CHAPTER 9 STUDY GUIDE
KEY WORDS
Asteroid Belt: a 1.5 AU-wide region between the orbits of Mars and Jupiter in which most of the asteroids are found
Belt Asteroid: an asteroid whose orbit lies within the asteroid belt
Kirkwood Gaps: gaps in the spacing of asteroid orbits discoverd by Daniel Kirkwood caused by gravitational attractions of planets
Stable Lagrange Points: locations throughout the solar system where the gravitational forces of the Sun and a planet keep space debris trapped
Trojan Asteroid: asteroid at a stable Lagrange point that shares Jupiter's orbit around the Sun
Apollo Asteroid: asteroids that are sometimes closer to the Sun than the Earth is
Comets: small bodies of ice and dust in orbit around the Sun
Kuiper Belt: a donut-shaped ring of space around the Sun beyond Pluto that contains many frozen comet bodies, some of which are occasionally deflected toward the inner solar system
Oort Cloud: a hollow spherical region of the solar system beyond the Kuiper Belt where most comets are believed to spend most their time
Comet Nucleus: a collection of ices and dust that constitutes the solid part of a comet
Coma: the nearly spherical, diffuse of gas surrounding the nucleus of a comet near the Sun
Hydrogen Envelope: the extremely large, tenuous sphere of hydrogen gas surrounding the head of the comet
Comet Tails: gas and dust particles from a comet's nucleus that have been swept away from the comet's nucleus by the radiation pressure of sunlight and impact of the solar winds
Gas (Ion) Tail: the relatively straight tail of a comet produced by the solar wind acting as ions in a comet's coma
Dust Tail: a comet tail caused by dust particles escaping from the comet's nucleus
Radiation (Photon) Pressure: the transfer of momentum carried by radiation to an object on which the radiation falls
Long-Period Comets: a comet that takes tens of thousands of years or more to orbit the Sun
Short-Period Comet: a comet that orbits the Sun in the vicinity of the planets, thereby rappearing with tails every 200 years or les
Meteoroid: a small rock in interplanetary space
Meteor: the streak of light seen when any space debris vaporized in the Earth's atmosphere; a "shooting star"
Meteor Shower: frequent meteors that seem to originate from a common point in the sky
Impact Crater: a crater on the surface of a planet or moon produced by the impact of a asteroid, meteoroid, or comet
Meteorite: a fragment of space debris that has survived passage through the Earth's atmosphere
Stony Meteorite: a meteorite composed of rock with very little iron; also called a "rock"
Iron Meteorite: a meteorite composed primarily of iron with an admixture of nickle
Stony-Iron Meteorite: a meteorite composed of roughly equal amounts of rock and iron
Widmanstätten Pattern: crystalline structure seen inside iron meteorites
Carbonaceous Chrondrite: a class of extremely ancient, carbon-rich meteorites
Amino Acids: the building blocks of proteins upon which terrestrial life is based; found inside carbonaceous chrondrites