Deck 23: Large-Scale Structure in the Universe

Question 1

Which of the following is NOT a way in which astronomers detect dark matter in clusters of galaxies?

A)by determining the amount of mass necessary to gravitationally collapse clouds of gas to form the number of stars present
B)by determining the amount of mass necessary to gravitationally hold onto the hot gas surrounding galaxy clusters
C)by determining the amount of mass necessary to gravitationally hold a cluster of galaxies together
D)by determining the amount of mass necessary to gravitationally lens images of distant objects
E)None of the above;all of these are ways that astronomers detect dark matter in galaxy clusters.

Answer 1

by determining the amount of mass necessary to gravitationally collapse clouds of gas to form the number of stars present

Question 2

As structure formed in the universe,galaxy-sized objects formed before cluster-sized objects.

Answer 2

True

Question 3

In clusters of galaxies,the total mass of dark matter exceeds the luminous matter by about a factor of 1,000.

Answer 3

False

Question 4

Which is NOT an ingredient needed to build a cosmological simulation of large-scale structure formation?

A)the spectrum of density fluctuations that quantum mechanics imprints on the early universe
B)the density of dark matter and luminous matter in the universe
C)the grand unified theory
D)the density of dark energy in the universe
E)None of the above;all of the above are necessary.

Question 5

The most common type of galaxy found in a galaxy cluster is a ________ galaxy.

A)spiral
B)giant elliptical
C)giant irregular
D)dwarf
E)barred spiral

Question 6

Structure formation in our universe:

A)occurs for the largest structures first
B)occurs for the smallest structures first
C)begins on all spatial scales at the same time
D)begins after clusters form
E)begins with planets

Question 7

Which of these shows the correct order of collections of galaxies,starting with the smallest and ending with the largest?

A)group,supercluster,cluster
B)cluster,supercluster,group
C)group,cluster,supercluster
D)cluster,group,supercluster
E)supercluster,group,cluster

Question 8

Even at its earliest moments,the universe had about as much structure in it as it has at the current time.

Question 9

The peculiar velocities of galaxies allow us to determine how matter is distributed in the universe.

Question 10

If a galaxy is a member of a large cluster of galaxies,like the Coma cluster,the galaxy would have a typical velocity of 1,000 km/s.If the cluster is 10 Mpc in diameter,how long would it take the galaxy to cross from one side of the cluster to another?

A)10,000 years
B)1 million years
C)10 million years
D)100 million years
E)10 billion years

Question 11

The Local Group is a part of the Virgo Supercluster.

Question 12

What process is most responsible for shaping the large-scale structure of the universe?

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

Question 13

Astronomers have determined that the Milky Way is being pulled toward a massive structure called the "Great Attractor" due to the mass of the Great Attractor alone.

Question 14

Peculiar velocities are produced by:

A)erroneous redshifts
B)gravity
C)supernovae
D)eclipsing binary stars
E)interstellar winds

Question 15

What does the large-scale structure of the universe look most like?

A)a sponge with many large holes
B)a loaf of wheat bread with many tiny holes
C)a plate of flat noodles
D)a jar of marbles
E)a pizza with evenly spread out pepperoni

Question 16

Which of these components makes up the largest amount of mass in a typical large cluster of galaxies?

A)supermassive black holes
B)stars
C)cold gas
D)hot gas
E)neutron and white dwarf stars

Question 17

The first stars formed in the universe did not require the effects of dark matter to form.

Question 18

There are fluctuations in the CMB due to the fact that clumps of dark matter had already begun to form in the universe when the light from the CMB was given off.

Question 19

We currently find ourselves in the stelliferous era in the history of our universe.

Question 20

Current theoretical models suggest that most of the universe is composed of hot dark matter.

Question 21

If astronomers discover a new ultrafaint galaxy,where would it most likely be found?

A)on its own,away from other galaxies
B)a few billion light years away from Earth
C)at high redshift
D)in a large galaxy cluster
E)orbiting the Milky Way

Question 22

Our current ideas on galaxy formation suggest that the visible parts of galaxies:

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 out over larger distances than dark matter halos

Question 23

If the quantum fluctuations imprinted on the dark matter halos at the time of the formation of the CMB were ten times larger and the Hubble Constant was the same as it is now,galaxies would likely be:

A)smaller than they are now
B)larger than they are now
C)more numerous than they are now
D)nonexistent
E)exactly the same as they are now

Question 24

Which of the following statements about the Dark Ages of the universe is FALSE?

