Description: (a) What is the Sun made of? Part A What is the Sun made of? ANSWER: 50 percent hydrogen, 25 percent helium, 25 percent other elements 98 percent hydrogen, 2 percent helium and other elements 70 percent helium, 28 percent hydrogen, 2 percent other elements 70 percent hydrogen, 28 percent helium, 2 percent other elements 100 percent hydrogen and helium Multiple Choice Question 8 Description: (a) What is the average temperature of the surface of the Sun? Part A What is the average temperature of the surface of the Sun? ANSWER: 10,000 K 100,000 K 6,000 K 1,000 K 1 million K Multiple Choice Question 14 Description: (a) The spectral sequence in order of decreasing temperature is... Part A The spectral sequence in order of decreasing temperature is ANSWER: OBAFGKM. ABFGKMO. OFBAGKM. BAGFKMO. OBAGFKM. Multiple Choice Question 22 Description: (a) Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram? Part A Which of the following best describes the axes of a Hertzsprung-Russell (H-R) diagram? ANSWER: mass on the horizontal axis and stellar age on the vertical axis surface temperature on the horizontal axis and luminosity on the vertical axis surface temperature on the horizontal axis and radius on the vertical axis mass on the horizontal axis and luminosity on the vertical axis interior temperature on the horizontal axis and mass on the vertical axis Multiple Choice Question 28 Description: (a) On a Hertzsprung-Russell diagram, where would we find white dwarfs? Part A On a Hertzsprung-Russell diagram, where would we find white dwarfs? ANSWER: lower left upper left upper right lower right Multiple Choice Question 7 Description: (a) What is interstellar reddening? Part A What is interstellar reddening? ANSWER: Interstellar dust absorbs more blue light than red light, making stars appear redder than their true color. Interstellar dust absorbs more red light than blue light, making stars appear redder than their true color. The spectral line shift due to a star's motion through the interstellar medium. Interstellar dust absorbs more blue light than red light, making stars appear bluer than their true color. Interstellar dust absorbs more red light than blue light, making stars appear bluer than their true color. Multiple Choice Question 32 Description: (a) What is the smallest mass a newborn star can have? Part A What is the smallest mass a newborn star can have? ANSWER: 8 times the mass of Jupiter about 1/800 the mass of our Sun 80 times the mass of Jupiter 800 times the mass of Jupiter about 1/80 the mass of our Sun Multiple Choice Question 3 Description: (a) What type of star is our Sun? Part A What type of star is our Sun? ANSWER: low-mass star high-mass star intermediate-mass star Multiple Choice Question 11 Description: (a) What happens when a star exhausts its core hydrogen supply? Part A What happens when a star exhausts its core hydrogen supply? ANSWER: It contracts, becoming hotter and brighter. Its core contracts, but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness. It contracts, becoming smaller and dimmer. Its core contracts, but its outer layers expand and the star becomes bigger and brighter. It expands, becoming bigger but dimmer. Multiple Choice Question 20 Description: (a) What is a planetary nebula? Part A What is a planetary nebula? ANSWER: the expanding shell of gas that is left when a white dwarf explodes as a supernova the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star what is left of the planets around a star after a low-mass star has ended its life the molecular cloud from which protostars form a disk of gas surrounding a protostar that may form into planets Multiple Choice Question 28 Description: (a) Which of the following statements about black holes is not true? Part A Which of the following statements about black holes is not true? ANSWER: If the Sun magically disappeared and was replaced by a black hole of the same mass, Earth would soon be sucked into the black hole. If 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. If we watch a clock fall toward a black hole, we will see it tick slower and slower as it falls nearer to the black hole. If you fell into a black hole, you would experience time to be running normally as you plunged rapidly across the event horizon. A black hole is truly a hole in spacetime, through which we could leave the observable universe. Multiple Choice Question 40 Description: (a) If you were to come back to our Solar System in 6 billion years, what might you expect to find? Part A If you were to come back to our Solar System in 6 billion years, what might you expect to find? ANSWER: a black hole a white dwarf a rapidly spinning pulsar a red giant star Everything will be pretty much the same as it is now. Multiple Choice Question 11 Description: (a) What is the major difference between an elliptical galaxy and a spiral galaxy? Part A What is the major difference between an elliptical galaxy and a spiral galaxy? ANSWER: An elliptical galaxy lacks a disk component. A spiral galaxy has a spherical halo. Elliptical galaxies are not as big as spiral galaxies. There are no dwarf spiral galaxies, but there are dwarf ellipticals. A spiral galaxy contains mostly younger stars. Multiple