Astronomy W11-14
Why does the Big Bang theory predict that the cosmic background radiation should have a perfect thermal radiation spectrum? A) The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe. B) The spectrum of pure hydrogen is a perfect thermal radiation spectrum. C) The spectrum of 75 percent hydrogen and 25 percent helium is a perfect thermal radiation spectrum. D) The light from all the stars and gas in the sky averaged over the entire universe is a perfect thermal radiation spectrum. E) It doesn't predict that the cosmic background radiation should have a perfect thermal radiation spectrum.
A) The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe.
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.
What are the typical features seen in quasar absorption lines of intergalactic clouds? A) The hydrogen line is wider and lines from heavy elements are weaker at higher redshifts. B) The hydrogen line is narrower and lines from heavy elements are weaker at higher redshifts. C) The hydrogen line is wider and lines from heavy elements are stronger at higher redshifts. D) The hydrogen line is narrower and lines from heavy elements are stronger at higher redshifts. E) A few weak absorption lines are always seen at higher redshift than the quasar.
A) The hydrogen line is wider and lines from heavy elements are weaker at higher redshifts.
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions? A) The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form. B) The temperature of the universe can be found by taking an average over the entire sky, but individual stars will create peaks in the spectrum over small angles. C) Dark matter consisting of WIMPs greatly smooths out the spectrum, but the small patches of "light" matter create peaks in the spectrum. D) The overall structure of the universe is very uniform, but the synthesis of different elements produces varying signatures within the background spectrum. E) The overall structure of the universe is very uniform, but intervening gas between us and the era of nuclei absorbs wavelengths depending on the composition and redshift of the gas.
A) The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form.
All of the following are true. Which of these gives evidence that quasars were more common in the early stages of the universe? A) They are more common at very great distances. B) They are very bright. C) They are active galactic nuclei. D) We don't see them in every galaxy.
A) They are more common at very great distances
What happened to the quarks that existed freely during the particle era? A) They combined in groups to make protons, neutrons, and their antiparticles. B) They froze out of the soup of particles at the end of the era. C) They evaporated. D) They combined in groups to make electrons and neutrinos. E) They combined in groups to make W and Z bosons.
A) They combined in groups to make protons, neutrons, and their antiparticles.
Why can't current theories describe what happened during the Planck era? A) We do not yet have a theory that links quantum mechanics and general relativity. B) We do not understand the properties of antimatter. C) We do not know how much energy existed during that time. D) It was a time period from which we cannot receive radiation. E) The Planck era was the time before the Big Bang, and we cannot describe what happened before that instant.
A) We do not yet have a theory that links quantum mechanics and general relativity.
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
Where are the X rays produced that are emitted by quasars and other active galactic nuclei? A) in hot gas in an accretion disk around a central black hole B) in ionization nebulae of interstellar gas that surround the accretion disk C) in dust grains in molecular clouds that encircle the active galactic nucleus D) in fast-moving electrons that jet from the active galactic nucleus E) all of the above
A) in hot gas in an accretion disk around a central black hole
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
What are the two key observational facts that led to widespread acceptance of the Big Bang model? A) the cosmic background radiation and the high helium content of the universe B) the cosmic background radiation and the expansion of the universe C) the cosmic background radiation and the near-critical density of the universe D) the predominance of matter over antimatter and the near-critical density of the universe E) the predominance of matter over antimatter and the large scale structure of galaxies
A) the cosmic background radiation and the high helium content of the universe
Which of the following types of galaxies are most commonly found in large clusters? A) spirals B) ellipticals C) lenticulars D) irregulars
B) ellipticals
Which of the following types of galaxies are most spherical in shape? A) spirals B) ellipticals C) lenticulars D) irregulars
B) ellipticals
If we represent the Milky Way Galaxy as the size of a grapefruit (10-cm diameter), the distance to the Andromeda Galaxy would be about A) 10 cm. B) 3 m. C) 30 m. D) 1 km. E) 100 km.
B) 3 m.
The most active galactic nuclei are usually found at large distances from us; relatively fewnearby galaxies have active galactic nuclei. What does this imply? A) Massive black holes existed only when the universe was young and no longer exist today. B) Active galactic nuclei tend to become less active as they age. C) Active galactic nuclei can form only at large distances from the Milky Way. D) The jets seen in many active galactic nuclei must cause them to move far away from us.
