Question 1

Which of the following best describes how galaxies are distributed on large scales in the universe?

Accepted Answer

A)   Galaxies are uniformly distributed
B)   Galaxies are randomly distributed
C)   Galaxies are distributed in a hierarchy of clusters, superclusters, and hyperclusters
D)   Galaxies appear to be distributed in chains and sheets that surround great voids
E)   Galaxies are distributed in a great shell expanding outward from the center of the universe

Question 2

An Accelerating Universe? Current evidence that the expansion of the universe is accelerating is based entirely upon observations of distant white dwarf supernova. List all of the assumptions that you can think of that are made in using white dwarf supernova as distance indicators. Is it conceivable that any of these assumptions may be incorrect?

Accepted Answer

The assumptions made in using white dwar...

Question 3

Although most astronomers assume dark matter really exists, there is at least one other possible explanation for the phenomena attributed to dark matter. What is it?

Accepted Answer

A)   There could be something wrong or incomplete with our understanding of how gravity operates on galaxy-size scales.
B)   The so-called dark matter is really just ordinary stars that are enshrouded in clouds of dust.
C)   We could just be having a hard time understanding the observations because they involve very distant galaxies.
D)   There could be something wrong with our understanding of how atoms produce light.

Question 4

Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?

Accepted Answer

A)   Globular clusters in the halo of the galaxy
B)   Brown dwarfs in the halo of the galaxy
C)   Planets in the halo of the galaxy
D)   You, if you happened to be floating in the halo of the galaxy

Question 5

The mass enclosed in any orbit can be estimated from the equation M(<r)  =v²r/ G. If the quantity (v²r)  is constant, regardless of radius, where is the mass located?

Accepted Answer

A)   The mass is concentrated in the center.
B)   The mass is spread out over large radius.
C)   Cannot be determined from the information given.
D)   The mass is distributed like a doughnut, with a hole in the center.

Question 6

The critical density of the universe is the ________.

Accepted Answer

A)   average density the universe would need for gravity to someday halt the current expansion if dark energy did not exist
B)   actual average density of the universe
C)   density of dark matter in the universe
D)   density of water

Question 7

It is more difficult to determine the total amount of dark matter in an elliptical galaxy than in a spiral galaxy. Why?

Accepted Answer

A)   Elliptical galaxies lack the atomic hydrogen gas that we use to determine orbital speeds at great distances from the centers of spiral galaxies.
B)   Elliptical galaxies contain much less dark matter than spiral galaxies, so it's much more difficult to measure.
C)   Stars in elliptical galaxies are dimmer, making them harder to study.
D)   We cannot observe spectral lines for elliptical galaxies.

Question 8

The visible parts of galaxies contribute about 10 percent of the critical density of the universe.

Accepted Answer

A) True 
 B)False

Question 9

Which of the following statements about large-scale structure is probably not true?

Accepted Answer

A)   Clusters and superclusters appear to be randomly scattered about the universe, like dots sprinkled randomly on a wall.
B)   Galaxies and clusters have grown around tiny density enhancements that were present in the early universe.
C)   Voids between superclusters began their existence as regions in the universe with a slightly lower density than the rest of the universe.
D)   Many cluster and superclusters are still in the process of formation as their gravity gradually pulls in new members.

Question 10

Which of the following methods used to determine the mass of a cluster of galaxies does not depend on Newton's law of gravity?

Accepted Answer

A)   measuring the orbital velocities of galaxies in the cluster
B)   measuring the temperature of X-ray gas in the intracluster medium
C)   measuring the amount of distortion caused by a gravitational lens
D)   none of the above

Question 11

MACHOs are expected to be found only in the disk of the Milky Way, whereas WIMPs would be found only in the halo.

Accepted Answer

A) True 
 B)False

Question 12

Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?

