot see through the interstellar medium.
A) by observing in high-energy wavelengths such as X-rays and long wavelengths of light such as radio waves
46) Why do scientists think that our solar system must have formed sometime after nearby supernovae explosions? A) existence of heavy elements B) solar temperature too low C) our Sun is a G-type star D) They don't—scientists believe our Sun is among the first generation of stars.
A) existence of heavy elements
25) During which stage is the star's energy supplied by gravitational contraction? A) ii B) iii C) v D) vi E) viii
A) ii
3) What type of star is our Sun? A) low-mass star B) intermediate-mass star C) high-mass star D) brown dwarf
A) low-mass star
2) Which two energy sources can help a star maintain its internal thermal pressure? A) nuclear fusion and gravitational contraction B) nuclear fission and gravitational contraction C) nuclear fusion and nuclear fission D) chemical reactions and gravitational contraction E) nuclear fusion and chemical reactions
A) nuclear fusion and gravitational contraction
29) Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest? A) parallax, Cepheid variables, Hubble's law B) parallax, Hubble's law, Cepheid variables C) parallax, white-dwarf supernovae, Hubble's law D) parallax, Hubble's law, white-dwarf supernovae
A) parallax, Cepheid variables, Hubble's law
8) Compared to spiral galaxies, elliptical galaxies are A) redder and rounder. B) redder and flattened. C) bluer and rounder. D) bluer and flattened. E) always much smaller.
A) redder and rounder.
19) What are cosmic rays? A) subatomic particles that travel close to the speed of light B) gamma rays and X-rays C) fast-moving dust particles in the interstellar medium D) any light waves from space E) lasers used as weapons by extraterrestrials
A) subatomic particles that travel close to the speed of light
2) White dwarfs are so called because A) they are both very hot and very small. B) they are the end-products of small, low-mass stars. C) they are the opposite of black holes. D) it amplifies the contrast with red giants. E) they are supported by electron degeneracy pressure.
A) they are both very hot and very small.
20) What two quantities did Edwin Hubble plot against each other to discover the expansion of the Universe? A) velocity and distance B) luminosity and distance C) velocity and temperature D) luminosity and temperature E) age and distance
A) velocity and distance
2) What is the thickness 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
B) 1,000 light-years
16) How many helium nuclei fuse together when making carbon? A) 2 B) 3 C) 4 D) varies depending on the reaction E) none of the above
B) 3
21) 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.
35) Why can't we see past the cosmological horizon? A) The universe extends only to this horizon. B) Beyond the cosmological horizon, we are looking back to a time before the universe had formed. C) We do not have telescopes big enough. D) We do not have sensitive enough detectors. E) The cosmological horizon is infinitely far away, and we can't see to infinity.
B) Beyond the cosmological horizon, we are looking back to a time before the universe had formed.
16) Why are Cepheid variables important? A) Cepheid variables are stars that vary in brightness because they harbor a black hole. B) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as "standard candles" for distance measurements. C) Cepheids are a type of young galaxy that helps us understand how galaxies form. D) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future.
B) Cepheids are pulsating variable stars, and their pulsation periods are directly related to their true luminosities. Hence, we can use Cepheids as "standard candles" for distance measurements.
34) Which of the following statements about the disk of the Milky Way is false? A) The average age of disk stars is less than that of halo stars. B) Disk stars are all younger than 5 billion years. C) Disk stars have a higher proportion of heavy elements, on average, than halo stars. D) Disk stars orbit in the same direction around the Galactic center. E) The length of the disk is about 100 times its thickness.
B) Disk stars are all younger than 5 billion years.
40) Black holes, by definition, cannot be observed directly. What observational evidence do scientists have of their existence? A) Theoretical models predict their existence. B) Gravitational interaction with other objects. C) Space is, overall, very black. D) We have sent spacecraft to nearby black holes. E) We have detected neutrinos from them.
B) Gravitational interaction with other objects.
14) Why are we unlikely to find Earth-like planets around halo stars in the Galaxy? A) Planets around stars are known to be extremely rare. B) Halo stars formed in an environment where there were few heavy elements to create rocky planets. C) Any such planets would have been ejected long ago by galactic mergers. D) Halo stars do not have enough mass to hold onto planets. E) Halo stars formed in a different way from disk stars.
B) Halo stars formed in an environment where there were few heavy elements to create rocky planets.
18) How did Edwin Hubble measure the distance to the Andromeda Galaxy? A) He measured its parallax. B) He applied the period-luminosity relation to Cepheid variables. C) He deduced it from its redshift. D) He used white dwarf supernovae.
B) He applied the period-luminosity relation to Cepheid variables.
15) Why does a star grow larger after it exhausts its core hydrogen? A) The outer layers of the star are no longer gravitationally attracted to the core. B) Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward. C) Helium fusion in the core generates enough thermal pressure to push the upper layers outward. D) Helium fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward. E) The internal radiation generated by the hydrogen fusion in the core has heated the outer layers enough that they can expand after the star is no longer fusing hydrogen.
B) Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.
11) How does a 1.2-solar-mass white dwarf compare to a 1.0-solar-mass white dwarf? A) It has a larger radius. B) It has a smaller radius. C) It has a higher surface temperature. D) It has a lower surface temperature. E) It is supported by neutron, rather than electron, degeneracy pressure.