Choice Question 13 Description: (a) Which of the following types of galaxies are most commonly found in large clusters? Part A Which of the following types of galaxies are most commonly found in large clusters? ANSWER: spirals lenticulars irregulars ellipticals Multiple Choice Question 28 Description: (a) What is the most accurate way to determine the distance to a nearby star? Part A What is the most accurate way to determine the distance to a nearby star? ANSWER: Hubble's law main-sequence fitting using Cepheid variables stellar parallax radar ranging Multiple Choice Question 31 Description: (a) Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest? Part A Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest? ANSWER: parallax, main-sequence fitting, Tully-Fisher relation, white-dwarf supernovae, Hubble's law parallax, main-sequence fitting, Cepheid variables, Tully-Fisher relation, Hubble's law main-sequence fitting, parallax, Cepheid variables, Tully-Fisher relation, Hubble's law main-sequence fitting, parallax, Hubble's law, Tully-Fisher relation, white-dwarf supernovae parallax, main-sequence fitting, Tully-Fisher relation, Cepheid variables, Hubble's law Multiple Choice Question 15 Description: (a) What kinds of atomic nuclei formed during the era of nucleosynthesis? Part A What kinds of atomic nuclei formed during the era of nucleosynthesis? ANSWER: nuclei of all the chemical elements hydrogen and helium and trace amounts of lithium, beryllium, and boron only hydrogen only helium roughly equal amounts of each of the following: hydrogen, helium, lithium, beryllium, and boron Multiple Choice Question 14 Description: (a) Approximately how long did the era of nucleosynthesis last? Part A Approximately how long did the era of nucleosynthesis last? ANSWER: 3 minutes 3 seconds 3 years 10-10 second 0.001 second Multiple Choice Question 14 Description: (a) Why do sunspots appear dark in pictures of the Sun? Part A Why do sunspots appear dark in pictures of the Sun? ANSWER: They are holes in the solar surface through which we can see to deeper, darker layers of the Sun. They actually are fairly bright but appear dark against the even brighter background of the surrounding Sun. They emit light in other wavelengths that we can't see. They are too cold to emit any visible light. They are tiny black holes, absorbing all light that hits them. Multiple Choice Question 16 Description: (a) How does the Sun generate energy today? Part A How does the Sun generate energy today? ANSWER: chemical reactions gradually expanding in size gravitational contraction nuclear fusion nuclear fission Multiple Choice Question 1 Description: (a) Approximately, what basic composition are all stars born with? Part A Approximately, what basic composition are all stars born with? ANSWER: 90 percent hydrogen, 10 percent helium, no more than 1 percent heavier elements three-quarters hydrogen, one-quarter helium, no more than 2 percent heavier elements 98 percent hydrogen, 2 percent helium one-quarter hydrogen, three-quarters helium, no more than 2 percent heavier elements half hydrogen, half helium, no more than 2 percent heavier elements Multiple Choice Question 7 Description: (a) Which of the following correctly states the luminosity-distance formula? Part A Which of the following correctly states the luminosity-distance formula? ANSWER: \rm apparent\,brightness = luminosity \times 4 \pi \times (distance)^2 \rm luminosity=\frac{apparent\,brightness}{4 \pi \times (distance)^2} \rm distance =\frac{luminosity}{4 \pi \times (apparent\,brightness)^2} \rm apparent\,brightness=\frac{luminosity}{4 \pi \times (distance)^2} Multiple Choice Question 23 Description: (a) On a Hertzsprung-Russell diagram, where would we find stars that are cool and dim? Part A On a Hertzsprung-Russell diagram, where would we find stars that are cool and dim? ANSWER: lower left upper right lower right upper left Multiple Choice Question 25 Description: (a) On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii? Part A On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii? ANSWER: lower left lower right upper right upper left Multiple Choice Question 29 Description: (a) You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the... Part A You observe a star in the disk of the Milky Way, and you want to plot the star on an H-R diagram. You will need to determine all of the following, except the ANSWER: spectral type of the star. apparent brightness of the star in our sky. rotation rate of the star. distance to the star. Multiple Choice Question 36 Description: (a) Which of the following is true about low-mass stars compared to high-mass stars? Part A Which of the following is true about low-mass stars compared to high-mass stars? ANSWER: Low-mass stars are hotter but less luminous than high-mass stars. Low-mass stars have the same temperature and luminosity as high-mass stars. Low-mass stars are cooler and less luminous than high-mass stars. Low-mass stars are cooler but more luminous than high-mass stars. Low-mass stars are hotter and more luminous than high-mass stars. Multiple Choice Question 40 Description: (a) Which of the following statements about an open cluster is true? Part A Which of the following statements