Download Ch. 3 Sec. 5 Notes

Ch. 3 Sec. 5 Notes
Comets
*Loose collections of ice, dust, and small rocky particles whose orbits are usually
very long, narrow ellipses
A Comet's Head
*When the comet gets close to the sun, the ice turns into gas, releasing gas and
dust
*Clouds of gas and dust form a fuzzy outer layer called a coma
*The solid inner core of a comet is called its nucleus
*The head is the brightest part of the comet and it's made up of the coma and
nucleus
A Comet's Tail
*As the ice turns the head into gas, it leaves a tail trailing behind it made of gas
and dust
*Comet means "long-haired star" in Greek
*A comet's tail can be more than 100 million km long and stretch across most of
the sky
Origin of Comets
*Most comets are found in one of two regions:
1. Kuiper belt: doughnut-shaped region that extends from beyond Neptune's orbit
to 100 times Earth's distance from the sun
2. Oort Cloud: spherical region of comets that surrounds the solar system out to
more than 1,000 times the distance between Pluto and the sun
Asteroids
*Rocky objects, called asteroids, are too small and too numerous to be considered
full-fledged planets
*Most asteroids revolve around the sun between the orbits of Mars and Jupiter
-Called the asteroid belt
*More than 100,000 asteroids have been discovered
*The largest asteroid, Ceres, was recently classified as a dwarf planet
*Some asteroids have an extremely elliptical orbit that crosses paths with Earth
-Someday, one of these asteroids could hit Earth and wipe out our entire
planet
*An asteroid did hit Earth 65 MYA and scientists believe this is the reason
dinosaurs and other organisms went extinct
Meteors
*A meteoroid is a chunk of rock or dust in space
-Come from comets or asteroids
*When a meteoroid enters Earth's atmosphere it turns into a meteor
*Meteor's that hit Earth's surface are called meteorites