B) It has a smaller radius.
12) What is happening inside a star while it expands into a subgiant? A) It is fusing hydrogen into helium in the core. B) It is fusing hydrogen into helium in a shell outside the core. C) It is fusing helium into carbon in the core. D) It is fusing helium into carbon in a shell outside the core. E) It is not fusing any element; it is contracting and heating up.
B) It is fusing hydrogen into helium in a shell outside the core.
25) How does the gravity of an object affect light? A) Light doesn't have mass; therefore, it is not affected by gravity. B) Light coming from a compact massive object, such as a neutron star, will be redshifted. C) Light coming from a compact massive object, such as a neutron star, will be blueshifted. D) Visible light coming from a compact massive object, such as a neutron star, will be redshifted, but higher frequencies such as X-rays and gamma rays will not be affected. E) Less energetic light will not be able to escape from a compact massive object, such as a neutron star, but more energetic light will be able to.
B) Light coming from a compact massive object, such as a neutron star, will be redshifted.
9) Which of the following spectral types is more likely to be a flare star? A) KIII B) MV C) GV D) I E) BII
B) MV
5) 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.
5) 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.
21) What is Hubble's law? A) The longer the time period between peaks in brightness, the greater the luminosity of the Cepheid variable star. B) The recession velocity of a galaxy is directly proportional to its distance from us. C) The recession velocity of a galaxy is inversely proportional to its distance from us. D) The faster a spiral galaxy's rotation speed, the more luminous it is. E) The faster a spiral galaxy's rotation speed, the less luminous it is.
B) The recession velocity of a galaxy is directly proportional to its distance from us.
32) How do we know that halo stars are older, on average, than disk stars? A) Halo stars orbit in random directions but disk stars have more ordered orbits. B) There are no blue halo stars. C) There are no red disk stars. D) Theories of galaxy formation tell us that the halo formed earlier than the disk. E) We see evidence for new stars forming in the disk today.
B) There are no blue halo stars.
38) How do we learn about what is going on in the center of our own galaxy (the Milky Way)? A) We have learned it only recently, thanks to the great photographs obtained by the Hubble Space Telescope. B) We cannot see the galactic center with visible or ultraviolet light, but radio and X-rays from the center can be detected. C) The gas and dust in the Milky Way prevent any type of direct observation of the galactic center, but theoretical models allow us to predict what is happening there. D) We must look at the centers of other galaxies and hope that ours is just like others. E) We can study it with visible telescopes as with any other star in the Galaxy.
B) We cannot see the galactic center with visible or ultraviolet light, but radio and X-rays from the center can be detected.
17) Which of the following is closest in size (radius) to a neutron star? A) Earth B) a city C) a football stadium D) a basketball E) the Sun
B) a city
20) From a theoretical standpoint, what is a pulsar? A) a star that alternately expands and contracts in size B) a rapidly rotating neutron star C) a neutron star or black hole that happens to be in a binary system D) a binary system that happens to be aligned so that one star periodically eclipses the other E) a star that is burning iron in its core
B) a rapidly rotating neutron star
41) What is SgrA*? A) a source of bright X-ray emission coming from the entire constellation of Sagittarius B) a source of bright radio emission in the center of our galaxy C) a source that is bright in the visible wavelengths in the center of our galaxy D) the brightest star in the constellation Sagittarius E) the bulge at the center of our galaxy
B) a source of bright radio emission in the center of our galaxy
39) If you were to come back to our Solar System in 6 billion years, what might you expect to find? A) a red giant star B) a white dwarf C) a rapidly spinning pulsar D) a black hole E) Everything will be pretty much the same as it is now.
B) a white dwarf
19) From an observational standpoint, what is a pulsar? A) a star that slowly changes its brightness, getting dimmer and then brighter with a period of anywhere from a few hours to a few weeks B) an object that emits flashes of light several times per second or more, with near perfect regularity C) an object that emits random "pulses" of light that sometimes occur only a fraction of a second apart and other times stop for several days at a time D) a star that changes color rapidly, from blue to red and back again E) a star that rapidly changes size as it moves off the main sequence
B) an object that emits flashes of light several times per second or more, with near perfect regularity
29) Compared with stars in the disk, orbits of stars in the halo A) are relatively uniform to each other. B) are elliptical, with random orientation. C) are elliptical but orbiting in the same direction. D) do not have to be around the galactic center. E) do not have to pass through the plane of the galaxy.
B) are elliptical, with random orientation.
33) 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
9) 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
13) Which of the following types of galaxies are most commonly found in large clusters? A) spirals B) ellipticals C) lenticulars D) irregulars
B) ellipticals
3) Which of the following types of galaxies are most spherical in shape? A) spirals B) ellipticals C) lenticulars D) irregulars
B) ellipticals
4) Which of the following types of galaxies are reddest in color? A) spirals B) ellipticals C) lenticulars D) irregulars
B) ellipticals
23) Compared to the star it evolved from, a white dwarf is A) hotter and brighter. B) hotter and dimmer. C) cooler and brighter. D) cooler and dimmer. E) the same temperature and brightness.
B) hotter and dimmer.
