We've all seen shooting stars. Those streaks of light in the sky are actually meteors: small particles (ranging in size from a grain of sand to an apple seed) that have entered Earth's atmosphere and are burning up from the friction with the air produced as they travel. They are called meteoroids if they are in space, and meteorites if they survive and hit the Earth. Most of these particles burn up at about 50 miles above the Earth -- but in 1982, a six-pound meteor crashed into a house in Wethersfield, Connecticut. And some scientists have linked the extinction of the dinosaurs to a gigantic meteorite believed to have struck the Earth millions of years ago.
A meteor shower produces a large number of meteors all coming from the same region of the sky, whenever the Earth passes through the debris from a comet's tail. Passing comets leave behind a trail of dust and tiny debris as the sun burns off part of its exterior; these spread out along the entire orbit of the comet to form meteor streams. Meteor storms or showers occur when the Earth crosses the orbit of a meteor stream at the same time that the main mass of that stream is crossing the orbit of the Earth. Meteor showers happen about 11 times each year.
Meteors enter the Earth's atmosphere at very high speeds: between 25,000 mph and 160,000 mph. The color of visible light produced as the particles burn depends on their speed. If they are traveling at the lower end of the speed range, they appear red to orange; if they are moving relatively fast, they appear in the blue to white regime of the spectrum.
TIPS FOR OBSERVING A METEOR SHOWER:
The American Astronomical Society contributed to the TV version of this story.