Astronomy – Final Exam
Summer 2011
Test form A
Name ________________________
Do not forget to write your name on your answer sheet and above as well, and fill in your
student ID bubbles and test form bubble A on your answer sheet. You have 120 minutes.
For each question, mark the best answer. The formulas you may want are:
F
GMm
d2
c = f
F = ma
c = 3108 m/sec
vrad shift  rest

c
rest
d
3.26 ly
p
P2 = a3
E = hf
(M + m) P2 = a3
P = knT
4
PeakT = 2900 Km
L = 4d2B
v = H0d
L T   R 
  

L  T   R 
2
H0 = 22 km/s/Mly
1. How is it possible that radio quasars, radio galaxies, and blazars might actually be
different aspects of the same phenomenon?
A) Objects may change over time: first a blazar, then a radio quasar, then a radio
galaxy
B) Not all of these objects have been observed at all wavelengths, and when we do
so we may discover they are all really the same
C) Some of these objects, being so distant from us, may be red shifted by varying
amounts
D) Their appearance may depend on what angle you look at them from, and
effectively we can only see any object at this distance from one angle
E) The gas and dust in our own galaxy may block certain wavelengths of light from
these objects
2. What has been going on with the expansion of the universe since it began?
A) It has always been decelerating, or slowing down
B) It has always been accelerating, or speeding up
C) It has always been going at approximately the same rate
D) Early on it was accelerating, now it’s decelerating
E) Early on it was decelerating, now it’s accelerating
3. In what sense is the cosmic distance ladder like a ladder?
A) The methods each work on only a certain horizontal branch of the H-R diagram,
so it looks like a ladder
B) Each method is getting better over time, much as a person slowly climbs a ladder
C) The method lets you get out into space, like a very tall ladder
D) The methods each work on only a very narrow band of distances, just as a
ladder’s rungs are skinny
E) Each method is like the rung of a ladder which must be used to reach the next
method, or rung on the ladder, until you get to the most distant methods at the top
4. Why in radio astronomy is it advantageous to use several telescopes, sometimes hundreds or even
thousands of kilometers apart?
A) This allows us to see large celestial objects, hundreds or even thousands of kilometers across
B) This allows one to get around the diffraction limit, allowing one to see smaller details of the
target
C) This allows one to compensate if there are clouds or interference at one site
D) This spreads the money among several congressional districts, increasing the chance of
getting funding
E) This allows one to image different sides of distant astronomical targets
5. During the protostar stage, a star gradually gets hotter and hotter. What is the source
of this heat?
A) Fusion of hydrogen to helium
B) Fusion of helium to carbon
C) Fusion of carbon to oxygen
D) Gravitational contraction; the star is shrinking and this is the source of heat
E) It isn’t really getting hotter, it is just gradually becoming more visible
6. What makes it harder to study the central portion of our galaxy than it is many other
galaxies?
A) Our galaxy has a lot of dust in it, very unusual for a spiral galaxy
B) Because we are within the disk, there is a lot of stuff between us and the center
C) The central portion of our galaxy is especially dim, making it hard to see
D) Because it is so close, we cannot take images of it all at once in our telescopes
E) We can use gravitational lensing to magnify the central portions of other galaxies,
helping us see them
7. Carlson stars have just been discovered! These highly variable stars can go brighter
or dimmer in as little as a millisecond. The fact that they vary so quickly tells us
A) They must be very small in size
B) They must not be very powerful
C) They must be some sort of white dwarf phenomenon
D) They must be undergoing nuclear fusion
E) They must be produced by alien civilizations
8. When we say the current temperature of the universe is about 2.72 K, what are we
referring to?
