AST 105 HW #6
Week of September 28th, 2015
Note: All Problems are from The Cosmic Perspective (6ed)
Chapter 8
Review Problems
1. What are the four major features of our solar system that provide clues to how it formed? Describe each
one briefly.
2. What is the nebular theory, and why is it widely accepted by scientists today?
4. Describe each of the three key processes that led the solar nebula to take the form of a spinning disk.
What observational evidence supports this scenario?
6. What was the frost line in the solar nebula? Explain how temperature difference let to the formation of
two distinct types of planets.
12. How do we think the Moon formed, and what evidence supports this hypothesis?
Quick Quiz
Choose the best answer to each of the following. Explain your reasoning with one or more complete
sentences.
25. How many of the planets orbit the Sun in the same direction that Earth does?
(a) a few (b) most (c) all
27. The solar nebular was 98%
(a) rock and metal.
(b) hydrogen compounds.
(c) hydrogen and helium.
30. Which lists the major steps of solar system formation in the correct order?
(a) collapse, accretion, condensation
(b) collapse, condensation, accretion
(c) accretion, condensation, collapse
32. Why didn't a terrestrial planet form at the location of the asteroid belt?
(a) There was never enough material in that part of the solar nebula.
(b) The solar wind cleared away nebular material there.
(c) Jupiter's gravity kept planetesmials from accreting.
34. About how old is the solar system?
(a) 4.5 million years
(b) 4.5 billion years
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(c) 4.5 trillion years
Quantitative Problems
Be sure to show all calculations clearly and state your final answers in complete sentences.
48. Radiometric Dating
You are analyzing rocks that contain small amounts of potassium-40 and argon-40. The half-life of
potassium-40 is 1.25 billion years.
a. You find a rock that contains equal amounts of potassium-40 and argon-40. How old is it? Explain
b. You find a rock that contains three times as much argon-40 as potassium-40. How old is it? Explain
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