Question 1

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

Accepted Answer

While a grand unified theory is an important theoretical concept in physics, it is not necessary to build a cosmological simulation of large-scale structure formation. The other options, including the spectrum of density fluctuations, the density of dark matter and luminous matter, and the density of dark energy, are all crucial ingredients in creating such a simulation.

Question 2

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

Accepted Answer

Observations of the cosmic microwave background, large-scale structure formation, and gravitational lensing all suggest that hot dark matter makes up only about 5% of the total matter in the universe. The remaining 95% is made up of cold dark matter (27%) and dark energy (68%).

Question 3

Which of the following provided the gravity to form galaxy fragments in the early universe?
A) cold dark matter halos
B) galaxy clusters
C) hot dark matter halos
D) large clouds of gas and dust

Accepted Answer

Cold dark matter halos are believed to have provided the gravitational pull necessary to collapse and shape the early universe's structures, including galaxy fragments. This process is known as hierarchical clustering. Galaxy clusters (B) form from the gradual accumulation of individual galaxies and are not responsible for the initial fragmentation of the universe. Hot dark matter (C) refers to particles that move at high velocities, which are believed to prevent them from clumping together and forming structures. Therefore, they are not likely to have contributed significantly to galaxy fragment formation. Large clouds of gas and dust (D) are the material from which stars and planets form, but they are not capable of providing the gravitational force necessary for the initial formation of galaxies.

Question 4

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 radiation.
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.

Accepted Answer

Dark matter cannot dissipate its energy through radiation, which is a key process that allows normal matter to collapse into denser structures like stars and galaxies. Without this ability to lose energy, dark matter remains more diffusely distributed around galaxies.

Question 5

Which of the following CANNOT be dark matter?
A) axions
B) positrons
C) photinos
D) neutrinos

Accepted Answer

Positrons are not a type of particle that can contribute to dark matter. They are anti-matter particles with the same mass as electrons, but opposite charge. Dark matter candidates must be stable, electrically neutral particles that interact very weakly with normal matter. Axions, photinos, and neutrinos are all possible candidates for dark matter based on current theories.

Question 6

Which of the following structures is the largest?
A) globular cluster
B) galaxy cluster
C) galaxy group
D) supercluster

Accepted Answer

A supercluster is the largest known structure in the universe, consisting of clusters and groups of galaxies bound together by gravity. It can span up to several hundred million light-years across. Therefore, it is larger than galaxy groups, galaxy clusters or globular clusters.

Question 7

Our Milky Way Galaxy is a member of:
A) the Local Group.
B) the Virgo Cluster.
C) the Virgo Supercluster.
D) all of the above

Accepted Answer

The Milky Way is part of the Local Group, which in turn is part of the Virgo Supercluster. The Virgo Cluster is a large cluster within the Virgo Supercluster, but the Local Group is separate from the Virgo Cluster itself. However, since the question's phrasing includes broader memberships, all options are technically correct.

Question 8

The earliest isotopes of low-mass nuclei (deuterium,helium,lithium,beryllium,boron)were formed in a process called:
A) Big Bang nucleosynthesis.
B) nuclear fission.
C) nuclear fusion.
D) stellar nucleosynthesis.

Accepted Answer

The process of forming the earliest isotopes of low-mass nuclei such as deuterium, helium, lithium, beryllium, and boron is known as Big Bang nucleosynthesis. It occurred during the first few minutes of the universe's existence when the temperature and density were high enough for nuclear reactions to occur. These elements were created through a series of fusion reactions, starting with hydrogen and helium nuclei combining to form deuterium, which then combined with more hydrogen to form helium-3 and eventually helium-4.

Question 9

The patterns of walls and voids that are observed:
A) only occur in the Virgo Cluster.
B) are optical illusions.
C) support the cosmological principle.
D) are made of dark matter.

Accepted Answer

The observation of walls and voids in the large-scale structure of the universe supports the cosmological principle, which states that the universe is homogeneous and isotropic on large scales. The patterns are not limited to the Virgo Cluster, nor are they optical illusions or made of dark matter.

Question 10

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.

Accepted Answer

According to current ideas on galaxy formation, visible parts of galaxies form only in the densest parts of dark matter halos. Dark matter halos are predicted to form first, with visible matter gradually being incorporated into them through a process called accretion.

Question 11

Galaxy clusters have been observed to be rich in hot,X-ray-emitting gas.What is keeping the gas in the cluster?
A) dark matter
B) the gravitational pull of the galaxies
C) the electromagnetic radiation emitted by the galaxies
D) the low speed of the hot gas

Accepted Answer

The answer of Galaxy clusters have been observed to be...

Question 12

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

Accepted Answer

The large-scale structure of the universe looks most like a sponge with many large holes, which is also known as the cosmic web. This is due to the distribution of galaxies and galaxy clusters forming filamentary structures that resemble the holes in a sponge.

