The Science Of Meteors

Ever wondered just where shooting stars come from, or just been curious about the difference between a meteor and a meteorite? No fear, we’ve got you covered!

Earth’s orbit around the sun is cluttered with tiny bits of dust, rock, and ice, many left behind by comets and asteroids traveling through space. Objects bigger than grains of sand but too small to be considered asteroids (the distinction can get a little fuzzy since there’s no official minimum size for an object to be called an asteroid) are known as meteoroids. The bits of really tiny space dust that weigh less than a gram are called micrometeoroids.

Bits of space rock and space dust are constantly entering Earth’s atmosphere as it orbits around the sun—an estimated 48.5 tons a day, according to NASA. As these objects travel through the atmosphere, the friction generated by the fall to Earth heats them up, leaving trails of light to mark their paths. The term meteor is synonymous with “shooting star”; it describes the glowing trail left by a meteoroid or micrometeoroid as it descends through Earth’s atmosphere. Most meteors occur between 50 and 75 miles above the planet, in a region of the atmosphere called the thermosphere. It’s a very brief stage in the life of a space object, usually lasting only a few seconds. For most pieces of space debris, it’s the last stop before oblivion.

Any old meteoroid or micrometeroid can turn into a meteor (or possibly a meteorite; more on that later), but meteor showers are a special occasion when meteors light up the sky every hour. They’re only seen as Earth passes through a dense cloud of debris left behind by comets (or, occasionally asteroids) that pass near Earth’s orbit.

A meteor shower is typically named for the constellation that it appears to “radiate” from (even though it doesn’t actually come from anywhere near those stars). So the Perseid meteors, which actually come from the tail of the Swift-Tuttle comet, appear to originate from a point in the constellation Perseus; the shower is named for this radiant.

If a meteor survives its hot passage through Earth’s atmosphere and hits the ground, we call that remnant a meteorite. These can be as small as grains of sand, or large as boulders. The biggest meteorite ever discovered was found in Namibia; dubbed the Hoba meteorite, it’s a chunk of iron 9 feet across weighing 119,000 pounds.