Astronomy LAST Set
What kinds of objects lie in the disk of our galaxy? -old K and M stars -gas and dust -O and B stars -open clusters -all of the above
-old K and M stars -gas and dust -O and B stars-open clusters -all of the above
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. -1 million years -300 years -300,000 years -10 to power of ((-10)) second -3 minutes
10 to power of ((-10)) second
Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cove the entire sky, the total number of galaxies in the observable universe is estimated to be approximately -10 billion. -100 billion. -1 trillion. -100 million. -1 billion.
100 billion.
What is the diameter of the disk of the Milky Way? -10,000 light-years -100,000 light-years -1,000,000 light-years -1,000 light-years -100 light-years
100,000 light-years
Approximately how far is the Sun from the center of the galaxy? -28 light-years -28 million light-years -28,000 light-years -280 light-years -2,800 light-years
28,000 light-years
Recall that Hubble's law is written v = HOd, where v is the recession velocity of a galaxy located a distance d away from us, and HO is Hubble's constant. Suppose HO = 65 km/s/Mpc. How fast would a galaxy located 500 megaparsecs distant be receding from us? -9 km/s -65 Mpc/s -65 km/s -0.65 times the speed of light -32,500 km/s
32,500 km/s
The most active galactic nuclei are usually found at large distances from us; relatively few nearby galaxies have active galactic nuclei. What does this imply? -The jets seen in many active galactic nuclei must cause them to move far away from us. -Active galactic nuclei tend to become less active as they age. -Massive black holes existed only when the universe was young and no longer exist today. -Active galactic nuclei can form only at large distances from the Milky Way.
Active galactic nuclei tend to become less active as they age.
What is the ultimate fate of an open universe? -Individual stars die but their gas is recycled through the interstellar medium and new stars form in a never-ending process. -Stars will expand away from each other and galaxies effectively "evaporate." -All matter eventually ends up in massive black holes. -the Big Crunch -All matter decays to a low-density sea of photons and subatomic particles.
All matter decays to a low-density sea of photons and subatomic particles.
What is the major difference between an elliptical galaxy and a spiral galaxy? -There are no dwarf spiral galaxies, but there are dwarf ellipticals. -A spiral galaxy contains mostly younger stars. -An elliptical galaxy lacks a disk component. -A spiral galaxy has a spherical halo. -Elliptical galaxies are not as big as spiral galaxies.
An elliptical galaxy lacks a disk component.
Why might inflation have occurred at the end of the GUT era? -here wasn't enough matter present to slow down the expansion at that time. -An enormous amount of energy was released when the strong force froze out from the GUT force. -Gravity was an extremely weak force at this period in time. -Large amounts of matter and antimatter annihilated at this time.
An enormous amount of energy was released when the strong force froze out from the GUT force.
Why can't we see past the cosmological horizon? -Beyond the cosmological horizon, we are looking back to a time before the universe had formed. -We do not have sensitive enough detectors. -We do not have telescopes big enough. -The universe extends only to this horizon. -The cosmological horizon is infinitely far away, and we can't see to infinity.
Beyond the cosmological horizon, we are looking back to a time before the universe had formed.
Why are Cepheid variables important? -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. -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 it 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.
Dr. X believes that the Hubble constant is HO = 55 km/s/Mpc. Dr. Y believes it is HO = 80 km/s/Mps. Which statement below automatically follows? -Dr. X believes that the universe is older than Dr. Y believes. -Dr. X believes that the universe has a much higher density than Dr. Y believes. -Dr. X believes that the universe will someday stop expanding, while Dr. Y believes it will expand forever. -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. -Dr. X believes that the universe is expanding, but Dr. Y does not.
Dr. X believes that the universe is older than Dr. Y believes.
What evidence supports the theory that elliptical galaxies come from denser clouds? -Elliptical galaxies have denser stars than spiral galaxies. -Elliptical galaxies are denser than spiral galaxies. -Elliptical galaxies are generally larger than spiral galaxies. -Elliptical galaxies have more gas than spiral galaxies. -Elliptical galaxies at high redshifts lack young, blue stars.
Elliptical galaxies at high redshifts lack young, blue stars.
Why is the era of nucleosynthesis so important in determining the chemical composition of the universe? -We can study the processes that occurred during the era of nucleosynthesis to determine how most of the elements in the universe were created. -By knowing how much matter was created during the era of nucleosynthesis, we can determine whether the universe is open or closed. -We can observe spectra from this era to determine what the primordial mix of the elements was at the beginning of the universe. -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. -All the elements except hydrogen were produced after the era of nucleosynthesis.