about an open cluster is true? ANSWER: All stars in the cluster are approximately the same color. All stars in the cluster are approximately the same age. All stars in the cluster have approximately the same mass. All stars in the cluster will evolve similarly. There is an approximately equal number of all types of stars in the cluster. Multiple Choice Question 20 Description: (a) What happens to the rotation of a molecular cloud as it collapses to form a star? Part A What happens to the rotation of a molecular cloud as it collapses to form a star? ANSWER: The rotation increases the speed of collapse and produces more massive stars. The rotation rate remains the same and results in stellar rotation. The rotation dissipates and any residual is left in small overall rotation of the star. The rotation rate increases and results in fast rotation of the star. The rotation rate increases and results in a disk of material around a protostar. Multiple Choice Question 37 Description: (a) For every star with a mass greater than 10 solar masses, about how many stars are there with masses less than a solar mass? Part A For every star with a mass greater than 10 solar masses, about how many stars are there with masses less than a solar mass? ANSWER: 10 1 100 3 30 Multiple Choice Question 13 Description: (a) Compared to the star it evolved from, a red giant is... Part A Compared to the star it evolved from, a red giant is ANSWER: hotter and dimmer. cooler and brighter. hotter and brighter. the same temperature and brightness. cooler and dimmer. Multiple Choice Question 16 Description: (a) How many helium nuclei fuse together when making carbon? Part A How many helium nuclei fuse together when making carbon? ANSWER: 2 4 3 varies depending on the reaction none of the above Multiple Choice Question 21 Description: (a) What happens to the core of a star after a planetary nebula occurs? Part A What happens to the core of a star after a planetary nebula occurs? ANSWER: It contracts from a protostar to a main-sequence star. It breaks apart in a violent explosion. It becomes a white dwarf. It becomes a neutron star. none of the above Multiple Choice Question 41 Description: (a) Which event marks the beginning of a supernova? Part A Which event marks the beginning of a supernova? ANSWER: the expansion of a low-mass star into a red giant the sudden outpouring of X rays from a newly formed accretion disk the beginning of neon burning in an extremely massive star the sudden collapse of an iron core into a compact ball of neutrons the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun Multiple Choice Question 4 Description: (a) Which of the following is closest in mass to a white dwarf? Part A Which of the following is closest in mass to a white dwarf? ANSWER: the Moon the Sun Earth Jupiter Multiple Choice Question 5 Description: (a) Why is there an upper limit to the mass of a white dwarf? Part A Why is there an upper limit to the mass of a white dwarf? ANSWER: The upper limit to the masses of white dwarfs was determined through observations of white dwarfs, but no one knows why the limit exists. 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. 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. White dwarfs come only from stars smaller than 1.4 solar masses. Multiple Choice Question 10 Description: (a) What is the upper limit to the mass of a white dwarf? Part A What is the upper limit to the mass of a white dwarf? ANSWER: 2 solar masses 1 solar mass There is an upper limit, but we do not yet know what it is. 1.4 solar masses There is no upper limit. Multiple Choice Question 12 Description: (a) Which of the following is closest in size (radius) to a white dwarf? Part A Which of the following is closest in size (radius) to a white dwarf? ANSWER: Earth a small city the Sun a basketball a football stadium Multiple Choice Question 16 Description: (a) What is the upper limit to the mass of a neutron star? Part A What is the upper limit to the mass of a neutron star? ANSWER: precisely 2 solar masses There is an upper limit less than 3 solar masses, but we do not yet know precisely what it is. 1.4 solar masses 1 solar mass There is no upper limit. Multiple Choice Question 21 Description: (a) From a theoretical standpoint, what is a pulsar? Part A From a theoretical standpoint, what is a pulsar? ANSWER: a star that alternately expands and contracts in size a binary system that happens to be aligned so that one star periodically eclipses the other a rapidly rotating neutron star a star that is burning iron in its core a neutron star or black hole that happens to be in a binary system Multiple Choice Question 25 Description: (a) What is the basic definition of a black hole? Part A What is the basic definition of a black hole? ANSWER: a dead star that has faded from view a dead galactic nucleus that can only be viewed in infrared any compact mass that emits no light any object made from dark matter any object from which the escape velocity exceeds the speed of light Multiple Choice Question 34 Description: (a) How do we know what happens at the event horizon of a black hole? Part A How do we know what happens at the event horizon of a black hole? ANSWER: Astronomers have detected