A) The temperature of the electromagnetic radiation (light) that pervades the
universe left over from early events in the universe
B) The temperature of the invisible background of neutrinos produced around the
time of nucleosynthesis
C) The average temperature of the dust that pervades the universe
D) The temperature averaged throughout all of space, including all the stars, empty
space, and everything else
E) The temperature to which an object would be heated by stars at an average
position in the universe
9. The four largest planets in our solar system are
A) Jupiter, Saturn, Earth, Venus
B) Jupiter, Saturn, Uranus, Neptune
C) Jupiter, Uranus, Neptune, Earth
D) Jupiter, Earth, Venus, Mars
E) Jupiter, Saturn, Uranus, Earth
10. The mass of the black hole at the center of our galaxy is probably around
A) 5 times Earth
B) 12 times Jupiter
C) 1/3 the Sun
D) 40 times the Sun
E) 4 million times the Sun
11. Which of the following is not a type of electromagnetic radiation?
A) X-rays
B) Neutrinos C) Ultraviolet D) Radio
E) Microwaves
12. The shape of the universe is now known to be
A) Definitely closed
B) Definitely open
C) Flat, or very close to flat
D) Open or flat; we can’t tell which, but definitely finite in size
E) We have no idea what the shape of the universe is
13. Why is there so much emphasis in astronomy these days on putting detectors of all
types (X-ray, gamma ray, microwave, infrared) in space?
A) This avoids the blocking of the atmosphere
B) It allows them to operate continuously, not just at night
C) This allows them to function at lower temperatures, where they are more efficient
D) This gets them closer to the objects they are looking at
E) This prevents them fro getting embroiled in political questions, since they are on
no one’s territory
14. For elliptical galaxies, how can we estimate the mass that is spread out in the halo?
A) Estimate the number of stars, and multiply by the mass of an average star
B) Measure the rotation rate of stars going around the galaxy
C) Study the hot gas emitting X-rays from the halo
D) Put it on a scale and weigh it
E) Measure the gravitational red shift from light coming deep in the heart of the
galaxy
15. What planet has liquid water on its surface, besides Earth?
A) Mars
B) Venus
C) Mercury
D) Saturn
E) There is no planet besides Earth with liquid water on its surface
16. In the many worlds interpretation of quantum mechanics, what happens when we
perform a measurement of something that is quantum mechanically probabilistic?
A) The system being measured was in a definite state, but we don’t know what it is
until we measure it, and the many worlds collapse into one
B) The system being measured is in an indefinite state, many possibilities existing
together, until we measure it and suddenly only what we measure exists.
C) The system being measured is in an indefinite state, and as we measure it we end
up in an indefinite state, effectively there are then many worlds which don’t
interact
D) The universe is already in an infinite number of worlds, and the outcome will
depend on which of these many worlds you are in
E) The fabric of spacetime gets ripped apart creating many worlds
17. Often behind a cluster of galaxies can be seen several galaxies with identical spectra
and other similar properties, such as identical quasars. Why does this occur?
A) The gravitational attraction of the cluster has caused several similar objects to
appear together behind it
B) Since a cluster defines a direction in space, and since objects that are similar tend
to be together, this isn’t really surprising
C) The background objects actually have very different spectra, but the foreground
cluster filters the light and makes all their spectra look the same
D) The huge gravity of the cluster causes objects actually IN the cluster to look like
they are behind it, because of their erroneous red shift
E) The cluster acts as a gravitational lens, causing several images of a single
background object to appear near each other
18. Star X is a main sequence star. It is the same spectral type (G2) as the Sun. What
does this tell us about how star X compares to the Sun?
A) It will have about the same temperature, luminosity, and radius
B) It will have about the same temperature and luminosity, but not necessarily the
same radius
C) It will have the same temperature, but not necessarily the same luminosity nor
radius
D) It will have the same luminosity, but not necessarily the same radius nor
temperature
E) This gives us no information about its temperature, luminosity nor radius
19. In which part of our galaxy can you find open clusters of stars?
A) The disk
B) The halo C) The nucleus D) The bulge
E) The corona
20. Who is credited with arguing that objects that are moving continue moving in a
straight line at constant speed?
A) Newton
B) Galileo
C) Einstein
D) Kepler
E) Tycho Brahe
21. I am standing on the Earth, and the Earth pulls down on me with a gravitational force
of about 195 lbs. (about 869 N). I also pull gravitationally on the Earth. How does
my gravitational pull on the Earth compare with the Earth’s pull on me?
