Download 1 Correct responses in BOLDFACE. 1. Henrietta Leavitt`s period

Exam 2
Version = Key ID B
SOLUTIONS
March 9, 2016
Correct responses in BOLDFACE.
1. Henrietta Leavitt's period luminosity relation for RR Lyrae stars proved important because:
a. it was the first significant astronomical discovery by a woman
b. it allowed the luminosity of these stars to be determined based on intrinsic properties, and thus their
distances from their apparent brightnesses
c. it allowed the astronomers of her time to test their models for the interiors of these stars, to see if they were
made of hydrogen
d. it explained why some star fields looked different in pictures taken at different times
e. it showed that they moved on the HR diagram
2. A rock sample is analyzed and found to have only 25% as much of a radioactive element as it would have been
predicted to contain originally. The half-life of the radioactive element is 2x108 years. How old is this rock?
a. 8x108 years
b. 1.0x108 years
c. 4x108 years
d. 2x108years
e. cannot be computed from the information given
3. The surface of Venus
a. is dominated by volcanic geology
c. is completely unknown to us
e. is a likely place to find life
b. is dominated by impact craters, similar to Mercury and our moon
d. has features suggesting that the planet once had abundant water
4. Astronomers like big telescopes because
a. big telescopes make them feel important
b. big telescopes can see smaller details (have higher resolution)
c. they actually prefer small ones because they are easier to move around
d. big telescopes can carry heavier instruments than small ones
5. Volcanoes on Mars
a. don't exist
d. don't have lava
b. are much larger than on Earth
e. are made of ice
c. are much smaller than on Earth
6. A white dwarf does not collapse further because
a. it is converting H to He
c. its electrons can't be squeezed together any more
e. gravity ceases in its core
b. it is converting He to C
d. it is made of dark matter
7. Stars with high concentrations of elements heavier than hydrogen and helium
a. are likely to be very old
c. are likely to have formed relatively recently
e. always have very low mass
b. are found in globular clusters
d. are members of population II
8. Mars is a high priority target for space exploration because
a. we think there are intelligent Martians hiding from us there
b. we want to build space colonies on it.
c. it appears to have many of the conditions needed for life in its early history, so we might find signs that
life formed.
d. the face on Mars suggests there is a dead civilization we might discover.
e. its huge mountains and canyons would be highly scenic.
9. The only body other than Earth to show signs of running water on its surface is
a. Venus
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b. Mars
c. Mercury
d. the Moon
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e. all inner planets have water on their surfaces
Exam 2
Version = Key ID B
SOLUTIONS
March 9, 2016
10. A remarkable observation from the 1987A supernova was
a. the detection of gravity waves
c. the detection of a pulsar
e. both a. and c.
b. the detection of neutrinos
d. the detection of a black hole
11. Greenhouse gases ____________
a. absorb visible light and transmit infrared light
b. absorb ultraviolet light and transmit visible light
c. absorb infrared light and transmit visible light d. absorb X-rays and transmit infrared light
12. The probability of a "fair" coin coming up heads is 1/2. What is the probability of it coming up heads three
times in a row?
a. 1/2
b. 1/4
c. 1/6
d. 1/8
e. 1/12
13. The planets in our solar system are thought to have come from
a. clumps of rocky material that exist between the stars
b. the same cloud of gas and dust in which the Sun formed
c. a cloud of gas in the Orion nebula
d. the Sun (they were flung out of the fast-spinning young sun)
14. You are sent to find dense and rocky planets. Where in the Solar System should you look?
a. very far from the sun
b. only in the middle
e. in regions with lots of moons
c. close to the sun
d. in circular orbits
15. Because of the temperatures in the protoplanetary disk from which the Solar System formed,
a. rocks, metals, and ices (hydrogen compounds) froze in the inner region only
b. rocks and metals froze in both the inner and outer regions, and ices froze only in the outer region
c. rocks and metals froze in the inner region only, and ices froze in the outer region only
d. rocks and metals froze in both the inner and outer regions, and ices and H and He gases froze only in the outer
region
16. Observations of the Moon show that the lunar mare have only 3% as many craters as the lunar highlands. It can
be reasoned that
a. lunar lava flowed across the surface BEFORE most of the Moon's larger craters were created
b. the lunar mare must be about 4.6 billion years old
c. comets have collided with the Moon more often than with Earth
d. lunar lava flowed across the surface AFTER most of the Moon's larger craters were created.