28) Which stage lasts the longest? A) i B) iii C) iv D) vi E) viii
B) iii
13) Where are most heavy elements made? A) in the interstellar medium B) in stars and supernovae C) in the Big Bang, when the universe first began D) none of the above E) all of the above
B) in stars and supernovae
25) Where do most dust grains form? A) in supernovae B) in the winds of red giant stars C) in planetary nebulae D) in molecular clouds E) all of the above
B) in the winds of red giant stars
26) During which stage does the star have an inert (nonburning) helium core? A) iii B) iv C) vi D) vii E) viii
B) iv
31) A 10-solar-mass main-sequence star will produce which of the following remnants? A) white dwarf B) neutron star C) black hole D) none of the above
B) neutron star
33) Hubble's "constant" is constant in A) time. B) space. C) space and time. D) our Galaxy but different in others.
B) space.
12) Most large galaxies in the universe are A) elliptical. B) spiral or lenticular. C) irregular. D) abnormal.
B) spiral or lenticular.
26) What is the most accurate way to determine the distance to a nearby star? A) radar ranging B) stellar parallax C) using Cepheid variables D) Hubble's law
B) stellar parallax
36) 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) two clumps, one blue with relatively low luminosity, one red with relatively high luminosity, and a valley in between with few galaxies C) a continuum from faint, blue galaxies to bright, red galaxies D) a continuum from faint, red galaxies to bright, blue galaxies E) a main sequence, just as for stars
B) two clumps, one blue with relatively low luminosity, one red with relatively high luminosity, and a valley in between with few galaxies
28) What is the most accurate way to determine the distance to a very distant irregular galaxy? A) using Cepheid variables B) using a white-dwarf supernova as a standard candle C) main sequence fitting D) Hubble's law
B) using a white-dwarf supernova as a standard candle
32) 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
11) What is the major difference between an elliptical galaxy and a spiral galaxy? A) A spiral galaxy contains mostly younger stars. B) A spiral galaxy has a spherical halo. C) An elliptical galaxy lacks a disk component. D) Elliptical galaxies are not as big as spiral galaxies. E) There are no dwarf spiral galaxies, but there are dwarf ellipticals.
C) An elliptical galaxy lacks a disk component.
40) Suppose the star Betelgeuse (the upper left shoulder of Orion) were to become a supernova tomorrow (as seen here on Earth). What would it look like to the naked eye? A) Because the supernova event destroys the star, Betelgeuse would suddenly disappear from view. B) We'd see a cloud of gas expanding away from the position where Betelgeuse used to be. Over a period of a few weeks, this cloud would fill our entire sky. C) Betelgeuse would remain a dot of light but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime. D) Betelgeuse would suddenly appear to grow larger in size, soon reaching the size of the full moon. It would also be about as bright as the full moon.
C) Betelgeuse would remain a dot of light but would suddenly become so bright that, for a few weeks, we'd be able to see this dot in the daytime.
30) Dr. X believes that the Hubble constant is H0 = 55 km/s/Mpc. Dr. Y believes it is H0 = 80 km/s/Mpc. Which statement below automatically follows? A) Dr. X believes that the universe is expanding, but Dr. Y does not. B) Dr. X believes that the Andromeda Galaxy (a member of our Local Group) is moving away from us at a slower speed than Dr. Y believes. C) Dr. X believes that the universe is older than Dr. Y believes. D) Dr. X believes that the universe will someday stop expanding, while Dr. Y believes it will expand forever. E) Dr. X believes that the universe has a much higher density than Dr. Y believes.
C) Dr. X believes that the universe is older than Dr. Y believes.
19) How was Edwin Hubble able to use his discovery of a Cepheid in Andromeda to prove that the "spiral nebulae" were actually entire galaxies? A) There are no Cepheids in the Milky Way, so his discovery proved that it had to be in another galaxy. B) He measured the stellar parallax of the Cepheid in Andromeda, was able to determine the distance to it, and showed that it was far outside the Milky Way Galaxy. C) From the period-luminosity relation for Cepheids, he was able to determine the distance to Andromeda and show that it was far outside the Milky Way Galaxy. D) Since a Cepheid is a type of luminous galaxy, when he found it in Andromeda he was able to prove that Andromeda was a separate galaxy from the Milky Way.
C) From the period-luminosity relation for Cepheids, he was able to determine the distance to Andromeda and show that it was far outside the Milky Way Galaxy.
33) 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.
36) What evidence suggests that the protogalactic cloud that formed the Milky Way resulted from several collisions among smaller clouds? A) The stars in the halo of the Milky Way are organized into several dense clusters arranged throughout the halo. B) The Milky Way resembles an elliptical galaxy more than other spirals do. C) Halo stars differ in age and heavy-element content, but these variations do not seem to depend on the stars' distance from the galactic center. D) The bulge of the Milky Way is surrounded by many globular clusters, just as elliptical galaxies are. E) The Milky Way is the central galaxy of a cluster of galaxies.
C) Halo stars differ in age and heavy-element content, but these variations do not seem to depend on the stars' distance from the galactic center.
21) What happens to the core of a star after a planetary nebula occurs? A) It contracts from a protostar to a main-sequence star. B) It breaks apart in a violent explosion. C) It becomes a white dwarf. D) It becomes a neutron star. E) none of the above
C) It becomes a white dwarf.
32) What do we mean by the singularity of a black hole? A) There are no binary black holes—each one is isolated. B) An object can become a black hole only once, and a black hole cannot evolve into anything else. C) It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions. D) It is the edge of the black hole, where one could leave the observable universe. E) It is the "point of no return" of the black hole; anything closer than this point will not be able to escape the gravitational force of the black hole.
