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Galaxies-Test1
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. Who first calibrated the Cepheid variable stars for use in determining distance?
a. Henrietta Leavitt
b. Edwin Hubble
c. John Glenn
d. Carl Sagan
e. Harlow Shapley
2. Which of the following is not a characteristic of the stars of the disk component of our galaxy?
a. circular orbits
b. randomly inclined orbits
c. higher metal abundance
d. young stars
e. star formation regions
3. A group of 10 to 100 stars that formed at the same time but are so widely scattered in space their
mutual gravity cannot hold them together is called
a. a globular cluster.
b. an open cluster.
c. an association.
d. a spherical component
e. an accretion disk.
4. Our galaxy is suspected to be surrounded by a galactic corona because the disk of the galaxy
a. rotates faster than expected in its outer region.
b. rotates more slowly than expected in its outer region.
c. rotates faster than expected in its inner region.
d. rotates more slowly than expected in its inner region.
e. is much flatter than expected.
5. Younger stars have more heavy elements because
a. old stars destroy heavy elements as they age.
b. young stars burn their nuclear fuels faster.
c. the heavy elements were made in previous generations of stars.
d. heavy elements haven't had time to settle to the core of these younger stars.
e. all of these
6. The first stars to form in our galaxy
a. had circular orbits.
b. had highly elliptical orbits.
c. were population I stars.
d. all had orbits in the same plane.
e. formed the galactic clusters we see today.
7. Good spiral tracers are all
I.
very old.
II.
III.
IV.
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9.
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very young.
very luminous.
moving with large radial velocities.
a. I & III
b. I & IV
c. II & III
d. II & IV
e. I, III, & IV
Radio maps of our galaxy show spiral arms because
a. the arms have larger Doppler shifts.
b. the gas in the spiral arms is very hot.
c. the dust in spiral arms is denser.
d. the gas in spiral arms is denser.
e. the stars in the spiral arms emit most of their energy at radio wavelengths.
If the spiral density wave were the only thing producing spiral arms, it would be expected that
a. all spiral arms would be dust free.
b. all galaxies would have only two smooth spiral arms.
c. the Milky Way would be more massive than observed.
d. the Milky Way wouldn't have any spiral arms.
e. the halo component of the Milky Way would show spiral arms as well.
The energy source at the center of our galaxy
a. is not visible at optical wavelengths.
b. produces x rays.
c. must be less than 10 AU in diameter.
d. all of the above.
e. none of the above.
__________ first noticed that for Cepheid variable stars, there was a direct relation between the
luminosity and the period of the variation in their brightness.
a. Henrietta Leavitt
b. Edwin Hubble
c. John Glenn
d. Carl Sagan
e. Annie Cannon
Population II stars
I.
II.
III.
IV.
a.
b.
c.
d.
e.
are primarily found in the disk of the galaxy.
contain more heavy metals than population I stars.
are primarily old low mass stars.
are located in globular clusters.
III & IV
I & II
II
IV
I, II, & III
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13. The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on
a. observations of globular clusters.
b. observations of open clusters.
c. 21-cm radiation from H I regions.
d. the rotation curve of the galaxy.
e. the energy produced by Sagittarius A*.
14. CO observations of the galaxy reveal
a. the location of dense neutral hydrogen clouds.
b. the location of population II stars.
c. the location of population I stars.
d. the location of the galactic corona.
e. the location of giant molecular clouds.
15. The chemical abundance of population I stars
a. indicates that they were formed before the population II stars.
b. indicates that the material they formed from had been enriched with material from
supernovae.
c. indicates that they contain very few heavy metals compared to halo stars.
d. depends on the temperature of the star.
e. depends on the mass of the star.
16. The center of our galaxy lies in the direction of the constellation of
a. Ursa Minor.
b. Ursa Major.
c. Sagittarius.
d. Orion.
e. Monoceros.
17. Nucleosynthesis
a. is the process by which energy is produced at the center of the galaxy.
b. is the process by which hydrogen and helium are converted into heavier elements.
c. describes the structure of a globular cluster.
d. describes how the magnetic field of the galaxy traps cosmic rays.
e. describes the method by which neutral hydrogen produces 21 cm radiation.
