Astronomy 3 Dr. Turner Name ______________________
June 14, 1996 Section ______________________
Final Exam
Use a #2 pencil; make marks clean and dark. Be sure to bubble in your name, ID#, and form on the answer
sheet; and write your name and section (TA name or time) on both test form and answer sheet. Matching means
each answer in the section is used once and only once; identify does not. Read all choices carefully; choose the
best answer.
Motions in the sky; gravity
Use the following diagram to answer the next questions. Note that not all of the sky is depicted here, only the
southern half.
1. What is the time of day, approximately?
A. noon
B. 6 am
C. 6 pm
D. midnight
2. Where might Mercury be? Use letters on diagram, or:
A. not shown
3. Where is the North Pole? Use letters on diagram, or:
A. not shown
4. The diagram represents the sky a couple of days after an eclipse. What type of eclipse was it?
A. solar
B. lunar
5. There are a number of problems with this diagram. Which of the following is NOT a problem with the
diagram? (i.e., is correctly depicted)
A. Saturn is far from the zodiac.
B. The crescent of the moon should face the sun, not away from it.
C. Venus is farther than 48 away from the sun.
D. The sun does not belong on the ecliptic.
E. Polaris should not be so close to the ecliptic.
6. Because of the motion of the sun through the zodiac, each day the sun rises .
A. the same time as the day before.
B. later than the day before.
C. earlier than the day before.
7. Which of the following is not a constellation?
A. Libra
B. Rigel
C. Scorpio
D. Pisces
E. Aquarius
8. Which city has the greatest number of daylight hours on June 21?
A. Sydney, Australia (latitude -34)
B. Anchorage, Alaska (latitude 62)
C. Los Angeles (latitude 34)
D. Paris, France (latitude 49 )
E. Honolulu, Hawaii (latitude 23 )
9. The moon's mass is only 1/81 times the mass of the earth. The gravitational force that the earth exerts
on the moon is times the gravitational force that the moon exerts on the earth.
A. 1
B. 6600 (81^2)
C. 81
D. 0.0002 (1/812)
E. 0.0123 (1/81)
10. A weather satellite is orbiting the earth in geosynchronous orbit (24 hr orbit). Would the astronauts on
the shuttle be able to carry out a repair on the satellite in orbit, as they did for HST, or is the satellite at too
high an altitude or too low an altitude for the shuttle to reach? (The shuttle is moving at a speed that carries
it around the earth once every 90 minutes)
A. the satellite is just the right altitude, astronauts can fix it
B. the satellite is too low to fix
C. the satellite is too high to fix
D. the satellite is at the right altitude for the shuttle to fix, but the shuttle moves too fast to rendevous
with it
Light and telescopes
11. Which are the bluest photons?
A. x-rays
B. radio
C. optical
D. infrared
E. ultraviolet
12. Which photons refract the most? (answers above)
What optical property is responsible for the operation of the following?
13. Newton's telescope
14. prism
15. eye
A. reflection
B. refraction
C. diffraction
16. What is the most important function of a telescope?
A. Magnification
B. Light gathering.
C. Resolution.
17. To produce an emission line, an electron in an atom must
A. jump down in energy level.
B. jump up in energy level.
C. stay and vibrate in the same energy level.
D. leave the atom completely.
Identify the type of spectrum produced by each of the following objects.
18. The optical spectrum of the Andromeda Nebula
19. Betelgeuse
20. Diffuse gas in the Milky Way
A. Continuous
B. Dark line
C. Bright line
What color (wavelength of peak intensity) are each of the following?
21. K star with a surface temperature of 5000 K
22. O star with a surface temperature of 30,000 K.
A. Ultraviolet (1000 )
B. Blue (3000 )
C. Yellow-orange (6000 )
D. Red (9000 )
E. Infrared (150,000 )
The planets
23. Which of the following lunar features was primarily caused by lava flows?
A. highlands
B. craters
C. maria
D. mountains
24. Why does Venus's atmosphere consist largely of carbon dioxide, while the Earth's is mostly nitrogen?
A. On Earth, carbon dioxide dissolved in the oceans, and also in sedimentary rock; this did not happen
on Venus.
