Comet: A body of ice, rock and dust that can be several miles in diameter and orbits the sun. Debris from comets is the source of many meteoroids. Meteoroid: A small rocky or metal object, usually between the size of a grain of sand or a boulder, that orbits the sun. It originates from a comet or asteroid. Meteor: A meteoroid that enters the earth's atmosphere and vaporizes. Also called a "shooting star." Meteorite: A meteor that hits Earth without burning up in the atmosphere. Meteor shower: A collection of meteors visible when Earth passes through a trail of debris left by a comet. Asteroid: An object larger than a meteoroid that orbits the sun and is made of rock or metal. Historically, objects larger than 10 meters across have been called asteroids.
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