A) My pull on the Earth is bigger
B) The Earth’s pull on me is bigger
C) My pull on the Earth is exactly the same as the Earth’s pull on me
D) The relative strength cannot be known without knowing the mass of the Earth
E) The relative strength cannot be known, even if we knew the mass of the Earth
22. Which of the following is NOT true of our galactic bulge?
A) It consists mostly of older stars
B) It contains little gas or dust
C) It looks more “blue” compared to the spiral arm “red”
D) It is currently believed to have a “bar” shape, rather than being round
E) Actually, all of these ARE true about the bulge
23. The Sun will end its life as a
A) Neutron star B) Black hole C) Pulsar
D) White dwarf E) Dark matter
24. Which of the following methods allows us to measure the distance to nearby galaxies
A) Radar distancing (only)
B) Cepheid variable stars (only)
C) Parallax (only)
D) Cepheid variable stars and Parallax, but not radar distancing
E) Radar distancing, Cepheid variable stars, and parallax
25. What is at the core of a double shell-burning star?
A) Inert hydrogen, not doing anything
B) Hydrogen fusing to helium
C) Inert helium, not doing anything
D) Helium fusing to carbon and oxygen
E) Inert carbon and oxygen, not doing anything
26. How luminous are the most luminous nuclei of active galaxies?
A) Thousands of times brighter than the Sun
B) Millions of times brighter than the Sun
C) Billions of times brighter than the Sun
D) About as bright as our entire galaxy
E) Thousands of times brighter than our entire galaxy
27. About which of the following eras do we have the least information, and really can
only speculate?
A) When the first galaxies and stars formed
B) Nucleosynthesis – when simple nuclei were made
C) Recombination – when electrons combined with atoms
D) Proton/neutron freezeout, when the ratio of protons to neutrons was fixed
E) The Planck era – when gravity and the other forces were one
28. Based on our best estimate, including uncertainties, how many intelligent
civilizations besides our own should there be in our galaxy?
A) 0
B) 1-10 C) 30-300
D) 30,000- 1 million E) We don’t know
29. The reason it is hotter in the summer than the winter is because
A) The Sun is closer to the Earth in summer
B) The Sun shines down more directly in the summer, thanks to the tilt of the Earth
C) There are fewer clouds in the summer to block the light
D) The Sun’s luminosity increases in the summer
E) Earth’s atmosphere is more transparent in the summer
30. Fusion in the Sun converts ______ into ________ .
A) Hydrogen, carbon
B) Hydrogen, oxygen
C) Hydrogen, helium
D) Helium, carbon
E) Helium, oxygen
31. Which technique allows us to actually measure how fast the universe was expanding
in the distant past?
A) Comparing current measurements of Hubble’s constant to those taken in the early
20th century
B) Using white dwarf supernovae and comparing the red shift vs. the distance for
very distant objects
C) Looking at the sizes of galactic clusters in the past compared to now
D) Comparing the spectra of stars at high Doppler shift to those now
E) Studying the masses of very early superclusters via gravitational lensing
32. The candy bar I gave you with this exam has
the same name as our
A) Stellar cluster
B) Galaxy cluster
C) Stellar system
D) Galaxy supercluster
E) Galaxy
33. If we look at a galaxy that is 500 million
light years away, what does this tell us?
A) What it looks like today
B) What it looked like very recently, but not
today
C) What it looked like approximately 500
million years ago
D) What it looked like near the beginning of
the universe
E) None of the above are correct
34. If I wanted to increase the gravitational force of the Earth on the Moon by a factor of
four, make it four times stronger, I could
A) Double the mass of the Earth
B) Double the mass of the Moon
C) Double the mass of the Earth and the Moon
D) Double the distance between the Earth and the Moon
E) Quadruple the distance between the Earth and the Moon
35. Which of the following is believed to have a thin layer of ice with a liquid ocean underneath?
A) Titan
B) Triton
C) Europa
D) Io
E) Ganymede
36. Which of the following factors do we have at least some idea of in our calculation of
Drake’s equation, the number of intelligent species in the galaxy?
A) The rate at which stars form in the galaxy (only)
B) The probability of a star having planets (only)
C) The probability of life appearing on a suitable planet (only)
D) A and B, but not C
E) A, B, and C are all true
37. Which of the following is made primarily of water ice?
A) The planet Venus
B) The rings of Saturn
C) Jupiter’s moon Io
D) The asteroid Ceres
E) Mars’ moon Phoebe
38. Which of the following was generally accepted by ancient astronomers, before
Copernicus?
