Question 1

What would be the observed wavelength for the Lyman-alpha emission at 121.6 nm from the distant galaxy at redshift z =8.68?

Accepted Answer

$\lambda$_observed = (1 + z)$\lambda$_emitted = (1 + 8.68)*121.6 nm = 1,177 nm,which is in the infrared portion of the spectrum.(Note that the galaxy emitted a UV photon and it is "received" as an IR photon.)

Question 2

How do we know how fast the Milky Way is moving relative to the local universe? What are we moving toward, and what do we think is mostly responsible for this motion?

Accepted Answer

The Doppler shift of the CMB tells us how fast we are moving relative to the CMB,which is the adopted rest frame relative to the universe at large.We are moving toward the Great Attractor,a mass overdensity so named because of gravitational attraction.The Great Attractor is the center of mass of the Laniakea Supercluster.The Milky Way and the Local Group are positioned at the outer edge of this supercluster.

Question 3

A galaxy has a peculiar velocity due to the effects of

Accepted Answer

A)  erroneous redshifts. 
B)  local gravitational attraction. 
C)  supernovae. 
D)  eclipsing binary stars. 
E)  interstellar winds. 
A)  erroneous redshifts. 
B)  local gravitational attraction. 
C)  supernovae. 
D)  eclipsing binary stars. 
E)  interstellar winds. B

Question 4

Reionization of the neutral gas in the universe occurred due to the

Accepted Answer

A)  decay of dark matter particles. 
B)  emission of neutrinos by the first stars that formed. 
C)  heating from the motion of high-velocity black holes. 
D)  radiation from the first stars, supernovae, and black holes that formed. 
E)  positron and electron annihilations. 
A)  decay of dark matter particles. 
B)  emission of neutrinos by the first stars that formed. 
C)  heating from the motion of high-velocity black holes. 
D)  radiation from the first stars, supernovae, and black holes that formed. 
E)  positron and electron annihilations.

Question 5

Telescopes like ALMA (working in the range 0.4-3.0 mm) and JWST (working in IR, in the range 0.6-28.5 micro-m) would help astronomers close a gap of observations that corresponds to the window

Accepted Answer

A)  z = 2-3, when the star formation rate peaked. 
B)  z = 10-1,000, between the epochs of recombination and reionization. 
C)  z = 0-0.5, when there was a big change in the relative fraction of irregular galaxies. 
D)  z $\gt$1,100, to directly observe the inflation epoch. 
E)  Such telescopes are actually designed to only explore planetary systems within the boundaries of our Milky Way. 
A)  z = 2-3, when the star formation rate peaked. 
B)  z = 10-1,000, between the epochs of recombination and reionization. 
C)  z = 0-0.5, when there was a big change in the relative fraction of irregular galaxies. 
D)  z $\gt$1,100, to directly observe the inflation epoch. 
E)  Such telescopes are actually designed to only explore planetary systems within the boundaries of our Milky Way.

Question 6

What has the dominant role in defining the large-scale structure of the universe?

Accepted Answer

A)  supernovae from the first generation of stars 
B)  the gravitational attraction of matter 
C)  matter/antimatter annihilation 
D)  magnetic fields 
E)  electric force 
A)  supernovae from the first generation of stars 
B)  the gravitational attraction of matter 
C)  matter/antimatter annihilation 
D)  magnetic fields 
E)  electric force

Question 7

How has the fraction of galaxies with irregular morphologies evolved from 4 billion years ago to the present epoch?

Accepted Answer

A)  About 10 percent of today's galaxies are peculiar, whereas 4 billion years ago more than half the galaxies were peculiar. 
B)  The fraction has remained at 50 percent over the last 4 billion to 5 billion years. 
C)  At the present epoch there are far more interacting galaxies than when the universe was about 9 billion to 10 billion years old. 
D)  The fraction has remained at 10 percent over the last 4 billion to 5 billion years. 
E)  There are no peculiar galaxies today, whereas 4 billion years ago they comprised nearly 10 percent of galaxies. 
A)  About 10 percent of today's galaxies are peculiar, whereas 4 billion years ago more than half the galaxies were peculiar. 
B)  The fraction has remained at 50 percent over the last 4 billion to 5 billion years. 
C)  At the present epoch there are far more interacting galaxies than when the universe was about 9 billion to 10 billion years old. 
D)  The fraction has remained at 10 percent over the last 4 billion to 5 billion years. 
E)  There are no peculiar galaxies today, whereas 4 billion years ago they comprised nearly 10 percent of galaxies.

Question 8

Which probably formed last in the course of the evolution of the universe?

Accepted Answer

A)  a typical proton inside a water molecule on Earth 
B)  a helium atom in the surface of the Sun 
C)  a typical star that is a member of a globular cluster star in our Milky Way 
D)  the Milky Way 
E)  the Virgo Supercluster 
A)  a typical proton inside a water molecule on Earth 
B)  a helium atom in the surface of the Sun 
C)  a typical star that is a member of a globular cluster star in our Milky Way 
D)  the Milky Way 
E)  the Virgo Supercluster

Question 9

Which of the following is likely to happen when two spiral galaxies collide?