17. Mercury's surface looks a lot like
a. the surface of Jupiter b. the surface of Mars
e. like no surface in the Solar System
c. the surface of the Moon
d. the surface of the earth
18. The lack of an atmosphere on the Moon implies that
a. it never had one
b. it escaped because of the Moon's weak gravity
c. it froze on the surface
d. it got ejected during crater formation
e. the Moon could never have been part of the earth
19. Some planets were able to retain their hydrogen and helium as they formed because
a. they were cooler
b. they were hotter
c. they were denser
d. they were smaller
e. they were closer to the sun
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Exam 2
Version = Key ID B
SOLUTIONS
March 9, 2016
20. If there were no plate motions and continent building,
a. the earth would look pretty much like it does now
b. everything would be under water
c. only the polar caps would stick out of the water
d. the continents would still be there, but the mountains would be much lower
e. the oceans would silt up
21. The convection of hot rocks in the mantle of the earth occurs because
a. water deep within the earth boils and forces rocks upward
b. the mantle is stirred by the magnetic field as the earth spins
c. over some ranges of depth, the density is almost constant, so the addition of heat makes some rocks expand
enough to become buoyant and rise
d. the motions of the continents stir up the rock underneath
e. the effects of tidal forces from the moon
22. The most useful means to explore the core and mantle of the earth is
a. studying earthquakes and seismic waves
b. drilling deep holes down into the earth
c. going down in very deep mines and making measurements
d. studying the motions of the continents
e. comparing the properties of the earth with those of other planets
23. A planet that is differentiated
a. was put together from different bodies with distinct compositions
b. formed from a dense, metallic object to which rocky debris got added later
c. developed a surface of low density rocks deposited through volcano eruptions
d. will have plate tectonics as a result
e. must have been sufficiently molten that the denser materials sank to the center
24. Which physical force dominates the process of star formation?
a. strong nuclear
b. weak nuclear
c. electrical
d. gravitational
e. reactional
25. A newly formed massive, hot star changes the surrounding interstellar gas into
a. a molecular cloud
b. a glowing cloud of excited gas called an HII region
c. a dark globule seen as a shadow against the background light
d. an HI region
e. interstellar dust
26. Why did astronomers in the 19th century believe that the solar system was close to the center of the Milky
Way?
a. we are close to the center
b. they did not have photographic plates to detect very faint stars
c. they needed UV detectors
d. their telescopes were too small to see the whole system
e. they did not realize how interstellar dust cut off their view
27. The approximate age of the Solar System is
a. 4500 years
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b. 4.5 billion years
c. 4.5 million years
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d. 10,000 years
e. we do not know the age
Exam 2
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SOLUTIONS
March 9, 2016
28. When clumps first collapse into young stars,
a. they cannot burn hydrogen because it has not settled into their cores yet
b. they cannot burn hydrogen until a spark ignites it
c. their activity level needs to rise before they can burn hydrogen
d. their cores must shrink and heat up to burn hydrogen
e. the hydrogen must be converted from molecular to atomic form to burn
29. The earth's atmosphere has
a. changed only due to the action of humans
b. remained the same since the earth formed
c. changed due to meteors
d. changed due to the moon
e. changed due to volcanoes, rainwater induced chemical reactions,
and photosynthesis
30. The arrow in the picture at left is pointing at
a. a molecular cloud
d. a planetary nebula
b. an HII region
e. a galaxy
c. an HI region
31. We know the interior of the earth is liquid because
a. on a quiet night, you can feel it slosh
b. the way the earth wobbles on its axis shows it is not all solid
c. deep gold mines reach the liquid layer
d. earthquake waves that can't go through liquids are blocked by
the interior of the earth
e. it is larger through the equator than through the poles
32. The diagram above shows the evolutionary track of a star like the Sun. At Point A, the star is
a. burning hydrogen in its core and helium in a shell
core
c. ejecting its outer layers
e. exploding as a supernova
