Question 1

The relationship between a galaxy and the galaxy cluster of which it is a part is similar to the relationship between a galaxy cluster and the supercluster of which it is a part, with one important difference. What is that difference?

Accepted Answer

A)   Clusters contain only like galaxies (spirals, etc.) ; superclusters combine clusters of various types.
B)   Superclusters rely on copious amounts of dark matter to bind them together; clusters do not.
C)   A cluster is a gravitationally bound system; a supercluster is not.
D)   The galaxy clusters in a supercluster orbit an enormous black hole; this is not the case with the galaxies in a cluster.E) None of the above
F) A) and B)

Question 2

Which of these observations are NOT used for the measurement of distances to distant galaxies?

Accepted Answer

A)   Cepheid variable stars
B)   width of the 21-cm H I radio emission line
C)   supernova explosions
D)   brightness and pulsation rates of pulsarsE) None of the above
F) C) and D)

Question 3

According to the Hubble classification scheme, an E3 galaxy

Accepted Answer

A)   is rounder-looking than an E5 galaxy.
B)   has more tightly wound spiral arms than an E5 galaxy.
C)   is more elongated than an E5 galaxy.
D)   has a shorter central bar in its disk than an E5 galaxy.E) A) and B)
F) A) and C)

Question 4

How does the number of barred spiral galaxies in the universe compare with the number of ordinary spiral galaxies?

Accepted Answer

A)   Barred spirals outnumber ordinary spirals.
B)   There are about equal numbers of barred spirals and ordinary spirals.
C)   The question is meaningless-barred spirals are simply ordinary spirals seen edge-on.
D)   Ordinary spirals outnumber barred spirals.E) C) and D)
F) B) and C)

Question 5

A typical spiral galaxy has _____ stars in a disk of diameter _____ ly.

Accepted Answer

A)   1011; 105
B)   1011; 1000
C)   109; 106
D)   106; 105E) A) and C)
F) All of the above

Question 6

Which single major problem perhaps puzzles astronomers MOST as they attempt to interpret the properties and behavior of clusters of galaxies?

Accepted Answer

A)   rate of supernova occurrence in galaxies in some clusters
B)   missing-mass problem, where the amount of mass needed for galactic cluster stability is estimated to be at least 10 times more than the observed visible mass
C)   presence of star formation in many galaxies long after it is expected to have died out
D)   structure and motion of spiral arms in galaxies in many clustersE) B) and C)
F) A) and C)

Question 7

Why is the Coma cluster of galaxies a favorite among astronomers?

Accepted Answer

A)   The Coma cluster is the cluster in which the Milky Way Galaxy is situated.
B)   The Coma cluster contains two quasars.
C)   The Coma cluster is the rich, regular cluster nearest Earth.
D)   The Coma cluster is the rich, irregular cluster nearest Earth.E) B) and C)
F) A) and C)

Question 8

Lenticular galaxies, S0, have no spiral arms. What is the difference between an S0 and an elliptical E0, which also has no spiral arms?

Accepted Answer

A)   There is no difference. These are two different designations for the same thing.
B)   An S0 will have more gas and dust than an E0.
C)   The S0 will contain primarily Population II stars while the E0 has primarily Population I stars.
D)   The S0 will be likely to contain supernova remnants while ellipticals never contain supernova remnants.E) C) and D)
F) None of the above

Question 9

Spiral density waves move through a medium that is also moving. The speed of the density waves

Accepted Answer

A)   is greater than the speed of the medium through which they pass.
B)   is the same as that of the medium through which they pass, thus forming a rigid spiral pattern.
C)   is less than that of the medium through which they pass.
D)   varies as the waves go around the galaxy, slowing down while passing through a spiral arm and speeding up in the regions in between.E) B) and D)
F) B) and C)

Question 10

In which of these types of galaxies is star formation no longer occurring?

Accepted Answer

A)   irregular galaxies
B)   barred spiral galaxies
C)   spiral galaxies
D)   elliptical galaxiesE) None of the above
F) All of the above

Question 11

Which one of these statements is NOT a characteristic of elliptical galaxies?

Accepted Answer

A)   Elliptical galaxies are almost devoid of interstellar gas and dust.
B)   Almost all star formation stopped in elliptical galaxies billions of years ago.
C)   Different elliptical galaxies appear to be flattened by different amounts.
D)   Elliptical galaxies have a disk and a central bulge but no spiral arms.E) B) and C)
F) None of the above

Question 12

What is an SBc galaxy?

Accepted Answer

A)   galaxy with a moderate nuclear bulge, moderately wound arms, and a bright core
B)   galaxy with a large nuclear bulge and tightly wound arms starting from the ends of a straight bar through the nuclear bulge
C)   galaxy with a small nuclear bulge and loosely wound arms coming from the center of the nuclear bulge
D)   galaxy with a small nuclear bulge and loosely wound arms starting from the ends of a straight bar through the nuclear bulgeE) A) and B)
F) A) and D)

Question 13

Suppose astronomers were able to detect radio signals from an intelligent civilization in the Coma cluster of galaxies. If they were to send a message to this civilization, how long would it take to get a reply?

Accepted Answer

A)   600 million years
B)   150 million years
C)   75 million years
D)   300 million yearsE) A) and B)
F) A) and D)

Question 14

The Tully-Fisher relationship relies on broadening of the 21-cm radio line in distant spiral galaxies. What causes this broadening?