C) It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions.
32) Which statement about this cluster is not true? A) It is likely to be located in the halo of the galaxy. B) It contains some stars that are burning helium in their cores. C) It is the type of cluster known as an open cluster of stars. D) It probably contains no young stars at all. E) It is likely to be spherical in shape.
C) It is the type of cluster known as an open cluster of stars.
29) What will happen to the star after stage viii? A) It will explode in a supernova. B) It will begin burning carbon in its core. C) It will eject a planetary nebula. D) It will collapse to make a neutron star. E) It will gain mass until it collapses under its own weight.
C) It will eject a planetary nebula.
22) How do we know that pulsars are neutron stars? A) We have observed massive-star supernovae produce pulsars. B) Pulsars and neutron stars look exactly the same. C) No massive object, other than a neutron star, could spin as fast as we observe pulsars spin. D) Pulsars have the same upper mass limit as neutron stars do. E) none of the above
C) No massive object, other than a neutron star, could spin as fast as we observe pulsars spin.
34) Prior to the 1990s, most astronomers assumed that gamma-ray bursts came from neutron stars with accretion disks. How do we now know that this hypothesis was wrong? A) We now know that gamma-ray bursts come not from neutron stars but from black holes. B) Theoretical work has proven that gamma rays cannot be produced in accretion disks. C) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky. D) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts occur too frequently to be attributed to neutron stars. E) Observations from the Compton Gamma-Ray Observatory have allowed us to trace gamma-ray bursts to pulsating variable stars in distant galaxies.
C) Observations from the Compton Gamma-Ray Observatory show that gamma-ray bursts come randomly from all directions in the sky.
8) Which of the following statements about novae is not true? A) A star system that undergoes a nova may have another nova sometime in the future. B) A nova involves fusion taking place on the surface of a white dwarf. C) Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now. D) When a star system undergoes a nova, it brightens considerably, but not as much as a star system undergoing a supernova. E) The word nova means "new star" and originally referred to stars that suddenly appeared in the sky, then disappeared again after a few weeks or months.
C) Our Sun will probably undergo at least one nova when it becomes a white dwarf about 5 billion years from now.
37) 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.
40) What evidence supports the theory that there is a black hole at the center of our galaxy? A) We observe an extremely bright X-ray source at the center of our galaxy. B) We can see gas falling into an accretion disk and central mass at the center of our galaxy. C) The motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about 1 parsec across. D) We observe a large, dark object that absorbs all light at the center of our galaxy. E) all of the above
C) The motions of the gas and stars at the center indicate that it contains a million solar masses within a region only about 1 parsec across.
43) What happens to two neutron stars that are orbiting so close together they emit gravitational waves? A) The neutron stars will fly apart from one another. B) It has no effect. C) The neutron stars will spiral together and merge. D) The neutron stars will recombine and form a new, young star.
C) The neutron stars will spiral together and merge.
14) Observationally, how can we tell the difference between a white-dwarf supernova and a massive-star supernova? A) A massive-star supernova is brighter than a white-dwarf supernova. B) A massive-star supernova happens only once, while a white-dwarf supernova can repeat periodically. C) The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not. D) The light of a white-dwarf supernova fades steadily, while the light of a massive-star supernova brightens for many weeks. E) We cannot yet tell the difference between a massive-star supernova and a white-dwarf supernova.
C) The spectrum of a massive-star supernova shows prominent hydrogen lines, while the spectrum of a white-dwarf supernova does not.
15) Which of the following is true about irregular galaxies? A) They are composed solely of old stars. B) They generally have significant bulge populations. C) They were more common when the universe was younger. D) They have reddish colors. E) They have well defined spiral arms.
C) They were more common when the universe was younger.
23) What is the primary practical difficulty that limits the use of Hubble's law for measuring distances? A) Redshifts of galaxies are difficult to measure. B) The recession velocities of distant galaxies are so great that they are hard to measure. C) We do not know Hubble's constant very accurately yet. D) Hubble's law is only useful theoretically; it is difficult to use in practice. E) The motion of Earth relative to the Milky Way is difficult to account for.
C) We do not know Hubble's constant very accurately yet.
22) What evidence supports the galactic fountain model? A) We see a jet of ionized gas shooting out of the bulge of our galaxy. B) We have mapped several spiral arms of the Milky Way Galaxy. C) We see hot gas above the disk of the galaxy and cool gas that appears to be raining down from the halo. D) We have observed a lot of water molecules in the interstellar medium. E) We have no evidence yet for the galactic fountain model.
C) We see hot gas above the disk of the galaxy and cool gas that appears to be raining down from the halo.
