Deck 22: The Origin of Structure

Question 1

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) 10 million years
C) 100 million years
D) 10 billion years

Answer 1

10 billion years

Question 2

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

Answer 2

True

Question 3

Which of the following is FALSE?

A) The Local Group contains approximately 30 galaxies.
B) The Local Group encompasses the region within 4 Mly of the Milky Way.
C) 98 percent of all the mass in the Local Group resides in two spiral galaxies.
D) Most galaxies in the local group are spiral galaxies.

Answer 3

Most galaxies in the local group are spiral galaxies.

Question 4

If dark energy were to instantly cease,our universe would continue to expand forever.

Question 5

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

Question 6

There are fluctuations in the CBR due to the fact that clumps of dark matter had already begun to form in the universe.

Question 7

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

A) spiral.
B) giant elliptical.
C) giant irregular.
D) dwarf.

Question 8

Structure formation in our universe

A) proceeds from the top down.
B) proceeds from the bottom and moves up.
C) begins on all spatial scales at the same time.
D) begins after clusters form.

Question 9

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

Question 10

In a massive cluster of galaxies,the most common type of galaxy is

A) a spiral.
B) a giant elliptical.
C) an elliptical.
D) an irregular.

Question 11

If the quantum fluctuations imprinted on the dark matter halos at the time of the formation of the CBR were ten times larger,galaxies would likely be

A) smaller.
B) larger.
C) more numerous.
D) nonexistent.

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

Question 13

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

A) Radiation pressure affected normal matter but not dark matter.
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 ten times more massive than normal matter.

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

Astronomers have determined that the Milky Way is being pulled toward a massive structure called the "Great Attractor" but are unable to observe it because it is too far away.

Question 19

The Local Group is a part of the Virgo Supercluster.

Question 20

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

Question 21

Which component 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

Question 22

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.

Question 23

Is the theory behind Type IV multiverses testable?

A) Yes,because if you wait long enough you can see past your current horizon.
B) Yes,because your universe is a part of a larger structure.
C) No,because the different multiverses cannot communicate with one another.
D) No,because quantum mechanics forbids it.

Question 24

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

Question 25

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

A) 5 percent
B) 25 percent
C) 45 percent
D) 90 percent

Question 26

Describe the large-scale structure of the universe.

Question 27

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.

Question 28

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) Primordial,stelliferous,degenerate,black hole,and dark eras.

Question 29

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

Question 30

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

Question 31

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

Question 32

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

Question 33

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.

Question 34

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.

Question 35

We currently live in the universe during its

A) era of stars.
B) era of degeneracy.
C) era of black holes.
D) era of darkness.

Question 36

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

Question 37

We expect the galaxies that we see at a redshift of 4 will be __________ than galaxies today.

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

Question 38

Which of the following CANNOT be dark matter?

A) Axions
B) Positrons
C) Photinos
D) Neutrinos

Question 39

Peculiar velocities are produced by

A) erroneous redshifts.
B) gravity.
C) supernovae.
D) eclipsing binary stars.

Question 40

We expect the kinds of galaxies that we see at a redshift of 4 (that is,when the universe was much younger)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.

Question 41

How do we know how fast the Milky Way is moving relative to the local universe? What are we moving toward,and why do we not know much about it?

Question 42

Put the following eras in the history of the evolution of the universe in their proper order from the earliest to the latest: black hole era,dark era,degenerate era,primordial era,stelliferous era.

Question 43

How do astronomers explain the formation of elliptical galaxies?

Question 44

What is the main reason that astrophysicists cannot calculate the evolution of galaxies exactly?

Question 45

Explain why there could be an infinite number of multiverses inside our own universe.Are they likely to be similar or different than our own universe?