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? -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. -Galaxies were much bigger in the past since they had not contracted completely. -Galaxy collisions shouldn't have been more common in the past than they are now. -Galaxies were more active in the past and therefore would have collided with each other more frequently. -Galaxies were closer together in the past because the universe was smaller.
Galaxies were closer together in the past because the universe was smaller.
How did Edwin Hubble measure the distance to the Andromeda Galaxy? -He measured its parallax. -He deduced it from its redshift. -He used main-sequence fitting. -He applied the period-luminosity relation to Cepheid variables. -He used white dwarf supernovae.
He applied the period-luminosity relation to Cepheid variables.
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? -Infrared observations show that many stars are forming near the centers of active galaxies. -Observed radiation from the galactic center varies significantly in brightness in times as short as a few days. -Radio observations sometimes show long jets of material extending millions of light-years out from the galactic center. -Spectral lines from the galactic center indicated that clouds of gas are orbiting a central object at very high speed. -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.
Infrared observations show that many stars are forming near the centers of active galaxies.
How does the interstellar medium obscure our view of most of the galaxy? -It produces so much visible light that it is opaque and blocks our view of anything beyond it. -It reflects most light from far distances of the galaxy away from our line of sight. -It absorbs visible, ultraviolet, and some infrared light. -It absorbs all wavelengths of light. -all of the above
It absorbs visible, ultraviolet, and some infrared light.
Why do we call dark matter "dark"? -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. -We cannot detect the type of radiation that it emits.
It emits no or very little radiation of any wavelength.
How does a lenticular galaxy differ from a normal spiral galaxy? -It has no bulge. -It has an elongated bulge resembling a bar more than a sphere. -It has no spiral arms. -It has no gas or dust. -It is flatter in shape.
It has no spiral arms.
What do we mean when we say that a particle is a weakly interacting particle? -It is so small that it doesn't affect objects in the universe. -It interacts only through the weak force and the force of gravity. -It is the only type of particle that interacts through the weak force. -It doesn't interact with any type of baryonic matter. -It interacts only through the weak force.
It interacts only through the weak force and the force of gravity.
Why can't the dark matter in galaxies be made of neutrinos? -We know that dark massive objects such as planets and neutron stars are not made of neutrinos. -Neutrinos travel at extremely high speeds and can escape a galaxy's gravitational pull. -Neutrinos do not have any mass; they interact only through the weak force. -There are not enough neutrinos to make up all the dark matter.
Neutrinos travel at extremely high speeds and can escape a galaxy's gravitational pull.
How do observations of distant galaxies help us learn about galaxy evolution? -We can observe the evolution of a single galaxy over time. -We can observe two galaxies merging and what the result is, helping us learn how mergers affect evolution. -We can observe the birth of galaxies. -We can see what our galaxy used to look like and therefore theorize about the physical processes that led to its current appearance. -Observations at different distances show galaxies of different ages and therefore different stages of evolution.
Observations at different distances show galaxies of different ages and therefore different stages of evolution.
What direct evidence do we have that the weak and electromagnetic forces were once unified as a single electroweak force? -Detectors on Earth have received photons and high-energy particles from this era. -Temperatures in the center of the Sun can reproduce the conditions during this era. -Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory. -We have no direct evidence of the electroweak force. -We have no direct evidence of the electroweak force.
Particle accelerators on Earth can reach energies equivalent to the high temperatures of this era and have produced particles predicted by the electroweak theory.
Why do we think tiny quantum ripples should have been present in the very early universe? -The shock wave of the Big Bang caused ripples that expanded outward with time. -The annihilation of matter and antimatter particles caused tiny explosions that perturbed the radiation field. -Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle. -Matter and antimatter particles that spontaneously formed from high-energy photons caused perturbations in the radiation field.
Quantum mechanics requires that the energy fields at any point in space be continually fluctuating as a result of the uncertainty principle.
Which constellation lies in the direction toward the galactic center? -the Big Dipper -Orion -Leo -Sagittarius -Taurus
Sagittarius
Why do we believe that starburst galaxies represent a temporary stage in galaxy evolution? -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. -We don't see any nearby starburst galaxies. -We observe starbursts to last only a few years at a time. -All starburst galaxies look like normal spiral galaxies, aside from the starbursts.
