Essential Cosmic Perspective 7th Edition By Bennett Test Bank

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Essential Cosmic Perspective 7th Edition By Bennett Test Bank

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WITH ANSWERS
Essential Cosmic Perspective 7th Edition By Bennett Test Bank

chapter 2

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Which of the following statements about the celestial equator is true at all latitudes?
A) It extends from your horizon due east, through your zenith, to your horizon due west.
B) It represents an extension of Earths equator onto the celestial sphere.
C) It extends from your horizon due north, through your zenith, to your horizon due south.
D) It lies along the band of light we call the Milky Way.
E) It cuts the dome of your local sky exactly in half.
1)
2) When we look into the band of light in our sky that we call the Milky Way, can we see distant
galaxies? Why or why not?
A) No, because the stars, gas, and dust of the Milky Way block us from seeing them.
B) Yes, there are many other galaxies that we see inside the Milky Way.
C) Yes, they appear as small, fuzzy patches on the other side of our galaxy.
D) No, because there are only galaxies above and below the plane of the Milky Way.
2)
3) If it is midnight in New York, it is
A) midnight everywhere.
B) daytime in Sydney, Australia.
C) midnight in Los Angeles.
D) midnight in Sydney, Australia.
E) midday in Rio de Janeiro, Brazil.
3)
4) How many arcseconds are in one degree?
A) 100 B) 10,000 C) 3,600 D) 60 E) 360
4)
5) What is a circumpolar star?
A) a star that is close to the north celestial pole
B) a star that is close to the south celestial pole
C) a star that is visible from the Arctic or Antarctic circles
D) a star that always remains above your horizon
E) a star that makes a daily circle around the celestial sphere
5)
6) Which of the following statements about circumpolar stars is true at all latitudes?
A) They make relatively small circles, traveling clockwise around the north celestial pole.
B) They are the stars close to the north celestial pole.
C) You cannot see them from the Southern Hemisphere.
D) They always remain above your horizon.
E) Like all other stars, they rise in the east and set in the west.
6)
7) What makes the North Star, Polaris, special?
A) It is the star straight overhead.
B) It is the brightest star in the sky.
C) It appears very near the north celestial pole.
D) It can be used to determine your longitude on Earth.
E) It is the star directly on your northern horizon.
7)
1
8) You are standing on Earths equator. Which way is Polaris, the North star?
A) on the northern horizon
B) 30 degrees up, due West
C) directly overhead
D) The answer depends on whether its winter or summer.
E) The answer depends on what time of day (or night) it is.
8)
9) By locating the north celestial pole (NCP) in the sky, how can you determine your latitude?
A) The altitude of the NCP is the same as your distance from the North Pole.
B) The altitude of the NCP is the same as your latitude.
C) The altitude of the NCP is your angular distance from the North Pole.
D) The direction of the NCP is the angular distance from the North Pole.
E) The direction of the NCP is the same as your latitude.
9)
10) Orion is visible on winter evenings but not summer evenings because of
A) baseball on television.
B) the precession of Earths axis.
C) the tilt of Earths axis.
D) interference from the full moon.
E) the location of Earth in its orbit.
10)
11) Why is it summer in the Northern Hemisphere when it is winter in the Southern Hemisphere?
A) The Northern Hemisphere is tilted away from the Sun and receives more indirect sunlight.
B) The Northern Hemisphere is on top of Earth and therefore receives more sunlight.
C) The Northern Hemisphere is tilted toward the Sun and receives more direct sunlight.
D) The Northern Hemisphere is closer to the Sun than the Southern Hemisphere.
E) It isnt; both hemispheres have the same seasons at the same time.
11)
12) Which of the following statements is true?
A) Both the Northern and Southern hemispheres receive the same amount of sunlight on the
equinoxes.
B) The Southern Hemisphere receives the most direct sunlight on the summer solstice.
C) The Northern Hemisphere receives the most direct sunlight on the summer solstice.
D) Both the Northern and Southern hemispheres receive the same amount of sunlight on the
solstices.
E) Both A and C are true.
12)
13) Which of the following statements about constellations is false?
A) Most constellations will be unrecognizable hundreds of years from now.
B) There are only 88 official constellations.
C) It is possible to see all the constellations from Earths equator.
D) Some constellations can be seen in both the winter and summer.
E) Some constellations can be seen from both the Northern and Southern hemispheres.
13)
14) Which of the following statements about lunar phases is true?
A) It is possible to have two full moons during January, but not during February.
B) The time from one new moon to the next new moon is the same as the time from
first-quarter moon to third-quarter moon.
C) The full moon sometimes rises around midnight.
D) The time between new moons is two weeks.
E) It is possible to have two full moons during November, but not during December.
14)
2
15) Which of the following is not a phase of the Moon?
A) first-quarter moon
B) full moon
C) third-quarter moon
D) half moon
E) new moon
15)
16) When someone on Earth observes the Moon in the first-quarter phase, someone on the Moon
facing Earth observes Earth in the
A) new Earth phase.
B) first-quarter Earth phase.
C) third-quarter Earth phase.
D) crescent Earth phase.
E) full Earth phase.
16)
17) If the Moon is setting at 6 A.M., the phase of the Moon must be
A) waning crescent.
B) first quarter.
C) third quarter.
D) new.
E) full.
17)
18) If the Moon is setting at noon, the phase of the Moon must be
A) first quarter.
B) third quarter.
C) waning crescent.
D) waxing crescent.
E) full.
18)
19) If the Moon is rising at midnight, the phase of the Moon must be
A) first quarter.
B) third quarter.
C) waning crescent.
D) waxing crescent.
E) full.
19)
20) At approximately what time would a full moon be on your meridian?
A) 6 A.M. B) midnight C) noon D) 6 P.M. E) 9 A.M.
20)
21) At approximately what time would a first quarter moon rise?
A) 6 P.M. B) midnight C) 6 A.M. D) noon E) 9 A.M.
21)
22) If the Moon rises around 3 A.M., its phase must be
A) waxing crescent.
B) full.
C) waning crescent.
D) third quarter.
E) first quarter.
22)
3
23) In which direction does a quarter moon rise?
A) south
B) north
C) east
D) west
E) The Moon becomes a quarter moon only after it has risen and changed phase.
23)
24) Which of the following statements about the Moon is true?
A) If you see a full moon from North America, someone in South America would see a new
moon.
B) The Moon is visible only at night.
C) The Moons distance from Earth varies during its orbit.
D) The Moon goes through a cycle of phases because it always has the same side facing Earth.
E) The side of the Moon facing away from Earth is in perpetual darkness.
24)
25) What effect or effects would be most significant if the Moons orbital plane were exactly the same
as the ecliptic plane?
