Sunday, December 12, 2010

Now playing in a sky near you: Winter meteor show


Flaming rocks are hurtling toward the Earth upon the arrival of the annual Geminid meteor shower, one of the biggest of the year.

The peak of the week-long shower will come just before dawn Tuesday, but the shooting stars were visible across the world late this past weekend, says Rebecca Johnson, editor of StarDate magazine, which is published by the McDonald Observatory, the University of Texas research unit near Fort Davis, Texas.

Where skies are clear, the viewing will be best before dawn Tuesday. "It starts to get light an hour before sunrise, so any time before that is going to be a good time to look," Johnson says.

Those who'd rather stay up late than get up early might want to wait until the moon sets around midnight on each night during the shower.

"You can still see meteors when the moon is up, but it will be better when the moon has set," Johnson says.

The peak will hit at 6 a.m. ET on Tuesday, Johnson says.

"If you're brave enough to brave the frigid, arctic cold that's prevailing in most of the Eastern part of the country, that's when you'll see them," says Bill Cooke, an astronomer at NASA's Marshall Space Flight Center, in Huntsville, Ala.

Meteor showers can be unpredictable in the number of fiery paths sketched across the sky, but the Geminids are among the most consistent. They're expected to generate between 60 to 80 meteors an hour, "about one a minute," Cooke says.

Meteors aren't really falling stars. In the case of the Geminid shower, they're tiny pieces of debris breaking off an asteroid called 3200 Phaethon as it orbits the sun. Although the shower was first seen in the 1860s, the asteroid wasn't discovered until 1983.

The Geminids carry a whiff of mystery. Most well-known meteor showers, such as the Perseids and the Leonids, come from comets, which are "big, dirty snowballs," in Cooke's words.

When comets get near the sun, the heat turns the ice into gas, freeing some of that dirt, which is then pulled into Earth's orbit and falls through the atmosphere. As the debris burns up, it creates the brilliant streaks we see as meteors.

The Geminids come not from a comet but an asteroid, "a big hunk of rock," Cooke says.

Exactly why 3200 Phaethon has so much material trailing behind it to burn up in our atmosphere is unclear.

Even if 3200 Phaethon is a clump of rock bits, which is one kind of asteroid, the Geminids are many hundreds of years old, so those bits should have long since been lost, "and yet (they are) still throwing stuff off. It's a weird meteor shower," Cooke says.

For those who can't make it out Tuesday morning, the meteors will be visible tonight and a day or two after the peak, just not as plentiful.

It's "a great shower that many people never see" because they come during cold weather, Cooke says. "The Perseids get all the press. It's much nicer to be out on a warm August night than to be freezing your rear in December."



Read More

http://www.usatoday.com/tech/science/space/2010-12-13-Geminids13_ST_N.htm

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