Question 1

The small density variations that subsequently led to the formation of large-scale structure in the universe are thought to have formed

Accepted Answer

A)  from quantum fluctuations during inflation. 
B)  due to the supernovae of the very first stars. 
C)  at the end of the recombination epoch. 
D)  as particle-antiparticle pairs annihilated. 
E)  as supermassive black holes powered the first quasars. 
A)  from quantum fluctuations during inflation. 
B)  due to the supernovae of the very first stars. 
C)  at the end of the recombination epoch. 
D)  as particle-antiparticle pairs annihilated. 
E)  as supermassive black holes powered the first quasars.

Question 2

Low-mass stars could form in the second generation because

Accepted Answer

A)  massive elements produced in the first stars coalesced into dust grains. 
B)  they formed in minihalos of cold dark matter. 
C)  gravitational waves led to the fragmentation of dark matter minihalos into microhalos. 
D)  there was a lot more raw material available for star formation after the demise of the first stars. 
E)  different types of fundamental forces controlled the formation of the first and second generation. 
A)  massive elements produced in the first stars coalesced into dust grains. 
B)  they formed in minihalos of cold dark matter. 
C)  gravitational waves led to the fragmentation of dark matter minihalos into microhalos. 
D)  there was a lot more raw material available for star formation after the demise of the first stars. 
E)  different types of fundamental forces controlled the formation of the first and second generation.

Question 3

Compared with what we see today, galaxies in the past were

Accepted Answer

A)  more ordered and more likely to have spiral structure. 
B)  more ordered and less likely to have spiral structure. 
C)  messier and more likely to have spiral structure. 
D)  messier and less likely to have spiral structure. 
E)  exactly the same as they are today. 
A)  more ordered and more likely to have spiral structure. 
B)  more ordered and less likely to have spiral structure. 
C)  messier and more likely to have spiral structure. 
D)  messier and less likely to have spiral structure. 
E)  exactly the same as they are today.

Question 4

The figure below shows snapshots taken from the Bolshoi simulation of the formation of the large-scale structure in the universe.Which one of these images shows the current structure of the universe?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  D 
E)  All of these occur at the same redshift, just in different regions of the universe. 
A)  A 
B)  B 
C)  C 
D)  D 
E)  All of these occur at the same redshift, just in different regions of the universe.

Question 5

What was the cooling mechanism that allowed the first stars to form?

Accepted Answer

The first stars must have been massive (

Question 6

You observe two galaxy clusters, cluster A and cluster B.Both have the same radius, but cluster B's outer galaxies are orbiting the cluster with circular velocities that are twice that of cluster A's circular velocities.The mass of cluster B is

Accepted Answer

A)  2 times cluster A's mass 
B)  4 times cluster A's mass. 
C)  half of cluster A's mass. 
D)  one-quarter of cluster A's mass. 
E)  equal to cluster A's mass. 
A)  2 times cluster A's mass 
B)  4 times cluster A's mass. 
C)  half of cluster A's mass. 
D)  one-quarter of cluster A's mass. 
E)  equal to cluster A's mass.

Question 7

What would be the observed wavelength for the Balmer H$\alpha$ line emitted at 486.1 nm by a quasar at redshift z =5?

Accepted Answer

A)  2.9 µm 
B)  81.0 nm 
C)  21.0 cm 
D)  121.6 nm 
E)  1.2 µm 
A)  2.9 µm 
B)  81.0 nm 
C)  21.0 cm 
D)  121.6 nm 
E)  1.2 µm

Question 8

Scientists think that neutrinos cannot be the dominant form of dark matter in the universe.Why?

Accepted Answer

A)  Neutrinos are an example of hot dark matter that could form large superclusters but not smaller structures. 
B)  Neutrinos interact too strongly with ordinary matter. 
C)  Neutrinos would decay over time and disappear, causing galaxies to fall apart. 
D)  Neutrinos would not gravitationally lens background galaxies. 
E)  Neutrinos are charged particles. 
A)  Neutrinos are an example of hot dark matter that could form large superclusters but not smaller structures. 
B)  Neutrinos interact too strongly with ordinary matter. 
C)  Neutrinos would decay over time and disappear, causing galaxies to fall apart. 
D)  Neutrinos would not gravitationally lens background galaxies. 
E)  Neutrinos are charged particles.

