AST1002 Exam 2 Review

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AST1002 Exam 2 Review
2013-03-28 08:37:49

AST1002 Exam 2 Review
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  1. Which of the following lists the planets of our solar system in the correct order from closest to farthest from the Sun?
    Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
  2. Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?
    All the planets orbit counterclockwise around the Sun.
  3. Which of the following statements about our Sun is not true?
    The Sun's diameter is about 5 times that of Earth.
  4. Which of the following is not true of Mercury?
    It has been studied closely by several NASA spacecraft.
  5. Which of the following statements about Mars is not true?
    We could survive on Mars without spacesuits, as long as we brought oxygen in scuba tanks.
  6. The planet in our solar system with the highest average surface temperature is _________.
  7. The terrestrial planets in our solar system are __________.
    Mercury, Venus, Earth, and Mars
  8. The jovian planets in our solar system are ______________.
    Jupiter, Saturn, Uranus, and Neptune
  9. Which Jovian planet does NOT have rings?
    All the jovian planets have rings.
  10. Which moons are sometimes called the Galilean moons?
    The four largest moons of Jupiter: Io, Europa, Ganymede and Callisto
  11. The Cassini mission to Saturn consists of:
    An orbiter that orbits Saturn and a probe that descended to the surface of Titan.
  12. Which planet (besides Earth) has been visited by the largest number of robotic spacecraft?
  13. When we say that jovian planets contain significant amounts of hydrogen compounds, we mean all the following chemicals EXCEPT _________.
    Carbon dioxide
  14. In essence, the nebular theory holds that _________.
    Our solar system formed in the collapse of an interstellar cloud of gas and dust.
  15. According to modern science, what was the approximate chemical composition of the solar nebula?
    98% hydrogen and helium, 2% everything else
  16. The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from?
    They were produced by stars that lived and died before our solar system was born.
  17. According to our theory of solar system formation, what three major changes occurred in the solar nebula as it shrank in size?
    It got hotter, its rate of rotation increased and it flattened into a disk.
  18. Which of the following types of material can condense into what we call ICE at low temperatures?
    Hydrogen compounds
  19. According to our present theory of solar system formation, which of the following lists the major ingredients of the solar nebula in order form the most abundant to the least abundant?
    Hydrogen and helium gas; hydrogen compounds; rock; metal
  20. What do we mean by the frost line when we discuss the formation of planets in the solar nebula?
    It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.
  21. What do we mean by ACCRETION in the context of planet formation?
    The growth of planetesimals from smaller solid particles that collided and stuck together.
  22. What do we mean by the period of HEAVY BOMBARDMENT in the context of the history of our solar system?
    The first few hundred million years after the planets formed, which is when most impact craters were formed.
  23. What is the GIANT IMPACT HYPOTHESIS for the origin of the Moon?
    The Moon formed from material blasted out of the Earth's mantle and crust by the impact of a Mars-sized object.
  24. Suppose you start with 1 kg of a radioactive substance that has a half-life of 10 years. Which of the following statements will be true after 20 years pass?
    You'll have 0.25 kg of the radioactive substance remaining.
  25. According to modern scientific dating techniques, approximately how old is the solar system?
    4.5 billion years
  26. What is an "extrasolar planet"?
    A planet that orbits a start that is not our own Sun
  27. In essence, the Kepler mission is searching for extrasolar planets by _________.
    monitoring stars for slight dimming that might occur as unseen planets pass in front of them
  28. Compared to the distance between Earth and Mars, the distance between Jupiter and Saturn is ___________.
    Much larger
  29. How is Einstein's famous equation, E=mc^2, important in understanding the Sun?
    The sun generates energy to shine by losing 4 million tons of mass each second.
  30. In what way is Venus most similar to Earth?
    Both planets are nearly the same size.
  31. Imagine that an alien spaceship crashed onto Earth. Which statement would MOST LIKELY be true?
    It would crash in the ocean.
  32. Which of the following statements about the recently-discovered object Eris is NOT true?
    It is thought to be the first example of a new class of object.
