Leonid Meteor Shower Puts on Show Overnight
Earth is safe, but if you're up late in a dark place, look to the sky.
Nov. 16, 2009 — -- This is one of those nights when you come to appreciate how nice it is to live on earth.
Right now it is passing through the trail of debris left by a passing comet called Tempel-Tuttle. Every year at this time it happens -- with tons of ice and rock vaporizing in the earth's protective atmosphere.
The result is the Leonid Meteor Shower, often a pleasant show for connoisseurs of things celestial. The best time to watch is between midnight and dawn. If you happen to be in a place with dark, clear skies, you may see 20 to 30 shooting stars an hour -- and maybe, if luck is with you, many more.
"Meteor showers are now very predictible," said Bill Cooke of NASA's Marshall Space Flight Center, who's worked to create complex computer models of the behavior of comets and the material that escapes from them. "Since the mid-1990s computers have advanced enough that we can now forecast their strength with pretty good accuracy. Forcasters put millions of particles into their models."
Understand that something very violent is happening in space. Pieces of comet debris are plunging into the earth's atmosphere at speeds of up to 160,000 miles per hour -- and the streak you see, for a few seconds, is from a piece of debris being vaporized by the intense heat of friction with air molecules.
But we on the ground are well-protected. Comet dust is small stuff, and it tends to burn up in the atmosphere at an altitude of about 60 miles. Comet Tempel-Tuttle is nowhere near us at the moment -- it follows an elliptical 33-year orbit that last brought it close to earth in 1998 -- but dust from it has spread out over much of its path.
It is a good year for the Leonids because they happen to coincide with a new moon. Since the moon won't be high in the sky to blot out the light of fainter meteors, the show should be better.
Why does one have to wait up past midnight? Because the morning side of the earth is its front side, as it were, as we orbit the sun at a speed of 66,000 mph. In effect, the earth is crashing into the comet dust as it goes. The afternoon-evening side of the planet is the trailing side, so shooting stars in the evening are more rare.
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