Astronomy 100

Section 2, Fall 2008

Homework G

Answers

1. Most of the asteroids are found between
d) Mars and Jupiter

2. Whether called a planet or not, Pluto really belongs to
b) the Kuiper belt (which lies outside Neptune's orbit)

3. Almost all meteorites come from
c) asteroids

4. Metallic asteroids are made mostly of
e) iron (and about 10 percent nickel)

5. Why are the inner planets made out of heavy materials?
a) they are close to the Sun and were hot

6. Amino acids and diamonds are found in
d) stony meteorites called carbonaceous chondrites

7. Comets have two tails, one made of gas, the other of
c) dust grains and fluffy rocks

8. Where do the gas tails of comets point?
b) away from the Sun (pushed out by the solar wind)

9. Short-period comets tend to
a) stick to the plane of the ecliptic (since they come from the Kuiper Belt)

10. A typical diameter for the nucleus of a comet is
b) a few to a few tens of kilometers

11. Comet nuclei are made mostly of
e) ice and fluffy rock

12. Where do long-period comets come from?
b) the Oort Cloud (so they don't stick to the ecliptic)

13. Why did the asteroids not make a planet?
a) Jupiter's gravity kept them stirred up

14. Most meteors are from
c) comets

15. Where do we believe most of the Earth's water came from?
e) comets

16. The terrestrial planets (and the cores of the giant planets) almost certainly accumulated from
c) dust grains in the solar nebula

17. Comets had to be formed
a) in the outer Solar System where it was cold (since they contain so much ice)

18. The "Perseids" are
c) meteors in a shower (They hit us around August 12, and are the leavings of Comet Swift-Tuttle, which has a 130 year orbital period)

19. What populated the Oort cloud?
c) the large outer planets throwing comets out of the early planetary system

20. Which statement is evidence that the planets formed from a disk around the Sun?
c) All the planets orbit the Sun in a well-defined disk and all in the same direction

21. The Sun is how many times more massive than Jupiter?
c) 1000

22. The Sun is made mostly of
a) gaseous hydrogen and helium

23. The diameter of the Sun is about
e) all of the above (860,000 miles, 1.5 million km, 109 Earth diameters, 0.01 AU)

24. The temperature of the solar photosphere (the optically visible "surface") is about
b) 6000 K

25. What causes the solar granulation?
b) convection