  33. Mars has two moons that are most similar in character to:
    small asteroids
  34. Which planet listed below has the most extreme seasons?
  35. In what way is Pluto more like a comet than a planet?
    It is made mostly of rock and ice
  36. Which of the following is NOT a major pattern of motion in the solar system?
    Nearly all comets orbit the Sun in the same direction and roughly the same plane
  37. Which of the following is NOT a major difference between the terrestrial and jovian planets in our solar system?
    Terrestrial planets contain large quantities of ice and jovian planets do not.
  38. The following statements are all true. Which one counts as an "exception to the rule" in being unusual for our solar system?
    The diameter of Earth's Moon is about 1/4 that of Earth
  39. About 2% of our solar nebula consisted of elements besides hydrogen and helium. However, the very first generation of star systems in the universe probably consisted only of hydrogen and helium. Which of the following statements is most likely to have been true about these first-generation star systems?
    There were no comets or asteroids in these first-generation star systems
  40. According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?
    The law of conservation of angular momentum
  41. According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?
    The law of conservation of energy
  42. According to our present theory of solar system formation, which of the following best explains why the solar nebula ended up with a disk shape as it collapsed?
    It flattened as a natural consequence of collisions between particles in the nebula.
  43. What is the primary basis upon which we divide the ingredients of the solar nebula into four categories (hydrogen/helium; hydrogen compound; rock; metal)?
    The temperatures at which various materials will condense from gaseous form to solid form.
  44. According to our present theory of solar system formation, which of the following statements about the growth of terrestrial and jovian planets is NOT true?
    The jovian planets began from planetesimals made only of ice, while the terrestrial planets began from planetesimals made only of rock and metal.
  45. Many meteorites appear to have formed very early in the solar system's history. How do these meteorites support our theory about how the terrestrial planets formed?
    The meteorities appearance and composition is just what we'd expect if metal and rock condensed and accreted as our theory suggests.
  46. According to present understanding, which of the following statements about the solar wind is NOT true?
    It is even stronger today than it was when the Sun was young.
  47. According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
    The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
  48. According to our present theory of solar system formation, why were solid planetesimals able to grow larger in the outer solar system than in the inner solar system?
    • Because only metal and rock could condense in the inner solar system, while ice also condensed in the outer solar system.
    • According to our basic scenario of solar system formation, why do the jovian planets have numerous large moons?
    • Small moons may be captured objects, but large moons are not (with the likely exception of Triton). Recall that capturing a moon is not easy, and capturing a large moon would be especially difficult.
  49. Which of the following is not evidence supporting the idea that our Moon formed as a result of a giant impact?
    The Pacific Ocean appears to be a large crater - probably the one made by the giant impact.
  50. Why are terrestrial planets denser than jovian planets?
    Only dense materials could condense in the inner solar nebula.
  51. Suppose you find a rock that contains 10 micrograms of radioactive potassium-40, which has a half-life of 1.25 billion years. By measuring the amount of its decay product (argon-40) present in the rock, you conclude that there must have been 80 micrograms of potassium-40 when the rock solidified. How old is the rock?
    3.75 billion years
  52. How do scientists determine the age of the solar system? 
    Radiometric dating of meteorites
  53. Which of the following statements is not true about the planets so far discovered around other stars?
    Photographs reveal that most of them have atmospheres much like that of Jupiter.
  54. Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
    Planets can migrate from the orbits in which they are born.
  55. You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
    The planet must be closer to the star than Earth is to the Sun.
  56. The region of our solar system between Mercury and Mars has very few asteroids, while the region between Mars and Jupiter has many asteroids. Based on what you have learned, what is the most likely explanation for the lack of asteroids between Mercury and Mars?
    There were very few planetary leftovers in this region, because most of the solid material was accreted by the terrestrial planets as the planets formed.
  57. Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?
    Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.
  58. Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of _________.
    a golf ball to a baseball
  59. From center to surface, which of the following correctly lists the interior layers of a terrestrial world?
    core, mantle, crust
  60. What do we mean when we say that the terrestrial worlds underwent differentiation?
    When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.