A) The Earth is a sphere (only)
B) The Moon goes around the Earth (only)
C) The Earth goes around the Sun (only)
D) A and B were accepted, but not C
E) A, B, and C were all accepted
39. What is the best evidence that our galaxy contains far more mass in dark matter than
visible, and this matter is not concentrated at the center?
A) Rotation curves, measured by studying the 21 cm line of hydrogen
B) X-ray measurements, which show a slight glow coming from the entire halo
C) Sudden changes of the orbits of halo stars, caused by its gravitational influence
D) The high rates of star formation and supernovae in the halo
E) Gravitational lensing from the dark matter of globular clusters
40. What factor is the primary determinant in how long a star will live?
A) Helium: The more helium it starts with, the shorter it lives
B) Helium: The more helium it starts with, the longer it lives
C) Mass: The more mass it has, the shorter it lives
D) Mass: The more mass it has, the longer it lives
E) No single factor dominates; there are many contributing factors
41. There was a total lunar eclipse (not visible to us) in mid-June, and another later in the
year. When is it most likely this other eclipse will be?
A) August
B) September C) October
D) November E) December
42. I am on a moon. There is a river nearby, but it is much too cold for water to flow. Through
the hazy atmosphere, I can just make out the planet
A) Mars
B) Uranus
C) Neptune
D) Saturn
E) Jupiter
43. From which of the following is it impossible for anything to escape, even light?
A) Black hole (only)
B) Neutron star (only)
C) White dwarf (only)
D) Black hole or neutron star, but not a white dwarf
E) Black hole, neutron star, or white dwarf
44. What planets has the largest valley in the Solar System?
A) Jupiter
B) Neptune
C) Earth
D) Mars
E) Venus
45. Which of the following is currently not well explained by the big bang theory?
A) Why the fraction of helium in the early universe is around 25% by mass
B) Where the cosmic microwave background comes from
C) What is the approximate current age of the universe
D) What is the nature of dark energy
E) Actually, all of these are explained by the big bang theory
46. Besides dimming their light, what other effect does dust have on the appearance of
stars?
A) It makes them appear bluer
B) It makes them appear redder
C) It causes a Doppler shift, making them look like they are moving away from us
D) It causes a Doppler shift, making them look like they are moving towards us
E) It blurs them, so they no longer look like sharply defined objects
47. Not counting our own galaxy, how many other galaxies comparable in size to our
own are there (more than 10% our galaxy in luminosity) in the Local Group?
A) 0
B) 1-2
C) 5-20
D) 50-100
E) 1000+
48. Carbon dioxide is being produced in huge quantities here on Earth. What effect does this
have on the Earth?
A) It causes global warming, increasing temperature
B) It is poisonous to plants
C) It is poisonous to animals
D) It causes increased ultraviolet radiation to penetrate our atmosphere
E) It ultimately causes our atmosphere to boil away into space
49. According to the inflation hypothesis, why is it that distant points in the universe are
almost exactly the same temperature?
A) Since inflation occurred everywhere in the same way, it was natural that it would
lead to uniform temperatures
B) Inflation allowed heat to be transported from one part of the universe to another,
making them uniform temperature
C) Inflation took points that initially were at almost the exact same place, where they
could reach the same temperature, and transported them to distant points
D) Inflation predicts that any temperature variations are wiped out by quantum
fluctuations as they get expanded
E) Inflation does nothing to explain this “horizon problem”
50. Why don’t we use radar distancing for the most distant objects in our universe?
A) Radar distancing is not very precise, so we use more accurate methods
B) This is the region where active galaxies are common, which create a similar
signal
C) The corrections for Doppler shift become prohibitively large at this distance
D) The reflected signal would be too weak and would take too long for this method
to work
E) The distance to these objects is not that interesting, so no one has done it
51. During which of the following stages is a star not undergoing any kind of fusion?
A) Red giant
B) Protostar
C) Core helium burning
D) Double shell burning
E) All of these have some sort of nuclear fusion going on
52. Which of the forces of nature can change protons to neutrons and vice versa?
A) Strong force B) Weak force C) Electromagnetism D) Gravity E) Higgs
53. Which of the following does NOT normally occur when two or more galaxies
collide?