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b. burning hydrogen in a shell around a collapsing
d. burning hydrogen in its core
Exam 2
Version = Key ID B
SOLUTIONS
March 9, 2016
33. In the Milky Way, the oldest stars are found in the
a. halo
b. bulge
c. bar
d. disk
e. tidal tails
34. Interstellar dust makes the things behind it look
a. bluer and fainter b. greener and brighter
e. redder and fainter
c. redder and more diffuse
d. it blots them out completely
35. These days, astronomers depend on ____________ for obtaining new observations of photons from the stars
a. their eyes
b. refracting telescopes
c. electronic detectors d. discovering notebooks of previous astronomers
36. Stars on the main sequence all
a. are in hydrostatic equilibrium
b. have the same mass
c. have the same temperature
d. have the same diameter
e. there is no property in common among main sequence stars
37. Heavy elements like silver and gold are formed
a. on planetary surfaces
c. in main sequence stars
e. in white dwarfs
b. in planetary nebulae
d. in supernova explosions
38. The escape velocity at a black hole's event horizon is
a. the same as from the earth
b. the speed of light
c. the same as from the Sun
d. different for different elementary particles
e. highly dependent on the black hole's characteristics
39. The Sun will end its life as
a. a neutron star
c. a black hole
e. none of the above
b. a pulsar
d. a white dwarf
40. The lowest luminosity stars on the main sequence
a. are the hottest
c. are the coolest
e. both a. and b.
b. have the longest lifetimes
d. both b. and c.
41. The Sun has been able to produce energy for billions of years by
a. a chemical process similar to burning coal b. gravitational contraction
d. nuclear fusion
e. none of these
c. absorbing light from distant stars
42. If you add mass to a white dwarf to "bulk it up" above 1.4 solar masses,
a. it will get smaller and smaller and finally collapse into a neutron star
b. it will develop strong coronal lines because of its high surface temperature
c. it will increase in radius in proportion to the cube root of the additional mass
d. the new matter will cause it to cool on the surface and get fainter
e. the matter will disappear beyond its event horizon and we will not know what happens
43. We know that the Crab nebula is a supernova remnant because
a. it contains a pulsar
b. Chinese astronomers witnessed the explosion
d. its gas is moving very rapidly e. all of the above
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c. it emits lots of x-rays
Exam 2
Version = Key ID B
SOLUTIONS
March 9, 2016
44. Planetary nebulae are
a. in the process of forming planets
c. the ejected outer layers of a dying star
e. the result of protostars having disks
b. molecular clouds
d. the precursors to black holes
45. Pulsars vary their light output by
a. sweeping a light beam across our line of sight
c. alternately expanding and contracting
e. changing their mass
b. alternately heating up and cooling off
d. converting H to He
46. The lower limit on the size of a star is set by
a. the gravitational field of a cloud
c. the amount of H that can coalesce
He
e. there is no lower limit
b. the size of cloud fragment that can form
d. the mass required to get the core hot enough for conversion of H to
47. To measure the luminosity of the sun from the earth, we need to know
a. Earth's distance from the sun
b. the flux Earth receives from the sun (the apparent brightness of the sun at the earth)
c. the sun's composition
d. all of a., b., and c.
e. both a. and b.
48. What is the closest location for finding material formed in a supernova explosion?
a. the Milky Way
b. the Orion nebula
c. the Crab Nebula
d. the Sun
e. your own body
49. Hydrogen fusion can produce energy because
a. at the end the electrons in the atoms have gone to lower energy levels and given off the energy they lost
b. the atoms join together into bigger molecules, and the molecular binding energy is released
c. the fusion products weigh a little less than the input materials, and the mass that is lost appears as
energy
d. the helium that is produced has been heated to very high temperature
e. the high pressure where the fusion takes place yields some of its energy
50. If we have a container of hydrogen gas sitting in a laboratory on Earth, why doesn't it turn into helium?
a. because trace elements are required
c. because the hydrogen needs other isotopes
e. it will become helium if you wait long enough
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b. because the temperature and pressure are too low
d. because an electric spark is needed
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