  61. A terrestrial world's lithosphere is ________.
    a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle
  62. The two most important processes in heating the interiors of the terrestrial worlds are:
    (1) Heat deposited by the process of formation; (2) heat released by radioactive decay.
  63. Which of the following is an example of convection?
    Warm air expanding and rising while cooler air contracts and fall.
  64. In general, which things below are affected by a magnetic field?
    Charged particles or magnetized materials (such as iron).
  65. What is a magnetosphere?
    a region of space around a planet in which the planet's magnetic field can trap charged particles
  66. The processes responsible for virtually all surface geology are _________.
    impact cratering, volcanisms, tectonics, and erosion
  67. In the context of planetary geology, what do we mean by outgassing?
    the release by volcanism of gases that had been trapped in a planetary interior
  68. Which of the following is not an example of tectonics?
    The gradual disappearance of a crater rim as a result of wind and rain.
  69. Which of the following is the most basic definition of a greenhouse gas?
    a gas that absorbs infrared light
  70. Suppose we represent Earth with a basketball. On this scale, most of the air in Earth's atmosphere would fit in a layer that is _________.
    about the thickness of a sheet of paper
  71. Which of the following best describes the lunar maria?
    relatively smooth, flat plains on the Moon
  72. Why does the Moon have a layer of "powdery soil" on its surface?
    It is the result of countless tiny impacts by small particles striking the Moon.
  73. What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius?
    the presence of many long, tall cliffs
  74. Olympus Mons is ______.
    a huge volcano on Mars
  75. Which of the following does not provide evidence that Mars once had abundant liquid water on its surface?
    the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell
  76. Based on its surface features, the most important event on Venus in the past billion years or so was _________.
    a global "repaving" that erased essentially all the surface features that had existed earlier
  77. What do we mean by a runaway greenhouse effect?
    a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere
  78. On average, how fast do the plates move on the Earth?
    a few centimeters per year
  79. How does seafloor crust differ from continental crust?
    Seafloor crust is thinner, younger, and higher in density.
  80. In the context of plate tectonics, what is a subduction zone?
    A place where a seafloor plate is sliding under a continental plate.
  81. What is the importance of the carbon dioxide (CO2) cycle?
    It regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate.
  82. Earth has been gradually warming over the past few decades. Based on a great deal of evidence, scientists believe that this warming is caused by _____.
    human activities that are increasing the concentration of greenhouse gases in Earth's atmosphere
  83. Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny?
    its size
  84. The cores of the terrestrial worlds are made mostly of metal because ______.
    metals sunk to the centers a long time ago when the interiors were molten throughout
  85. Which internal heat source still generates heat within the terrestrial worlds today?
    Heat from radioactive decay
  86. The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that _________.
    a large baked potato takes longer to cool than a small baked potato
  87. Suppose we had a device that allowed us to see Earth's interior. If we looked at a typical region of the mantle, what would we see happening?
    not much - on human time scales, the mantle looks like solid rock
  88. Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
    Mars's interior has cooled so much its molten core layer no longer undergoes convection.
  89. Which of the following most likely explains why Venus does not have a global magnetic field like Earth?
    Its rotation is too slow.
  90. What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?
    plate tectonics and widespread erosion
  91. Which of the following general statements about Earth's atmosphere is not true?
    The nitrogen and oxygen in Earth's atmosphere keep the surface pleasantly warm.
  92. Why is the sky blue (on Earth)?
    Because molecules scatter blue light more effectively than red light
  93. Which of the following best describes how the greenhouse effect works?
    A planet's surface absorbs visible sunlight and returns this absorbed energy to space as infrared light. Greenhouse gases slow the escape of this infrared radiation, which thereby heats the lower atmosphere.
  94. Suppose that Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be ________.
    well below the freezing point of water
  95. Most of the Moon's surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
    • The maria formed after the heavy bombardment ended.
