580 PART 4^ |^ THE SOLAR SYSTEM
Learning to Look
- What do you see in the image to the
right that tells you the size of plan-
etesimals when the solar system was
forming? - Discuss the surface of the asteroid
Mathilde, pictured to the right. What do
you see that tells you something about
the history of the asteroids? - What do you see in this image of the
nucleus of Comet Borrelly that tells you
how comets produce their comae and
tails?
telescopes is about 1 arc second and of Hubble about 0.1 arc second.
Ceres’s average distance from the sun is 2.8 AU.)- What is the orbital period of Ceres? (Hints: Use Kepler’s third law and
refer to the previous problem for Ceres’s average distance from the
sun.) - At what distances from the sun would you expect to fi nd Kirkwood
gaps where the orbital period of asteroids is one-half of, and one-third
of, the orbital period of Jupiter? Compare your results with Figure
25-9. (Hint: Use Kepler’s third law.) - If the velocity of the solar wind is about 400 km/s and the visible tail
of a comet is 1 108 km long, how long does it take a solar wind
atom to travel from the nucleus to the end of the visible tail? - If you saw Comet Halley when it was 0.7 AU from Earth and it had a
visible tail 5° long, how long was the tail in kilometers? Suppose that
the tail was not perpendicular to your line of sight. Is your fi rst answer
too large or too small? (Hint: Use the small-angle formula, Chapter 3.) - What is the orbital period of a comet nucleus in the Oort cloud? What
is its orbital velocity? (Hints: Use Kepler’s third law. The circumference
of a circular orbit 2 πr. Refer to the text for typical Oort cloud object
distances from the sun.) - The mass of an average comet’s nucleus is about 10^12 kg. If the Oort
cloud contains 2 1011 comet nuclei, what is the mass of the cloud in
Earth masses? Compare that with Jupiter’s mass. (Hint: See Appendix
Table A-10.)
Russell Kempton, New England MeteoriticalServicesVisual NASAVisual NASA