B. Plant life on Earth produced the nitrogen and oxygen; Venus has had no plant life.
C. Venus atmosphere is too cold to generate nitrogen and oxygen in the CNO cycle.
D. Earth is too warm and too small to hang onto carbon dioxide.
E. None of the above: both Venus and Earth have atmospheres dominated by carbon dioxide.
25. The mean densities of the planets with increasing distance from the sun.
A. Decrease.
B. Increase.
26. Is this coincidental, or not, and why?
A. Not coincidental. The denser, more massive planets are generally found farther from the sun because
the more massive planets are accelerated less than the lighter planets by the sun's gravity; therefore they
are found farther away from the sun.
B. Not coincidental. The closer planets have higher densities because the sun vaporized the light
elements from them as the solar system was forming, leaving the heavy elements.
C. Coincidental. The density of a planet is not related to its distance from the sun.
27. Icy, massive, low density, hydrogen & helium: are these more characteristic of terrestrial or Jovian
planets?
A. Terrestrial
B. Jovian
28. If a planet has a dipole magnetic field, what must be true?
A. It is a Jovian planet.
B. It must have a rocky, magnetized surface.
C. Its spin axis is oriented at an angle to its magnetic axis.
D. It has a molten core, and it rotates fairly rapidly.
E. It is a terrestrial planet.
29. Which of the following is not true about a comet?
A. Comets have two tails.
B. Part of the tail is gaseous.
C. Part of the tail is dusty.
D. The tail gets brighter as the comet approaches the sun.
E. The entire tail points behind the comet, opposite to its direction of motion.
30. Where do comets come from?
A. The asteroid belt.
B. A second ring of asteroids just beyond Pluto.
C. The Oort cloud, which extends to 50,000 A. U. from the sun.
D. Chunks of Saturn's rings that have been kicked out of orbit by Jupiter's pull.
31. The average density of the sun is
A. near that of water (1.0 gm/cm3)
B. near that of the moon (3.5 gm/cm3)
C. near that of Earth (5.5 gm/cm3)
D. near that of lead (11.4 gm/cm3)
32. The temperature of the center of the sun is roughly
A. 10^4 K
B. 10^5 K
C. 10^6 K
D. 10^7 K
E. 10^8 K
33. If the sun obtained its energy from gravitational collapse rather than fusion reactions, the source of this
energy would be
A. kinetic energy to heat
B. electromagnetic energy to heat
C. weak and strong force energy to heat
D. potential energy to heat
34. How long does it take for the energy generated in the sun's interior to make it out to the sun's surface?
(Not the neutrinos they don't interact with anything so they won't deliver energy, within the solar system
anyway.)
A. 2 seconds
B. 8 minutes
C. 11 years
D. 10^5 -10^6 years
35. The main sequence lifetime of the sun is
A. 300,000 years.
B. 1,000,000 years.
C. 10 million (10^6) years.
D. 1 billion years.
E. 10 billion (10^9) years.
36. Why does fusion only take place at very high temperatures?
A. High temperatures and pressures are required to confine the hydrogen plasma so that fusion can take
place.
B. High temperatures mean high collisional velocities, which can allow protons to overcome their mutual
electrical repulsion.
C. High temperatures produce bluer, more energetic photons that are required to initiate the fusion
reaction sequence.
D. Gamma rays, a product of fusion reactions, can only exist at very high temperatures.
37. The distance to the nearest star (other than the sun) is about
A. 0.001 parsec.
B. 1 parsec.
C. 10 parsecs.
D. 100 parsecs.
E. 105 parsecs.
38. a Centauri A, one of the closest stars, is a main sequence G star. Yet even though a Centauri A is a
fairly bright naked-eye star, it is 1010 times fainter than the sun. How far away is a Centauri A?