Question 9

The best hypothesis about the nature of dark matter is that it consists of particles with no electric charge.What is one reason why dark matter particles must have zero electric charge?

Accepted Answer

A)  They cannot be more massive than an electron. 
B)  If they did, they would emit photons as they move in external magnetic fields. 
C)  All charged particles would have been annihilated in particle-antiparticle collisions in the early universe. 
D)  No elementary particle has electric charge. 
E)  Charged particles formed only later inside stars. 
A)  They cannot be more massive than an electron. 
B)  If they did, they would emit photons as they move in external magnetic fields. 
C)  All charged particles would have been annihilated in particle-antiparticle collisions in the early universe. 
D)  No elementary particle has electric charge. 
E)  Charged particles formed only later inside stars.

Question 10

Which of the following is true about the Great Attractor?

Accepted Answer

A)  It is about 5 Mpc away. 
B)  It is in fact a black hole the size of a galaxy. 
C)  It can only be detected in radio wavelengths. 
D)  It is at the center of the Laniakea Supercluster. 
E)  It has no gravitational effects. 
A)  It is about 5 Mpc away. 
B)  It is in fact a black hole the size of a galaxy. 
C)  It can only be detected in radio wavelengths. 
D)  It is at the center of the Laniakea Supercluster. 
E)  It has no gravitational effects.

Question 11

What do the arcs seen in the Hubble Space Telescope image below represent?

Accepted Answer

The bright arcs represent the distorted

Question 12

Explain why the physics of formation of second-generation stars is more complex than that of the first generation.

Accepted Answer

The formation of stars in the second gen

Question 13

Explain and contrast the top-down and bottom-up scenarios for all of star, galaxy, and galaxy cluster formation, respectively.

Accepted Answer

The formation of galaxies is a hierarchi

Question 14

What is the expected future of our galaxy?

Accepted Answer

A)  Its contents will eventually be pulled in by the supermassive black hole at its center, Sagittarius A*. 
B)  Eventually all its matter will be in the form of iron atoms. 
C)  It will eventually be made of nothing but white dwarfs, neutron stars, and black holes, and then will collapse in on itself in a Big Crunch. 
D)  It will merge with nearby galaxies and then eventually decay into photons. 
E)  It will expand with the universe, but will stop expanding once enough stars become black holes. 
A)  Its contents will eventually be pulled in by the supermassive black hole at its center, Sagittarius A*. 
B)  Eventually all its matter will be in the form of iron atoms. 
C)  It will eventually be made of nothing but white dwarfs, neutron stars, and black holes, and then will collapse in on itself in a Big Crunch. 
D)  It will merge with nearby galaxies and then eventually decay into photons. 
E)  It will expand with the universe, but will stop expanding once enough stars become black holes.

Question 15

Scientists estimate the following quantities for the Coma Cluster: the total mass of the cluster is Mtotal ~ 1.3 *1015 MSUN, the total mass of all stars is Mstars ~ 3 *1013 MSUN, and the mass of the hot X-ray-emitting gas is Mgas ~ 1 * 1014 MSUN.What is the corresponding percentage of dark matter within the Coma Cluster?

Accepted Answer

A)  4 percent 
B)  25 percent 
C)  72 percent 
D)  90 percent 
E)  There is no dark matter contribution. 
A)  4 percent 
B)  25 percent 
C)  72 percent 
D)  90 percent 
E)  There is no dark matter contribution.

Question 16

Which of the following provides direct evidence for the existence of dark matter?

Accepted Answer

A)  the rotation curves of spiral galaxies 
B)  the motions of galaxies in clusters 
C)  the temperature of the diffuse intergalactic gas within clusters 
D)  the gravitational lensing produced by galaxy clusters 
E)  all of these 
A)  the rotation curves of spiral galaxies 
B)  the motions of galaxies in clusters 
C)  the temperature of the diffuse intergalactic gas within clusters 
D)  the gravitational lensing produced by galaxy clusters 
E)  all of these

Question 17

Our current understanding of galaxy formation suggests that the visible parts of galaxies

Accepted Answer

A)  form first and are incorporated into dark matter halos later. 
B)  form only in the densest parts of dark matter halos. 
C)  can tell you the total size of the dark matter halo. 
D)  can tell you everything about the formation history of that galaxy. 
E)  spread over distances larger than those of dark matter halos. 
A)  form first and are incorporated into dark matter halos later. 
B)  form only in the densest parts of dark matter halos. 
C)  can tell you the total size of the dark matter halo. 
D)  can tell you everything about the formation history of that galaxy. 
E)  spread over distances larger than those of dark matter halos.