Accepted Answer

A)   thermal motion of the gases in the galaxy
B)   random motions of the stars in the galaxy
C)   rotation of the galaxy
D)   general expansion of the universe (Hubble flow) E) B) and C)
F) All of the above

Question 15

The mathematical form of the Hubble law for the expanding universe concept relates the velocity of recession v to the distance of the observed object r (with H0 the Hubble constant)  as follows:

Accepted Answer

A)   r = H0 *v
B)   v = H0* r
C)   v = H0/r
D)   v = H0/r2E) None of the above
F) All of the above

Question 16

The amount of visible matter in a typical cluster of galaxies is

Accepted Answer

A)   just sufficient to hold the inner regions of the cluster together, but the fringe galaxies are drifting away from this center.
B)   not sufficient to hold the cluster together by a factor of 2, such that the cluster is slowly spreading out.
C)   insufficient to hold the cluster together, by about a factor of 10.
D)   far more than enough to hold the cluster together gravitationally and is slowly concentrating the cluster into a very tight supercluster.E) A) and C)
F) None of the above

Question 17

Most of the light from a galaxy comes from the inner parts. If this means that most of the galaxy's mass is also in the inner region, then how would the galaxy's speed of rotation behave in its outer region?

Accepted Answer

A)   The rotation speed should increase with increasing distance from the center.
B)   The rotation speed should decrease sharply to zero at the outer edge of the visible galaxy.
C)   The rotation speed should not change appreciably with increasing distance from the center (i.e., a "flat" rotation curve) .
D)   The rotation speed should decrease smoothly with increasing distance from the center.E) A) and B)
F) None of the above

Question 18

The Hubble law states that

Accepted Answer

A)   all objects appear to have the same velocity away from the Sun, regardless of distance from the Sun.
B)   mutual gravitational attraction of all objects in the universe means that all objects appear to be moving toward the Sun, the closest ones traveling fastest.
C)   all distant objects are moving toward the Sun, the most distant objects fastest.
D)   the farther an object is from the Sun, the faster it appears to be moving away from the Sun.E) A) and C)
F) B) and D)

Question 19

Overall, through space, galaxies are

Accepted Answer

A)   distributed uniformly, out to the farthest distances.
B)   clustered together in several high-density centers with very little matter linking them together.
C)   concentrated around one position in space, presumably the original site of the Big Bang.
D)   concentrated on filaments separated by huge open spaces or voids.E) B) and C)
F) A) and D)

Question 20

In discussing galaxies and the universe, astronomers often talk about "voids." What are voids?

Accepted Answer

A)   large expanses of space between galaxies where there is essentially no gas or dust
B)   holes in some galaxies where a collision by another, smaller galaxy has removed the dust, gas, and stars in that region
C)   volumes of space hundreds of millions of light-years across that contain almost no galaxies
D)   regions in clusters of galaxies that seem to be devoid of matterE) A) and B)
F) None of the above

Exam 17: Galaxies

Suppose astronomers were able to detect radio signals from an intelligent civilization in the Coma cluster of galaxies. If they were to send a message to this civilization, how long would it take to get a reply?

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According to the Hubble classification scheme, an E3 galaxy

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In which of these types of galaxies is star formation no longer occurring?

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The relationship between a galaxy and the galaxy cluster of which it is a part is similar to the relationship between a galaxy cluster and the supercluster of which it is a part, with one important difference. What is that difference?

Correct AnswerverifiedShow Answer

The Hubble law states that

Correct AnswerverifiedShow Answer

The mathematical form of the Hubble law for the expanding universe concept relates the velocity of recession v to the distance of the observed object r (with H0 the Hubble constant) as follows:

Correct AnswerverifiedShow Answer

How does the number of barred spiral galaxies in the universe compare with the number of ordinary spiral galaxies?

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Which single major problem perhaps puzzles astronomers MOST as they attempt to interpret the properties and behavior of clusters of galaxies?

Correct AnswerverifiedShow Answer

Most of the light from a galaxy comes from the inner parts. If this means that most of the galaxy's mass is also in the inner region, then how would the galaxy's speed of rotation behave in its outer region?

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Which of these observations are NOT used for the measurement of distances to distant galaxies?

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Which one of these statements is NOT a characteristic of elliptical galaxies?

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Overall, through space, galaxies are

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The Tully-Fisher relationship relies on broadening of the 21-cm radio line in distant spiral galaxies. What causes this broadening?

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A typical spiral galaxy has _____ stars in a disk of diameter _____ ly.

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The amount of visible matter in a typical cluster of galaxies is

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What is an SBc galaxy?

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In discussing galaxies and the universe, astronomers often talk about "voids." What are voids?

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Lenticular galaxies, S0, have no spiral arms. What is the difference between an S0 and an elliptical E0, which also has no spiral arms?

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Why is the Coma cluster of galaxies a favorite among astronomers?

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Spiral density waves move through a medium that is also moving. The speed of the density waves

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The mathematical form of the Hubble law for the expanding universe concept relates the velocity of recession v to the distance of the observed object r (with H₀ the Hubble constant) as follows:

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A typical spiral galaxy has _ stars in a disk of diameter _ ly.

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