A. 10^20 A.U., or 10^15 parsecs
B. 10^10 A.U., or 10^5 parsecs
C. 10^5 A.U., or 1 parsec
D. 10 A.U.
E. 1 A. U.
39. What do you call the technique you just used to get the distance to a Centauri A?
A. Kepler's third law
B. trigonometric parallax (or plain "parallax")
C. Doppler shift
D. spectroscopic parallax
40. What is the correct order of the spectral sequence from bluest stars reddest stars?
A. O N R S A B F G K M
B. O B A F G K M R N S
C. O B A F G K N M R S
D. S N R M K G F A O B
E. M S N R K G F A B O
41. The differences in stellar spectra leading to the spectral sequence are primarily due to differences
among the stars in
A. radius.
B. distance.
C. luminosity.
D. surface temperature.
E. chemical composition.
42. Hydrostatic equilibrium in stars is the balance between
A. thermal pressure and gravity.
B. the strong and weak nuclear forces.
C. gravity and centrifugal force.
D. the forces of the earth and sun on each other.
E. the gravitational forces between two binary stars.
43. Very faint stars with very high surface temperatures
A. are redder in color than the sun.
B. have diameters comparable to that of the sun.
C. have diameters large compared to the sun.
D. have small diameters compared to that of the sun.
44. Capella is a G star with an intrinsic luminosity 100 times that of the sun, or 100 L0. How big is
Capella, in units of solar radii?
A. 0.01 R0
B. 0.1 R0
C. 1 R0
D. 10 R0
E. 100 R0
45. A red giant has the same surface temperature as a main sequence M star, but emits 10,000 times as
much energy (luminosity). It therefore has spectral type:
A. xO
B. xB
C. xA
D. xG
E. xM
46. Main sequence O stars are thousands of times more luminous than main sequence G stars. Why?
A. They are more massive: the greater gravitational force causes higher internal pressures and
temperatures, and the higher the internal temperature, the faster fusion proceeds, hence more luminosity.
B. The core of the O star is pure helium and cannot support itself against gravity, so the core slowly
contracts and heats, causing fusion to proceed faster in the hydrogen-burning shell.
C. They are more massive, and their sole source of energy is from the conversion of gravitational
potential energy into heat: since they are so much bigger than G stars they are much more luminous.
47. Which of the following represents the approximate range of stellar masses?
A. all stars have roughly the same mass
B. 1.0 to 10 M0
C. 0.1 to 10 M0
D. 0.08 to 100 M0
E. 0.001 to 200 M0
48. The quantity that determines a star's central pressure and temperature is
A. luminosity.
B. surface temperature.
C. chemical composition.
D. radius.
E. mass.
Stellar Evolution
49. Stars evolve because of changes in
A. mass of the star.
B. luminosity of the star.
C. chemical composition of the core.
D. chemical composition of the surface.
E. surface temperature.
Use the H-R diagram below to answer the following questions.