Accepted Answer

A)   WIMPs are light enough that they have expanded out into the halo.
B)   WIMPs were produced in the early stages of galaxy evolution, and objects in the halo, such as globular clusters, were formed first.
C)   WIMPS cannot produce photons, and they rarely interact and exchange energy with other particles.
D)   Shock waves from generations of supernovae have blown the WIMPs out into the halo.
E)   WIMPs annihilate when they come into contact with ordinary matter, such as stars.

Question 13

What evidence suggests that the Milky Way contains dark matter?

Accepted Answer

A)   We observe clouds of atomic hydrogen far from the galactic center orbiting the galaxy at unexpectedly high speeds, higher speeds than they would have if they felt only the gravitational attraction from objects that we can see.
B)   We see many lanes of dark material blocking out the light of stars behind them along the band of the Milky Way.
C)   We see many dark voids between the stars in the halo of the Milky Way.
D)   When we observe in different wavelengths, such as infrared or radio, we see objects that don't appear in visible-light observations.
E)   When we look at the galactic center, we are able to observe a large black hole that is composed of dark matter.

Question 14

Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?

Accepted Answer

A)   Dark matter is the dominant form of mass in both clusters and in individual galaxies.
B)   Dark matter is present between galaxies in clusters, but not within individual galaxies.
C)   Dark matter is present in individual galaxies, but there is no evidence that it can exist between the galaxies in a cluster.
D)   Within individual galaxies, dark matter is always concentrated near the galactic center, and within clusters it is always concentrated near the cluster center.

Question 15

When we measure the broadening of absorption lines in the spectrum of an elliptical galaxy, we can infer

Accepted Answer

A)   the galaxy's rotation curve.
B)   the amount of gas and dust in the galaxy.
C)   how fast the stars in the galaxy are moving relative to one another.
D)   how quickly the galaxy is forming new stars.
E)   the mass of the black hole at the galaxy's center.

Question 16

Which hypothetical universe has an older age, all other things being equal?

Accepted Answer

A)   Dark matter doesn't affect the inferred age of the universe.
B)   The one with less dark matter
C)   The one with more dark matter

Question 17

Your cell phone friend left your house and is now driving 40 miles per hour, but she has been speeding up the whole time since she left your house, and has gone 10 miles. How long has she been driving?

Accepted Answer

A)   Longer than 15 minutes
B)   15 minutes
C)   Shorter than 15 minutes

Question 18

Which of the following is an example of baryonic matter?

Accepted Answer

A)   you
B)   the particles produced by physicists in particle accelerators
C)   electrons and positrons produced by pair production
D)   WIMPs
E)   neutrinos

Question 19

What is one of the alternatives to the hypothesized existence of dark matter?

Accepted Answer

A)   The observations are incorrect.
B)   The theory of gravity is wrong.
C)   The astronomers are misrepresenting the observations.
D)   The current theory of gravity is being used incorrectly.

Question 20

What evidence tells us that at least some dark matter consists of objects made of ordinary matter that orbit in the halo of the galaxy?

Accepted Answer

A)   We have detected gravitational lensing of distant objects that appears to be caused by unseen objects in the halo of our galaxy.
B)   Radio observations have detected numerous such objects in the galactic halo.
C)   Powerful new telescopes can see even the dimmest objects in the halo.
D)   The rotation curve of the Milky Way Galaxy shows that some dark matter must be ordinary.

Exam 16: Dark Matter, Dark Energy, and the Fate of the Universe

Which of the following best describes how galaxies are distributed on large scales in the universe?

Correct Answer
verified

What evidence suggests that the Milky Way contains dark matter?

Correct Answer
verified

Which hypothetical universe has an older age, all other things being equal?

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The assumptions made in using white dwar...
View Answer

MACHOs are expected to be found only in the disk of the Milky Way, whereas WIMPs would be found only in the halo.

Correct Answer
verified

Which of the following is an example of baryonic matter?

Correct Answer
verified

What evidence tells us that at least some dark matter consists of objects made of ordinary matter that orbit in the halo of the galaxy?