A)The first stars began forming during the Dark Ages.
B)The end of the Dark Ages coincided with reionization.
C)The Dark Ages lasted from 200 to 600 million years after the Big Bang.
D)During the Dark Ages,photons could travel freely through the universe.
E)Recombination occurred before the Dark Ages.

Question 25

Which of these lists shows the correct chronological order of the events listed,starting with the earliest and ending with the most recent?

A)reionization,dark matter halos collapse,recombination,first galaxies are formed
B)dark matter halos collapse,reionization,first galaxies are formed,recombination
C)reinonization,first galaxies are formed,dark matter halos collapse,reionization
D)recombination,dark matter halos collapse,first galaxies are formed,reionization
E)first galaxies are formed,dark matter halos collapse,reionization,recombination

Question 26

How much of the total mass of the universe is made up of hot dark matter?

A)less than 1 percent
B)5 percent
C)25 percent
D)45 percent
E)90 percent

Question 27

Ignoring the effect of redshift,we expect the galaxies that we see at a redshift of z = 3 will be __________ than galaxies today.

A)more irregular and redder
B)larger and redder
C)smaller and bluer
D)smaller and redder
E)larger and bluer

Question 28

If neutrinos have mass but do not interact much with normal matter,why can't they be the dominant form of dark matter in the universe?

A)Structure formation would have started with large objects fragmenting into smaller objects.
B)Structure formation would have started with small objects merging to form larger objects.
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 29

The first stars formed in the universe had __________ compared to the stars formed today.

A)higher metallicity and higher mass
B)higher metallicity and lower mass
C)lower metallicity and higher mass
D)lower metallicity and lower mass
E)higher mass and longer lifetimes

Question 30

The "Lambda-CDM" model combines the properties of __________ to explain the formation of structure in the universe.

A)black holes and neutron stars
B)dark energy and cold dark matter
C)star formation and angular momentum
D)nucleosynthesis and hot dark matter
E)gravity and nuclear forces

Question 31

Which of these statements about black holes in the early universe is NOT true?

A)Supermassive black holes affected the star formation rates in early galaxies.
B)The growth of supermassive black holes is likely linked with galaxy mergers.
C)The first generation of stars had high enough masses to leave black holes behind after exploding as supernova.
D)The black holes in the early universe should have been larger than those seen today.
E)Supermassive black holes may have formed from mergers of smaller black holes.

Question 32

Quantum fluctuations in the early universe:

A)were the seeds that grew into today's galaxies
B)are the reason dark matter exists
C)were made of small black holes
D)had no effect on the current structure of the universe
E)can be observed with radio telescopes

Question 33

The most distant galaxies visible to us at z ≈ 10 are best observed with __________ wavelengths of light.

A)infrared
B)visible
C)X-ray
D)gamma ray
E)radio

Question 34

Which of the following is NOT a possible candidate for dark matter?

A)axions
B)positrons
C)photinos
D)neutrinos
E)None of the above;all of these could be dark matter.

Question 35

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

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

Question 36

In the early universe,why were inhomogeneities in the distribution of normal matter much smaller than the inhomogeneities in the dark matter?

A)Normal matter is pushed away by supernova explosions.
B)Magnetic fields smoothed the distribution of charged particles in the normal matter but not in dark matter.
C)Dark matter particles were more massive and cooled off before normal matter,thus dark matter fluctuations had a longer time over which to grow.
D)Dark matter was 10 times more massive than normal matter.
E)Radiation pressure affected normal matter but not dark matter.

Question 37

Which of the following best explain the difference between the heavy-element abundances seen in the first stars and those seen in stars that we observe today?

A)Stars today have more heavy elements,because modern stars have higher masses,allowing them to create more heavy elements through nuclear fusion.
B)Stars today have more heavy elements,because the gas that formed the current stars was enriched by the higher mass elements that were formed in the first stars.
C)Stars today have a fewer heavy elements,because they have been around long enough to use up the larger mass atoms.
D)Stars today have a smaller abundance of heavy elements because they haven't been around long enough to make as many of the larger atoms.
E)The stars that astronomers observe now are the first generation of stars.

