The Leonid meteor shower is at its best tonight. Unfortunately, it has some competition: a bright gibbous Moon. The moonlight will overpower most of the meteors, leaving only a handful of the brightest "shooting stars" to shine through.
The Leonids are caused by a solar-system sandstorm -- a cloud of debris from Comet Tempel-Tuttle.
The comet is a ball of frozen water and gases mixed with bits of rock and dust. As the comet approaches the warm Sun, some of the ice at its surface vaporizes. That releases some of the rock and dust into space.
Over time, this material spreads out along Tempel-Tuttle's path around the Sun. And every November, Earth flies through this trail of debris. The dust grains ram into the upper atmosphere at tens of thousands of miles an hour. They generate intense heat and pressure, creating the streaks of light known as meteors.
Most of the meteors are quite faint, though. Almost none of them shines through the murky skies of a city. And the glare of a bright Moon overpowers them, too. Only a handful shine through the moonlight -- those formed by larger chunks of material -- the size of a small pebble or larger.
The Leonids take their name from the constellation Leo. If you traced their paths across the sky, they'd all appear to "rain" from Leo, which rises in the wee hours of the morning. But a meteor can zip across any part of the sky, so you don't need to look at Leo to see one of his shooting stars.
Script by Damond Benningfield, Copyright 2008
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