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.
Why does the Big Bang theory predict that the cosmic background radiation should have a perfect thermal radiation spectrum? -It doesn't predict that the cosmic background radiation should have a perfect thermal radiation spectrum. -The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe. -The spectrum of pure hydrogen is a perfect thermal radiation spectrum. -The spectrum of 75 percent hydrogen and 25 percent helium is a perfect thermal radiation spectrum. -The light from all the stars and gas in the sky averaged over the entire universe is a perfect thermal radiation spectrum.
The background radiation came from the heat of the universe, with a peak corresponding to the temperature of the universe.
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? -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. -The cosmic background radiation is expected to have a perfect thermal spectrum, and observations from the COBE spacecraft verify this prediction. -The cosmic background radiation is expected to look essentially the same in all directions, and it does. -The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does. -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).
The cosmic background radiation is expected to contain spectral lines of hydrogen and helium, and it does.
What is the Tully-Fisher relation? -The smaller a galaxy appears, the further away it is. -The longer the period of a galaxy's variable stars, the more luminous it is. -The further away a galaxy is, the faster its recession velocity. -The redder a galaxy's color, the further away it is. -The faster a spiral galaxy's rotation speed, the more luminous it is.
The faster a spiral galaxy's rotation speed, the more luminous it is.
Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy? -The force of gravity can pull the material into a more spherical shape. -The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form. -The thickness of the dense cloud prevents a disk from forming. -The higher density of gas had a stronger force of gravity, and therefore the cloud collapses more quickly. -The more frequent collisions between particles randomize the particle orbits.
The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form.
What evidence supports the theory that there is a black hole at the center of our galaxy? -We can see gas falling into an accretion disk and central mass at the center of our galaxy. -We observe an extremely bright X-ray source at the center of our galaxy. -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. -We observe a large, dark object that absorbs all light at the center of our galaxy.-all of the above.
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.
Why do we believe 90 percent of the mass of the Milky Way is in the form of dark matter? -Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk, suggesting that the halo is full of dark matter. -Our view of distant galaxies is sometimes obscured by dark blotches in the sky, and we believe these blotches are dark matter located in the halo. -Although dark matter emits no visible light, it can be seen with radio wavelengths, and such observations confirm that the halo is full of this material. -The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo.
The orbital speeds of stars far from the galactic center are surprisingly high, suggesting that these stars are feeling gravitational effects from unseen matter in the halo.
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions? -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. -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. -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. -The overall structure of the universe is very uniform, but the synthesis of different elements produces varying signatures within the background spectrum. -Dark matter consisting of WIMPs greatly smooths out the spectrum, but the small patches of "light" matter create peaks in the spectrum.
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.
Why did the era of nuclei end when the universe was about 300,000 years old? -All the free particles had combined to form the nuclei of atoms. -Neutrinos and electrons were finally able to escape the plasma of the early universe and no longer heated the other particles. -Photons were finally able to escape the plasma of the early universe and no longer heated the hydrogen and helium ions. -The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form.
The universe had expanded and cooled to a temperature of about 3,000 K, cool enough for stable, neutral atoms to form.
Which of the following cannot be true of the very first stars formed in the Universe? -They may have formed in large clusters. -They may have formed singly, in isolation. -They may have had rocky planets around them. -They may have all exploded as supernovae by now. -Some may still exist in the Milky Way today.
They may have had rocky planets around them.
How do we learn about what is going on in the center of our own galaxy (the Milky Way)? -We cannot see the galactic center with visible or ultraviolet light, but radio and X rays from the center can be detected. -We have learned it only recently, thanks to the great photographs obtained by the Hubble Space Telescope. -We must look at the centers of other galaxies and hope that ours is just like others. -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.
We cannot see the galactic center with visible or ultraviolet light, but radio and X rays from the center can be detected.
Why can't current theories describe what happened during the Planck era? -The Planck era was the time before the Big Bang, and we cannot describe what happened before that instant. -We do not yet have a theory that links quantum mechanics and general relativity. -We do not know how much energy existed during that time. -It was a time period from which we cannot receive radiation. -We do not understand the properties of antimatter.
We do not yet have a theory that links quantum mechanics and general relativity.
What might be causing the universe to accelerate? -MACHOs -dark gravity -WIMPs -We don't know!—but we call it "dark energy."
We don't know!—but we call it "dark energy."