A) Solar eclipses would be much rarer.
B) Solar eclipses would be much more frequent.
C) Total solar eclipses would last much longer.
D) both A and C
E) both B and C
25)
26) What conditions are required for a solar eclipse?
A) The phase of the Moon can be new or full, and the nodes of the Moons orbit must be nearly
aligned with Earth and the Sun.
B) The phase of the Moon must be full, and the Moons orbital plane must lie in the ecliptic.
C) The phase of the Moon must be new, and the Moons orbital plane must lie in the ecliptic.
D) The phase of the Moon must be full, and the nodes of the Moons orbit must be nearly
aligned with Earth and the Sun.
E) The phase of the Moon must be new, and the nodes of the Moons orbit must be nearly
aligned with Earth and the Sun.
26)
27) What conditions are required for a lunar eclipse?
A) The phase of the Moon can be new or full, and the nodes of the Moons orbit must be nearly
aligned with Earth and the Sun.
B) The phase of the Moon must be new, and the nodes of the Moons orbit must be nearly
aligned with Earth and the Sun.
C) The phase of the Moon must be full, and the Moons orbital plane must lie in the ecliptic.
D) The phase of the Moon must be new, and the Moons orbital plane must lie in the ecliptic.
E) The phase of the Moon must be full, and the nodes of the Moons orbit must be nearly
aligned with Earth and the Sun.
27)
28) In addition to the conditions required for any solar eclipse, what must also be true in order for you
to observe a total solar eclipse?
A) Earth must lie completely within the Moons penumbra.
B) The Moons penumbra must touch the area where you are located.
C) Earth must lie completely within the Moons umbra.
D) Earth must be near aphelion in its orbit of the Sun.
E) The Moons umbra must touch the area where you are located.
28)
4
29) If part of the full moon passes through Earths umbra, we will see a(n)
A) partial solar eclipse.
B) annular eclipse.
C) penumbral lunar eclipse.
D) total lunar eclipse.
E) partial lunar eclipse.
29)
30) If the Moon is relatively far from Earth, so that its umbra does not reach Earth, someone directly
behind the umbra will see
A) an annular eclipse.
B) a partial solar eclipse.
C) a partial lunar eclipse.
D) no eclipse.
E) a penumbral lunar eclipse.
30)
31) When are eclipse seasons?
A) during an eclipse
B) in the spring and fall
C) when the nodes of the Moons orbit are nearly aligned with the Sun
D) when Earth, the Sun, and the Moon are exactly aligned for an eclipse
E) in the summer and winter
31)
32) The precession of the Moons nodes means that
A) the vernal equinox will be in Aquarius in a few hundred years.
B) there is a lunar eclipse every 6 months.
C) the eclipse seasons occur less than 6 months apart.
D) there are never two solar eclipses in the same year.
E) there is a solar eclipse every 6 months.
32)
33) Ancient people who knew the saros cycle could
A) predict what type of eclipse would occur.
B) predict when theyd see the next total solar eclipse in their area.
C) predict when an eclipse would happen, but not necessarily what type and where it would be
visible.
D) completely predict every solar eclipse.
E) completely predict every lunar eclipse.
33)
34) What happens during the apparent retrograde motion of a planet?
A) The planet appears to move eastward with respect to the stars over a period of many nights.
B) The planet moves through constellations that are not part of the zodiac.
C) The planet moves backward in its orbit around the Sun.
D) The planet moves backward through the sky.
E) The planet rises in the west and sets in the east.
34)
5
35) What causes the apparent retrograde motion of the planets?
A) Apparent retrograde motion is an illusion created by turbulence in Earths atmosphere.
B) When planets are farther from the Sun, they move slower than when they are nearer the
Sun; it is during this slower period that they appear to move backwards.
C) As Earth passes another planet, the other planet appears to move backward with respect to
the background stars, but the planets motion does not really change.
D) The other planets never really appear to move backward; the background stars shift due to
Earths revolution around the Sun.
E) As Earth passes another planet, its gravitational pull slows down the other planet so that it
appears to be traveling backward.
35)
36) Which of the following never goes in retrograde motion?
A) Venus B) Saturn C) the Sun D) Mars E) Jupiter
36)
37) Which of the following statements about parallax is not true?
A) The existence of stellar parallax is direct proof that Earth orbits the Sun.
B) Measurement of stellar parallax allows us to determine distances to nearby stars.
C) The technique of stellar parallax was used by Hubble to determine that the Andromeda
Galaxy (M 31) is about 2 million light-years away.
D) Ancient astronomers were unable to measure parallax and used the absence of observed
parallax as an argument in favor of an Earth-centered universe.
E) You can demonstrate parallax simply by holding up a finger and looking at it alternately
from your left and right eyes.
37)
38) Which of the following statements about stellar parallax is true?
A) We observe all stars to exhibit at least a slight amount of parallax.
B) The closer a star is to us, the more parallax it exhibits.
C) It takes at least 10 years of observation to measure a stars parallax.
D) The amount of parallax we see depends on how fast a star is moving relative to us.
E) Stellar parallax was first observed by ancient Greek astronomers.
38)
39) We cant detect stellar parallax with naked-eye observations. Which of the following would make
parallax easier to observe?
A) slowing down Earths orbital motion
B) getting away from streetlights
C) Speeding up the precession of Earths axis
D) speeding up Earths orbital motion
E) increasing the size of Earths orbit
39)
40) Why were ancient peoples unable to detect stellar parallax?
A) They did not have the ability to measure very small angles.
B) They did not look for it.
C) They could not see distant stars.
D) They did not observe for long enough periods of time.
E) They did detect it, but they rejected the observations.
40)
41) How many arcseconds are in one arcminute?
A) 60 B) 10,000 C) 100 D) 3600 E) 360
41)
42) How many arcminutes are in one degree?
A) 60 B) 100 C) 3600 D) 10,000 E) 360
42)
6
43) Has Polaris always been the North Star?
A) No, because it is a young star that only formed a few hundred years ago.
B) No, because the Earths axis slowly changes the direction it points.
C) No, because the Milky Way blocked our line of site to it for a long time.
D) Yes, because the stars are unchanging.
43)
44) If you see Polaris directly overhead at midnight, you must be at
A) the South Pole. B) the North Pole.
C) the equator. D) the Tropic of Cancer.
44)
45) You experience night-time when
A) the side of the Earth you occupy is facing away from the Sun.
B) the Earths axis precesses.
C) the Earth revolves 90 degrees in its orbit.
D) the Moon blocks the Suns light.
45)
46) If the Moon is setting at noon, then it rose at
A) noon. B) 6 A.M. C) 6 P.M. D) midnight. E) 9 A.M.