35) What is the CNO cycle? A) the process by which helium is fused into carbon, nitrogen, and oxygen B) the process by which carbon is fused into nitrogen and oxygen C) a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts D) the period of a massive star's life when carbon, nitrogen, and oxygen are fusing in different shells outside the core E) the period of a low-mass star's life when it can no longer fuse carbon, nitrogen, and oxygen in its core
C) a type of hydrogen fusion that uses carbon, nitrogen, and oxygen atoms as catalysts
24) What is the basic definition of a black hole? A) any compact mass that emits no light B) a dead star that has faded from view C) any object from which the escape velocity exceeds the speed of light D) any object made from dark matter E) a dead galactic nucleus that can only be viewed in infrared
C) any object from which the escape velocity exceeds the speed of light
39) Which of the following does not accurately describe what we observe toward the Galactic center? A) at radio wavelengths, we see giant gas clouds threaded by powerful magnetic fields B) at infrared wavelengths, we see a massive stellar cluster C) at optical wavelengths, we see a cluster of old, red stars D) at X-rays, we see faint emission from an accretion disk around a black hole
C) at optical wavelengths, we see a cluster of old, red stars
23) What is the most common form of gas in the interstellar medium? A) molecular hydrogen B) molecular helium C) atomic hydrogen D) atomic helium E) ionized hydrogen
C) atomic hydrogen
35) Why do astronomers consider gamma-ray bursts to be one of the greatest mysteries in astronomy? A) because they are so rare B) because we know they come from pulsating variable stars but don't know how they are created C) because the current evidence suggests that they are the most powerful bursts of energy that ever occur anywhere in the universe, but we don't know how they are produced D) because current evidence suggests that they come from our own Milky Way, but we have no idea where in the Milky Way they occur E) because current evidence suggests that they come from massive black holes in the centers of distant galaxies, adding to the mystery of black holes themselves
C) because the current evidence suggests that they are the most powerful bursts of energy that ever occur anywhere in the universe, but we don't know how they are produced
34) Based on current estimates of the value of Hubble's constant, how old is the universe? A) between 4 and 6 billion years old B) between 8 and 12 billion years old C) between 12 and 16 billion years old D) between 16 and 20 billion years old E) between 20 and 40 billion years old
C) between 12 and 16 billion years old
4) What is the range of star masses for high-mass stars? A) between 500 and about 1,000 solar masses B) between 200 and about 500 solar masses C) between 8 and about 100 solar masses D) between 2 and about 10 solar masses E) between 2 and about 5 solar masses
C) between 8 and about 100 solar masses
15) How are interstellar bubbles made? A) by the collapse of a gas cloud to form stars B) by planetary nebulae from low-mass stars C) by the winds of massive stars and supernovae D) by collisions between galaxies E) by the rapidly rotating magnetic fields of pulsars
C) by the winds of massive stars and supernovae
17) The helium fusion process results in the production of A) hydrogen. B) oxygen. C) carbon. D) nitrogen. E) iron.
C) carbon.
7) All of the following are involved in carrying energy outward from a star's core except A) convection. B) radiative diffusion. C) conduction. D) neutrinos.
C) conduction.
13) 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.
3) What kinds of objects lie in the halo of our galaxy? A) open clusters B) O and B stars C) globular clusters D) gas and dust E) all of the above
C) globular clusters
8) Which stars have convective cores? A) low-mass stars B) intermediate-mass stars C) high-mass stars D) all of the above E) none of the above
C) high-mass stars
31) Where does most star formation occur in the Milky Way today? A) in the halo B) in the bulge C) in the spiral arms D) in the Galactic center E) uniformly throughout the Galaxy
C) in the spiral arms
10) Harlow Shapley concluded that the Sun was not in the center of the Milky Way Galaxy by A) looking at the shape of the "milky band" across the sky. B) mapping the distribution of stars in the galaxy. C) mapping the distribution of globular clusters in the galaxy. D) mapping the distribution of gas clouds in the spiral arms. E) looking at other nearby spiral galaxies.
C) mapping the distribution of globular clusters in the galaxy.
16) A teaspoonful of neutron star material on Earth would weigh A) about the same as a teaspoonful of Earth-like material. B) a few tons. C) more than Mt. Everest. D) more than the Moon. E) more than Earth.
C) more than Mt. Everest.
20) What can cause a galactic fountain? A) winds and jets from newly-formed protostars B) a supernova occurring in the halo C) multiple supernovae occurring together D) the combined effect of spiral density waves E) molecular clouds falling towards the galactic center
C) multiple supernovae occurring together
28) Compared with our Sun, most stars in the halo are A) young, red, and dim and have fewer heavy elements. B) young, blue, and bright and have much more heavy element material. C) old, red, and dim and have fewer heavy elements. D) old, red, and dim and have much more heavy element material. E) old, red, and bright and have fewer heavy elements.
C) old, red, and dim and have fewer heavy elements.
9) The disk component of a spiral galaxy includes which of the following parts? A) halo B) bulge C) spiral arms D) globular clusters E) all of the above
C) spiral arms
38) What types of stars end their lives with supernovae? A) all stars that are red in color B) all stars that are yellow in color C) stars that are at least several times the mass of the Sun D) stars that are similar in mass to the Sun E) stars that have reached an age of 10 billion years
C) stars that are at least several times the mass of the Sun
29) When we see X-rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system. Which one would force us to immediately rule out the possibility of a black hole? A) bright X-ray emission that varies on a time scale of a few hours B) spectral lines from the companion star that alternately shift to shorter and longer wavelengths C) sudden, intense X-ray bursts D) visible and ultraviolet light from the companion star
C) sudden, intense X-ray bursts
1) What do astronomers mean when they say that we are all "star stuff"? A) that life would be impossible without energy from the Sun B) that Earth formed at the same time as the Sun C) that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores D) that the Sun formed from the interstellar medium: the "stuff" between the stars E) that the Universe contains billions of stars
C) that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores
24) Most interstellar dust grains are produced in A) the Big Bang. B) the interstellar medium. C) the atmospheres of red giant stars. D) supernova explosions. E) the solar nebula.
