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How Meteor Showers Work

A Perseid meteor over the Very Large Telescope array in Chile. ESO / Stephane Guisard

Have you ever observed a meteor shower? If so, you've watched small bits of solar system history, streaming from comets and asteroids (which formed some 4.5 billion years ago) get vaporized as they crashed through our atmosphere.

Meteor Showers Occur Each Month

More than two dozen times a year, Earth plunges through a stream of debris left behind in space by an orbiting comet (or more rarely, the breakup of an asteroid). When this happens, we see swarms of meteors flash through the sky. They seem to emanate from the same area of the sky called a "radiant". These events are called meteor showers, and they can sometimes produce dozens or hundreds of streaks of light in an hour.

The meteroid streams that produce showers contain chunks of ice, bits of dust, and pieces of rock the size of small pebbles. They stream away from their "home" comets as the cometary nucleus gets close to the Sun in its orbit.The Sun warms the icy nucleus (which likely originated from the Kuiper Belt or the Oort Cloud), and that frees up the ices and rocky bits to spread out behind the comet. Some streams come from asteroids.

Earth doesn't always intersect all the meteoroid streams in its region, but there are around 21 or so streams it does encounter. These are the sources of the best-known meteor showers. Such showers occur when the cometary and asteroid debris left behind actually slams into our atmosphere. The pieces of rock and dust get heated by friction and begin to glow. Most of the cometary and asteroid debris vaporizes high above the ground, and that is what we see as a meteroid passes through our sky. We call that flare a meteor. If a piece of the meteoroid happens to survive the trip and falls to the ground, it is then known as a meteorite.

From the ground our perspective makes it look as though all the meteors from a specific shower are coming from the same point in the sky—called the radiant. Think of it like driving through a dust cloud or a snowstorm. Particles of dust or snowflakes appear to come at you from the same point in space. It's the same with meteor showers.