    • Which of the following best describes the geological histories of the Moon and Mercury?
    • Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
  96. What makes us think that Mars must once have had an atmosphere that was warmer and had higher surface pressure?
    The atmosphere is too cold and thin for liquid water today, yet we see evidence that water flowed on the surface in the past.
  97. All the following statements about Mars are true. Which one might have led to a significant loss of atmospheric gas to space?
    Mars lost any global magnetic field that it may once have had.
  98. Why is Mars red?
    Chemical reactions between surface rock and atmospheric oxygen literally rusted the surface.
  99. All of the statements below are true. Which one gives the primary reason why the surface of Venus today is some 450°C hotter than the surface of Earth?
    Venus has a much stronger greenhouse effect than Earth.
  100. Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
    The high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle
  101. Which of the following best explain what we think happened to outgassed water vapor on Venus?
    Ultraviolet light split the water molecules, and the hydrogen then escaped to space.
  102. Which of the following is the underlying reason why Venus has so little wind erosion?
    its slow rotation
  103. All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
    Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
  104. Why are there fewer large impact craters on the Earth's seafloor than on the continents?
    Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.
  105. Why is Earth's continental crust lower in density than seafloor crust?
    Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.
  106. Which two factors are most important to the existence of plate tectonics on Earth?
    mantle convection and a thin lithosphere
  107. Why does Earth have so little carbon dioxide in its atmosphere compared to Venus?
    Earth has just as much carbon dioxide as Venus, but most of it is locked up in carbonate rocks rather than being free in the atmosphere.
  108. Which two factors are critical to the existence of the carbon dioxide (CO2) cycle on Earth?
    plate tectonics and liquid water oceans
  109. Suppose Earth were to cool down a little. How would the carbon dioxide cycle tend to restore temperatures to normal?
    Cooler temperatures lead to slower formation of carbonate minerals in the ocean, so carbon dioxide released by volcanism builds up in the atmosphere and strengthens the greenhouse effect.
  110. Which of the following is not an expected consequence of global warming?
    The entire Earth will warm up by the same amount.
  111. The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
    Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
  112. The choices below describe four hypothetical planets. Which one's surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
    Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
  113. The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
    Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
  114. What's the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead?
    its small size compared to Earth
  115. Which of the following is not a general characteristic of the four jovian planets in our solar system?
    They are higher in average density than are the terrestrial planets.
  116. Which of the following best describes the internal layering of Jupiter, from the center outward?
    Core of rock, metal, and hydrogen compounds; thick layer of metallic hydrogen; layer of liquid hydrogen; layer of gaseous hydrogen; cloud layer
  117. Which of the following statements comparing the jovian interiors is not thought to be true?
    They all have the same exact set of internal layers, though these layers differ in size.
  118. Overall, Jupiter's composition is most like that of _________.
    the Sun
  119. Jupiter's colors come in part from its three layers of clouds. Which of the following is not the primary constituent of one of Jupiter's cloud layers?
    clouds of sulfuric acid
  120. How do typical wind speeds in Jupiter's atmosphere compare to typical wind speeds on Earth?
    They are much faster than hurricane winds on Earth.
  121. What is the Great Red Spot?
    a long-lived, high-pressure storm on Jupiter
  122. What atmospheric constituent is responsible for the blue color of Uranus and Neptune?
  123. How does the strength of Jupiter's magnetic field compare to that of Earth's magnetic field?
    Jupiter's magnetic field is about 20,000 times as strong as Earth's.
  124. Which of the following statements about the moons of the jovian planets is not true?
    Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids.
  125. Which statement about Io is true?
    It is the most volcanically active body in our solar system.
  126. Which moon has a thick atmosphere made mostly of nitrogen?
  127. The Huygens probe took numerous pictures as it descended to Titan's surface in 2005. What did the pictures show?
    • features or erosion, including what appeared to be dry river valleys and lakebeds
    • Which moon is considered likely to have a deep, subsurface ocean of liquid water?
