Perseid Meteors

StarDate: August 9, 2009

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The Perseid meteor shower is heating up, but unfortunately, the Moon will cool it off.

Like all meteor showers, the Perseids are the progeny of a comet -- in this case, Comet Swift-Tuttle, which orbits the Sun every 135 years or so. As it gets close to the Sun, solar heat vaporizes some of its outer layers of frozen water and gases. This also releases small grains of solid material.

Over time, these grains spread out along the comet's orbit. Earth flies through this dusty pathway every summer, sweeping up some of the dust grains. As they slam into the atmosphere, they explode into streaks of superhot gas -- the streaks of light known as meteors or shooting stars.

But the Perseids are "clumpy." Big clouds of dust grains stick together. Many of the clumps are close to the comet itself. So when Swift-Tuttle returns to the inner solar system, the number of meteors goes way up.

The comet last passed our way a decade and a half ago, but there's still a possibility that we could pass through one of the dense clumps this year.

But when the shower reaches its peak on Tueday night, the bright Moon will be in the sky during the best hours for meteor watching, so it'll overpower all but the brightest Perseids.

To try your luck, though, the best time to look is after midnight, as your portion of Earth turns more directly into the meteor stream. Find a dark but safe site away from city lights, then scan the sky for the fireworks.

Script by Damond Benningfield, Copyright 2009

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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