How do we determine the amount of dark matter in elliptical galaxies? -We measure the speeds of stars at different radii from the galactic center and determine how much mass is interior to the orbit. -We measure how fast the galaxy rotates as a whole. -We search for dark lanes of dust and black holes within the galaxy. -We measure the orbital velocities of star-forming gas clouds around the outer portions of the galaxy. -We count the number of stars in the galaxy and determine its volume, so that we can calculate the galaxy's density.
We measure the speeds of stars at different radii from the galactic center and determine how much mass is interior to the orbit.
What evidence suggests that the Milky Way contains 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. -We see many dark voids between the stars in the halo of the Milky Way. -We see many lanes of dark material blocking out the light of stars behind them along the band 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. -When we observe in different wavelengths, such as infrared or radio, we see objects that don't appear in visible-light observations.
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.
How do we know that there are intergalactic clouds between a distant quasar and us? -We see hydrogen emission lines at redshifts greater than that of a quasar. -We see hydrogen emission lines at redshifts smaller than that of the quasar. -We see that the emission lines from the quasar are lessened by intervening gas and dust. -We see hydrogen absorption lines at redshifts smaller than that of the quasar. -We see hydrogen absorption lines at redshifts greater than that of the quasar.
We see hydrogen absorption lines at redshifts smaller than that of the quasar.
What is the evidence for an accelerating universe? -White-dwarf supernovae are slightly brighter than expected for a coasting universe. -White-dwarf supernovae are slightly dimmer 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 the same brightness regardless of redshift. -There is far more dark matter than visible matter in the universe.
White-dwarf supernovae are slightly dimmer than expected for a coasting universe.
White-dwarf supernovae are good standard candles for distance measurements for all the following reasons except which? -All white-dwarf supernovae involve the explosion of stars of nearly the same mass. -White-dwarf supernovae are so bright that they can be detected even in very distant galaxies. -All white-dwarf supernovae have similar light curves, which makes them easy to distinguish from massive-star supernovae. -White-dwarf supernovae are common enough that we detect several every year. -White-dwarf supernovae occur only among young and extremely bright stars.
White-dwarf supernovae occur only among young and extremely bright stars.
Which of the following types of protogalactic clouds is most likely to form an elliptical galaxy? -a dense cloud with quite a bit of angular momentum -a low-density cloud with quite a bit of angular momentum -a dense cloud with very little angular momentum -a very low-density cloud with very little angular momentum -a very massive cloud with any density and a lot of angular momentum
a dense cloud with very little angular momentum
What is Sgr A*? -a source of bright X-ray emission coming from the entire constellation of Sagittarius -the brightest star in the constellation Sagittarius -a source of bright radio emission in the center of our galaxy -the bulge at the center of our galaxy -a source that is bright in the visible wavelengths in the center of our galaxy
a source of bright radio emission in the center of our galaxy
What do we mean by inflation? -what happened the instant after the Big Bang -a sudden expansion of the universe after the strong force froze out from the GUT force -the expansion of the universe that we still observe today -the separation that occurs after two photons collide and create a particle and an antiparticle -the sudden release of photons when a particle and antiparticle annihilate each other
a sudden expansion of the universe after the strong force froze out from the GUT force
Which types of galaxies have a clearly defined spheroidal component? -ellipticals only -spirals only -irregulars only -lenticulars only -all but irregulars
all but irregulars
What do astronomers consider heavy elements? -elements that are heavier than carbon -elements that are heavier than uranium -elements that are heavier than iron -elements that are heavier than hydrogen -all elements besides hydrogen and helium
all elements besides hydrogen and helium
If an object doubles its luminosity in 10 hours, how large can the emitting source of light be? -about 10 light-hours across -about 10 parsecs across -about 10 light-years across -varies depending on how far away the object is -varies depending on how luminous the object is
about 10 light-hours across
What evidence supports the idea that a collision between two spiral galaxies might lead to the creation of a single elliptical galaxy? -the fact that elliptical galaxies dominate the galaxy populations at the cores of dense clusters of galaxies -observations of some elliptical galaxies with stars and gas clouds in their cores that orbit differently from the other stars in the galaxy -observations of giant elliptical galaxies at the center of dense clusters that may have grown by consuming other galaxies -observations of some elliptical galaxies surrounded by shells of stars that probably formed from stars stripped out of smaller galaxies -all of the above
all of the above
Which of the following is evidence for supermassive black holes in active galaxies? -very high speed orbital motions around galactic nuclei -the discovery of powerful jets coming for a compact core -quasars emit approximately equal power at all wavelengths from infrared to gamma rays -rapid changes in the luminosity of the galaxy nucleus -all of the above
all of the above
What is a standard candle? -an object for which we are likely to know the true luminosity -an object for which we can easily measure the apparent brightness -a long, tapered candle that lights easily -any star for which we know the exact apparent brightness -a class of objects in astronomy that all have exactly the same luminosity
an object for which we are likely to know the true luminosity
The distribution of the dark matter in a spiral galaxy is -predominantly concentrated in the spiral arms. -approximately spherical and about the same size as the galaxy halo. -flattened in a disk and about the same size as the stellar disk. -flattened in a disk but about ten times larger than the stellar disk. -approximately spherical and about ten times the size of the galaxy halo.