Question 13

What is the method used to measure the distances to the farthest galaxies when mapping out large-scale structure?
A) Cepheid variables
B) parallax
C) redshifts and Hubble's law
D) RR Lyrae variables

Accepted Answer

Redshifts and Hubble's law are used to measure the distances to farthest galaxies when mapping out large-scale structure. The redder the shift, the more distant the object. Hubble's law explains the relationship between the recession velocity of a galaxy and its distance from us.

Question 14

If the quantum fluctuations imprinted on the dark matter halos at the time of the formation of the cosmic microwave background radiation were 10 times larger,galaxies would likely be:
A) smaller.
B) larger.
C) more numerous.
D) nonexistent.

Accepted Answer

If the quantum fluctuations imprinted on the dark matter halos were 10 times larger, it would mean that there would be more variation in density in the universe. This would cause regions of higher density to collapse more quickly and form larger structures such as galaxies, making them larger than they are in our current universe.

Question 15

What is the importance of the observation that the observed amount of normal matter in the universe matches the amount predicted by Big Bang nucleosynthesis?
A) It shows that dark matter cannot be made up of primarily normal matter, such as protons and neutrons.
B) It shows that dark matter is made up primarily of normal matter, such as protons and neutrons.
C) It shows that there is no need to require dark matter in our understanding of the large-scale structure of the universe.
D) It shows that dark matter is made up primarily of neutrinos.

Accepted Answer

The observation that the amount of normal matter matches predictions from Big Bang nucleosynthesis supports the idea that dark matter must be something other than normal, baryonic matter (such as protons and neutrons). This is because the amount of normal matter observed is insufficient to account for the total mass and gravitational effects observed in the universe, indicating that dark matter must be composed of something else.

Question 16

Which of the following makes up a significant amount of hot dark matter?
A) axions
B) neutrinos
C) photinos
D) photons

Accepted Answer

Neutrinos make up a significant amount of hot dark matter. Unlike other particles like axions, photinos, or photons, neutrinos have mass and can contribute to the overall density of dark matter in the universe. However, they are considered "hot" dark matter because they were moving at high speeds during the early universe and thus do not cluster as strongly as other forms of "cold" dark matter.

Question 17

Axions and photinos are examples of:
A) cold dark matter.
B) hot dark matter.
C) neutrinos.
D) normal matter.

Accepted Answer

Axions and photinos are hypothetical particles that are predicted to exist in some models of particle physics and are considered candidates for cold dark matter. Hot dark matter refers to particles that move at relativistic speeds and would not form structures like galaxies, whereas neutrinos are a type of hot dark matter. Normal matter, on the other hand, interacts electromagnetically and forms stars and galaxies.

Question 18

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.

Accepted Answer

Neutrinos' weak interaction with normal matter means they could not cluster in the same way as other matter due to their high speeds. Structure formation would have begun with large objects fragmenting into smaller ones, rather than the reverse. This makes it unlikely that neutrinos could be the dominant form of dark matter in the universe.

Question 19

The observed abundances of helium and deuterium in the universe:
A) support models of Big Bang nucleosynthesis.
B) disprove the Big Bang model of the universe.
C) do not match predictions.
D) contradict the density of matter observed in the universe.

Accepted Answer

The observed abundances of helium and deuterium in the universe are consistent with the predictions of Big Bang nucleosynthesis, which is one of the pillars of the Big Bang model of the universe. This provides strong support for the Big Bang model.

Question 20

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

Accepted Answer

Gravity is the most responsible process for shaping the large-scale structure of the universe. It pulls matter together to form galaxies, groups of galaxies, and clusters of galaxies. Supernovae, matter/antimatter annihilation, and magnetic fields do not have as significant an impact on the overall structure of the universe.

Quiz 17: Formation of Structure

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

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

Which of the following provided the gravity to form galaxy fragments in the early universe?

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

Which of the following CANNOT be dark matter?

Which of the following structures is the largest?

Our Milky Way Galaxy is a member of:

The earliest isotopes of low-mass nuclei (deuterium,helium,lithium,beryllium,boron) were formed in a process called:

The patterns of walls and voids that are observed:

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

Galaxy clusters have been observed to be rich in hot,X-ray-emitting gas.What is keeping the gas in the cluster?

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

What is the method used to measure the distances to the farthest galaxies when mapping out large-scale structure?

If the quantum fluctuations imprinted on the dark matter halos at the time of the formation of the cosmic microwave background radiation were 10 times larger,galaxies would likely be:

What is the importance of the observation that the observed amount of normal matter in the universe matches the amount predicted by Big Bang nucleosynthesis?

Which of the following makes up a significant amount of hot dark matter?

Axions and photinos are examples of:

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?

The observed abundances of helium and deuterium in the universe:

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