    • Europa
  128. Which large jovian moon is thought to have been captured into its present orbit?
  129. Suppose you could float in space just a few meters above Saturn's rings. What would you see as you looked down on the rings?
    countless icy particles, ranging in size from dust grains to large boulders
  130. Which statement about planetary rings is not true?
    Saturn's rings formed along with its moons 4.6 billion years ago.
  131. Which of the following gases is not a significant ingredient of the jovian planet atmospheres?
    carbon dioxide
  132. Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?
    They actually contain relatively little material in a gaseous state.
  133. What would happen to Jupiter if we could somehow double its mass?
    Its density would increase but its diameter would barely change.
  134. According to our theory of solar system formation, why did Uranus and Neptune end up to be much less massive than Jupiter and Saturn?
    Particles in the solar nebula were more spread out at greater distances, so that accretion took longer and there was less time to pull in gas before the solar wind cleared the nebula.
  135. Why does Jupiter have three distinct layers of clouds?
    The three layers represent clouds made of gases that condense at different temperatures.
  136. Which of the following best why we see horizontal "stripes" in photographs of Jupiter and Saturn?
    The light stripes are regions of high clouds, and the dark stripes are regions where we can see down to deeper, darker clouds.
  137. Uranus and Neptune have methane clouds but Jupiter and Saturn do not. Which factor explains why?
    Temperatures on Jupiter and Saturn are too high for methane to condense.
  138. Which jovian planet should have the most extreme seasonal changes?
  139. Why is the radiation so intense in the region that traces Io's orbit around Jupiter (the Io torus)?
    The region is full of gases that become ionized after they are released from volcanoes on Io.
  140. Which of the following best explains why many jovian moons have been more geologically active than the Moon or Mercury?
    Jovian moons are made mostly of ice that can melt or deform at lower temperatures than can the rock and metal that make up the Moon and Mercury.
  141. All the following statements are true. Which one is most important in explaining the tremendous tidal heating that occurs on Io?
    Io orbits Jupiter on an elliptical orbit, due to orbital resonances with other satellites.
  142. Which of the following is not a piece of evidence supporting the idea that Europa may have a subsurface ocean?
    Astronomers have detected small lakes of liquid water on Europa's surface.
  143. Which of the following is most unlikely to be found on Titan?
    lakes of liquid water in the warmer equatorial regions
  144. Why do astronomers believe that Triton is a captured moon?
    Triton orbits Neptune in a direction opposite that of Neptune's rotation.
  145. Which statement about Saturn's rings is not true?
    The rings must look much the same today as they did shortly after Saturn formed.
  146. According to current understanding, which of the following is required in order for a planet to have rings?
    The planet must have many small moons that orbit relatively close to the planet in its equatorial plane.
  147. Which of the following statements is not true?
    Objects in the Kuiper belt are made mostly of rock and metal.
  148. A rock found on Earth that crashed down from space is called _________.
    a meteorite
  149. The asteroid belt is located _________.
    between the orbits of Mars and Jupiter
  150. Which statement about asteroids is not true?
    If we could put all the asteroids together, they would make an object about the size of Earth.
  151. A typical meteor is created by a particle about the size of a _________.
  152. What do we mean by a primitive meteorite?
    a piece of rock that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago
  153. Among discovered meteorites, we have found some with all the following origins except _________.
    being a fragment from Comet Halley
  154. Which statement is not thought to be true of all comets in our solar system?
    Comets always have tails.
  155. Which direction do a comet's dust and plasma tails point?
    generally away from the Sun
  156. When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _________.
    the coma
  157. The total number of comets orbiting the Sun is estimated to be about _________.
    1 trillion
  158. What is Charon?
    the largest of Pluto's three known moons
  159. According to current evidence, Pluto is best explained as ______.
    a large member of the Kuiper belt
  160. What is Eris?
    An icy object that orbits in the Kuiper belt and is larger than Pluto
  161. What was the Shoemaker-Levy 9 impact?
    the 1994 impact of a chain of comet fragments into Jupiter
  162. What do we mean by a mass extinction?
    the extinction of a large fraction of the world's plant and animal species in a relatively short period of time
  163. If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because ______.
    of global climate effects initiated by dust and smoke that entered the atmosphere after the impact
  164. Which of the following statements best describes the size of the largest asteroid, Ceres?
    It is a little less than half the diameter of our Moon.