Accepted Answer

A)  A more massive elliptical galaxy might form out of the merger. 
B)  The two supermassive black holes at their centers could form a binary black hole system. 
C)  A burst of star formation will occur in the merged galaxy. 
D)  The cold gas in the merged galaxy might be blown away by supernovae. 
E)  All of these are likely. 
A)  A more massive elliptical galaxy might form out of the merger. 
B)  The two supermassive black holes at their centers could form a binary black hole system. 
C)  A burst of star formation will occur in the merged galaxy. 
D)  The cold gas in the merged galaxy might be blown away by supernovae. 
E)  All of these are likely.

Question 10

Describe the large-scale structure of the universe.

Accepted Answer

The structure of the universe

Question 11

How do astronomers explain the formation of elliptical galaxies?

Accepted Answer

Most elliptical galaxies likely formed t

Question 12

Understanding the distribution of galaxies in the universe requires the construction of a three-dimensional map where for each galaxy we need to know its position and

Accepted Answer

A)  mass. 
B)  redshift. 
C)  dust content. 
D)  morphological type. 
E)  star formation rate. 
A)  mass. 
B)  redshift. 
C)  dust content. 
D)  morphological type. 
E)  star formation rate.

Question 13

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

Accepted Answer

The total mass M_total=M

Question 14

Outline a few fundamental differences between the formation of the very first stars and that of the second or subsequent generations.

Accepted Answer

1)The first stars must have formed insid

Question 15

Explain why a galaxy can collapse to a much smaller size than its dark matter halo.

Accepted Answer

Dark matter collapses down until the ran

Question 16

Which of the following is true about ultrafaint dwarf galaxies?

Accepted Answer

A)  They are surrounded by dark dust and gas. 
B)  They are sites of active star formation. 
C)  They are dominated by dark matter. 
D)  They have been predicted but have never been observed. 
E)  They are more massive than most dwarf galaxies. 
A)  They are surrounded by dark dust and gas. 
B)  They are sites of active star formation. 
C)  They are dominated by dark matter. 
D)  They have been predicted but have never been observed. 
E)  They are more massive than most dwarf galaxies.

Question 17

Use Hubble's law to explain how measurements of redshift help astronomers map the large-scale structure of the universe.

Accepted Answer

Hubble's law (v = H₀ *D)state

Question 18

The second generation of stars

Accepted Answer

A)  is indistinguishable from the first generation. 
B)  have all left the main sequence. 
C)  can only be found in galactic disks. 
D)  are all giant stars. 
E)  contain some elements heavier than lithium. 
A)  is indistinguishable from the first generation. 
B)  have all left the main sequence. 
C)  can only be found in galactic disks. 
D)  are all giant stars. 
E)  contain some elements heavier than lithium.

Question 19

The image below shows faint high-redshift galaxy GN-z11(enlarged in inset), with a redshift of
z =11.1.Why are images like this relatively rare, and interesting to astronomers?

Accepted Answer

Scientists currently have little direct

Question 20

What role do cosmological computer simulations play in the scientific method?

Accepted Answer

A)  They create virtual observations, allowing scientists to test hypotheses without gathering data. 
B)  They design experiments. 
C)  They create predictions that can be tested with additional observations. 
D)  Simulations do not tie into the scientific method; they are only used to verify the math within theories. 
E)  Simulations do not tie into the scientific method; they only provide scientists tools to visualize concepts. 
A)  They create virtual observations, allowing scientists to test hypotheses without gathering data. 
B)  They design experiments. 
C)  They create predictions that can be tested with additional observations. 
D)  Simulations do not tie into the scientific method; they are only used to verify the math within theories. 
E)  Simulations do not tie into the scientific method; they only provide scientists tools to visualize concepts.

Exam 23: Large-Scale Structure in the Universe

What would be the observed wavelength for the Lyman-alpha emission at 121.6 nm from the distant galaxy at redshift z =8.68?

How do we know how fast the Milky Way is moving relative to the local universe? What are we moving toward, and what do we think is mostly responsible for this motion?

A galaxy has a peculiar velocity due to the effects of

Reionization of the neutral gas in the universe occurred due to the

Telescopes like ALMA (working in the range 0.4-3.0 mm) and JWST (working in IR, in the range 0.6-28.5 micro-m) would help astronomers close a gap of observations that corresponds to the window

What has the dominant role in defining the large-scale structure of the universe?

How has the fraction of galaxies with irregular morphologies evolved from 4 billion years ago to the present epoch?

Which probably formed last in the course of the evolution of the universe?

Which of the following is likely to happen when two spiral galaxies collide?

Describe the large-scale structure of the universe.

How do astronomers explain the formation of elliptical galaxies?

Understanding the distribution of galaxies in the universe requires the construction of a three-dimensional map where for each galaxy we need to know its position and

Outline a few fundamental differences between the formation of the very first stars and that of the second or subsequent generations.

Explain why a galaxy can collapse to a much smaller size than its dark matter halo.

Which of the following is true about ultrafaint dwarf galaxies?

Use Hubble's law to explain how measurements of redshift help astronomers map the large-scale structure of the universe.

The second generation of stars

The image below shows faint high-redshift galaxy GN-z11(enlarged in inset), with a redshift of z =11.1.Why are images like this relatively rare, and interesting to astronomers?

What role do cosmological computer simulations play in the scientific method?

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