approximately spherical and about ten times the size of the galaxy halo.
Compared with stars in the disk, orbits of stars in the halo -are relatively uniform to each other. -are elliptical, with random orientation. -do not have to be around the galactic center. -do not have to pass through the plane of the galaxy. -are elliptical but orbiting in the same direction.
are elliptical, with random orientation.
Which of the following does not accurately describe what we observe toward the Galactic center? -at X rays, we see faint emission from an accretion disk around a black hole -at optical wavelengths, we see a cluster of old, red stars -at radio wavelengths, we see giant gas clouds threaded by powerful magnetic fields -at infrared wavelengths, we see a massive stellar cluster
at optical wavelengths, we see a cluster of old, red stars
What produces the 21-cm line that we use to map out the Milky Way Galaxy? -molecular hydrogen -helium-ionized hydrogen -atomic hydrogen -carbon monoxide
atomic hydrogen
Why are telescopes sometimes called "time machines"? -because astronomers can use telescopes to see the Milky Way as it was when it was much younger -because the author, H.G. Wells, used the term to describe telescopes in a book -because observations of distant objects reveal them as they were in the past -because some of the oldest telescopes are still in use today -It's a journalistic misnomer: you cannot travel into the past or the future.
because observations of distant objects reveal them as they were in the past
How are interstellar bubbles made? -by the rapidly rotating magnetic fields of pulsars -by the collapse of a gas cloud to form stars -by collisions between galaxies -by planetary nebulae from low-mass stars -by the winds of massive stars and supernovae
by the winds of massive stars and supernovae
In the 1960s, Maarten Schmidt determined that quasars were very distant objects by -determining how small the source of light was from its variations in luminosity. -determining their parallax angles. -determining their redshifts. -discovering that they were embedded in distant galaxies. -determining how luminous they were.
determining their redshifts.
Which of the following types of galaxies are most spherical in shape? -spirals -ellipticals -irregulars -lenticulars
ellipticals
What makes up the interstellar medium? -open clusters -gas and dust -O and B stars-K and M stars -all of the above
gas and dust
What kinds of objects lie in the halo of our galaxy? -gas and dust -open clusters -globular clusters -O and B stars -all of the above
globular clusters
Compared to the central regions of spiral galaxies, we expect elliptical galaxies to have -higher mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals. -lower mass-to-light ratios because elliptical galaxies have less gas and dust than spirals. -lower mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals. -the same mass-to-light ratio because they are made of the same material, stars and dark matter. -higher mass-to-light ratios because stars in elliptical galaxies do not have high orbital velocities.
higher mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals.
Where are the X rays produced that are emitted by quasars and other active galactic nuclei? -in ionization nebulae of interstellar gas that surround the accretion disk -in hot gas in an accretion disk around a central black hole -in dust grains in molecular clouds that encircle the active galactic nucleus -in fast-moving electrons that jet from the active galactic nucleus -all of the above
in hot gas in an accretion disk around a central black hole
Where are most heavy elements made? -in the Big Band, when the universe first began -in the interstellar medium -in stars and supernovae -none of the above -all of the above
in stars and supernovae
Where does most star formation occur in the Milky Way today? -in the spiral arms -uniformly throughout the Galaxy -in the bulge -in the Galactic center -in the halo
in the spiral arms
Harlow Shapley concluded that the Sun was not in the center of the Milky Way Galaxy by -mapping the distribution of stars in the galaxy. -mapping the distribution of globular clusters in the galaxy. -mapping the distribution of gas clouds in the spiral arms. -looking at other nearby spiral galaxies. -looking at the shape of the "milky band" across the sky.
mapping the distribution of globular clusters in the galaxy.