18. The nuclear bulge of our galaxy
a. contains stars that are primarily population I stars.
b. contains relatively large amounts of gas and dust.
c. contains stars primarily associated with the spherical component of our galaxy.
d. contains stars primarily associated with the disk component of our galaxy.
e. a, b, and d
19. The orbits of population I stars
I.
II.
III.
IV.
a. I
are confined to disk of the galaxy.
are very elliptical.
are nearly circular.
are randomly inclined to the disk of the galaxy.
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21.
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b. IV
c. I & IV
d. II & IV
e. I & III
The traditional theory states that the galaxy formed
a. as a large spherical cloud of gas that was rotating very slowly.
b. from a large cloud of material that broke off a larger galaxy.
c. from material that had been ejected in the violent explosion of a dying galaxy.
d. as a result of mergers between several smaller groups of gas, dust, and stars.
e. as two massive galaxies collided.
The traditional theory of the formation of our galaxy cannot explain
a. the existence of the disk of the galaxy
b. the fact that the oldest stars in the galaxy are not metal free.
c. the spherical distribution of the globular clusters
d. the difference in metal abundance of the population I and II stars.
e. the existence of the nuclear bulge.
Radio maps of the spiral arms of our galaxy
a. reveal that our galaxy is a grand design spiral.
b. map the location of Hot O and B stars by the radio radiation they emit.
c. reveal that the spiral arms are winding up and growing closer together.
d. reveal that the sun is currently located in the center of a spiral arm.
e. map the location of dense neutral hydrogen clouds.
Sgr A* is believed to be the center of the Milky Way galaxy because
I.
II.
III.
IV.
a.
b.
c.
d.
e.
It lies in the general direction of the center of the galaxy based on
observations of globular clusters.
It is located near the galactic corona.
It is easily visible with optical telescopes and has the appearance of a massive
black hole.
It does not move with respect to the rest of the galaxy.
I & II
II & III
I & IV
II & IV
I, III, & IV
Figure 12-1
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24. See Figure 12-1 above. A Type II Cepheid has been located in a distant globular cluster with a
period of 10 days. What is the star's absolute magnitude?
a. -1
b. 0
c. -4
d. -6
e. The absolute magnitude of a Cepheid variable cannot be determined unless its
distance is known.
25. See Figure 12-1 above. A Type I Cepheid has been located in an open cluster. The period of the
Cepheid variable is 30 days and the variables apparent visual magnitude is 10. What is the distance
to this open cluster?
a. 100 pc
b. 10,000 pc
c. 20 pc
d. 300 pc
e. 2500 pc
26. An E galaxy contains
a. mostly lower-main sequence stars and giants.
b. mostly upper main sequence stars and giants.
c. mostly upper main sequence stars and gas and dust.
d. roughly equal numbers of upper and lower main sequence stars.
e. mostly white dwarfs and supergiants.
27. An spiral galaxy contains
a. mostly lower-main sequence stars and giants.
b. mostly upper main sequence stars and giants.
c. mostly upper main sequence stars and gas and dust.
d. upper and lower main sequence stars and gas and dust.
e. mostly white dwarfs and supergiants.
28. An irregular galaxy contains mostly
a. lower-main sequence stars and giants.
b. upper main sequence stars and giants.
c. upper main sequence stars and gas and dust.
d. upper and lower main sequence stars and gas and dust.
e. white dwarfs and supergiants.
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29. A megaparsec is equivalent to
a. 3.26 light-years.
b. 206,265 light years.
c. 206,265 AU.
d. 3,260,000 light-years.
e. the diameter of the Milky Way galaxy.
30. Which of the following is not used as a distance indicator?
a. large globular clusters
b. Herbig-Haro objects
c. H II regions
d. Cepheid variable stars
e. Supernovae
31. The look-back time is
a. the time it takes for the light from an object to reach Earth.
b. numerically equal to the distance in light-years.
c. smaller for more distant objects.
d. all of the above
e. a and b above
32. The mass of a single galaxy might be found by
a. the double galaxy method.
b. the rotation curve method.
c. the cluster method.
d. any of these methods.
e. none of these methods.