46)
TRUE/FALSE. Write T if the statement is true and F if the statement is false.
47) In South Africa, its usually quite warm around the time of the December solstice and quite cool
around the time of the June solstice.
47)
48) You can find the tilt of Earths axis by measuring the angle between your horizon and the North
Star.
48)
49) The Milky Way can be seen only from the Northern Hemisphere. 49)
50) The seasons on Earth are caused by its elliptical orbit around the Sun. 50)
51) At midnight it is sometimes possible to observe the crescent moon on the meridian. 51)
52) It is possible to see the third-quarter moon near the western horizon at sunrise. 52)
53) It is possible to see the full moon rising just before sunrise. 53)
54) If you lived on the Moon, youd see full Earth when we see new moon. 54)
55) It is possible to view the Moon in first-quarter phase the day after a total lunar eclipse. 55)
56) The Moon and the Sun are approximately the same angular size. 56)
57) A solar eclipse occurs only when the Moon is new. 57)
58) A lunar eclipse occurs only when the Moon is new. 58)
59) The Moon and Sun are approximately the same physical size. 59)
7
ESSAY. Write your answer in the space provided or on a separate sheet of paper.
60) Models in Science: Models play a central role in astronomy and science in general. Two models used extensively
in this chapter are the celestial sphere and the heliocentric (Sun-centered) model for the solar system.
Astronomers clearly believe that the celestial sphere model is false and the heliocentric model is true. Given this,
why do you think astronomers persist in using the celestial sphere model to describe the night sky?
61) Cognitive Dissonance? You are talking to a friend who insists that the seasons are caused by a varying Earth-Sun
distance over the course of a year. What other fact does your friend likely know that completely contradicts this
view of how the seasons are caused? Can you think of other examples of two beliefs that many people feel are
both true but which completely contradict each other? How does science view this situation?
62) The Sidereal Day: Using your wristwatch and observations of the night sky over the course of a few weeks, how
can you demonstrate to a friend that 24 hours cannot be the true rotation period of the Earth (often called the
sidereal day)? What assumptions do you make in this argument?
63) Scientific Reasoning: The scientific method requires that we put any hypothesis about how the universe works to
the test by conducting observations of the natural world. Consider the Greek reaction to the idea of a
heliocentric (Sun-centered) solar system. Why did most Greeks reject this hypothesis in favor of the geocentric
(Earth-centered) model? Do you think that the Greeks were following a scientific form of reasoning to reach
this conclusion? Does the fact that the Greeks reached the wrong conclusion affect your answer?
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
The choices below are for the following questions. For each question, choose the letter for the real motion that is responsible for the
apparent motion as seen from Earth.
A. Earth rotates once each day.
B. Earth revolves around the Sun once each year.
C. The direction of Earths axis in space precesses with a period of 26,000 years.
D. Stars appear to move randomly in the local solar neighborhood.
E. The universe is expanding.
64) Polaris will no longer be the North Star 1,000 years from now. 64)
65) In the year A.D. 15,000, Vega will be a better north star than Polaris. 65)
66) The Big Dipper will look different 100,000 years from now than it does today. 66)
67) The Moon rises in the east and sets in the west. 67)
68) The stars of Orions belt rise in the east and set in the west. 68)
69) A million years from now, Alpha Centauri will no longer be the nearest star system to our
own.
69)
70) The stars visible at night change over the course of the year. 70)
71) The stars visible just after sunset are different from those visible just before sunrise. 71)
8
72) If Earths axis had no tilt, would we still have seasons? Why or why not? 72)
73) Consider the following statement, and explain whether or not it is sensible: If you had a
very fast spaceship, you could travel to the celestial sphere in about 100 years.
73)
74) Consider the following statement, and explain whether or not it is sensible: When I looked
into the dark fissure of the Milky Way with my binoculars, I saw what must have been a
cluster of distant galaxies.
74)
75) Why does the Milky Way appear as a band of light in the sky? 75)
76) Consider the following statement, and explain whether or not it is sensible: Although all
the known stars appear to rise in the east and set in the west, we might someday discover
a star that will appear to rise in the west and set in the east.
76)
77) At what altitude and in what direction in your sky does the north or south celestial pole
appear?
77)
78) Consider the following statement, and explain whether or not it is sensible: My sign is
Ursa Major because the Sun was in Ursa Major when I was born.
78)
79) Consider the following statement, and explain whether or not it is sensible: Last night I
saw Jupiter in the constellation Ursa Major.
79)
80) Answer each of the following questions for our local sky.
A. Where is the north celestial pole in our sky?
B. Is Polaris a circumpolar star in our sky? Explain.
C. Describe the meridian in our sky.
D. Describe the celestial equator in our sky.
80)
81) Consider the following statement, and explain whether or not it is sensible: If you lived on
the Moon, youd see full Earth when we see new moon.
81)
82) Suppose you lived on the Moon near the center of the face that we see from Earth. During
the phase of full moon, what phase would you see for Earth? Would it be day or night at
your home?
82)
83) Suppose you lived on the Moon near the center of the face that we see from Earth. During
the phase of new moon, what phase would you see for Earth? Would it be day or night at
your home?
83)
84) Suppose you lived on the Moon near the center of the face that we see from Earth. At
what phase of the Moon would you see sunset? What phase of Earth would you see at this
time?
84)
85) Suppose you lived on the Moon near the center of the face that we see from Earth. At
what phase of the Moon would you see sunrise? What phase of Earth would you see at
this time?
85)
9
86) What would you see if you were on the near side of the Moon during a lunar eclipse? 86)
87) Why is the Moon not completely invisible (it appears as a very deep red color) to the
naked eye during a total lunar eclipse?
87)
88) What would you see on Earth if you were on the near side of the Moon during a solar
eclipse?
88)
89) Suppose the distance to the Moon were twice its actual value. Could we still have solar
eclipses? If so, what type(s)?
89)
90) Consider the following statement, and explain whether or not it is sensible: Last night I
saw Mars move westward through the sky in its apparent retrograde motion.
90)
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
91) If the Earths rotation axis were tilted by 45 degrees instead of 23.5 degrees, what are some of the
implications, and why?
A) The seasons would be more extreme, because the surface of the Earth would be closer to the
Sun in the summer, and farther from the Sun in the winter.
B) The seasons would be more extreme, because the Suns rays would be more direct in
summer, and less direct in winter.
C) The seasons would be less extreme, because the surface of the Earth would be farther from
the Sun in the summer, and closer to the Sun in the winter.
D) The seasons would be less extreme, because the Suns rays would be less direct in summer,
and more direct in winter.
91)
92) You see a crescent Moon setting after the Sun sets. Is it waning or waxing?
