|
| The Outermost Planets |
 |
1. | For a planet and moon of similar density, the Roche Limit is 2.44 planetary radii. Do the rings of Saturn, Jupiter, Uranus, and Neptune lie inside or outside the Roche Limit? |
|
2. | Compare the densities of Uranus, Saturn, and Jupiter. Use the escape velocity calculator and the molecular speed calculator to give a possible explanation in terms of the concentration of lighter elements. |
 |
3. | In what year will Neptune complete one orbit since its discovery? |
|
4. | If you lived at the north pole of Uranus, describe the motion of the Sun over the 84-year orbit of Uranus. |
|
5. | Dynamo theories for the origin of magnetic fields typically predict that the magnetic dipole does not align exactly with the rotation axis, but that it should not tilt very much (not more than 10 degrees of tilt, say). By this criterion, which planets have anomalous (that is, "unusual") magnetic fields? |
|
6. | Uranus has a magnetic field comparable in strength to that of Earth and Van Allen belts, but the concentration of charged particles in these belts seems to be less than for Earth (as inferred, for example, from aurora intensities). Can you propose a simple explanation? Hint: Does the distance from the Sun matter? |
|
7. | The solar constant for the Earth is about 1400 watts per square meter. What is the corresponding solar constant for Pluto? |
|
8. | The moon Nereid of Neptune has an orbital period of 359 days. What is wrong with the following (incorrect) logic: Since this is about one Earth year, by Kepler's third law the radius of the orbit for this moon must be about 1 AU. |
|
9. | What is the angle subtended by Neptune on the celestial sphere as viewed from Earth? |
|
10. | Methane gas absorbs most strongly at 619 and 890 nm. What color regions are these in and what effect will methane have on white light that passes through it? |
|
11. | Several of the small moons discovered by Voyager around Neptune orbit inside the rings. How do we know that they must be captured objects? |
|
12. | What are two things that suggest that Triton may be a captured object? |
 |
13. | Neptune's large moon Nereid is on a very large, very elliptical orbit, with an orbital period of a little over 359 days. Use Kepler's laws to determine the average separation of Nereid from Neptune. |
|
14. | How large would Charon appear in the sky as viewed from Pluto (relative to the size of the Moon as viewed from Earth). |
|
15. | Repeat the preceding question, but now how large would Pluto appear in the sky as viewed from Charon? |
|
16. | Describe the motion of Charon as viewed from a point on Pluto. |
|
17. | Repeat the above question but for the motion of Pluto as viewed from Charon. |
|
18. | How long does it take light to travel from the Sun to Pluto if Pluto is at its average separation from the Sun? |