A meteor is a bright streak of light that appears briefly in the sky. Meteors are often called shooting stars or falling stars because they look like stars falling from the sky. Brightest meteors are sometimes called fireballs. A meteor appears when a particle or chunk of metallic or stony matter called a meteoroid enters the earth's atmosphere from outer space. Air friction heats the meteoroid so that it glows and creates a shining trail of gases and melted meteoroid particles. The gases include vaporized meteoroid material and atmospheric gases that heat up when the meteoroid passes through the atmosphere. Most meteors glow for about a second.
Most meteoroids disintegrate before reaching the earth. But some leave a trail that lasts several minutes. Meteoroids that reach the earth are called meteorites
Millions of meteors occur in the earth's atmosphere every day. Most meteoroids that cause meteors are about the size of a pebble. They become visible between about 40 and 75 miles (65 and 120 kilometers) above the earth. They disintegrate at altitudes of 30 to 60 miles (50 to 95 kilometers).
Meteoroids travel around the sun in a variety of orbits and at various velocities. The fastest ones move at about 26 miles per second (42 kilometers per second). The earth travels at about 18 miles per second (29 kilometers per second). Thus, when meteoroids meet the earth's atmosphere head-on, the combined speed may reach about 44 miles per second (71 kilometers per second).