A) cant distinguish based on the information provided
B) waning
C) waxing
92)
93) Tonight, your telescope shows you RXJ1800, a galaxy, very near in the sky to the bright star Vega.
What can you conclude from this observation?
A) Vega and RXJ1800 must be very close to each other, less than a few light years.
B) Vega orbits the center of mass of RXJ1800.
C) RXJ1800 and Vega will drift apart from each other on the sky, over a matter of nights.
D) RXJ1800 and Vega will set in the west, at very similar times.
93)
94) If the Sun passes almost in front of the center of our Milky Way Galaxy, it does so
A) only in 2012, at the end of the Mayan calendar.
B) once a day.
C) once a year.
D) once a month.
94)
95) The Greeks rejected the notion that the Earth orbits the Sun. Why?
A) They could not measure a change in stars positions on the sky.
B) They believed that the Sun is a God.
C) They werent as smart as we are.
D) They could not measure how big the Earth was.
95)
10
96) Your friend tells you that last night, they saw Mars high in the sky at midnight. You conclude that
A) Mars must be in retrograde.
B) Mars must be at its farthest distance from the Earth.
C) Mars must be at its closest distance from the Sun.
D) Your friend must be mistaken: Mars can never be seen at midnight.
96)
97) If the Moon is 3rd quarter phase, when does it rise?
A) sunset B) noon C) never D) sunrise E) midnight
97)
98) The Moons orbit around the Earth is tilted by about 5 degrees with respect to Earths orbit around
the Sun. As a result, the approximate number of solar eclipses that occur each year is
approximately
A) 24. B) 0. C) 2. D) 12.
98)
99) During a lunar eclipse the Moons phase must be
A) full. B) 1st quarter. C) new. D) 3rd quarter.
99)
100) If the Moon is 3rd quarter phase, what shape does it have in the sky?
A) a full circle
B) a half circle
C) a quarter circle
D) nothing (It is impossible to view a 3rd quarter moon.)
100)
101) Which planet is moving most slowly around the Sun?
A) Earth
B) Venus
C) Jupiter
D) They are all moving with the same speed around the Sun.
101)
102) Which of these (hypothetical) modifications would cause lunar eclipses to happen once per month?
A) Make the Moon orbit the Earth twice as fast.
B) Change the orbital plane of the Moon so it lies in the same plane as Earths orbit around the
Sun.
C) Change the Moons orbital plane so it tilts the opposite way.
D) Relocate the Moon to twice its current distance from the Earth.
102)
103) The Moon is nearly tidally locked to the Earth, which means the Moons rotation period is almost
the same as its orbital period. If you were camped at the equator of the Moon, you would
experience (approximately)
A) (14 24) hours of darkness followed by (14 24) hours of sunshine.
B) sunshine (day) all the time.
C) 14 hours of darkness followed by 14 hours of sunshine.
D) sunshine all the time, except when the Earth blocks the Sun.
103)
104) Gibbous means a nearly full moon. If I see a waxing gibbous moon tonight, what moon phase
will I see in one week?
A) waxing crescent B) waning crescent
C) waning gibbous D) waxing gibbous
104)
11
105) Which of the following conditions must exist for a solar eclipse to occur?
A) The only condition is that the phase of the Moon must be full.
B) Moon phase is full, and the Moon is passing through the Earths orbital plane.
C) The only condition is that the phase of the Moon must be new.
D) Moon phase is new, and the Moon is passing through the Earths orbital plane.
105)
106) Which of the following situations would result in the longest days during the summer? (Assume
an axis tilt of 0 degrees is an axis perpendicular to the ecliptic plane.)
A) axis tilt -10 degrees B) axis tilt 90 degrees
C) axis tilt 23.5 degrees D) axis tilt 0 degrees
106)
107) About how many stars are visible to the naked eye on a clear, dark night away from city lights?
A) a few dozen B) a few hundred billion
C) a couple thousand D) several million
107)
108) What do astronomers mean by a constellation?
A) A constellation is a region in the sky as seen from Earth.
B) A constellation is a group of stars related through an ancient story.
C) A constellation is a group of stars that are all located in about the same place in space.
D) A constellation is any random grouping of stars in the sky.
108)
109) What is the ecliptic?
A) a half-circle extending from your horizon due north, through your zenith, to your horizon
due south
B) the path traced by the Moons shadow on Earth during a solar eclipse
C) the path the Sun appears to trace around the celestial sphere each year
D) the Suns daily path from east to west in our sky
109)
110) What is the celestial sphere?
A) The celestial sphere is a model of how the stars are arranged in the sky relative to our Sun,
which is in the middle of the sphere.
B) It represents a belief in an Earth-centered universe, and hence is no longer considered to
have any use.
C) The celestial sphere is a representation of how the entire sky looks as seen from Earth.
D) The celestial sphere is a model that shows the true locations in space of the Sun and a few
thousand of the nearest stars.
110)
111) What do we mean when we talk about the Milky Way in our sky?
A) the whitish patch of light we see when we look toward the center of the Milky Way Galaxy
B) the patchy band of light that outlines the plane of the Milky Way Galaxy as seen from Earth
C) the spiral-shaped galaxy in which we live
D) the bright stars of the constellations that lie along the ecliptic in our sky
111)
112) Which of the following statements does not use the term angular size or angular distance correctly?
A) The angular size of the Sun is about the same as that of the Moon.
B) The angular distance between those two bright stars in the sky is about 2 meters.
C) You can use your outstretched hand against the sky to estimate angular sizes and angular
distances.
D) The angular distance between those two houses in the distance is 30 degrees.
112)
12
113) Which of the following correctly describes the meridian in your local sky?
A) a half-circle extending from your horizon due north, through your zenith, to your horizon
due south
B) the point directly over your head
C) a half-circle extending from your horizon due east, through your zenith, to your horizon due
west
D) a half-circle extending from your horizon due east, through the north celestial pole, to your
horizon due west
113)
114) The point directly over your head is called ________.
A) the north celestial pole B) the zenith
C) the North Star D) the meridian
114)
115) Stars that are visible in the local sky on any clear night of the year, at any time of the night, are
called ________.
A) bright B) seasonal C) celestial D) circumpolar
115)
116) We describe a location on Earths surface by stating its ________.
A) meridian and longitude B) altitude and direction (or azimuth)
C) latitude and longitude D) latitude and direction
116)
117) If you are located in the Northern Hemisphere, which of the following correctly describes a
relationship between the sky and your location?
A) The altitude of the celestial equator equals your latitude.
B) The altitude of the north celestial pole equals your longitude.
C) The altitude of the north celestial pole equals your latitude.
D) The longitude of the north celestial pole is circumpolar, and therefore crosses your zenith at
the meridian.
117)
118) Which of the following best describes why we have seasons on Earth?
