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| 1 |  |  Why was it necessary for Herschel to observe Uranus on more than a single night for him to be convinced that he had discovered a new object within our solar system? |
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| 2 |  |  What was the reason that, after the discovery of Uranus, astronomers began to believe that there was a planet beyond Uranus? |
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| 3 |  |  The discovery of Neptune is usually attributed to John Couch Adams and Urbain Leverrier. What did they do to warrant this recognition? |
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| 4 |  |  Why is it sometimes said that the discovery of Pluto near the position predicted by Percival Lowell was a lucky accident? |
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| 5 |  |  In what ways are Uranus and Neptune similar and in what ways are they different? |
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| 6 |  |  Describe why the pattern of sunlight and darkness for a hypothetical inhabitant of Uranus's polar regions has little relationship to the rotational period of Uranus. |
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| 7 |  |  Why doesn't the severe tilt of the rotation axis of Uranus result in great temperature differences between the day side and the night side of the planet? |
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| 8 |  |  What may be the reason that Uranus sometimes lacks the cloud features found on Neptune? |
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| 9 |  |  Neptune is 50% farther from the Sun than Uranus is, yet their atmospheric temperatures are nearly the same. How is this possible? |
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| 10 |  |  What evidence do we have that the rock and ice in Uranus and Neptune are concentrated near the centers of those planets? |
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| 11 |  |  How do the icy-rocky cores of Neptune and Uranus compare with those of Jupiter and Saturn? |
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| 12 |  |  What is unusual about the magnetic fields of Uranus and Neptune compared with those of the other planets? |
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| 13 |  |  What evidence do we have to suggest that the magnetic fields of Uranus and Neptune don't originate in currents in the central regions of those planets? |
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| 14 |  |  How were the ring systems of Uranus and Neptune detected before they were actually seen in Voyager 2 images? |
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| 15 |  |  How does the appearance of the rings of Uranus compare with the appearance of the rings of Saturn? |
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| 16 |  |  How do we know that there is fine dust between the rings of Uranus? |
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| 17 |  |  What is the reason that some of the predicted occultations of stars by Neptune's rings could not be detected from the Earth? |
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| 18 |  |  Why is it sometimes incorrect to say that Pluto is the further from the Sun than is Neptune? |
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| 19 |  |  How do we know the length of the rotation period of Pluto? |
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| 20 |  |  How did the discovery of Pluto's satellite, Charon, make it possible to calculate the mass of Pluto? |
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| 21 |  |  What arguments can be used to refute the proposition that Pluto is an escaped satellite of Neptune? |
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| 22 |  |  Describe the different ways in which searches for solar system planets beyond Pluto have been carried out. What were the results of those searches? |
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| 23 |  |  How do dwarf planets differ from planets? |
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