Question 38

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

A)decay of dark matter particles
B)emission of neutrinos by the first stars that formed
C)release of jets of charged particles from supermassive black holes
D)radiation from the first stars,supernovae,and black holes that formed
E)positron and electron annihilations

Question 39

Why can't dark matter halos collapse to be the same size as the visible parts of galaxies?

A)Dark matter can't dissipate its energy through collisions.
B)Dark matter is mostly made of mini-black holes.
C)Dark matter has much more angular momentum.
D)Dark matter annihilates when it begins to get that dense.
E)Dark matter particles are too large to collapse that much.

Question 40

Structure formation in the universe proceeds hierarchically,meaning that:

A)large objects collapse then fragment to form smaller objects
B)large objects form at the same times as smaller objects
C)small objects collapse then merge to form larger objects
D)only small objects form and are stable over time
E)normal matter collapses first and dark matter collapses later

Question 41

Compared to what we see today,galaxies in the past are:

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 42

How do astronomers explain the formation of elliptical galaxies?

Question 43

Which of these statements about galaxy clusters is true?

A)Galaxy clusters do not require dark matter in order to form.
B)Galaxy clusters are the largest structures in the universe.
C)Small galaxy clusters form first,then merge together to form larger galaxy clusters.
D)Galaxy clusters are evenly distributed throughout the universe.
E)There are such large distances between galaxy clusters that they never actually run into each other.

Question 44

Which of the following is NOT likely to happen when two spiral galaxies collide?

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)Individual stars collide to create many supernovae.
D)A burst of star formation will occur in the merged galaxy.
E)The cold gas in the merged galaxy might be blown away by supernovae.

Question 45

We currently live in the universe during the:

A)era of stars
B)era of degeneracy
C)era of black holes
D)era of darkness
E)era of particle-antiparticle formation

Question 46

In order from first to last,the specific eras in the universe's history are known as the:

A)primordial,stelliferous,degenerate,and dark eras
B)stelliferous,black hole,and entropy eras
C)primordial,stelliferous,black hole,and entropy eras
D)primodial,degenerate,and black hole eras
E)primordial,stelliferous,degenerate,black hole,and dark eras

Question 47

Explain how computer simulations of structure formation and observations of the structure in the universe today can help astronomers determine the nature of dark matter.

Question 48

Why do astronomers think that cold dark matter (as opposed to hot dark matter)is the primary component of dark matter in galaxies?

Question 49

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?

Question 50

In the future,we expect our universe will go through the ___________ era,when most of the normal matter in the universe is locked up in brown dwarfs,white dwarfs,neutron stars,and black holes.

A)remnant
B)neutral
C)degenerate
D)retirement
E)quiet

Question 51

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

Question 52

Each of these statements describes the steps that occur during star formation.Which of these is NOT also true for galaxy formation?

A)Angular momentum leads to the formation of a disk.
B)For both stars and galaxies,the largest objects form first,with smaller objects coming together later.
C)A gas cloud radiates energy,allowing it to collapse further than when it was hotter.
D)Gravitational instability leads to collapse.
E)The original large gas cloud splits into smaller fragments because areas with higher density also have greater gravitational pull.

Question 53

What is the fundamental difference between the two basic types of dark matter? List an example of each type.

Question 54

What do astronomers believe will be the final state of our universe?

A)a Big Crunch in which everything collapses back in on itself
B)an ever-expanding universe filled with nothing but hydrogen and helium gas
C)a universe that stops expanding and is filled with nothing but white dwarfs,neutron stars,and black holes
D)an ever-expanding universe filled with photons and elementary particles
E)a universe that stops expanding once enough stars become black holes

Question 55

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

Question 56

Describe the large-scale structure of the universe.

Question 57

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

A)a typical proton inside a water molecule on the Earth
B)a helium atom on 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 58

Describe two ways in which you could measure the mass of a galaxy cluster.

Question 59

By measuring the star formation rate in galaxies as a function of their redshift,we have learned that the average star formation rate in galaxies peaked approximately _________ years ago.

A)1 billion
B)3 billion
C)5 billion
D)7 billion
E)12 billion