33. Most of the mass of a galaxy is contained in the
a. massive O and B stars in the galaxy.
b. H I regions of the galaxy.
c. H II regions of the galaxy.
d. dark matter of the galaxy.
e. disk of the galaxy.
34. Galactic cannibalism refers to
a. binary galaxies.
b. the merging of galaxies.
c. galaxies drawing in gas from the intergalactic medium.
d. the destruction of a galaxies globular clusters by the galaxies nucleus.
e. none of these
35. Astronomers now speculate that a galaxy's shape depends on all of the following except
a. the rate of star formation.
b. the history of past collisions.
c. the mass.
d. the chemical composition.
e. All of these are important in determining a galaxy's shape.
36. Based on the galaxies found in the Local Group of galaxies, the most common type of galaxy in
the universe is expected to be
a. the spiral galaxies.
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b. the barred spiral galaxies.
c. the dwarf elliptical galaxies.
d. the irregular galaxies.
e. the giant elliptical galaxies.
We should expect galaxies to collide fairly often because
a. they are large with respect to their separation distances.
b. galaxies contain large amounts of neutral hydrogen.
c. galaxies occur in clusters.
d. a and c
e. none of the above
__________ galaxies contain large clouds of gas and dust, both young and old stars, but have no
obvious spiral arms or nucleus.
a. Irregular
b. S0
c. E7
d. Sa
e. E0
__________ is an irregular galaxy that is believed to have collided with the Milky Way and is
expected to merge with the Milky Way in the future.
a. The Andromeda galaxy
b. The Small Magellanic Cloud
c. M87
d. The Virgo cluster
e. The Whirlpool galaxy
The rotation curve of a galaxy can be used to determine
a. the relative number of hot young stars in the galaxy.
b. the relative amount of gas and dust in the galaxy.
c. the radius of the galaxy.
d. the luminosity of the galaxy.
e. the mass of the galaxy.
The Milky Way galaxy is part of
a. the Virgo cluster.
b. the Large Magellanic Cloud.
c. the Small Magellanic Cloud.
d. the Local Group.
e. a rich cluster.
It is believed that ring galaxies form
a. when two galaxies collide nearly head on at high speed.
b. when two spiral galaxies collide, but not directly head on.
c. from a large cloud of gas and dust with very little angular momentum.
d. from a large cloud of gas and dust with a very high angular momentum.
e. when more than two galaxies collide at the same time.
Observations of galaxies and clusters of galaxies indicate that about __________ per cent of the
universe is dark matter.
a. 5
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b. 25
c. 50
d. 75
e. 95
Starburst galaxies
a. contain a large number of very young stars, but very little evidence of gas clouds.
b. contain a large number of very old stars and almost no gas or dust.
c. are often associated with a galaxy that is colliding with another galaxy.
d. are common in rich clusters.
e. are composed of filaments and voids.
An elliptical galaxy could
a. evolve into an irregular galaxy when it has used up all of its gas and dust.
b. be formed from the collision and merger of spiral galaxies.
c. evolve from a single spiral galaxy when the spiral has used up all of its gas and
dust.
d. become a starburst galaxy if it were to move through the hot intergalactic medium
of a cluster.
e. evolve from an S0 galaxy if the S0 galaxy were to increase its rotation rate.
The Virgo cluster
a. is the galactic cluster that contains the Milky Way
b. is the oldest known cluster of galaxies.
c. is located at the center of the universe.
d. contains mostly spiral galaxies and very few elliptical galaxies.
e. is a rich cluster and the closest cluster of galaxies outside of the Local Group.
Supermassive black holes are believed to be located at the center of many galaxies because
a. the rotation curve of the galaxy indicates that 90% of the galaxy is dark matter.
b. the orbital motion of material near the center is very fast and indicates a very
massive core.
c. the shape of the bulge in all spiral galaxies can only be supported by a
supermassive black hole.
d. the spiral structure requires a black hole to maintain the spiral arms.
e. the orbital speeds of a globular clusters in the galaxy are greater than the speed of
light.
