comets • A comet is a small, icy celestial body that orbits around the sun. (a “dirty snowball”) • We see the ice turn into gas as the comet gets near the sun. It is made up of a: a) nucleus- solid, frozen ice, gas and dust b) coma- water vapor, CO2, and other gases c) tail - made of dust and ionized gases; develops when the comet is near the Sun. Its long tail always points away from the sun, because of the force of the solar wind. The tail is most of what we see.
Comets, such as Halley’s Comet, are named by the person who discovered them. Halley’s Comet is visible from Earth every 76 years.*TheOort Cloud is the area where comets originate (come from) • A comet’s tail can be 250 kilometers long!
meteoroids • meteoroids are small bodies that travel through space. a )smaller than asteroids; most are smaller than the size of a pebble. b) most come from asteroidsthat are broken apart by impacts with other asteroids. Other meteoroids come from the Moon, from comets and from the planet Mars. c) made from iron or nickel
How meteoroids are named: c) meteoroid-in space; • meteor- when it glows in Earth’s atmosphere (a “shooting star”) • meteorite- when falls to Earth
asteroids • Asteroids are rocky or metallic objects in space that revolve around the Sun. • Most orbit the Sun in the asteroid belt between Mars and Jupiter. • Asteroids are also known as planetoids or minor planets.
There are about 40,000 known asteroids that are over 0.5 miles (1 km) in diameter in the asteroid belt. • The first one discovered (and the biggest) is named Ceres. • 2 types: • a) dark ones made of metal, mostly iron and nickel • b) lighter-colored ones made of rock