Gravitational lensing occurs when -telescope lenses are distorted by gravity. -massive objects bend light beams that are passing nearby. -massive objects cause more distant objects to appear much larger than they should and we can observe the distant objects with better resolution. -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.
What can cause a galactic fountain? -the combined effect of spiral density waves -a supernova occurring in the halo -molecular clouds falling towards the galactic center -winds and jets from newly -formed protostars -multiple supernovae occurring together
multiple supernovae occurring together
Compared with our Sun, most stars in the halo are -young, blue, and bright and have much more heavy element material. -old, red, and dim and have much more heavy element material. -old, red, and bright and have fewer heavy elements. -young, red, and dim and have fewer heavy elements. -old, red, and dim and have fewer heavy elements.
old, red, and dim and have fewer heavy elements.
Which of the following sequences lists the methods for determining distance in the correct order from nearest to farthest? -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, Cepheid variables, Tully-Fisher relation, Hubble's law -parallax, main-sequence fitting, Tully-Fisher relation, Cepheid variables, Hubble's law -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
Which of the following particles are baryons? -quarks -protons -neutrinos -photons -electrons
protons
Compared to spiral galaxies, elliptical galaxies are -redder and flattened. -always much smaller. -bluer and flattened. -redder and rounder. -bluer and rounder.
redder and rounder.
Which types of galaxies have a clearly defined disk component? -irregulars only -spirals only -ellipticals only -lenticulars only -spirals and lenticulars
spirals and lenticulars
What is meant by "dark energy"? -any unknown force that opposes gravity -the energy associated with dark matter through E=mc2 -highly energetic particles that are believed to constitute dark matter -the agent causing the universal expansion to accelerate -the total energy in the Universe after the Big Bang but before the first stars
the agent causing the universal expansion to accelerate
What are the two key observational facts that led to widespread acceptance of the Big Bang model? -the cosmic background radiation and the expansion of the universe -the cosmic background radiation and the near-critical density of the universe -the cosmic background radiation and the high helium content of the universe -the predominance of matter over antimatter and the large scale structure of galaxies -the predominance of matter over antimatter and the near-critical density of the universe
the cosmic background radiation and the high helium content of the universe
What is a quasar? -a specialized astronomical instrument for observing distant stars -a starlike object that actually represents a bright patch of gas in the Milk Way -the extremely bright center of a distant galaxy, thought to be powered by a massive black hole -a very large galaxy thought to be formed by the merger of several smaller galaxies, typically found in the center of a galaxy cluster -another name for very bright stars of spectral type O
the extremely bright center of a distant galaxy, thought to be powered by a massive black hole
Which of the following is a consequence of Hubble's Law? -all galaxies are moving away from us equally fast -more distant galaxies appear younger -the more distant a galaxy is from us, the faster it moves away from us -the closer a galaxy is to us, the faster it moves away from us -the Big Bang
the more distant a galaxy is from us, the faster it moves away from us
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? -the one that appears smallest in size -the one that is reddest in color -the one that is farthest away -the one that is closest to us -the one that is bluest in color
the one that is farthest away
When we see that a spectral line of a galaxy is broadened, that is, spanning a range of wavelengths, we conclude that -we are actually measuring the orbital velocity of dark matter. -there are different Doppler shifts among the individual stars in the galaxy. -we are actually measuring the orbital velocity of a cloud of atomic gas. -there are many stars traveling at extremely high orbital velocities. -we do not have very good resolution of a star's orbital velocity.
there are different Doppler shifts among the individual stars in the galaxy.
How are rotation curves of spiral galaxies determined beyond radii where starlight can be detected? -through observations of the 21 cm line of atomic hydrogen -through observations of spectral lines of dark matter -by measuring the broadening of absorption lines -by watching the galaxies rotate over a period of years -by extrapolation
through observations of the 21 cm line of atomic hydrogen
What is the most accurate way to determine the distance to a nearby galaxy? -radar ranging -Hubble's law -using Cepheid variables -the Tully-Fisher relation -stellar parallax
using Cepheid variables
What two quantities did Edwin Hubble plot against each other to discover the expansion of the Universe? -age and distance -luminosity and distance -velocity and distance -luminosity and temperature -velocity and temperature
velocity and distance