  165. If we could put all the asteroids together, their total mass would be _________.
    much less than the mass of any terrestrial planet
  166. Why didn't a planet form where the asteroid belt is now located?
    Gravitational tugs from Jupiter prevented material from collecting together to form a planet.
  167. Gaps in the asteroid belt (often called Kirkwood gaps) are caused by ______.
    orbital resonances with Jupiter
  168. When you see the bright flash of a meteor, what are you actually seeing?
    the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere
  169. In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder-size objects. Which of the following real things in our solar system would look most like such science fiction dangers?
    the rings of Saturn
  170. Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements must be true?
    Your meteorite is a fragment from the core of a large asteroid that shattered in a collision.
  171. Which of the following objects are probably not located in the same general region of the solar system in which they originally formed?
    Oort cloud comets
  172. Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different?
    It would have only one tail instead of two.
  173. Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?
    It has been on its current orbit for only a very short time compared to the age of our solar system.
  174. When we see a meteor shower, it means that _________.
    Earth is crossing the orbit of a comet
  175. Why won't Pluto collide with Neptune?
    • Pluto orbits the Sun exactly two times for every three Neptune orbits, which ensures they never come close together.
    • What is Pluto's moon Charon thought to have in common with our own Moon?
    • It probably formed as a result of a giant impact.
  176. Which of the following is not a piece of evidence supporting the idea that Pluto is a large comet of the Kuiper belt?
    Pluto grows a coma and a long tail when it is at the point in its orbit closest to the Sun.
  177. The discovery of Eris __________.
    was not surprising, because other Kuiper belt objects approaching the size of Pluto had already been discovered
  178. Which of the following is not a piece of evidence supporting the idea that an impact caused the mass extinction that occurred 65 million years ago?
    Fossilized dinosaur bones contain fragments of rock from the impact.
  179. Suppose that large jovian planets had never formed in our solar system. Which of the following would most likely be true?
    Neither the asteroid belt nor Oort cloud would exist.
  180. According to modern science, approximately how old is the Sun?
    4 1/2 billion years
  181. The Sun will exhaust its nuclear fuel in about ______.
    5 billion years
  182. Which of the following correctly describes how the process of gravitational contraction can make a star hot?
    When a star contracts in size, gravitational potential energy is converted to thermal energy.
  183. What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
    gravitational force and outward pressure
  184. The source of energy that keeps the Sun shining today is _________.
    nuclear fusion
  185. Energy balance in the Sun refers to a balance between _________.
    the rate at which fusion generates energy in the Sun's core and the rate at which the Sun's surface radiates energy into space
  186. When we say that the Sun is a ball of plasma, we mean that _________.
    the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)
  187. What is the Sun made of (by mass)?
    70% hydrogen, 28% helium, 2% other elements
  188. From center outward, which of the following lists the "layers" of the Sun in the correct order?
    Core, radiation zone, convection zone, photosphere, chromosphere, corona
  189. What are the appropriate units for the Sun's luminosity?
  190. The Sun's surface, as we see it with our eyes, is called the _________.
  191. The Sun's average surface (photosphere) temperature is about ______.
    5,800 K
  192. What is the solar wind?
    a stream of charged particles flowing outward from the surface of the Sun
  193. The fundamental nuclear reaction occurring in the core of the Sun is _________.
    nuclear fusion of hydrogen into helium
  194. The proton-proton chain is _________.
    the specific set of nuclear reactions through which the Sun fuses hydrogen into helium
  195. The overall result of the proton-proton chain is:
    4 H becomes 1 He + energy
  196. To estimate the central temperature of the Sun, scientists _________.
    use computer models to predict interior conditions
  197. Why are neutrinos so difficult to detect?
    They have a tendency to pass through just about any material without any interactions.