B) Active galactic nuclei tend to become less active as they age.
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.
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.
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.
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.
Which of the following gives the two main assumptions of theoretical models of galaxy evolution? A) The beginning of the universe is modeled after a supernova explosion, and all the elements were produced in the proper quantities by the star. B) Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others. C) Hydrogen and helium filled all of space, and all the universe was exactly the same density. D) The universe has always been expanding, and denser areas contracted to form the first stars. E) The universe was composed originally only of hydrogen, and all the other elements came from stars.
B) Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others.
Which of the following is not a piece of evidence supporting the conclusion that active galactic nuclei are powered by accretion disks around massive black holes? A) Observed radiation from the galactic center varies significantly in brightness in times as short as a few days. B) Infrared observations show that many stars are forming near the centers of active galaxies. C) Radio observations sometimes show long jets of material extending millions of light-years out from the galactic center. D) The total amount of radiation coming from the galactic center is, in some cases, comparable to the amount of radiation put out by 10 billion or more ordinary stars. E) Spectral lines from the galactic center indicate that clouds of gas are orbiting a central object at very high speed.
B) Infrared observations show that many stars are forming near the centers of active galaxies.
Why is the Hyades Cluster important for building up a catalog of the true luminosities of main-sequence stars? A) It is an extremely bright cluster. B) It is close enough to us that the distance to the cluster stars can be found by stellar parallax. C) It is an old globular cluster that has been around our galaxy for several billion years. D) We have brightness measurements for the stars in the cluster over many decades, so we know how the stars vary in brightness. E) It contains many Cepheid variables.
B) It is close enough to us that the distance to the cluster stars can be found by stellar parallax.
Which of the following types of galaxies are reddest in color? A) spirals B) ellipticals C) lenticulars D) irregulars
B) ellipticals
Which of the following statements about the cosmic background radiation is not true? A) It has a temperature of about 3 degrees K above absolute zero. B) It is the result of a mixture of radiation from many independent sources, such as stars and galaxies. C) It had a much higher temperature in the past. D) It was discovered by Penzias and Wilson in the early 1960s. E) It appears essentially the same in all directions (it is isotropic).
B) It is the result of a mixture of radiation from many independent sources, such as stars and galaxies.
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.
Why do we believe that starburst galaxies represent a temporary stage in galaxy evolution? A) We observe starbursts to last only a few years at a time. B) Such galaxies produce so much light that they would have consumed all their gas long ago if they had always been forming stars at this high rate. C) We don';t see any nearby starburst galaxies. D) All starburst galaxies look like normal spiral galaxies, aside from the starbursts.
B) Such galaxies produce so much light that they would have consumed all their gas long ago if
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.
Why did the era of nuclei end when the universe was about 300,000 years old? A) All the free particles had combined to form the nuclei of atoms. B) The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form. C) Neutrinos and electrons were finally able to escape the plasma of the early universe and no longer heated the other particles. D) Photons were finally able to escape the plasma of the early universe and no longer heated the hydrogen and helium ions. E) No theory can explain this.
B) The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form
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.
How do we know that there are intergalactic clouds between a distant quasar and us? A) We see hydrogen emission lines at redshifts smaller than that of the quasar. B) We see hydrogen absorption lines at redshifts smaller than that of the quasar. C) We see hydrogen emission lines at redshifts greater than that of the quasar. D) We see hydrogen absorption lines at redshifts greater than that of the quasar. E) We see that the emission lines from the quasar are lessened by intervening gas and dust.
B) We see hydrogen absorption lines at redshifts smaller than that of the quasar.
What evidence suggests that small galaxies in our Local Group have undergone two or more starbursts in the past? A) We observe several small galaxies currently undergoing massive star formation. B) We see small galaxies in which many stars have one age and many others have another age that is billions of years older. C) We see evidence that small galaxies in our Local Group have experienced several collisions in the past. D) We see evidence that several small galaxies were shot out of larger galaxies in our Local Group during an age of starburst activity. E) We do not have any evidence that galaxies in our Local Group were once starburst galaxies.
