Astronomy 1002
Homework #4


1. How do Saturn’s rings rotate?
  1. like a solid body
  2. according to Kepler’s laws
  3. slowly in the inner and outer regions and rapidly in the middle areas


2. Jupiter gives off more energy than it receives from the Sun. What is the source of this excess energy?
  1. lightning bolts in the atmosphere
  2. internal heat left over from its formation
  3. the tidal force between the planet and the Sun
  4. energy absorbed from beyond the solar system and then re-emitted


3. What is Jupiter’s Great Red Spot thought to be?
  1. a disturbance in its atmosphere where some type of asteroid hit the planet
  2. the outgassing of an enormous volcano
  3. a violent and long-lived storm, like a cyclone
  4. a portion of the atmosphere where the composition is different, causing it to reflect different colors
  5. an enormous lake of burning sulfur


4. From the observed densities of the Jovian planets, we infer that they are made primarily of ?
  1. oxygen.
  2. iron.
  3. carbon dioxide.
  4. nitrogen.
  5. hydrogen.


5. Why do the giant planets have rings and the terrestrial planets do not?
  1. coincidence
  2. The inner solar system was cleared of debris by the solar wind early in its history.
  3. The large gravity of the giant planets meant that colliding satellites would break up into smaller pieces that would form a ring.
  4. The large gravity of the giant planets produced strong tidal forces that prevented satellite formation close to the planet.
  5. Only the giant planets have a Roche limit.


6. Amalthea is a small and irregularly shaped satellite orbiting close to Jupiter. What is a reasonable inference about Amalthea?
  1. It might be a captured asteroid.
  2. It is material that broke away from Jupiter.
  3. It broke off one of the larger Jovian satellites.
  4. It is small because tidal forces prevented it from becoming larger.
  5. No inference can be made without further information.


7. What makes it possible for astronomers to calculate the masses of the Jovian planets?
  1. the presence of magnetic fields.
  2. the presence of satellites.
  3. their known diameters.
  4. their known densities.
  5. their known distances.


8. Which one of the Jovian planets and Pluto has the most extreme seasonal variations?
  1. Saturn
  2. Pluto
  3. Jupiter
  4. Uranus
  5. Neptune


9. Which of the following quantities determines whether a planet will exhibit seasons?

  1. average distance from the Sun
  2. rotation period
  3. density
  4. atmospheric composition
  5. axial tilt

10. What do astronomers infer about Jupiter from the presence of its magnetic field?
  1. the presence of a small metallic core.
  2. the presence of a rotating core of liquid metallic hydrogen in the interior.
  3. the presence of a metallic core occupying at least 50% of the planet’s volume.
  4. the presence of extensive storm systems on the planet’s surface.
  5. the emission of about twice as much energy as is received from the Sun.


11. Jupiter’s Galilean satellites have higher densities than the satellites of the other Jovian planets. We can infer that the Galilean satellites contain more _____ than the satellites of the other Jovian planets.
  1. water ice
  2. methane and ammonia ices
  3. liquid water
  4. silicate materials like the Moon
  5. mixtures of all the above


12. Which features characterize Io?

  1. a heavily cratered surface
  2. a smooth, featureless surface
  3. volcanic flows
  4. cratered regions as well as smooth, mare-like areas
  5. regions containing linear fault-like structures


13. What features characterize Ganymede?
  1. a heavily cratered surface
  2. a smooth, featureless surface
  3. volcanic flows
  4. cratered regions as well as smooth, mare-like areas
  5. regions containing fault-like structures


14. What might you reasonably conclude about the origin of a small Jovian satellites that orbit in a direction opposite to the largest satellites?
  1. They were captured asteroids.
  2. They were captured comets.
  3. They formed from debris left over after the larger satellites formed.
  4. They formed from debris that was produced when two other Jovian satellites collided.
  5. No reasonable hypotheses are available.


15. How can one explain the observation that so many

of Saturn’s satellites are so different on opposite sides?
  1. each satellite is formed differently
  2. the rotation periods are the same as the revolution period
  3. tidal heating of the satellites closest to the planet
  4. different chemical compositions on different sides
  5. rapid rotations for the satellites


16. What features characterize Titan?

  1. bright, wispy structures covering the surface
  2. the presence of an extremely large crater
  3. the presence of an atmosphere
  4. one side being bright and the other being dark
  5. a bright, geologically young surface


17. Why were the ring "spokes" observed in Saturn’s ring system unexpected?
  1. Because, according to Newton’s laws, the material forming the spokes should form a small satellite.
  2. Because, according to Newton’s laws, as the particles collide, they should be ejected from the ring system.
  3. Because, according to Kepler’s 3rd law, the particles forming the spokes should spread around the rings rapidly.
  4. Because, according to the theory of the Roche limit, the dust particles making the spokes should not be present.


18. What is at least one reason why rings are thought to be sharp-edged, rather than fuzzy-edged?
  1. They are inside the Roche limit
  2. Saturn’s gravity does not act beyond the edge of the ring
  3. The presence of shepherd satellites
  4. Saturn’s magnetic field
  5. passing comets disrupt material outside the ring, thus making it sharp-edged


19. In which one of the following ways is Pluto similar to the Jovian?
  1. It has a low density.
  2. It has a strong magnetic field.
  3. It has a satellite.
  4. Its composition is hydrogen and helium.