A) The varying speed of Earth in its orbit around the Sun gives us summer when we are moving
fastest and winter when we are moving slowest.
B) The tilt of Earths axis causes different portions of the Earth to receive more or less direct
sunlight at different times of year.
C) Earths elliptical orbit means we are closer to the Sun and therefore receive more intense
sunlight at some times of year than at others.
D) The tilt of Earths axis causes the northern hemisphere to be closer to the Sun than the
southern hemisphere in summer, and vice versa in winter.
118)
13
119) Each choice below describes how a few astronomical phenomena are related to time periods.
Which list is entirely correct? (Careful: some lists are partially correct.)
A) Earths rotation defines a day.
The cycle of the Moons phases takes about a week.
Earths orbit defines a year.
Earths cycle of axis precession defines a month.
B) Earths rotation defines a day.
The Suns rotation defines a week.
The Moons rotation defines a month.
Earths orbit defines a year.
C) Earths rotation defines a day.
The saros cycle of eclipses defines a month.
Earths orbit defines a year.
Earths cycle of axis precession takes 26,000 years.
D) Earths rotation defines a day.
The cycle of the Moons phases takes about a month.
Earths orbit defines a year.
Earths cycle of axis precession takes 26,000 years.
119)
120) If we have a new moon today, when we will have the next full moon?
A) in about 2 weeks B) in about 1 month
C) in about 1 week D) in about 6 months
120)
121) We cannot see a new moon in our sky because ________.
A) it is above the horizon during the daytime
B) a new moon is quite near the Sun in the sky
C) no sunlight is illuminating the Moon
D) it is obscured by Earths shadow
121)
122) Lunar eclipses can occur only during a ________.
A) third quarter moon B) full moon
C) new moon D) first quarter moon
122)
123) What is the saros cycle?
A) the annual cycle of the seasons
B) the roughly 18-year cycle over which the pattern of eclipses repeats
C) the roughly one-month cycle of lunar phases in the sky
D) the 26,000-year cycle of the Earths precession
123)
124) During the time that a planet is in its period of apparent retrograde motion, ________.
A) the planet appears to rise in the west and set in the east, rather than the usual rising in the
east and setting in the west
B) the planet is getting closer to the Sun in its orbit
C) over many days or weeks, the planet moves westward relative to the stars, rather than the
usual eastward relative to the stars
D) the planet moves backwards (clockwise as viewed from above Earths north pole) in its orbit
of the Sun
124)
14
125) What is stellar parallax?
A) It is the slight back-and-forth shifting of star positions that occurs as we view the stars from
different positions in Earths orbit of the Sun.
B) It is the daily rise and set of the stars.
C) It is the change in the set of constellations that we see at different times of year in the evening
sky.
D) It describes the fact that stars are actually moving relative to one another, even though to our
eyes the stars appear fixed in the constellations.
125)
126) Which of the following statements about the celestial sphere is not true?
A) When we look in the sky, the stars all appear to be located on the celestial sphere.
B) The celestial sphere does not exist physically.
C) The Earth is placed at the center of the celestial sphere.
D) The celestial sphere is another name for our universe.
126)
127) The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda.
Suppose instead it were located in the same direction in space as the center of the Milky Way
Galaxy (but still at its current distance). How would it appear to the eye in that case?
A) It would look about the same, but it would be harder to pick out because its cloud-like
appearance would make it blend in with the cloud-like appearance of the Milky Way in our
sky.
B) It would be much brighter because it would be illuminated by the many stars in the center of
our galaxy.
C) We could not see it at all.
D) It would look about the same, but would be in the constellation Sagittarius instead of
Andromeda.
127)
128) An angle of 1 arcsecond is ________.
A) about the width of a finger held at arms length
B) about the width of your fist held at arms length
C) slightly more than the width of a basketball held at arms length
D) less than the thickness of a human hair held at arms length
128)
129) When traveling north from the United States into Canada, youll see the North Star (Polaris)
getting ________.
A) dimmer B) higher in the sky
C) brighter D) lower in the sky
129)
130) Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees
above your horizon. Then you must be located at ________.
A) latitude 40 degrees south B) latitude 40 degrees north
C) longitude 40 degrees D) latitude 50 degrees south
130)
131) Suppose you are facing north and you see the Big Dipper close to your northern horizon, with
Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
A) still in the same place, below Polaris
B) directly above Polaris
C) to the right of Polaris; that is, 90 degrees counterclockwise from its current position
D) to the left of Polaris; that is, 90 degrees clockwise from its current position
131)
15
132) In any particular place on Earth, certain constellations are visible in the evening only at certain
times of the year because ________.
A) some constellations are circumpolar
B) our evening view of space depends on where Earth is located in its orbit around the Sun
C) on any particular night, we can only see stars that are directly opposite (180 degrees away
from) the Sun in the sky
D) during some times of year, some constellations drop below the southern horizon
132)
133) The Suns path, as viewed from the equator, is highest in the sky on ________.
A) the spring and fall equinoxes B) the winter solstice
C) the summer solstice D) the day when Earth is closest to the Sun
133)
134) Suppose Earths axis tilt was significantly greater than its current 23.5 degrees, but Earths rotation
period and orbital period were unchanged. Which statement below would not be true?
A) Polaris would not be our North star.
B) Summers and winters would be more severe (for example, hotter and colder, respectively)
than they are now.
C) The length of each season (for example, the number of days from the summer solstice to the
fall equinox) would be significantly longer than it is now.
D) The region of Earth where the Sun does not rise on the winter solstice would be larger
(extending farther south) than it is now.
134)
135) If our year were twice as long (that is, if Earth took twice as many days to complete each orbit
around the Sun), but Earths rotation period and axis tilt were unchanged, then ________.
A) stars would take twice as long to rise and set
B) the Earth would not have seasons
C) the cycle of precession would take 13,000 years instead of 26,000 years
D) the four seasons would each be twice as long as they are now
135)
136) How does Earths varying distance from the Sun affect our seasons?
A) It doesntEarths orbital distance plays no significant role in the seasons.
B) It causes the seasons to be more extreme than they would be if the Earths distance from the
Sun were always the same.
C) It is responsible for the fact that the seasons are opposite in the Northern and Southern
hemispheres.
D) It makes summer warmer in the Northern Hemisphere than in the Southern Hemisphere.
136)
137) Suppose you live in the United States and you see a crescent moon in your evening sky tonight.
What will a friend in South America see tonight?
A) Your friend will see a gibbous moon.
B) Your friend wont see the Moon tonight, because it is up only in the morning.
C) Your friend will also see a crescent moon.
D) Your friend will see a first quarter moon.
137)
138) Suppose it is full moon. What phase of Earth would someone on the Moon see at this time?