B) We see small galaxies in which many stars have one age and many others have another age that is billions of years older.
Which of the following types of protogalactic clouds is most likely to form an elliptical galaxy? A) a very low-density cloud with very little angular momentum B) a dense cloud with very little angular momentum C) a low-density cloud with quite a bit of angular momentum D) a dense cloud with quite a bit of angular momentum E) a very massive cloud with any density and a lot of angular momentum
B) a dense cloud with very little angular momentum
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
What do we mean by inflation? A) what happened the instant after the Big Bang B) a sudden expansion of the universe after the strong force froze out from the GUT force C) the expansion of the universe that we still observe today D) the sudden release of photons when a particle and antiparticle annihilate each other E) the separation that occurs after two photons collide and create a particle and an antiparticle
B) a sudden expansion of the universe after the strong force froze out from the GUT force
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.
The Planck era refers to the time period A) before the Big Bang. B) before the Planck time. C) after the Planck time. D) after inflation. E) after the GUT era.
B) before the Planck time.
What is a galactic wind? A) a jet of ionized particles shot out of a starburst galaxy B) hot gas erupting into intergalactic space from a large superbubble C) the heat (infrared radiation) emitted by dust grains in the large molecular clouds of starburst galaxies D) the cooler gas pushed out of a starburst galaxy by the intense radiation pressure E) a wind created by the expansion of the universe that can move galaxies around
B) hot gas erupting into intergalactic space from a large superbubble
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
Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest? A) main-sequence fitting, parallax, Cepheid variables, Hubble's law B) parallax, main-sequence fitting, Cepheid variables, Hubble's law C) parallax, main-sequence fitting, Hubble's law, Cepheid variables D) parallax, main-sequence fitting, white-dwarf supernovae, Hubble's law E) main-sequence fitting, parallax, Hubble's law, white-dwarf supernovae
B) parallax, main-sequence fitting, Cepheid variables, Hubble's law
Hubble's "constant" is constant in A) time. B) space. C) space and time. D) our Galaxy but different in others.
B) space.
Most large galaxies in the universe are A) elliptical. B) spiral or lenticular. C) irregular. D) abnormal.
B) spiral or lenticular
What is the most accurate way to determine the distance to a nearby star? A) radar ranging B) stellar parallax C) main-sequence fitting D) using Cepheid variables E) Hubble's law
B) stellar parallax
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
How many forces operated in the universe during the GUT era? A) one, what we call the "super force" B) two, gravity and the GUT force C) two, gravity and the electroweak force D) three, gravity, the strong force, and the electroweak force E) all of the above forces
B) two, gravity and the GUT force
How long after the Big Bang was the Planck time, before which our current theories are completely unable to describe conditions in the universe? A) 10-10 second B) 10-35 second C) 10-43 second D) 3 minutes E) 300,000 years
C) 10-43 second
Why is the era of nucleosynthesis so important in determining the chemical composition of the universe? A) All the elements except hydrogen were produced after the era of nucleosynthesis. B) We can observe spectra from this era to determine what the primordial mix of the elements was at the beginning of the universe. C) Except for the small amount of matter produced later by stars, the chemical composition of the universe is the same now as at the end of the era of nucleosynthesis. D) We can study the processes that occurred during the era of nucleosynthesis to determine how most of the elements in the universe were created. E) By knowing how much matter was created during the era of nucleosynthesis, we can determine whether the universe is open or closed.
C) Except for the small amount of matter produced later by stars, the chemical composition of the universe is the same now as at the end of the era of nucleosynthesis.
Why should galaxy collisions have been more common in the past than they are today? A) Galaxies were more active in the past and therefore would have collided with each other more frequently. B) Galaxies were much bigger in the past since they had not contracted completely. C) Galaxies were closer together in the past because the universe was smaller. D) Galaxies attracted each other more strongly in the past because they were more massive; they had not yet turned most of their mass into stars and light. E) Galaxy collisions shouldn't have been more common in the past than they are now.
C) Galaxies were closer together in the past because the universe was smaller.
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 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.
