Shooting stars are just pea-sized rocks... and other space wonders

Every time you wish on a shooting star, you are looking at a pea-sized piece of rock burning up 60 miles above your head. That rock has been traveling through the solar system since before the planets formed, and it is moving so fast that friction with the atmosphere turns it into a streak of superheated plasma. Most of these fragments never reach the ground. Instead, they vaporize completely, adding microscopic dust to the atmosphere and, in a very real sense, helping the Earth continue to grow.

What a shooting star actually is

The term "shooting star" is a misnomer, but the phenomenon is arguably more interesting than a falling star would be. The bright streak we see is not a star at all. It is a meteor: the visible trail of light produced when a piece of space rock or debris enters Earth's atmosphere at high speed. Planetary scientist Melissa Rice, who works on NASA's Mars rover missions, explains that the object causing the streak is usually tiny. "Probably no bigger than a pea most of the time," she says. That small rock, called a meteoroid while it is still in space, is traveling so fast that it compresses the air in front of it. The compression heats the rock to thousands of degrees, causing it to glow and often to disintegrate entirely.