A) first quarter Earth
B) new Earth
C) full Earth
D) Earth does not go through phases as seen from the Moon.
138)
16
139) Its 6 a.m. and the Moon is at its highest point in your sky (crossing the meridian). What is the
Moons phase?
A) third quarter B) new C) first quarter D) full
139)
140) You observe a full moon rising at sunset. What will you see at midnight?
A) a first quarter moon B) a third quarter moon
C) a waning gibbous moon D) a full moon high in the sky
140)
141) All the following statements are true. Which one explains the reason that there is not a solar eclipse
at every new moon?
A) The Moon is only about 1/4 as large as Earth in diameter.
B) The nodes of the moons orbit precess with an 18-year period.
C) The Moon goes through a complete cycle of phases about every 29 1/2 days.
D) The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.
141)
142) For most of history, the lack of observable stellar parallax was interpreted to mean that ________.
A) Galileos theories of the universe were essentially correct
B) stars must all lie at the same distance from Earth, on the celestial sphere
C) stars were too far away for parallax to be measured with available technology
D) Earth is stationary at the center of the universe
142)
143) During the period each year when we see Mars undergoing apparent retrograde motion in our
sky, what is really going on in space?
A) Earth and Mars are getting closer together.
B) Mars is moving around the Sun in the opposite direction from which Earth is moving around
the Sun.
C) Earth and Mars are on opposite sides of the Sun.
D) Earth is catching up with and passing by Mars in their respective orbits.
143)
144) Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter
Jupiter). This photo might have been taken by ________.
A) the Hubble Space Telescope (which orbits Earth)
B) the Galileo spacecraft that orbited Jupiter in the 1990s
C) the Keck telescope on Mauna Kea, Hawaii
D) the Arecibo radio telescope in Puerto Rico
144)
145) RXJ1800, a galaxy, lies very near in the sky to the bright star Vega. What is the best explanation for
them appearing close together?
A) Vega must have recently formed in RXJ1800 and been ejected.
B) They coincidentally lie along the same line of sight.
C) Their random motions have caused RXJ1800 and Vega to drift to within a few light-years of
each other.
D) Vega orbits the center of mass of RXJ1800.
145)
17
Answer Key
Testname: UNTITLED30
1) B
2) A
3) B
4) C
5) D
6) D
7) C
8) A
9) B
10) E
11) C
12) E
13) A
14) A
15) D
16) C
17) E
18) B
19) B
20) B
21) D
22) C
23) C
24) C
25) B
26) E
27) E
28) E
29) E
30) A
31) C
32) C
33) C
34) A
35) C
36) C
37) C
38) B
39) E
40) A
41) A
42) A
43) B
44) B
45) A
46) D
47) TRUE
48) FALSE
49) FALSE
50) FALSE
18
Answer Key
Testname: UNTITLED30
51) FALSE
52) FALSE
53) FALSE
54) TRUE
55) FALSE
56) TRUE
57) TRUE
58) FALSE
59) FALSE
60) Will vary.
61) Will vary.
62) Will vary.
63) Will vary.
64) C
65) C
66) D
67) A
68) A
69) D
70) B
71) A
72) We would no longer have seasons, because the Suns light would hit at the same angle all throughout the year,
depending only on where you lived. The slight change in distance between Earth and the Sun during the year would
not produce much of an effect.
73) This statement does not make sense because the celestial sphere is a concept and not a physical object.
74) This statement does not make sense because we cannot see through the band of light we call the Milky Way to
external galaxies; the dark fissure is gas and dust blocking our view.
75) The solar system lies in the outer parts of the thin disk of a spiral galaxy. Thus when we look along the plane of the
disk, we see large numbers of stars that, to the naked eye, merge into a band of light. When we look out of the plane of
the disk, there are very few stars and the night sky is much darker.
76) This statement does not make sense. The stars arent really rising and setting, they only appear to rise in the east and
set in the west because Earth rotates.
77) Answers will vary with your latitude; latitude = altitude of NCP (or SCP in Southern Hemisphere).
78) Not sensible: The Sun appears only in the constellations of the zodiac-and Ursa Major is not one of these.
79) This statement does not make sense because Jupiter, like all the planets, is always found very close to the ecliptic in the
sky. The ecliptic passes through the constellations of the zodiac, so Jupiter can appear to be only in one of the 12
zodiac constellationsand Ursa Major is not one of these.
80) A. Answers will vary with latitude; here is a sample for 40N: The north celestial pole appears at an altitude of 40, in
the direction due north.
B. Yes, for any location in the Northern Hemisphere; no, for any location in the Southern Hemisphere. Polaris is
circumpolar because it never rises or sets in our sky. It makes a daily circle, less than 1 in radius, around the north
celestial pole.
C. The meridian is a half-circle that stretches from the due south point on the horizon, through the zenith, to the due
north point on the horizon.
D. Answers will vary with latitude; here is a sample answer for 40N: The celestial equator is a half-circle that
stretches from the due east point on the horizon, through an altitude of 50 due south, to the due west point on the
horizon.
81) This is true, because at full moon Earth lies between the Sun and the Moon. Thus, an observer on the Moon would be
looking at the night side of Earth.
82) During the full moon, it would be daytime and you would see the phase of new Earth.
19
Answer Key
Testname: UNTITLED30
83) During the new moon, it would be nighttime and you would see the phase of full Earth.
84) Sunset would occur at the Moons third-quarter phase. You would see Earth in first-quarter phase at this time.
85) Sunrise would occur at the Moons first-quarter phase. You would see Earth in third-quarter phase at this time.
86) During a lunar eclipse, you would see Earth pass in front of the Sun. It would be completely dark where you were.
87) The Moon shines through reflected light from the Sun and thus it becomes very dark during a lunar eclipse since the
Moon lies within Earths shadow at this time. However, some sunlight still gets through because it is bent (similar to
the way a lens works) by Earths atmosphere. We see the reflection of this faint light and thus the Moon is not
completely invisible. (The bending of light is called refraction and the effect is strongest at long wavelengths. Thus it is
most pronounced for red light and the eclipsed Moon appears dark red.)
88) During a solar eclipse, you would see a small circular shadow traveling across a portion of Earths surface.
89) If the Moon were twice its actual distance from us, we would no longer be able to see total solar eclipses because the
Moon would not be able to completely cover the surface of the Sun; however, we would still see partial and annular
eclipses, although the Moon would not block as much of the Sun during these times.
90) This statement does not make sense because the apparent retrograde motion is noticeable only over many nights, not
during a single night. (Of course, like all celestial objects, Mars moves from east to west over the course of every
night.)