Evidence that the cosmic background radiation really is the remnant of a Big Bang comes from predicting characteristics of remnant radiation from the Big Bang and comparing these predictions with observations. Four of the five statements below are real. Which one is fictitious? A) The cosmic background radiation is expected to have a temperature just a few degrees above absolute zero, and its actual temperature turns out to be about 3 K (actually 2.7 K). B) The cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the COBE spacecraft verify this prediction. C) The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does. D) The cosmic background radiation is expected to look essentially the same in all directions, and it does. E) The cosmic background radiation is expected to have tiny temperature fluctuations at the level of about 1 part in 100,000. Such fluctuations were found in the COBE data.
C) The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does.
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.
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.
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.
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
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
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
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
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
What kinds of atomic nuclei formed during the era of nucleosynthesis? A) only hydrogen B) only helium C) hydrogen and helium and trace amounts of deuterium and lithium D) roughly equal amounts of each of the following: hydrogen, helium, deuterium and lithium E) nuclei of all the chemical elements
C) hydrogen and helium and trace amounts of deuterium and lithium
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
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.
When we say that the electromagnetic and weak forces "freeze out" from the electroweak force at 10-10 seconds after the Big Bang, we mean that A) these forces are important only at temperatures below the freezing point of water-a temperature that the universe reached at an age of about 10-10 second. B) "freezing out" was a term coined by particle physicists who think that the Big Bang theory is really cool. C) prior to this time the electromagnetic and weak forces maintained a single identity, but they possessed separate identities following this time. D) following this time neither the electromagnetic nor the weak force was ever important in the universe again. E) quantum fluctuations by high-speed, relativistic particles in a state of false vacuum cause disturbances in the spacetime continuum, leading to the process described in the question this answer refers to.
C) prior to this time the electromagnetic and weak forces maintained a single identity, but they possessed separate identities following this time.
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
What is postulated to have caused a sudden inflation of the early universe? A) the annihilation of matter and antimatter B) the separation of the electromagnetic and weak forces C) the "freezing out" of the strong force from the GUT force D) the energy released in the fusion of protons and neutrons to produce helium E) giant quantum fluctuations
C) the "freezing out" of the strong force from the GUT force
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
Which of the following processes slowed the collapse of protogalactic clouds? A) the formation of the first generation of stars B) the conversion of gravitational potential energy into kinetic and thermal energy as the cloud collapsed C) the shock waves from the exploding supernovae of the earliest stars D) the pull of gravity of the mass of the cloud material E) the radiating away of thermal energy
C) the shock waves from the exploding supernovae of the earliest stars
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) main sequence fitting E) Hubble's law
C) using Cepheid variables
What is the most accurate way to determine the distance to a very distant irregular galaxy? A) main-sequence fitting B) using Cepheid variables C) using a white-dwarf supernova as a standard candle D) main sequence fitting E) Hubble's law
C) using a white-dwarf supernova as a standard candle
Which types of galaxies have a clearly defined spheroidal component? A) spirals only B) ellipticals only C) lenticulars only D) irregulars only E) all but irregulars
E) all but irregulars
Approximately how long did the era of nucleosynthesis last? A) 10-10 second B) 0.001 second C) 5 seconds D) 5 minutes E) 5 years
D) 5 minutes
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.
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
What direct evidence do we have that the weak and electromagnetic forces were once unified as a single electroweak force? A) The most advanced telescopes are able to see back to this era in the universe. B) Detectors on Earth have received photons and high-energy particles from this era. C) Temperatures in the center of the Sun can reproduce the conditions during this era. D) Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory. E) We have no direct evidence of the electroweak force.
D) Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory.
Which of the following is not true of quasars? A) Some quasars are more than a thousand times more luminous than the Milky Way. B) Quasars were more common in the past. C) Quasars are powered by the energy radiated by matter falling into a central black hole. D) Quasars are powered by the intense production of large numbers of stars that can only be sustained for a relatively short time. E) Some quasars can change their brightness every few hours.
D) Quasars are powered by the intense production of large numbers of stars that can only be sustained for a relatively short time.
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.
Olbers' paradox is an apparently simple question, but its resolution suggests that the universe is finite in age. What is the question? A) What would it be like to ride on a beam of light? B) Can we measure the position and momentum of an electron at the same time? C) How does the Sun produce energy? D) Why is the sky dark at night? E) How many stars are in the universe?
