Meteor showers are when Earth encounters many meteoroids at one time. It happens as the Earth crosses through the debris stream left behind by a comet or asteroid.
Comets, like Earth, orbit our Sun. As they get closer to the Sun, their icy surface breaks up, releasing a trail of dust and bits of rock scattered along the comet’s path. Then, at some point, as Earth makes its trip around the Sun, its orbit crosses through the field of debris left behind by the comet.
Since Earth’s orbit will repeatedly cross these same debris fields, we can determine when we will experience these annual meteor showers.
There are several different showers throughout the year. All are named after the constellations of stars visible in that part of the sky from which the meteors appear to originate. This area is called the radiant point. Locating the constellation and radiant point is a great way to know where to keep watch for the upcoming celestial fireworks.
For example, the Leonids is named after the constellation Leo. The Leonid meteors appear to be coming from the constellation, when in fact, they are nowhere near the actual stars, but the Earth is moving through the debris field left behind by the Comet Temple-Tuttle. This is an optical illusion.