50. Which star has the largest radius?
51. An object that is not presently undergoing thermonuclear reactions
52. A star burning helium in its core
53. A hydrogen-shell burning star
54. Which star is most likely to end its nuclear lifetime as a supernova?
55. The star with the shortest lifetime?
A. Spica
B. Capella
C. Sirius B
D. Sirius A
E. Betelgeuse
56. Which star could be nearly as old as the universe?
A. Spica
B. Sirius A
C. Betelgeuse
D. Capella
E. Proxima Centauri
57. Which of the following pairs of stars do not have the same surface temperature?
A. Sirius A and Sirius B
B. Spica and Betelgeuse
C. Betelgeuse and Proxima Centauri
D. Sun and Capella
58. A planetary nebula is
A. an expanding gas cloud that was ejected by a red giant star.
B. a collapsing gas cloud out of which planets will form.
C. the cloud of gas blown off by protostar.
D. a gas cloud which goes into the formation of red giants.
59. The end state of a one solar mass star is a
A. neutron star.
B. pulsar.
C. black hole.
D. main sequence star.
E. white dwarf.
60. A neutron star has a radius the size of
A. the sun's radius.
B. a large city.
C. the earth's radius.
D. the orbit of the earth.
61. High mass stars evolve more quickly than low mass ones because the high mass stars
A. are larger.
B. have higher core densities.
C. are made of more massive elements.
D. have higher energy outputs.
E. are in the lower right corner of the H-R diagram.
62. In the most massive stars, the heaviest element that will be produced in the core through fusion is
A. helium
B. iron
C. oxygen
D. silicon
E. uranium
63. Red giant/Asymptotic Giant Branch stars are
A. hydrogen core burning stars
B. shell burning stars
C. helium core burning stars
D. pre-main sequence stars
E. main Sequence Stars
64. A star which has a main sequence mass of 810 M0 will most likely end up as
A. a white dwarf.
B. a black hole.
C. a brown dwarf.
D. a neutron star.
65. The surface temperature of a brown dwarf is very low, possibly about 1000 K. What is the best part
of the spectrum to use to look for a brown dwarf?
A. X-rays
B. optical
C. radio
D. ultraviolet
E. infrared
66. You want to observe a black hole. What type of object gives you the best chance at detecting it?
A. HII region
B. binary star system
C. spiral arm
D. planetary system
E. planetary nebula
67. In what wavelength region of the spectrum does emission from a black hole appear?
A. X-rays
B. radio waves
C. infrared waves
D. microwaves
68. What is the Schwarzschild radius?
A. The radius of a neutron star.
B. The radius of a white dwarf star.
C. The radius measured out to the photosphere of the sun.
D. The radius of the solar corona.
E. The radius of a black hole (within which nothing can escape).
Identify the following as being associated with either general relativity (A) or special relativity (B) or neither
(C).
69. The speed of light is a constant in a vacuum.
70. Nothing can go faster than the speed of light.
71. Inertial mass is the same as gravitational mass.
72. E=mc2
73. Gravitational lensing.
74. How was Einstein's theory of relativity confirmed by Sir Arthur Eddington in 1919?
A. Eddington measured the speed of light to be 186,000 miles/sec by shooting light beams between two
mountaintops and measuring their arrival times.
B. He measured the locations of stars near the sun during an eclipse and showed that the light from them
was bent due to the sun's gravity.
C. He produced the first fusion reactions in his Cambridge laboratory and verified that E=mc2.
D. He showed that all objects at the earth's surface fall at 9.8 meters/sec2.
75. What is a major difference between Newton's theory of gravity and Einstein's?
A. In Einstein's theory, gravity can be repulsive as well as attractive; thus it is identical in form to the
electromagnetic force.
B. Einstein found that gravity causes a warp in the geometry of space-time that can be felt by massless
particles, including photons.
C. Einstein came up with a more precise value of the gravitational constant G.
D. Einstein showed that photons have masses.
76. What happens to a neutron star that is formed with a mass greater than about 3 M0?
A. It becomes a pulsar.
B. It blows off its outer layers forming a planetary nebula and becomes a red dwarf star.
C. It evolves to the Asymptotic Giant Branch.
D. Its Schwarzschild radius is bigger than its physical radius and it becomes a black hole.
E. It becomes a white dwarf star.
Identify the method by which the following groups of elements are produced.
77. Gold, copper, silver, uranium
78. Oxygen, magnesium, iron
79. Hydrogen
80. Helium, carbon, but nothing heavier
A. Main-sequence nucleosynthesis
B. Low mass post-main sequence nucleosynthesis
C. High mass post-main sequence nucleosynthesis
D. Supernovae
E. Big bang
81. It takes light how long to travel from the nearest galaxy to us?
A. minutes
B. days
C. years
D. centuries
E. millions of years
82. Our solar system is located within
A. the galactic nucleus.
B. the galactic halo.
C. the galactic disk.
D. none of the above; the solar system is not located within a galaxy.
83. In a cluster 89 billion years old, which of the following types of stars would NOT be found on the
main sequence?