  198. The light radiated from the Sun's surface reaches Earth in about 8 minutes, but the energy of that light was released by fusion in the solar core about _________.
    a few hundred thousand years ago
  199. What happens to energy in the Sun's convection zone?
    Energy is transported outward by the rising of hot plasma and sinking of cooler plasma.
  200. What do sunspots, solar prominences, and solar flares all have in common?
    They are all strongly influenced by magnetic fields on the Sun.
  201. Which of the following is not a characteristic of the 11-year sunspot cycle?
    The sunspot cycle is very steady, so that each 11-year cycle is nearly identical to every other 11-year cycle.
  202. How is the sunspot cycle directly relevant to us here on Earth?
    Coronal mass ejections and other activity associated with the sunspot cycle can disrupt radio communications and knock out sensitive electronic equipment.
  203. In the late 1800s, Kelvin and Helmholtz suggested that the Sun stayed hot due to gravitational contraction. What was the major drawback to this idea?
    It predicted that the Sun could shine for about 25 million years, but geologists had already found that Earth is much older than this.
  204. When is/was gravitational contraction an important energy generation mechanism for the Sun?
    It was important when the Sun was forming from a shrinking interstellar cloud of gas.
  205. What do we mean when we say that the Sun is in gravitational equilibrium?
    There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
  206. Which of the following is the best answer to the question, "Why does the Sun shine?"
    As the Sun was forming, gravitational contraction increased the Sun's temperature until the core become hot enough for nuclear fusion, which ever since has generated the heat that makes the Sun shine.
  207. How does the Sun's mass compare to Earth's mass?
    The Sun's mass is about 300,000 times the mass of the Earth.
  208. Which of the following best describes why the Sun emits most of its energy in the form of visible light?
    Like all objects, the Sun emits thermal radiation with a spectrum that depends on its temperature, and the Sun's surface temperature is just right for emitting mostly visible light.
  209. The Sun's surface seethes and churns with a bubbling pattern. Why?
    We are seeing hot gas rising and cool gas falling due to the convection that occurs beneath the surface.
  210. Which of the following correctly compares the Sun's energy generation process to the energy generation process in human-built nuclear power plants?
    The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
  211. Every second, the Sun converts about 600 million tons of hydrogen into 596 million tons of helium. The remaining 4 million tons of mass is _________.
    converted to an amount of energy equal to 4 million tons times the speed of light squared
  212. Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
    Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold.
  213. If the Sun's core suddenly shrank a little bit, what would happen in the Sun?
    • The core would heat up, fusion rates would increase, the core would re-expand.
    • Why does the Sun emit neutrinos?
    • Fusion in the Sun's core creates neutrinos.
  214. If the Sun suddenly stopped emitting neutrinos, what might we infer (after checking that our neutrino detectors were still operational)?
    Fusion reactions in the Sun have ceased.
  215. Why do sunspots appear dark in pictures of the Sun?
    They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.
  216. The star Alpha Centauri A is the same type of star as the Sun, but its luminosity is about 1.6 times that of the Sun. What can we conclude?
    Alpha Centauri A fuses hydrogen into helium in its core at a higher rate than our Sun.
  217. How can we best observe the Sun's chromosphere and corona?
    The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.
  218. The intricate patterns visible in an X-ray image of the Sun generally show _________.
    extremely hot plasma flowing along magnetic field lines
  219. How can we measure the strength of magnetic fields on the Sun?
    By looking for the splitting of spectral lines in the Sun's spectrum
  220. Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because _________.
    Earth's upper atmosphere tends to expand during solar maximum, exerting drag on satellites in low orbits
  221. Which of the following choices is not a way by which we can study the inside of the Sun?
    We can send a space probe into the Sun's photosphere.
  222. A computer accessory salesman attempts to convince you to purchase a "solar neutrino" shield for your new computer. (It's even "on sale" !) Why do you turn down this excellent offer?
    Neutrinos rarely, if ever, interact with your computer.