C) the atmospheres of red giant stars.
20) What is a planetary nebula? A) a disk of gas surrounding a protostar that may form into planets B) what is left of the planets around a star after a low-mass star has ended its life C) the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star D) the molecular cloud from which protostars form E) the expanding shell of gas that is left when a white dwarf explodes as a supernova
C) the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
22) Which of the following is a consequence of Hubble's Law? A) the Big Bang B) all galaxies are moving away from us equally fast C) the more distant a galaxy is from us, the faster it moves away from us D) the closer a galaxy is to us, the faster it moves away from us E) more distant galaxies appear younger
C) the more distant a galaxy is from us, the faster it moves away from us
2) Suppose that we look at a photograph of many galaxies. Assuming that all galaxies formed at about the same time, which galaxy in the picture is the youngest? A) the one that is reddest in color B) the one that is bluest in color C) the one that is farthest away D) the one that is closest to us E) the one that appears smallest in size
C) the one that is farthest away
An advanced civilization lives on a planet orbiting a close binary star system that consists of a 15MSun red giant and a 10MSun black hole. Assume that the two stars are quite close together, so that an accretion disk surrounds the black hole. The planet on which the civilization lives orbits the binary star at a distance of 10 AU. 36) Sometime within the next million years or so, their planet is likely to be doomed because A) jets of material shot out of the accretion disk will shoot down their planet. B) their planet receives most of its energy from the red giant. However, this star will soon be completely devoured in the accretion disk and thus will no longer exist. C) the red giant will probably undergo a supernova explosion within the next million years. D) tidal forces from the black hole will rip the planet apart. E) the planet's orbit gradually will decay as it is sucked in by the black hole.
C) the red giant will probably undergo a supernova explosion within the next million years.
41) 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
17) Sound waves in space A) do not exist. B) travel so slowly that they are unnoticeable. C) travel much faster than sound on Earth but have such low density that they are inaudible. D) travel much faster than sound on Earth and are therefore very loud. E) can travel through the halo but not the disk of the galaxy.
C) travel much faster than sound on Earth but have such low density that they are inaudible.
27) What is the most accurate way to determine the distance to a nearby galaxy? A) radar ranging B) stellar parallax C) using Cepheid variables D) Hubble's law
C) using Cepheid variables
10) What is the upper limit to the mass of a white dwarf? A) There is no upper limit. B) There is an upper limit, but we do not yet know what it is. C) 2 solar masses D) 1.4 solar masses E) 1 solar mass
D) 1.4 solar masses
1) 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.
14) At approximately what temperature can helium fusion occur? A) 100,000 K B) 1 million K C) a few million K D) 100 million K E) 100 billion K
D) 100 million K
1) 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
30) Approximately how long does it take the Sun to orbit the Milky Way Galaxy? A) 23,000 years B) 230,000 years C) 2.3 million years D) 230 million years E) 23 billion years
D) 230 million years
11) Approximately how far is the Sun from the center of the galaxy? A) 27 light-years B) 270 light-years C) 2,700 light-years D) 27,000 light-years E) 27 million light-years
D) 27,000 light-years
30) What is the Schwarzschild radius of a 100 million-solar-mass black hole? The mass of the Sun is about 2 × 1030 kg, and the formula for the Schwarzschild radius of a black hole of mass M is: Rs = (G = 6.67 × 10-11 ; c = 3 × 108 m/s) A) 3 km B) 30 km C) 3,000 km D) 300 million km E) 3 million km
D) 300 million km
31) Dr. Smith believes that the Hubble constant is H0 = 70 km/s/Mpc. Dr. Jones believes it is H0 = 50 km/s/Mpc. Which statement below automatically follows? A) Dr. Smith believes that the universe is expanding, but Dr. Jones does not. B) Dr. Smith believes that the Andromeda Galaxy (a member of our Local Group) is moving away from us at a faster speed than Dr. Jones believes. C) Dr. Smith believes that the universe is older than Dr. Jones believes. D) Dr. Smith believes that the universe is younger than Dr. Jones believes. E) Dr. Smith believes that the universe will someday stop expanding, while Dr. Jones believes it will expand forever.
D) Dr. Smith believes that the universe is younger than Dr. Jones believes.
39) 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.
35) Which of the following statements about halo stars is false? A) Halo stars have random orbits about the Milky Way center. B) Halo stars are no longer being formed at the current epoch. C) All halo stars are less massive than our Sun. D) Halo stars are made entirely of hydrogen and helium with no heavy elements. E) Halo stars are some of the oldest known objects in the universe.
D) Halo stars are made entirely of hydrogen and helium with no heavy elements.
27) Which of the following statements about black holes is not true? A) If you watch someone else fall into a black hole, you will never see him or her cross the event horizon. However, he or she will fade from view as the light he or she emits (or reflects) becomes more and more redshifted. B) If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls nearer to the black hole. C) A black hole is truly a hole in spacetime, through which we could leave the observable universe. D) If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole. E) If you fell into a black hole, you would experience time to be running normally as you plunged rapidly across the event horizon.