A. A
B. G
C. K
D. M
84. The oldest objects in the Milky Way are located
A. near the sun.
B. in the spiral arms.
C. in the halo.
D. in the galactic center.
True or false: Spiral arms are most easily seen in the following objects ("tracers"):
85. O and B stars
86. 21 cm line of hydrogen gas
87. red main sequence stars
88. globular clusters
89. Spiral arms in a disk-shaped galaxy are caused by a process most similar to which of the following:
A. Spiral patterns painted on a phonograph record, which is spinning
B. Sports fans doing "the wave" in a stadium
C. A whirling octopus
90. The disk-like shape of the Milky Way provides evidence that the early galaxy
A. rotated.
B. was a strong X-ray emitter.
C. had a high temperature.
D. had a strong magnetic field.
E. had a high abundance of heavy elements.
91. Kepler's third law as modified by Newton is generally usd to find a galaxy's
A. distance.
B. velocity.
C. rotation speed.
D. radius.
E. mass.
92. Which of the following is a member of the "Local Group"
A. Betelgeuse
B. the Orion Nebula
C. Pisces
D. the Andromeda Nebula
E. x3C273, a quasar
93. Which of the following is likely to be the oldest object in the Milky Way?
A. an O star
B. a red giant star.
C. a globular cluster.
D. a neutron star.
E. our solar system.
94. Cepheid or RR Lyrae variable stars are important to astronomy primarily because they allow us to
determine stellar
A. mass.
B. distance.
C. temperature.
D. pulsation period.
E. chemical composition.
95. Possible energy sources for quasars and other active galaxies are
A. stellar explosions.
B. neutron star clusters.
C. central supermassive black holes.
D. electron collisions.
Cosmology
96. If galaxy A is 9 times farther away than galaxy B, the velocity of galaxy A is the velocity of galaxy
B.
A. the same as
B. 3 times larger (faster) than
C. 9 times larger (faster) than
D. 3 times smaller (slower) than
E. 9 times smaller (slower) than
97. The temperature of the cosmic microwave background is approximately
A. 3 K
B. 10 K
C. 30 K
D. 100 K
E. 1000 K
98. The wavelength of peak intensity of the cosmic microwave background radiation is determined by
A. the temperature of the hot gas at the time of recombination in the first few hundred thousand years of
the universe
B. the redshift of the gas at the time of recombination
C. the wavelength of the hydrogen alpha emission (Ha) line, which dominates the emission from the
early universe because hydrogen is very abundant
D. both A. and B.
99. The cosmic microwave background radiation was caused by
A. the universe not long after the Big Bang.
B. the formation of galaxies.
C. the formation of stars in the early universe.
D. the formation of planets in the early universe.
E. the formation of supernovae in the early universe.
100. A better knowledge of which of the following would most aid us in determining whether the universe
is open or closed?
A. The age of the earth.
B. The age of the solar system.
C. The distance to the Andromeda Galaxy.
D. All of the above would help about equally.
E. The average density of the universe.
101. If present data is correct, the universe will
A. stop its expansion and contract, but then may explode again.
B. expand forever, at constant velocity.
C. expand forever but slowly approaching zero velocity.
102. The reason the Hubble constant yields only a maximum age for the universe and not the true age is
because:
A. the universe is decelerating, but we don't know how fast it is decelerating.
B. the universe is really static (not moving).
C. the universe is accelerating, but we don't know how fast it is accelerating.
103. When we observe distant galaxies we are observing galaxies when they are
A. approximately the same age as the Milky Way.
B. very young.
C. very old.
D. just galaxies; no statement can be made about age.
104. Which of the following is NOT observational evidence in favor of the Big Bang?
A. The fact that small, irregular galaxies outnumber large spirals and ellipticals in the present universe.
B. The Hubble law.
C. The fact that the composition of the universe is 30% helium by mass, and nearly all the rest is
hydrogen.
D. The cosmic microwave background radiation.
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