If H equals 70 km/sec/Mpc, then a galaxy with a radial velocity of 2100 km/sec has a distance of
approximately
a. 2170 Mpc
b. 2030 Mpc
c. 30 Mpc
d. 0.03 Mpc
e. 147,000 Mpc
If a galaxy has a radial velocity of 8000 km/sec and the Hubble constant is 70 km/sec/Mpc, what is
the distance to this galaxy?
3
a.
Mpc
9
b.
Mpc
5
c.
Mpc
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d. 114 Mpc
-3
e.
Mpc
50. If the absolute magnitude of a supernova is -19 and a galaxy is found that contains a supernova
with an apparent magnitude of 16, what is the distance to the galaxy?
a. 100 AU
b. 100 pc
c. 100 ly
d. 100 kpc
e. 100 Mpc
Completion
Complete each sentence or statement.
51. The center of our galaxy is believed to be occupied by the radio source known as __________.
52. The __________ of the galaxy contains population I stars, open clusters, and gas clouds.
53. __________ are groups of 100,000 to 1,000,000 population II stars firmly bound by gravity.
54. In the diagram below, the approximate absolute magnitude of a Type II Cepheid with a period of
30 days is __________.
55. The rotation curve of the galaxy provides evidence for the existence of the __________ which
extends beyond the halo of the galaxy.
56. The units on the Hubble constant are __________.
57. __________ clusters of galaxies contain closely spaced galaxies and often contain giant elliptical
galaxies and a hot intergalactic medium.
58. Measuring the Doppler shift of material at various distances from the center of a galaxy can be
used to construct a(n) __________ for that galaxy.
59. __________ galaxies have a definite disk component, but contain no evidence of spiral pattern,
few hot young stars, and little gas and dust.
60. Due to the extremely rapid orbital velocities of material near the center of many galaxies, these
galaxies are believed to contain __________ at their centers.
True/False
Indicate whether the sentence or statement is true or false.
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61. The center of our galaxy is located in the direction of the constellation of Orion.
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62. Shapley found the distance to the center of the galaxy by studying the distance to open clusters.
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63. The disk of the Milky Way is approximately 20,000 ly in diameter.
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64. The rapid rotation in the outer disk suggests that our galaxy is more massive than previously
thought.
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65. Old stars are poor in heavy atoms because there were very few previous generations of stars before
the old stars formed.
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66. The disk of the galaxy is older than the halo.
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67. Spiral tracers tend to be old, luminous stars.
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68. Giant molecular cloud complexes are located in spiral arms.
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69. The density wave theory explains spurs and branches along the spiral arms.
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70. The center of our galaxy shows signs of past eruptions.
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71. Elliptical galaxies contain more gas, dust and young stars than do Sa galaxies.
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72. Until recently, most astronomers thought elliptical galaxies were shaped like oblate spheroids.
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73. Cepheid variable stars are more luminous than the sun.
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74. The look-back time is numerically equal to the distance to a galaxy in light-years.
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75. The rotation curve method can be applied only to pairs of galaxies orbiting each other.
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76. Some large clusters of galaxies do not appear to contain enough mass to hold themselves together.
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77. If H equals 50 km/sec/Mpc, then a galaxy with a radial velocity of 50,000 km/sec will have a
distance of about 1 Mpc.
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78. When two galaxies collide, they pass through each other and their stars almost never collide.
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79. When a large galaxy collides with a small galaxy, the smaller galaxy may be pulled apart by tidal
forces.
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80. Poor clusters of galaxies often contain an excess of E and SO galaxies.
Galaxies-Test1
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
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ANS:
E
B
C
A
C
B
C
D
B
D
A
A
A
E
B
C
B
C
E
A
B
E
C
A
B
A
D
D
D
B
E
B
D
B
D
C
D
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
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A
B
E
D
A
E
C
B
E
B
C
D
E
COMPLETION
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
ANS:
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Sgr A* or Sagittarius A*
disk
Globular clusters
-2
galactic corona
km/sec/Mpc
Rich
rotation curve
S0
a supermassive black hole
TRUE/FALSE
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
ANS:
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ANS:
F
F
F
T
T
F
F
F
F
T
F
T
T
74.
75.
76.
77.
78.
79.
80.
ANS:
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T
F
T
F
T
T
F