91) B
92) C
93) D
94) C
95) A
96) A
97) E
98) C
99) A
100) B
101) C
102) B
103) A
104) C
105) D
106) B
107) C
108) A
109) C
110) C
111) B
112) B
113) A
114) B
115) D
116) C
117) C
118) B
119) D
120) A
121) B
122) B
123) B
124) C
20
Answer Key
Testname: UNTITLED30
125) A
126) D
127) C
128) D
129) B
130) A
131) C
132) B
133) A
134) C
135) D
136) A
137) C
138) B
139) A
140) D
141) D
142) D
143) D
144) B
145) B
21

 

chapter 18

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1) Why do we call dark matter dark?
A) It emits no visible light.
B) It blocks out the light of stars in a galaxy.
C) It emits no or very little radiation of any wavelength.
D) We cannot detect the type of radiation that it emits.
1)
2) What evidence suggests that the Milky Way contains dark matter?
A) We see many dark voids between the stars in the halo of the Milky Way.
B) When we look at the galactic center, we are able to observe a large black hole that is
composed of dark matter.
C) When we observe in different wavelengths, such as infrared or radio, we see objects that
dont appear in visible-light observations.
D) We see many lanes of dark material blocking out the light of stars behind them along the
band of the Milky Way.
E) We observe clouds of atomic hydrogen far from the galactic center orbiting the galaxy at
unexpectedly high speeds, higher speeds than they would have if they felt only the
gravitational attraction from objects that we can see.
2)
3) What is the best alternative explanation for the dark matter in the Milky Way based on the
observed orbital motions of stars and gas?
A) We are not measuring the orbital velocities of gas clouds and stars properly.
B) We are not measuring the distances to gas clouds and stars properly.
C) We are not observing all the visible matter in the Milky Way.
D) We are not attributing enough mass to the visible matter in the Milky Way.
E) There is something wrong with our understanding of how gravity works.
3)
4) How are rotation curves of spiral galaxies determined for distances beyond where starlight can be
detected?
A) by measuring the broadening of the galaxys absorption lines
B) by observations of the 21 cm line of atomic hydrogen
C) by extrapolation of the measured rotation curve
D) by watching the galaxies rotate over a period of decades
E) by observations of spectral lines emitted by dark matter
4)
5) The distribution of the dark matter in a spiral galaxy is
A) approximately spherical and about the same size as the galaxy halo.
B) flattened in a disk but about ten times larger than the stellar disk.
C) flattened in a disk and about the same size as the stellar disk.
D) predominantly concentrated in the spiral arms.
E) approximately spherical and about ten times the size of the galaxy halo.
5)
6) How do we determine the amount of dark matter in elliptical galaxies?
A) We search for dark lanes of dust and black holes within the galaxy.
B) We measure the broadening of the galaxys absorption lines to infer the speeds of stars at
different distances from the galactic center.
C) We measure the orbital velocities of star-forming gas clouds in the outer portion of the
galaxy.
D) We measure how fast the galaxy rotates as a whole.
E) We count the number of stars in the galaxy. Combining this with the galaxys volume, we
can calculate the galaxys density.
6)
1
7) Why can we not measure the mass of elliptical galaxies using the 21-cm line of hydrogen gas?
A) The disorderly motion of the material in elliptical galaxies prevents us from measuring
different velocities at different sides of the galaxy.
B) Elliptical galaxies have little gas, so do not have strong 21-cm line emission.
C) All elliptical galaxies are too far away for us to detect the 21-cm line.
D) Supermassive black holes in the center of elliptical galaxies disturb measurements of the
21-cm line.
7)
8) When we measure the broadening of absorption lines in the spectrum of an elliptical galaxy, we
can infer
A) the galaxys rotation curve.
B) how fast the stars in the galaxy are moving relative to one another.
C) how quickly the galaxy is forming new stars.
D) the amount of gas and dust in the galaxy.
E) the mass of the black hole at the galaxys center.
8)
9) A mass-to-light ratio for a galaxy of much greater than one indicates that
A) the galaxy is not very massive.
B) on average, each solar mass of matter in the galaxy emits much less light than our Sun.
C) on average, each solar mass of matter in the galaxy emits much more light than our Sun.
D) the galaxy is very massive.
E) most stars in the galaxy are more massive than our Sun.
9)
10) Which of the following methods used to determine the mass of a cluster of galaxies does not
depend on Newtons law of gravity?
A) measuring the temperature of X-ray gas in the intracluster medium
B) measuring the amount of distortion caused by a gravitational lens
C) measuring the orbital velocities of galaxies in the cluster
D) none of the above
10)
11) How do X-ray measurements help us measure the amount of dark matter in galaxy clusters?
A) Dark matter absorbs X-rays. Therefore, more dark matter leads to weaker X-ray emission
from galaxy clusters.
B) X-rays are emitted by hot gas, and the intracluster gas is heated by the gravitational effects
of dark matter. More dark matter leads to greater heating, and hence stronger X-ray
emission.
C) X-rays are emitted by hot gas, and the intracluster gas is heated by collisions with dark
matter particles. More dark matter leads to greater heating, and hence stronger X-ray
emission.
11)
12) A gravitational lens occurs when
A) a massive object causes more distant objects to appear much larger than they should, and we
can observe the distant objects with better resolution.
B) a massive object bends light beams that are passing nearby.
C) a telescope lens is distorted by gravity.
D) dark matter builds up in a particular region of space, leading to a very dense region and an
extremely high mass-to-light ratio.
12)
2
13) The gravitational lens effect has been verified by
A) observations of the bending of starlight by the Sun during a 1919 eclipse.
B) single images of highly distorted, high-redshift galaxies seen towards massive galaxy
clusters.
C) observations of multiple images of the same background galaxy seen towards a massive
galaxy cluster.
D) all of the above
E) None of the above; this effect is purely hypothetical.
13)
14) Which of the following is not evidence for dark matter?
A) X-ray observations of hot gas in galaxy clusters
B) the flat rotation curves of spiral galaxies
C) the broad absorption lines found in the spectra of elliptical galaxies
D) the expansion of the universe
E) gravitational lensing around galaxy clusters
14)
15)
This figure shows the X-ray emission from hot gas in two colliding galaxy clusters (red) and the
distribution of mass (blue). Which of these are reasonable conclusions that can be drawn from this
image?
I) The mass found by gravitational lensing in these colliding galaxy clusters is in a separate
physical location from the hot gas that resulted from the collision.
II) Dark matter does not physically interact with regular matter, other than through gravity.
III) Hot intracluster gas makes up the majority of the mass of galactic clusters.
A) only I B) I and II C) I and III D) I, II, and III
15)
16) Which of the following are candidates for galactic dark matter?
