Download Astronomy HOMEWORK Chapter 8

Astronomy
HOMEWORK Chapter 8 - 9th Edition
Study and be prepared: 1-26, except “Interactive Questions.”
Turn in:
1. Which is the most massive planet in the solar system? Jupiter (d) is the most massive planet in
our solar system – more than 3 times the mas of Saturn, which is in second place.
2. Which of the following planets does NOT have rings? Choose only one. (a) Mars; (b) Uranus;
(c) Neptune; (d) Saturn; (e) Jupiter.
Mars (a) does not have rings. All 4 of the outer planets do have rings. Saturn’s are far and away the
most prominent.
9. What is liquid metallic hydrogen? Which planets contain this substance? What [conditions
produce ] this form of hydrogen?
Liquid metallic hydrogen is a phase of hydrogen which conducts electricity. Only Jupiter and Saturn
contain hydrogen in this form. This form of hydrogen exists only at cool or cold temperatures, and at
extreme pressure. No other planet has enough mass to produce enough pressure. The Sun has plenty
of gravity, but is too hot.
16. Why do features in Saturn’s atmosphere appear much fainter and “washed out” than comparable
features in Jupiter’s atmosphere?
Saturn has less than 1/3 the mass of Jupiter. Therefore, there is less surface gravity to drive the flows
which create the banded structure.
17. Explain how shepherd satellites affect some planetary rings. Is “shepherd satellites” an appropriate term for these objects? Explain your answer.
Two shepherd satellites for Saturn (Prometheus and Pandora) keep particles in the thin F-ring by
alternately speeding them up slightly (the inner satellite) and slowing them down slightly (the outer
satellite). Since they are keeping the ring particles moving in a herd, as do good sheep-herding dogs,
the term is appropriate. Other shepherd satellites keep other rings in place. For example, Mimas
maintains the Cassini division from a distance by gravitational resonance.
26. Explain why Triton will never collide with Neptune, even though it is spiraling toward that
Planet.
Triton will be torn apart by tidal stresses before it collides. It will then form a prominent ring system.
37. What IF: Jupiter, at its present location, were a star? What would Earth be like? (Hint: Recall
that to be a star, Jupiter would have to have 75 times more mass than it has today.) [To make the
question a little less open-ended, let’s give it a mass of 0.1 times that of the Sun, which is 100× its
current mass. Such a star will have a light/heat output of 0.001 that of the Sun.]
Jupiter would be much brighter when visible in the night sky. With the parameters I gave, it turns
out that StarJup would be somewhat brighter than the full moon. This would not be enough to warm
the Earth significantly, but would affect nocturnal life. The position of StarJup relative to the Sun
would be more significant than the phase of the Moon. StarJup’s increased gravity would clear out
debris much faster, but would also perturb orbits to a much greater extent. Orbits would be unstable
and planets could well be ejected from this hypothetical system.