chapters 13 and 14

The atmosphere of Venus is mostly carbon dioxide, and the atmosphere of Earth has water vapor. Why are these two gases absent in the atmosphere of the satellite around Saturn called Titan?

Titan is so cold that carbon dioxide and water vapor freeze out

asteroid

a stony or metallic object orbiting the Sun that is smaller than a planet but that shows no evidence of an atmosphere or of other types of activity associated with comets

near-earth asteroid

an Earth-approaching asteroid, one whose orbit could bring it on a collision course with our planet

One of the key reasons that professional astronomers (as opposed to the public) are interested in comets is that they

are icy pieces left over from the time that our solar system formed can give us clues about that early time

Why were asteroids not discovered until the 19th century?

asteroids are generally small compared to planets and require a good telescope and patient searching to spot them

asteroid belt

the region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found; the main belt, where the orbits are generally the most stable, extends from 2.2 to 3.3 AU from the Sun

nucleus of a comet

the solid chunk of ice and dust in the head of a comet

Chunks of solid material that survive passing through the Earth's atmosphere and are found on the Earth's surface are called

meteorites

The large reservoir of comet nuclei far beyond Pluto, from which we believe new long-period comets come into the inner solar system, is called

the Oort Cloud

Near Earth Object

a comet or asteroid whose path intersects the orbit of Earth

Kuiper Belt

a region of space beyond Neptune that is dynamically stable (like the asteroid belt); the source region for most short-period comets

comet

a small body of icy and dusty matter that revolves about the Sun; when a comet comes near the Sun, some of its material vaporizes, forming a large head of tenuous gas and often a tail

tail of a comet

a tail consisting of two parts: the dust tail is made of dust loosened by the sublimation of ice in a comet that is then pushed by photons from the Sun into a curved stream; the ion tail is a stream of ionized particles evaporated from a comet and then swept away from the Sun by the solar wind

If there are at least a million asteroids, how did spacecraft like Galileo survive their trip through the asteroid belt?

although there are many asteroids, they are widely spaced

One of the most perplexing issues raised by the discovery of thousands of exoplanets is the existence of "hot Jupiters" - planets with the masses and compositions of Jupiter, but orbiting closer to their stars than Mercury does in our solar system. What is our best idea currently about how such "hot Jupiters" came to be?

hot Jupiters formed further out in their star system, and then migrated inward somehow

the first technique that allowed astronomers to find exoplanets involved

measuring changes in the radial velocity (Doppler shift) of the star caused by the pull of orbiting planets

accretion

the gradual accumulation of mass, as by a planet forming from

Comets change as they approach the Sun in their orbits. Which of the following statements about a comet approaching the Sun is FALSE?: when the ice evaporates some dust frozen into the ice is freed up to join the comets coma and tail, the evaporation is not always even, but can occur in spurts (where jets of material are seen moving away from the comet nucleus), the gravity of the comet nucleus holds on to the evaporated material, and it all eventually freezes back into the nucleus, the solid water ice in a comet begins to evaporate just beyond the orbit of Mars, comets close to the Sun can evaporate enough material to become as large or larger than Jupiter

the gravity of the comet nucleus holds on to the evaporated material, and it all eventually freezes back into the nucleus

Oort Cloud

the large spherical region around the Sun from which most "new" comets come; a reservoir of objects with aphelia at about 50,000 AU

Among solid worlds, which type of world is most likely to have significant geological activity?

those that are the largest (and retain heat the best)