A) WIMPs
B) brown dwarfs
C) Jupiter-size objects
D) faint red stars
E) all of the above
16)
3
17) Visible, luminous matter (such as the stars within galaxies) amounts to what percentage of the
critical density (the density of mass-energy needed to make the geometry of the universe flat)?
A) 25 percent B) less than 1 percent
C) 10 percent D) 50 percent
17)
18) The actual matter density of the universe, accounting for all of the luminous matter and all of the
dark matter known to exist in galaxies and clusters, is what fraction of the critical density?
A) 100 percent
B) 10 percent
C) 25 percent
D) 200 percent
E) 1 percent
18)
19) Measuring the amount of deuterium in the universe allows us to set a limit on
A) the current age of the universe.
B) the expansion rate of the universe.
C) the temperature of the universe at the end of the era of nuclei.
D) the density of ordinary (baryonic) matter in the universe.
E) the total amount of mass in the universe.
19)
20) Based on the observed amount of deuterium in the universe, we can conclude that
A) we live in a critical-density universe.
B) most of the deuterium that was created during the era of nucleosynthesis has since been
destroyed.
C) neutrons outnumber protons 7 to 1 in the universe.
D) the density of ordinary (baryonic) matter is about 5 percent of the critical density.
E) ordinary (baryonic) matter makes 75 percent of the mass of the universe.
20)
21) What do we mean when we say that a particle is weakly interacting?
A) It interacts with other particles only through the weakest force, gravity.
B) It interacts only with other weak particles, such as neutrinos.
C) It interacts with other particles only through the weak force and the force of gravity.
D) It interacts with other particles only through the weak force.
E) It doesnt interact with any type of baryonic matter.
21)
22) Why cant the dark matter in galaxies be made of neutrinos?
A) We know that dark massive objects, such as planets and neutron stars, are not made of
neutrinos.
B) There are not enough neutrinos to make up all the dark matter.
C) Neutrinos travel at extremely high speeds and can escape a galaxys gravitational pull.
D) Neutrinos have zero mass like the photon.
22)
23) Why do we expect WIMPs to be distributed throughout galactic halos, rather than settled into the
galaxys disk?
A) WIMPs are light enough that they have expanded out into the halo.
B) Shock waves from generations of supernovae have blown the WIMPs out into the halo.
C) WIMPs annihilate when they come into contact with ordinary matter, such as stars.
D) WIMPs were produced in the early stages of galaxy evolution, and objects in the halo, such
as globular clusters, were formed first.
E) WIMPS cannot produce photons, therefore they rarely interact and exchange energy with
other particles.
23)
4
24) Why isnt the space within our solar system or the Milky Way expanding according to Hubbles
Law?
A) Hubbles law of expansion applies only to the space between galaxies.
B) The gravity exerted by the solar system and the Milky Way is strong enough to hold them
together against the expansion of the universe.
C) The universe is not old enough for the solar system or Milky Way to have begun their
expansion.
D) As we are inside our solar system and the Milky Way, we cannot observe their expansion.
24)
25) If all the dark matter in our universe were to be instantaneously removed, which of the following
would not happen?
A) The Milky Way would fly apart.
B) The universe would expand forever.
C) Clusters of galaxies would fly apart.
D) The Solar System would fly apart.
E) All of the above
25)
26) How do astronomers create three-dimensional maps of the universe?
A) through the comparison of computer models of galaxy formation with observations
B) by using a galaxys position on the sky and its brightness as a measure of distance along the
line of sight
C) by interpreting the peculiar velocities of each galaxy
D) by using a galaxys position on the sky and its redshift to determine its distance along the line
of sight
E) by carefully measuring the parallax of each galaxy
26)
27) Which of the following best describes how galaxies are distributed on large scales in the universe?
A) Galaxies are distributed in a hierarchy of clusters, superclusters, and hyperclusters.
B) Galaxies are randomly distributed.
C) Galaxies appear to be distributed in chains and sheets that surround great voids.
D) Galaxies are distributed in a great shell expanding outward from the center of the universe.
E) Galaxies are uniformly distributed.
27)
28) How have astronomers measured the acceleration of the universe?
A) by comparing lookback times for white-dwarf supernovae (by measuring their apparent
brightness) with the average distance between galaxies (based on their cosmological
redshifts)
B) by measuring changes in galaxies redshifts from year to year
C) They have not. It is a purely hypothetical idea.
28)
29) Which model of the universe gives the youngest age for its present size and expansion rate?
A) a re-collapsing universe
B) an accelerating universe
C) a critical universe
D) a coasting universe
E) All models give the same age.
29)
5
30) What might be causing the universe to accelerate?
A) WIMPs
B) dark energy
C) brown dwarfs
D) white-dwarf supernovae
E) gravitation
30)
31) Which observation(s) support(s) the idea that dark energy accounts for about 70% of the total
mass-energy density of the universe?
A) This is just the right amount of a repulsive force to explain the observed acceleration in the
expansion of the universe.
B) This is just the right amount of energy, in addition to the observed matter and dark matter, to
explain the pattern of temperatures in the cosmic microwave background.
C) It is the right amount of energy to make the universe geometrically flat, which is
mathematically easier to work with than a curved geometry.
D) A and B
E) B and C
31)
32) The more baryons there are in the universe (a higher density of baryonic matter), the lower the
ratio of deuterium to hydrogen is. Therefore, if Harry measures a higher ratio of deuterium to
hydrogen than Sally, Harry infers
A) a lower density of baryons than Sally.
B) the same density of baryons as Sally.
C) a higher density of baryons than Sally.
32)
6
33) The graph above shows 4 models for how the average distance between galaxies could change
with time, from the past (left) to now (middle ) to the future (right hand side ). The graph also
shows real data, based on studies of supernovae. Each black dot on the graph is for one supernova
explosion. The data are plotted with dots and black lines that indicate the range of uncertainty of
each individual measurement. Use this graph to answer the following questions about
cosmological models for the expansion of the universe. (Note that the models are in the same
order, from top to bottom, whether on the right hand side of the graph or the left hand side. For
example the accelerating model is the top line on both sides of the graph. You should also have a
handout with a better version of this graph.)
Which model(s) predict that galaxies are getting farther apart NOW?
A) accelerating B) coasting C) critical
D) recollapsing E) all of them F) none of them
33)
34) Consider the graph of expansion models. Which model(s) predicts that galaxies will eventually get
closer together?
A) accelerating B) coasting C) critical
D) recollapsing E) all of them F) none of them
34)
35) Comparing the following 4 models, which model predicts that galaxies had the largest separations
in the past? (Use the graph of expansion models as a guide.)
A) accelerating B) coasting C) critical D) recollapsing
35)
36) Consider the data points together with the models in the graph of expansion models. Which model
is most strongly su

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