D) If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole.
8) How does the interstellar medium obscure our view of most of the galaxy? A) It produces so much visible light that it is opaque and blocks our view of anything beyond it. B) It reflects most light from far distances of the galaxy away from our line of sight. C) It absorbs all wavelengths of light. D) It absorbs visible, ultraviolet, and some infrared light. E) all of the above
D) It absorbs visible, ultraviolet, and some infrared light.
23) 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.
37) Which constellation lies in the direction toward the galactic center? A) Orion B) the Big Dipper C) Leo D) Sagittarius E) Taurus
D) Sagittarius
26) Suppose you read somewhere that 10 percent of the matter in the Milky Way is in the form of dust grains. Should you be surprised? If so, why? A) There is nothing surprising about 10 percent of the matter being dust grains because dust grains are the material from which stars are born. B) Given how easily dust grains form, 10 percent is a surprisingly low fraction of material to be in that form. C) Ten percent is surprisingly high because dust grains can form only at low temperatures. D) The 10 percent figure cannot be correct, because dust grains are solid but only about 2 percent of the matter in our galaxy is made of anything besides hydrogen and helium.
D) The 10 percent figure cannot be correct, because dust grains are solid but only about 2 percent of the matter in our galaxy is made of anything besides hydrogen and helium.
44) You discover a binary star system in which one member is a 15MSun main-sequence star and the other star is a 10MSun giant. Why should you be surprised, at least at first? A) It doesn't make sense to find a giant in a binary star system. B) The odds of ever finding two such massive stars in the same binary system are so small as to make it inconceivable that such a system could be discovered. C) The two stars in a binary system should both be at the same point in stellar evolution; that is, they should either both be main-sequence stars or both be giants. D) The two stars should be the same age, so the more massive one should have become a giant first. E) A star with a mass of 15MSun is too big to be a main-sequence star.
D) The two stars should be the same age, so the more massive one should have become a giant first.
38) Through a bizarre (and scientifically unexplainable) fluctuation in the spacetime continuum, a copy of a book titled Iguoonos: How We Evolved appears on your desk. As you begin to read, you learn that the book describes the evolution of the people living in the star system described above. In the first chapter, you learn that these people evolved from organisms that lived 5 billion years ago. Which of the following statements should you expect to find as you continue to read this book? A) As a result of traumatic experiences of their evolutionary ancestors, they dislike television. B) Their immediate ancestors were chimpanzees. C) They found that the presence of two stars in their system was critical to their evolution. D) They evolved on a different planet in a different star system and moved to their current location. E) They evolved from primitive wormlike creatures that had 13 legs, 4 eyes, and bald heads, thus explaining why such critters are now considered a spectacular delicacy.
D) They evolved on a different planet in a different star system and moved to their current location.
42) What evidence do we have that the halo population of stars are older than other stars in the galaxy? A) They are farther away. B) They have higher masses than other stars in the galaxy. C) They have fewer planets. D) They have a smaller proportion of heavy elements. E) They move slower than other stars in the galaxy.
D) They have a smaller proportion of heavy elements.
24) White-dwarf supernovae are good standard candles for distance measurements for all the following reasons except which? A) All white-dwarf supernovae involve the explosion of stars of nearly the same mass. B) White-dwarf supernovae are so bright that they can be detected even in very distant galaxies. C) White-dwarf supernovae are common enough that we detect several every year. D) White-dwarf supernovae occur only among young and extremely bright stars. E) All white-dwarf supernovae have similar light curves, which makes them easy to distinguish from massive-star supernovae.
D) White-dwarf supernovae occur only among young and extremely bright stars.
3) A teaspoonful of white dwarf material on Earth would weigh A) the same as a teaspoonful of Earth-like material. B) about the same as Mt. Everest. C) about the same as Earth. D) a few tons. E) a few million tons.
D) a few tons.
1) Degeneracy pressure is the source of the pressure that stops the crush of gravity in all the following except A) a brown dwarf. B) a white dwarf. C) a neutron star. D) a very massive main-sequence star. E) the central core of the Sun after hydrogen fusion ceases but before helium fusion begins.
D) a very massive main-sequence star.
13) 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
31) 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.
6) What makes up the interstellar medium? A) open clusters B) O and B stars C) K and M stars D) gas and dust E) all of the above
D) gas and dust
42) How are elements more massive than iron produced? A) inside white dwarfs B) inside two merging white dwarfs C) inside neutron stars D) inside two merging neutron stars
D) inside two merging neutron stars
36) Which element has the lowest mass per nuclear particle and therefore cannot release energy by either fusion or fission? A) hydrogen B) oxygen C) silicon D) iron E) uranium
D) iron
14) Approximately how many stars does a dwarf elliptical galaxy have? A) 1 trillion B) 100 billion C) 10 billion D) less than a billion E) less than a million
D) less than a billion
28) In some cases, a supernova in a binary system may lead to the eventual formation of an accretion disk around the remains of the star that exploded. All of the following statements about such accretion disks are true except A) X-rays are emitted by the hot gas in the accretion disk. B) the accretion disk consists of material that spills off the companion star. C) the central object about which the accretion disk swirls may be either a neutron star or a black hole. D) several examples of flattened accretion disks being "fed" by a large companion star can be seen clearly in photos from the Hubble Space Telescope. E) the radiation from an accretion disk may vary rapidly in time.
