CHAPTER 14 Review & Discussion:

1. The Trojan asteroids are located at the stable Lagrange points 60 degrees ahead of and behind the orbit of Jupiter. The Apollo asteroids cross the orbit of Earth. The Amor asteroids cross the orbit of Mars but not the orbit of Earth.

6. Far from the Sun, comets are just cold, compact, ``dirty snowballs.'' However, when they approach the Sun in the inner solar system, the icy part of the comet begins to sublimate, leading to the production of the comet's tail.

7. Most long-period comets are found in the Oort cloud. Most short-period comets are found in the Kuiper belt. The Oort cloud probably contains many times more comets than the Kuiper belt.

8. Close to the sun, the central part of the comet is the icy nucleus. Surrounding the nucleus is the coma, made of gas that has sublimated off the nucleus. Extending from the coma is the tail.

15. Radioactive dating of meteorites reveals that the age of the solar system is about 4.4 - 4.6 billion years.

CHAPTER 15 Review & Discussion:

1. Three examples are the tilt of the spin axis of Uranus; the flipped-over spin of Venus; and the strange surface of the Uranus moon Miranda. This is because all three of these phenomena are though to be due to random collisions, rather than the general processes that formed the overall structure of the solar system.

2. In the evolutionary theories, changes occur gradually. In the catastrophic theories, changes occur suddenly as the result of random one-time events such as violent collisions.

3. Three methods astronomers use to search for extrasolar planets are: (a) the transit method, (b) the detection of planets around pulsar, and (c) using the Doppler shifts in the spectrum of the host star.

9. The Jovian planets are much larger than the terrestrial planets because they formed out of large ``icebergs'' of frozen gases that existed in the outer solar system due to the low temperatures there. In addition to this, the Jovian planets may have also had a head start by forming out of large eddies in the turbulent solar nebula. The observation of "hot Jupiters" in other solar systems challenges this hypothesis because these giant planets formed close to the host star.

14. The habitable zone is the region around a host star where water can exist in a liquid state on the planet's surface.

CHAPTER 16 Review & Discussion:

1. The main regions of the Sun are the core; the radiation zone; the convection zone; the photosphere; the chromosphere; the corona; the solar wind. See the text for definitions.

2. Luminosity is the total energy output from a star in the form of radiation. In the case of the Sun, we can calculate the luminosity by measuring the energy flux observed at Earth, and then multiplying by the surface area of a sphere with radius equal to the Earth's orbital radius.

3. The solar core has a temperature of about 15 million K. The solar surface (the photosphere) has a temperature of about 6,000K.

4. Helioseismology is the study of seismic waves observed at the Sun's surface.

5. The data provided by helioseismology are used along with mathematical equations representing the physical laws to model the interior structure of the Sun.

6. Energy generated at the center of the Sun reaches the Earth by first traveling through the Radiation Zone in the form of photons, and then traveling througth the Convection Zone in the form of hot, turbulent gas, and then leaving the Photosphere in the form of visible light.

12. The Sun's energy output is powered by nuclear reactions taking place in the hot core.