20. Pluto’s formation is puzzling. How do astronomers now believe it formed?
  1. It was an ejected satellite from Neptune.
  2. It was an ejected satellite from Uranus.
  3. It was torn from a passing cloud of material.
  4. It condensed from the solar nebula.
  5. Either A or D could be correct



21. Which of the following planets would come closest to floating in a giant interplanetary bathtub filled with water?
  1. Jupiter
  2. Mercury
  3. Saturn
  4. Neptune
  5. Uranus


22. Why is the interior of Io so hot?
  1. Jupiter exerts strong tidal forces on it.
  2. Jupiter’s magnetic field causes an electrical current to flow through it.
  3. Jupiter bombards Io with radioactivity from its Van Allen belts.
  4. It has active volcanoes.
  5. It is often struck by passing comets and asteroids.


23. How are the periodic variations (every 6 days) seen in Pluto’s brightness explained?
  1. by aurorae generated by Pluto’s magnetic field as the planet spins
  2. by small amounts of volcanic activity
  3. by seasonal changes affecting the colors of the planet’s surface
  4. by the changing distance of Pluto from the Sun
  5. by bright and dark areas on the surface of a rotating planet


24. A friend of yours argues that Pluto is probably an escaped satellite of one of the giant planets. What piece of evidence could you cite that would best argue -against- this idea?
  1. Pluto has a Moon of its own.
  2. The inclination of Pluto’s orbit to the ecliptic plane.
  3. Pluto has a very low mass.
  4. The eccentricity of Pluto’s orbit.
  5. Pluto would be orbiting in the other direction if this idea was true.


25. Two planets have equal mass and equal amounts of atmosphere of identical chemical composition, but one is closer to the Sun than the other. Which statement will be true?
  1. After a time, the planet closer to the Sun will have less atmosphere
  2. After a time, the planet closer to the Sun will have more atmosphere
  3. Distance from the Sun should not affect the amount of atmosphere


26. Which one of the following is composed primarily of hydrogen and helium?
  1. the giant planets only
  2. the terrestrial planets only
  3. all of the planets
  4. none of the planets


27. What is density?
  1. the volume containing a mass of 1 mass unit.
  2. the weight contained inside a volume of 1 volume unit.
  3. the amount by which something is condensed.
  4. the number of molecules of air inside one square centimeter.
  5. the amount of mass inside a volume of 1 volume unit.


28. Which of the following is -not- characteristic of the terrestrial planets?
  1. short period of rotation around the Sun
  2. closeness to the Sun
  3. small number of natural satellites
  4. high density
  5. large mass


29. Why did proto-terrestrial planets have a different chemical composition than proto-jovian planets?
  1. They formed from radically different material.
  2. Terrestrial planets are smaller than Jovian planets.
  3. High temperatures in the inner solar system made the difference.
  4. The many satellites of the Jovian planets changed the planet’s atmosphere.
  5. Jovian planets are much larger than terrestrial planets.


  1. Which of the following lists the planets in order of their average distance from the Sun?
  1. Mercury, Earth, Venus, Mars, Jupiter, Saturn, Neptune, Uranus, Pluto
  2. Mercury, Venus, Earth, Mars, Uranus, Jupiter, Saturn, Neptune, Pluto
  3. Mars, Venus, Earth, Mercury, Jupiter, Saturn, Uranus, Neptune, Pluto
  4. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto
  5. Mars, Venus, Earth, Mercury, Saturn, Jupiter, Uranus, Neptune, Pluto


31. Why is Pluto not always the most distant planet from the Sun?
  1. Its epicycle is so large that it carries the planet both closer and farther than Neptune from the Sun.
  2. Its orbit is more elliptical than the orbit of other planets.
  3. The statement is false; Pluto is always the most distant planet.


32. Which one of the following statements concerning comets is correct?
  1. Comets appear to come primarily from the direction of the constellation Hercules.
  2. Comets are observed in all directions on the celestial sphere.
  3. Comets are best seen after midnight.
  4. Comets orbit the Sun in nearly circular orbits.


33. Suppose you wanted to study objects whose chemical make-up was most like that of the solar system at the time it formed. Thus, you would want to study objects that had undergone the least amount of chemical change. Which one of the following would contain such material and thus be the best to study?
  1. the giant planets
  2. the asteroids
  3. the comets
  4. iron meteorites
  5. the Earth


34. What is the source of particles that impinge on the Earth during a meteor shower?
  1. stray material from the asteroid belt
  2. a pervasive distribution of dust particles that exists throughout the ecliptic plane of the solar system
  3. material evaporated from and strewn out along the orbits of comets
  4. ejecta from impacts on the lunar surface that fall to Earth
  5. primary cosmic ray particles


35. What is a meteor?
  1. a rock traveling through space
  2. a rock traveling through the Earth’s atmosphere
  3. a luminous trail left by a rock passing through the atmosphere
  4. a rock from space that has passed through the atmosphere and landed on the Earth’s surface
  5. all the above


36. Which of the following best argues -against- the asteroids coming from the breakup of a planet?
  1. The asteroid orbits are confined to the ecliptic.
  2. The average asteroid diameter is only a few kilometers in size.
  3. Some asteroids are reddish while others are dark.
  4. The total amount of mass in the asteroid belt is small compared to a planet.
  5. The asteroids are gaseous while the planets are rocky.


37. What is a strong piece of evidence that the solar system is surrounded by some kind of "comet cloud"?
  1. The effect of the cloud’s gravity on the orbit of Neptune.
  2. The detection of faint objects in the comet cloud by sensitive telescopes.
  3. The fact that nearby stars perturb objects in the cloud into orbits that pass near the Sun.
  4. The fact that the composition of comets gives us clues about the composition of the early Solar Nebula.
  5. The fact that comets exist now, 5 billion years after the solar system formed.