1. Chapter 20 Section 5: Comets, Asteroids, Meteors
Key Concepts: What are the characteristics of comets? Where are most asteroids found? What are meteoroids and how do they form?
Key terms: comet, coma, nucleus, Kuiper belt, Oort cloud, asteroid, asteroid belt, meteoroid, meteor, meteorite

2. Comets
Loose collections of ice, dust, and rocky particles whose orbits are usually long, narrow ellipses
Comet’s head – when a comet gets close enough to the sun, ice turns to gas, releasing gas and dust. They form an outer layer called a coma. The nucleus is the inner core.
Tail – gas and dust heat up and form a tail – gas tail and dust tail. Can be 100 million km long

3. Origin of comets
Most comets are found in one of two regions: Kuiper belt and Oort Cloud
Kuiper belt is a doughnut-shaped region that extends from beyond Neptune’s orbit to about 100 times the Earth’s distance to the sun
Oort Cloud – spherical region of comets that surrounds the solar system out to more than 1000 times the distance between Pluto and the sun

4. Asteroids
Most revolve around the sun between the orbits of Mars and Jupiter (called the asteroid belt)
4 largest – Ceres, Pallas, Juno, Vesta
More than 100,000
Most are small
Elliptical orbits
Maybe killed dinosaurs

5. Meteors
Meteoroid is a chunk of rock or dust in space. They come from comets or asteroids.
When entering Earth’s atmosphere, friction creates heat and produces a streak of light in the sky - a meteor
Meteoroids that pass through the atmosphere completely and hit Earth’s surface are called meteorites.