D) several examples of flattened accretion disks being "fed" by a large companion star can be seen clearly in photos from the Hubble Space Telescope.
37) One foolhardy day, a daring major (let's call him Tom) in the space force decides to become the first of his race to cross the event horizon of the black hole. To add to the drama, he decides to go in wearing only a thin space suit, which offers no shielding against radiation, no cushioning against any forces, and so on. Which of the following is most likely to kill him first (or at least cause significant damage)? (Hint: The key word here is first. Be sure to consider the distances from the black hole at which each of the noted effects is likely to become damaging.) A) the crush of gravity at the singularity embedded within the black hole B) the tidal forces due to the black hole C) the strong acceleration as he descends towards the black hole D) the X-rays from the accretion disk E) the sucking force from the black hole, which will cause his head to explode
D) the X-rays from the accretion disk
21) What is the galactic fountain model? A) the idea that there is a lot of interstellar water vapor B) the theory that the Milky Way is a spiral galaxy and looks like a whirlpool from above C) the theory that hot, ionized gas blows out of the galactic center like a jet or fountain D) the theory that hot, ionized gas blown out of the galactic disk and into the halo by superbubbles cools down and falls back into the disk E) none of the above
D) the theory that hot, ionized gas blown out of the galactic disk and into the halo by superbubbles cools down and falls back into the disk
7) If you were to take a voyage across the Milky Way, what kind of material would you spend most of your time in? A) empty space—a pure vacuum B) dusty molecular clouds C) star clusters D) warm, rarefied clouds of atomic hydrogen E) cool, dense clouds of atomic hydrogen
D) warm, rarefied clouds of atomic hydrogen
5) What can we learn about a star from a life track on an H-R diagram? A) how long ago it was born B) when it will die C) where it is located D) what surface temperature and luminosity it will have at each stage of its life E) all of the above
D) what surface temperature and luminosity it will have at each stage of its life
10) How does a lenticular galaxy differ from a normal spiral galaxy? A) It has no bulge. B) It has an elongated bulge resembling a bar more than a sphere. C) It is flatter in shape. D) It has no gas or dust. E) It has no spiral arms.
E) It has no spiral arms.
43) 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.
33) How do we know what happens at the event horizon of a black hole? A) Physicists have created miniature black holes in the lab. B) Astronomers have sent spacecraft through the event horizon of a nearby black hole. C) Astronomers have analyzed the light from matter within the event horizon of many black holes. D) Astronomers have detected X-rays from accretion disks around black holes. E) We don't know for sure: we only know what to expect based on the predictions of general relativity.
E) We don't know for sure: we only know what to expect based on the predictions of general relativity.
6) Which types of galaxies have a clearly defined halo component? A) spirals only B) ellipticals only C) lenticulars only D) irregulars only E) all but irregulars
E) all but irregulars
12) What do astronomers consider heavy elements? A) elements that are heavier than iron B) elements that are heavier than carbon C) elements that are heavier than hydrogen D) elements that are heavier than uranium E) all elements besides hydrogen and helium
E) all elements besides hydrogen and helium
4) What kinds of objects lie in the disk of our galaxy? A) open clusters B) O and B stars C) old K and M stars D) gas and dust E) all of the above
E) all of the above
10) Which of the following properties make flare stars so active? A) fast rotation rates B) deep convection zones C) convecting cores D) strong stellar winds E) both A and B
E) both A and B
25) What makes white-dwarf supernovae good standard candles? A) They are very bright, so they can be used to determine the distances to galaxies billions of light-years away. B) They should all have approximately the same luminosity. C) They occur so frequently that we can use them to measure the distances to virtually all galaxies. D) We have had several occur close to us in the Milky Way, so we have been able to determine their luminosities very accurately. E) both A and B
E) both A and B
15) 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
42) After a supernova event, 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
5) Which of the following comprise the oldest members of the Milky Way? A) the Sun and other solar mass stars B) O stars C) red giant stars in spiral arms D) Cepheid variables E) globular clusters
E) globular clusters
27) The image of our galaxy in radio emission from CO, mapping the distribution of molecular clouds, is closest to the image of our galaxy in A) 21-cm-line radio emission from atomic hydrogen. B) visible light, showing the edges of supernova bubbles. C) visible light, which is closest to how the night sky appears from Earth. D) X-rays from hot gas bubbles in the disk. E) infrared emission from interstellar dust grains.
E) infrared emission from interstellar dust grains.
22) Which of the following sequences correctly describes the stages of life for a low-mass star? A) red giant, protostar, main-sequence, white dwarf B) white dwarf, main-sequence, red giant, protostar C) protostar, red giant, main-sequence, white dwarf D) protostar, main-sequence, white dwarf, red giant E) protostar, main-sequence, red giant, white dwarf
E) protostar, main-sequence, red giant, white dwarf
7) Which types of galaxies have a clearly defined disk component? A) spirals only B) ellipticals only C) lenticulars only D) irregulars only E) spirals and lenticulars
E) spirals and lenticulars
4) Which of the following is closest in mass to a white dwarf? A) the Moon B) Earth C) Jupiter D) Neptune E) the Sun
E) the Sun
27) During which stage does the star have an inert (nonburning) carbon core? A) ii B) iii C) iv D) vi E) viii
E) viii