Question 18

Dark matter is essential in understanding the formation of the large-scale structure in the universe in that it

Accepted Answer

A)  was clumpier than normal matter in the early universe. 
B)  consists exclusively of antimatter particles. 
C)  has a repulsive effect, just like the dark energy. 
D)  explains the physics of black holes. 
E)  cannot be made of elementary particles. 
A)  was clumpier than normal matter in the early universe. 
B)  consists exclusively of antimatter particles. 
C)  has a repulsive effect, just like the dark energy. 
D)  explains the physics of black holes. 
E)  cannot be made of elementary particles.

Question 19

In order to use Hubble's law to find the distance to a galaxy, astronomers need to measure that galaxy's

Accepted Answer

A)  radius. 
B)  rotational velocity. 
C)  mass. 
D)  peculiar velocity. 
E)  redshift. 
A)  radius. 
B)  rotational velocity. 
C)  mass. 
D)  peculiar velocity. 
E)  redshift.

Question 20

We expect the kinds of galaxies that we see at redshift of z   4 to be

Accepted Answer

A)  much like what we see today. 
B)  smaller and much more irregular looking than today. 
C)  smaller versions of what we see today. 
D)  far more numerous but with fewer spiral galaxies. 
E)  larger versions of what we see today. 
A)  much like what we see today. 
B)  smaller and much more irregular looking than today. 
C)  smaller versions of what we see today. 
D)  far more numerous but with fewer spiral galaxies. 
E)  larger versions of what we see today.

Exam 23: Large-Scale Structure in the Universe

The small density variations that subsequently led to the formation of large-scale structure in the universe are thought to have formed

Low-mass stars could form in the second generation because

Compared with what we see today, galaxies in the past were

The figure below shows snapshots taken from the Bolshoi simulation of the formation of the large-scale structure in the universe.Which one of these images shows the current structure of the universe?

What was the cooling mechanism that allowed the first stars to form?

You observe two galaxy clusters, cluster A and cluster B.Both have the same radius, but cluster B's outer galaxies are orbiting the cluster with circular velocities that are twice that of cluster A's circular velocities.The mass of cluster B is

What would be the observed wavelength for the Balmer H α\alphaα line emitted at 486.1 nm by a quasar at redshift z =5?

Scientists think that neutrinos cannot be the dominant form of dark matter in the universe.Why?

The best hypothesis about the nature of dark matter is that it consists of particles with no electric charge.What is one reason why dark matter particles must have zero electric charge?

Which of the following is true about the Great Attractor?

What do the arcs seen in the Hubble Space Telescope image below represent?

Explain why the physics of formation of second-generation stars is more complex than that of the first generation.

Explain and contrast the top-down and bottom-up scenarios for all of star, galaxy, and galaxy cluster formation, respectively.

What is the expected future of our galaxy?

Which of the following provides direct evidence for the existence of dark matter?

Our current understanding of galaxy formation suggests that the visible parts of galaxies

Dark matter is essential in understanding the formation of the large-scale structure in the universe in that it

In order to use Hubble's law to find the distance to a galaxy, astronomers need to measure that galaxy's

We expect the kinds of galaxies that we see at redshift of z 4 to be

Thinking Like an Astronomer

Patterns in the Skymotions of Earth and the Moon

Motion of Astronomical Bodies

Gravity and Orbits

Light

The Tools of the Astronomer

The Formation of Planetary Systems

The Terrestrial Planets and Earths Moon

Atmospheres of the Terrestrial Planets

Worlds of Gas and Liquidthe Giant Planets

Planetary Moons and Rings

Dwarf Planets and Small Solar System Bodies

Taking the Measure of Stars

Our Starthe Sun

The Interstellar Medium and Star Formation

Evolution of Low-Mass Stars

Evolution of High-Mass Stars

Relativity and Black Holes

Galaxies

The Milky Waya Normal Spiral Galaxy

The Expanding Universe

Cosmology

Life

Filters

What would be the observed wavelength for the Balmer H $\alpha$ line emitted at 486.1 nm by a quasar at redshift z =5?