A) Clouds of gas in each galaxy collide
B) Individual stars in each galaxy collide
C) The galaxies may have their shape disrupted
D) One galaxy may “eat” the other and add its stars to its own
E) The gas in the galaxies may be heated to high temperatures
54. Spiral arms are believed to be a phenomenon of galaxies caused by
A) Winding – an initially straight line of stars gets wound into a spiral as the galaxy
rotates
B) Stellar formation fronts – regions of star forming create pressure waves that
propagate around the galaxy, forming spiral structure
C) Extraction – the gravitational attraction of nearby galaxies pulls out and then
winds up the spiral arms
D) Density waves – high density regions have gravitational effects that cause them to
propagate around the galaxy, causing star formation and making the arms
E) Illusion – Light from the center of the galaxy is perturbed by gravitational
influences, distorting a nearly spherical shape to make it look like a spiral
55. The actual total value of  includes
A) Only ordinary matter
B) Only dark matter
C) Only dark energy
D) All of the above
E) None of the above
56. The total diameter of the disk of our galaxy is about
A) 1,000 AU B) 100,000 AU C) 1,000 ly D) 100,000 ly E) 10,000,000 ly
57. What do the methods of spectroscopic parallax, main sequence fitting, Cepheid
variable stars, and white dwarf supernovae have in common?
A) They are all usable on the largest of scales in the universe
B) They all rely on main sequence stars to make them work
C) They all are standard candle methods that rely on an object having consistently
the same luminosity
D) They all rely exclusively on the spectrum of the target to make their predictions
E) They all can be used within the solar system to accurately measure distance
58. When two galaxies of equal size collide, under what circumstance would we expect
the greatest disruption of the two galaxies?
A) If they are both elliptical
B) If they are both spiral
C) If they are both irregular
D) If they collide at high speeds
E) If they collide at low speeds
59. Where are most Kuiper belt objects compared to the planets?
A) They are much closer than Mercury
B) They are between the orbits of Mars and Jupiter
C) They are between the orbits of Earth and Mars
D) They are between the orbits of Jupiter and Saturn
E) They are farther away than Neptune
60. If you wanted to measure the distance to a very distant galaxy using Hubble’s Law,
the first step would be to
A) Measure the spectrum of the galaxy so you can get its Doppler shift
B) Measure the position of the galaxy compared to the background over the course of
a year
C) Measure the brightness of the galaxy
D) Search for white dwarf supernovae in the galaxy
E) Buy a really long tape measure from the hardware store
61. Which of the following is NOT a standard classification of galaxies?
A) Spiral
B) Barred Spiral
C) Elliptical
D) Spindle E) Irregular
62. As viewed from the local group of galaxies, the rest of the universe is expanding
away from us, with a speed proportional to distance. What does it look like if we
viewed things from some distant group or cluster?
A) It would look exactly the same, with everything expanding away
B) You would see everything contracting towards you
C) Other galaxies would look stationary to you
D) Nearby objects would be moving towards you, distant objects would be moving
away
E) Nearby objects would be moving away from you, distant objects would be
moving towards
63. Where do elements like iron come from?
A) They were produced in the big bang during nucleosynthesis
B) Mostly low mass stars, which recycle their gas during the planetary nebula stage
C) Supernovae (both types) which explode and send gas out to be recycled
D) Nova, which involve massive explosions on the surface of white dwarfs
E) X-ray binaries, which produce iron in the high density neutron star environment
64. The most common component of the protoplanetary disk from which the Solar System
formed was
A) Hydrogen and helium gas
B) Rock
C) Metal
D) Water ice
E) Ammonia and methane
65. What is the best way to detect molecular clouds in our galaxy or other galaxies?
A) Light from the stars forming in them
B) The 21 cm line coming from the spin reversal of the electron in hydrogen
C) Radio waves coming from various molecules like carbon monoxide
D) X-rays caused by collision of the ions making up the molecular cloud
E) Infrared light emitted by dust in the cloud
66. What is the difference between the various types of spiral galaxies – Sa, Sb, Sc, and
Sd?
A) Sa have tight, short spiral arms; Sd have long, loose spiral arms
B) Sa have long, loose spiral arms; Sd have tight, short spiral arms
C) Sa consist primarily of young stars; Sd primarily of old stars
D) Sa consist primarily of old stars; Sd primarily of young stars
E) Sa have more spherical bulges; Sd more bar-shaped bulges