Correct Answer
verified

The mass enclosed in any orbit can be estimated from the equation M(<r) =v²r/ G. If the quantity (v²r) is constant, regardless of radius, where is the mass located?

Correct Answer
verified

What is one of the alternatives to the hypothesized existence of dark matter?

Correct Answer
verified

It is more difficult to determine the total amount of dark matter in an elliptical galaxy than in a spiral galaxy. Why?

Correct Answer
verified

Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?

Correct Answer
verified

Which of the following statements about large-scale structure is probably not true?

Correct Answer
verified

When we measure the broadening of absorption lines in the spectrum of an elliptical galaxy, we can infer

Correct Answer
verified

Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?

Correct Answer
verified

Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?

Correct Answer
verified

Your cell phone friend left your house and is now driving 40 miles per hour, but she has been speeding up the whole time since she left your house, and has gone 10 miles. How long has she been driving?

Correct Answer
verified

The visible parts of galaxies contribute about 10 percent of the critical density of the universe.

Correct Answer
verified

The critical density of the universe is the ________.

Correct Answer
verified

Which of the following methods used to determine the mass of a cluster of galaxies does not depend on Newton's law of gravity?

Correct Answer
verified

Although most astronomers assume dark matter really exists, there is at least one other possible explanation for the phenomena attributed to dark matter. What is it?

Correct Answer
verified

Exam 16: Dark Matter, Dark Energy, and the Fate of the Universe

Which of the following best describes how galaxies are distributed on large scales in the universe?

Correct AnswerverifiedShow Answer

What evidence suggests that the Milky Way contains dark matter?

Correct AnswerverifiedShow Answer

Which hypothetical universe has an older age, all other things being equal?

Correct AnswerverifiedShow Answer

Correct AnswerAnswered by ExamLex AIThe assumptions made in using white dwar...View AnswerShow Answer

MACHOs are expected to be found only in the disk of the Milky Way, whereas WIMPs would be found only in the halo.

Correct AnswerverifiedShow Answer

Which of the following is an example of baryonic matter?

Correct AnswerverifiedShow Answer

What evidence tells us that at least some dark matter consists of objects made of ordinary matter that orbit in the halo of the galaxy?

Correct AnswerverifiedShow Answer

The mass enclosed in any orbit can be estimated from the equation M(<r) =v²r/ G. If the quantity (v²r) is constant, regardless of radius, where is the mass located?

Correct AnswerverifiedShow Answer

What is one of the alternatives to the hypothesized existence of dark matter?

Correct AnswerverifiedShow Answer

It is more difficult to determine the total amount of dark matter in an elliptical galaxy than in a spiral galaxy. Why?

Correct AnswerverifiedShow Answer

Some dark matter may be ordinary matter that orbits in the halo of the galaxy. Which of the following would not be considered a type of ordinary dark matter?

Correct AnswerverifiedShow Answer

Which of the following statements about large-scale structure is probably not true?

Correct AnswerverifiedShow Answer

When we measure the broadening of absorption lines in the spectrum of an elliptical galaxy, we can infer

Correct AnswerverifiedShow Answer

Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the galaxy's disk?

Correct AnswerverifiedShow Answer

Which of the following statements best summarizes current evidence concerning dark matter in individual galaxies and in clusters of galaxies?

Correct AnswerverifiedShow Answer

Your cell phone friend left your house and is now driving 40 miles per hour, but she has been speeding up the whole time since she left your house, and has gone 10 miles. How long has she been driving?

Correct AnswerverifiedShow Answer

The visible parts of galaxies contribute about 10 percent of the critical density of the universe.

Correct AnswerverifiedShow Answer

The critical density of the universe is the ________.

Correct AnswerverifiedShow Answer

Which of the following methods used to determine the mass of a cluster of galaxies does not depend on Newton's law of gravity?

Correct AnswerverifiedShow Answer

Although most astronomers assume dark matter really exists, there is at least one other possible explanation for the phenomena attributed to dark matter. What is it?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
The assumptions made in using white dwar...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified