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Exam 4; Stars & Galaxies



Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 1. 

Herschel's grindstone and Kapteyn's star system were too small because
a.
they did not count the brightest stars.
b.
they did not study the southern sky.
c.
they did not have large enough telescopes.
d.
they only observed stars in the disk of the galaxy and not the halo.
e.
they did not know about interstellar dust clouds.
 

 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.
heavy elements were made in previous generations of stars.
d.
all of these
e.
heavy elements haven't had time to settle to the core of these younger stars.
 

 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.
very young
III.
very luminous
IV.
moving with large radial velocities
a.
I & III
b.
I & IV
c.
II & III
d.
II & IV
e.
I, III, & IV
 

 8. 

Radio maps of our galaxy show spiral arms because the
a.
arms have high Doppler shifts.
b.
gas in the spiral arms is hot enough to emit photons.
c.
dust in spiral arms is more dense than it is between the spiral arms.
d.
gas in spiral arms is more dense than it is between the spiral arms.
e.
stars in the spiral arms emit most of their energy at radio wavelengths.
 

 9. 

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 grand design spiral patterns.
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.
 

 10. 

The energy source at the center of our galaxy
a.
is not visible at optical wavelengths.
b.
produces gamma rays.
c.
must be less than 10 AU in diameter.
d.
all of the above
e.
none of the above.
 

 11. 

The magnetic field of the galaxy
a.
is stronger than the magnetic field of the sun.
b.
traps cosmic rays in the disk of the galaxy.
c.
creates the spiral density waves that initiate star formation.
d.
forces the halo stars to follow highly inclined orbits.
e.
produces 21-cm radiation that allows us to map the spiral arms.
 

 12. 

Population II stars

I.
are primarily found in the disk of the galaxy.
II.
contain more heavy metals than population I stars.
III.
are primarily old low mass stars.
IV.
are located in globular clusters.
a.
III & IV
b.
I & II
c.
II
d.
IV
e.
I, II, & III
 

 13. 

The first scientific attempt to map the Milky Way galaxy
a.
showed that the sun was located near the edge of the galaxy.
b.
showed that the halo of the galaxy contained population II stars.
c.
showed that our galaxy contained spiral arms.
d.
used globular clusters to determine the location of the center of the galaxy.
e.
was completed by William and Caroline Herschel.
 

 14. 

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*
 

 15. 

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.
 

 16. 

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.
 

 17. 

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.
 

 18. 

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.
 

 19. 

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
 

 20. 

The orbits of population I stars

I.
are confined to disk of the galaxy.
II.
are very elliptical.
III.
are nearly circular.
IV.
are randomly inclined to the disk of the galaxy.
a.
I
b.
IV
c.
I & IV
d.
II & IV
e.
I & III
 

 21. 

The traditional theory for the formation of the Milky Way Galaxy suggests that the galaxy formed
a.
as material accreted around a massive black hole currently at the center of our galaxy.
b.
from a large cloud of material that formed stars and star clusters and slowly flattened to a disk..
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.
 

 22. 

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.
 

 23. 

Halo stars located in the disk are easy to detect because they
a.
are the only low mass stars in the disk.
b.
are only found in globular clusters.
c.
are primarily O and B supergiants.
d.
move at an angle across the disk.
e.
emit cosmic rays.
 

 24. 

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.
 

 25. 

An irregular 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.
 

 26. 

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.
 

 27. 

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
 

 28. 

The look-back time is
a.
how long the light from an object takes 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
 

 29. 

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.
 

 30. 

If H equals 50 km/sec/Mpc, then a galaxy with a radial velocity of 2000 km/sec probably has a distance of
a.
2050 Mpc
b.
1950 Mpc
c.
40 Mpc
d.
0.025 Mpc
e.
100,000 Mpc
 

 31. 

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
 

 32. 

We should expect galaxies to collide with each other fairly often because
a.
a galaxy's size is only a little smaller than the average distance between galaxies.
b.
galaxies contain large amounts of neutral hydrogen.
c.
galaxies occur in clusters.
d.
a and c
e.
none of the above
 

 33. 

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 the above are important in determining a galaxy's shape.
 

 34. 

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.
b.
the barred spiral galaxies.
c.
the dwarf elliptical galaxies.
d.
the irregular galaxies.
e.
the giant elliptical galaxies.
 

 35. 

_______________ 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
 

 36. 

_______________ 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
 

 37. 

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
 

 38. 

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.
 

 39. 

The _______________ is caused by gas and dust located in the disk of the Milky Way that absorbs light and doesn't allow us to see distant galaxies in line with the plane of the Milky Way.
a.
Dwingeloo
b.
zone of avoidance
c.
Large Magellanic Cloud.
d.
hot intercluster medium
e.
Virgo cluster
 

 40. 

The dark matter in galaxies has been hypothesized to be composed of
a.
neutral hydrogen clouds.
b.
dust particles.
c.
weakly interacting massive particles.
d.
H II regions.
e.
all of the above.
 

 41. 

Voids are
a.
regions in an elliptical galaxy where few clouds of gas and dust are found.
b.
regions in the Local Group where light from distant galaxies is blocked by gas and dust.
c.
regions in a cluster of galaxies where no spiral galaxies are found
d.
regions in the universe that separate the filaments of superclusters.
e.
regions swept clean by the hot intergalactic medium.
 

 42. 

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.
 

 43. 

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.
 

 44. 

The Great Wall
a.
is a filament of galactic superclusters.
b.
is a bridge of hydrogen stretching from the Milky Way to the Large Magellanic Cloud.
c.
is a structure in the Local Group composed of the most massive spiral galaxies.
d.
is formed by gas and dust in the disk of the Milky Way.
e.
is the result of a collision between three spiral galaxies.
 

 45. 

Most of the mass of a galaxy is
a.
contained in the massive O and B stars in the galaxy.
b.
contained in the H I regions of the galaxy.
c.
contained in the H II regions of the galaxy.
d.
contained in the dark matter of the galaxy.
e.
contained in the disk of the galaxy
 

 46. 

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?
a.
8.75sgc_exam_4_files/i0470000.jpg103 Mpc
b.
2.4sgc_exam_4_files/i0470001.jpg109 Mpc
c.
5.6sgc_exam_4_files/i0470002.jpg105 Mpc
d.
114 Mpc
e.
8.75sgc_exam_4_files/i0470003.jpg10-3 Mpc
 

Completion
Complete each sentence or statement.
 

 47. 

The center of our galaxy is believed to be occupied by the radio source known as _______________.
 

 

 48. 

The _______________ of the galaxy contains population I stars, open clusters, and gas clouds
 

 

 49. 

_______________ are groups of 100,000 to 1,000,000 population II stars firmly bound by gravity.
 

 

 50. 

The rotation curve of the galaxy provides evidence for the existence of the _______________ which extends beyond the halo of the galaxy.
 

 

 51. 

The units on the Hubble constant are _______________.
 

 

 52. 

_______________ clusters of galaxies contain closely spaced galaxies, and often contain giant elliptical galaxies and a hot intergalactic medium
 

 

 53. 

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.
 

 

 54. 

_______________ galaxies have a definite disk component; but contain no evidence of spiral pattern, few hot young stars, and little gas and dust.
 

 

True/False
Indicate whether the sentence or statement is true or false.
 

 55. 

Astronomers before Shapely underestimated the size of the Milky Way galaxy because they lacked large enough telescopes.
 

 56. 

Shapley found the distance to the center of the galaxy by studying the distance to open clusters.
 

 57. 

The disk of the Milky Way is approximately 20,000 ly in diameter.
 

 58. 

The rapid rotation in the outer disk suggests that our galaxy is more massive than previously thought.
 

 59. 

Old stars are poor in heavy atoms because there were no previous generations of stars.
 

 60. 

The disk of the galaxy is older than the halo.
 

 61. 

Spiral tracers tend to be old, luminous stars.
 

 62. 

Giant molecular cloud complexes are located in spiral arms.
 

 63. 

The density wave theory explains spurs and branches along the spiral arms.
 

 64. 

The center of our galaxy shows signs of past eruptions.
 

 65. 

Elliptical galaxies contain more gas, dust, and young stars than do Sa galaxies.
 

 66. 

Until recently, most astronomers thought elliptical galaxies were shaped like oblate spheroids.
 

 67. 

Cepheid variable stars are more luminous than the sun.
 

 68. 

The look-back time is numerically equal to the distance to a galaxy in light-years.
 

 69. 

The rotation curve method can be applied only to pairs of galaxies orbiting each other.
 

 70. 

Some large clusters of galaxies do not appear to contain enough mass to hold themselves together.
 

 71. 

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.
 

 72. 

When two galaxies collide, they pass through each other, and their stars almost never collide.
 

 73. 

When a large galaxy collides with a small galaxy, the smaller galaxy may be pulled apart by tidal forces.
 

 74. 

Poor clusters of galaxies often contain an excess of E and SO galaxies.
 



 
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