D) Why is the sky dark at night?
What is a central dominant galaxy? A) a galaxy around which many other smaller galaxies orbit B) a giant spiral galaxy that exerts large tidal forces on other nearby galaxies C) a spiral galaxy from which many smaller galaxies form when it is stripped apart by tidal forces D) a giant elliptical galaxy at the center of a dense cluster E) a hypothesized galaxy type that no longer exists but once dominated the structure of the universe
D) a giant elliptical galaxy at the center of a dense cluster
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
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
Helium originates from A) stellar nucleosynthesis only. B) the Big Bang only. C) stellar nucleosynthesis with a small contribution from the Big Bang. D) the Big Bang with a small contribution from stellar nucleosynthesis. E) radioactive decay of heavier elements only.
D) the Big Bang with a small contribution from stellar nucleosynthesis.
Where do the photons in the cosmic background radiation originate? A) the moment of the Big Bang B) the end of the Planck era C) during the era of nucleosynthesis D) the end of the era of nuclei E) during the era of galaxy formation
D) the end of the era of nuclei
What is a quasar? A) a starlike object that actually represents a bright patch of gas in the Milky Way B) a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster C) a specialized astronomical instrument for observing distant stars D) the extremely bright center of a distant galaxy, thought to be powered by a massive black hole E) another name for very bright stars of spectral type O
D) the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
Starburst galaxies produce most of their light in the wavelength range of A) X rays. B) the ultraviolet. C) the visible. D) the infrared. E) all wavelengths.
D) the infrared.
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
A GUT (grand unified theory) refers to theories that A) unify all four forces. B) unify gravity and the electromagnetic and weak forces. C) unify gravity and the strong and weak forces. D) unify the strong force and the electromagnetic and weak forces. E) unify the electromagnetic and weak forces.
D) unify the strong force and the electromagnetic and weak forces.
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
To date, physicists have investigated the behavior of matter and energy at temperatures as high as those that existed in the universe as far back as ________ after the Big Bang. A) 1 million years B) 300,000 years C) 300 years D) 3 minutes E) 10-10 second
E) 10-10 second
Why might inflation have occurred at the end of the GUT era? A) Gravity was an extremely weak force at this period in time. B) Large amounts of matter and antimatter annihilated at this time. C) There wasn't enough matter present to slow down the expansion at that time. D) The universe was too small and needed to grow quickly. E) An enormous amount of energy was released when the strong force froze out from the GUT force.
E) An enormous amount of energy was released when the strong force froze out from the GUT force.
Which of the following is not a strong argument for the theory that some large elliptical galaxies formed as the result of galaxy collisions? A) Elliptical galaxies dominate the population in dense galaxy clusters. B) Some ellipticals have stars and gas that rotate opposite to the rest of the galaxy. C) Some elliptical galaxies are surrounded by shells of stars. D) Computer simulations predict that the product of a galaxy collision is generally an elliptical galaxy. E) Galaxy collisions are common and most galaxies in the universe are elliptical.
E) Galaxy collisions are common and most galaxies in the universe are elliptical.
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.
Why do we think tiny quantum ripples should have been present in the very early universe? A) The shock wave of the Big Bang caused ripples that expanded outward with time. B) The energy released when the strong force froze out of the GUT force caused shock waves that produced ripples in the universe. C) Matter and antimatter particles that spontaneously formed from high-energy photons caused perturbations in the radiation field. D) The annihilation of matter and antimatter particles caused tiny explosions that perturbed the radiation field. E) Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle.
E) Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle.
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.
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.
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
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
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
Which of the following is evidence for supermassive black holes in active galaxies? A) the discovery of powerful jets coming from a compact core B) rapid changes in the luminosity of the galaxy nucleus C) quasars emit approximately equal power at all wavelengths from infrared to gamma rays D) very high speed orbital motions around galactic nuclei E) all of the above
E) all of the above
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
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
Which forces have physicists shown to be the same force under conditions of very high temperature or energy, as confirmed by experiments in particle accelerators? A) gravity and the weak force B) gravity and the strong force C) the strong and weak forces D) the strong and electromagnetic forces E) the electromagnetic and weak forces
E) the electromagnetic and weak forces