Asteroids, Comets, and Meteoroids

Asteroids• Fragments of rock that orbit the sun

• Orbits are ellipses

• Largest known asteroid is Ceres

• Most are located in the ‘asteroid belt’ between the planets Mars and Jupiter

• Composition:– Silicate minerals (look like earth rocks)– Iron and nickel (shiny metallic appearance)– Carbon (have a dark color and are rare)

Comets• Small bodies of ice, rock, and cosmic dust.• Have highly elliptical orbits around the sun.• Most originate in the Oort Cloud (spherical cloud of

dust and ice that lies far beyond Pluto’s orbit and that contains the nuclei of billions of comets).

• Bright appearance results from sunlight reflected by the comet’s coma

• Has Several Parts:– core/nucleus– Coma (together with the core form the head of the comet)– Tail (always points a way from the sun because electrically

charged particles from the sun push it away)

Famous Comets

• Halley’s Comet– Passes by Earth every 76 years– Last passed Earth in 1986 – Will return in 2061

• Comet Hale-Bopp– Passes by Earth every 5-10 years– Last passed by Earth in 1997

Meteoroids

• A small, rocky body that travels through space.

• Most have a diameter less than 1 mm.

• Most meteoroids burn up in the atmosphere due to increased friction with more molecules as it gets closer to Earth.

Meteor

• Bright streak of light caused when a meteoroid burns up in the atmosphere.

• Also known as “shooting stars” (click picture)

• Picture to the right is a meteor shower.

Meteorite

• Any part of a meteoroid that is left when a meteoroid hits Earth.

• Three Types of Meteorites:– Stony (similar to rocks on Earth)– Iron (metallic in appearance)– Stony-iron (contain iron and stone, are rare)