The meteors peaked overnight Friday, USA Today reported. The shower continues through early Sunday.
While the meteors appear to come from the constellation Leo, giving the shower its name, they are actually fragments of the Tempel-Tuttle comet. Like Earth, the comet orbits the sun, although on a long elliptical orbit.
"A comet is a often called a 'dirty snowball,' as it's made up of pieces of rock held together by ice. As a comet orbits the sun, it heats up and some of the ice is vaporized, releasing bits of rock along the orbit," Rebecca Johnson of StarDate magazine said.
The fragments flare up when they hit Earth's atmosphere, becoming what appear to be falling stars. Few meteorites make it to Earth's surface.
Every 33 years, when Tempel-Tuttle passes close to Earth, the Leonid shower becomes spectacular, with 1,000 visible shooting stars an hour. This year, the average is believed to be more like 20 an hour.
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