X rays from accretion disks around black holes. We don't know for sure: we only know what to expect based on the predictions of general relativity. Astronomers have sent spacecraft through the event horizon of a nearby black hole. Physicists have created miniature black holes in the lab. Astronomers have analyzed the light from matter within the event horizon of many black holes. Multiple Choice Question 3 Description: (a) What kinds of objects lie in the halo of our galaxy? Part A What kinds of objects lie in the halo of our galaxy? ANSWER: globular clusters gas and dust O and B stars open clusters all of the above Multiple Choice Question 2 Description: (a) What is the thickness of the disk of the Milky Way? Part A What is the thickness of the disk of the Milky Way? ANSWER: 10,000 light-years 100 light-years 1,000 light-years 100,000 light-years 1,000,000 light-years Multiple Choice Question 6 Description: (a) What makes up the interstellar medium? Part A What makes up the interstellar medium? ANSWER: O and B stars K and M stars open clusters gas and dust all of the above Multiple Choice Question 28 Description: (a) Compared with our Sun, most stars in the halo are... Part A Compared with our Sun, most stars in the halo are ANSWER: young, red, and dim and have fewer heavy elements. old, red, and bright and have fewer heavy elements. old, red, and dim and have fewer heavy elements. young, blue, and bright and have much more heavy element material. old, red, and dim and have much more heavy element material. Multiple Choice Question 37 Description: (a) Which constellation lies in the direction toward the galactic center? Part A Which constellation lies in the direction toward the galactic center? ANSWER: the Big Dipper Leo Sagittarius Orion Taurus Multiple Choice Question 2 Description: (a) 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? Part A 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? ANSWER: the one that is closest to us the one that is bluest in color the one that is farthest away the one that is reddest in color the one that appears smallest in size Multiple Choice Question 16 Description: (a) Why are Cepheid variables important? Part A Why are Cepheid variables important? ANSWER: Cepheids are a type of young galaxy that helps us understand how galaxies form. 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. 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. Cepheid variables are stars that vary in brightness because they harbor a black hole. Multiple Choice Question 22 Description: (a) What is Hubble's law? Part A What is Hubble's law? ANSWER: The recession velocity of a galaxy is inversely proportional to its distance from us. The longer the time period between peaks in brightness, the greater the luminosity of the Cepheid variable star. The faster a spiral galaxy's rotation speed, the less luminous it is. The faster a spiral galaxy's rotation speed, the more luminous it is. The recession velocity of a galaxy is directly proportional to its distance from us. Multiple Choice Question 1 Description: (a) Why do we call dark matter "dark"? Part A Why do we call dark matter "dark"? ANSWER: We cannot detect the type of radiation that it emits. It emits no visible light. It emits no or very little radiation of any wavelength. It blocks out the light of stars in a galaxy. Multiple Choice Question 5 Description: (a) What evidence suggests that the Milky Way contains dark matter? Part A What evidence suggests that the Milky Way contains dark matter? ANSWER: We see many lanes of dark material blocking out the light of stars behind them along the band of the Milky Way. We see many dark voids between the stars in the halo of the Milky Way. When we look at the galactic center, we are able to observe a large black hole that is composed of dark matter. We observe clouds of atomic hydrogen far from the galactic center orbiting the galaxy at unexpectedly high speeds, higher speeds than they would have if they felt only the gravitational attraction from objects that we can see. When we observe in different wavelengths, such as infrared or radio, we see objects that don't appear in visible-light observations. Multiple Choice Question 18 Description: (a) Gravitational lensing occurs when... Part A Gravitational lensing occurs when ANSWER: massive objects cause more distant objects to appear much larger than they should and we can observe the distant objects with better resolution. telescope lenses are distorted by gravity. dark matter builds up in a particular region of space, leading to a very dense region and an extremely high mass-to-light ratio. massive objects bend light beams that are passing nearby. Multiple Choice Question 38 Description: (a) What is the evidence for an accelerating universe? Part A What is the evidence for an accelerating universe? ANSWER: There is far more dark matter than visible matter in the universe. White-dwarf supernovae are the same brightness regardless of redshift. White-dwarf supernovae are slightly brighter than expected for a coasting universe. The Andromeda Galaxy is moving away from the Milky Way at an ever-increasing speed. White-dwarf supernovae are slightly dimmer than expected for a coasting universe.