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Earthgrazers and Fireballs: The Strange Side of The Leonid Meteor Shower
Space.com ^ | November 16, 2001 | By Robert Roy Britt, Senior Science Writer, SPACE.com

Posted on 11/17/2001 3:31:38 AM PST by MeekOneGOP

Friday November 16 09:37 AM EST

Earthgrazers and Fireballs: The Strange Side of The Leonid Meteor Shower

By Robert Roy Britt
Senior Science Writer, SPACE.com

  
The Leonid meteor shower is a strange show. Its meteors are among the fastest known. It is notoriously difficult to predict. And it is a total night owl, refusing to show its best stuff until well after midnight.

But while the 2001 Leonids will likely be remembered for the sheer volume of shooting stars, there are some strange characters to look for as the shower's source ekes above the eastern horizon late Saturday night and early Sunday morning.

A handful of meteors will first zoom across the horizon for long stretches of time. Earthgrazers, they're called. And if you're real lucky, you might spot some fireballs -- larger meteors that explode upon impact with Earth's atmosphere, generating spectacular blazes of light (not to mention fear of alien spacecraft and calls to local law enforcement offices).

Earthgrazers

Leonid meteors will take their time arriving Saturday night. Wherever you are on Earth, you're viewing location has to rotate into the stream of space dust that causes the Leonids. The shooting stars will appear to emanate from a point in the sky known as the radiant, which for the Leonids happens to be in the constellation Leo (hence the name).

No knowledge of this is needed to find an earthgrazer. Just go out and look to the East. The timing depends on where you live. Figure mid-evening for high northern latitudes, such as Canada; late evening hours for mid-northern latitudes, as in most of the United States; and after midnight for equatorial regions and the Southern Hemisphere.

What might you see?

"When the radiant lies near the horizon the Leonid meteors cannot penetrate far into the Earth's atmosphere," explains Robert Lunsford of the American Meteor Society. "At this time they are only able to skim the upper atmosphere."

These earthgrazers, as scientists call them, often last several seconds and can span a great distance of the sky, Lunsford said.

To see an earthgrazer, you'll need an unobstructed view of the eastern horizon.

Later, as Earth continues rotating, the Leonid radiant moves higher into the sky, along with its host constellation and all the stars. Meteors will strike the atmosphere at a more direct angle, Lunsford explains, creating shorter paths. But the paths will still span much of the sky, so you don't need to face East. In fact, the best views will be everywhere but directly East.

Just go out, look up.

Fireballs

Most Leonid meteors are created by sand-sized grains of dust that vaporize about 60 miles up due to the friction caused by Earth's atmosphere. But Tempel-Tuttle, the comet that has left all this Leonid raw material in space, also deposits a few larger chunks of itself each time it swings around the Sun (which it does every 33 years).

A comet fragment the size of a marble can generate a glorious fireball of light as it burns up. Instead of slicing through the atmosphere like a small bit of dust, such a pebble sometimes goes splat upon meeting up with a certain density of air.

"The Leonids can have fireballs, but they're not especially noted for them," said Bill Cooke, a meteor researcher at NASA (news - web sites)'s Marshall Space Flight Center. Cooke said the number of fireballs each year depends in part on which streams of cometary debris Earth plows through.

In 1998, observers noted several fireballs when the planet moved through a stream that comet Tempel-Tuttle had deposited in the 14th Century. The Sun's radiation had blown much of that ancient dust into a widely dispersed region of space, so the 1998 Leonids did not produce a great number of shooting stars.

But the larger material -- fireball material -- was still relatively concentrated. In fact, Cooke said, scientists are learning that gravity acts on these larger fragments, causing them to be huddled more closely together over time. They call the process "gravitational focusing."

So what are the chances for fireballs this year?

People in Asia will see shooting stars caused by material that has been waiting to be swallowed up by Earth since 1633, so there should be some fireballs there, Cooke said. The North American peak will be caused by material left by Tempel-Tuttle in the 1700s, however, and should provide fewer fireballs, but probably still some.

Cooke is quick to point out that the Leonids can surprise, however. There could be fewer meteors overall. Or there could be more fireballs. Meteor forecasting is a young profession. And, for now at least, meteor showers are still somewhat strange -- even to the scientists.

LEONIDS SPECIAL REPORT: When, where and how to watch, plus a full forecast

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Wow!


TOPICS: Front Page News; News/Current Events
KEYWORDS: archaeology; ggg; godsgravesglyphs; history; realscience
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To: MeeknMing
I wouldn't trade my horizon to horizon view without a tree for anything. I grew up in Ga. My dad called the fairways on our golf courses "pine canyons". We have fifty acres in a partnership where there is only one tree, a lone palm tree. My partner and I were speculating on whether we wanted palm tree lined parkway for the entry into out planned subdivision. Like me, he thought that lone palm was the only tree we needed. He treasured our horizon to horizon unobstructed view as much as I did.
61 posted on 11/18/2001 4:34:18 AM PST by B. A. Conservative
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Comment #62 Removed by Moderator

To: Central Scrutiniser
Well, right now, I'm in Phuket Thailand, skies are cloudy however, but tommorow night I'll be on a boat. Meteor showers last a few days, hopefully I'll get some tommorow..
Let us know how the viewing is tonight, then. . .

"Never pet a dog that is on fire"

I have been able to obey that law all of MY life! LOL! ;-)

63 posted on 11/18/2001 5:49:45 AM PST by MeekOneGOP
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To: MeeknMing
It was beautiful here in Durham, North Carolina. Husband and I went and laid on the ground outside between 5 and 6 am. Lot's of blankets.

God's light show was beautiful. It sure put things in the proper presepective.

64 posted on 11/18/2001 6:48:45 AM PST by FR_addict
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To: FR_addict
Agreed! They were beautiful here on the North Oregon Coast and some had long comet-like tails - awesome!
65 posted on 11/18/2001 6:54:01 AM PST by bevlar
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To: FR_addict; bevlar
God's light show was beautiful. It sure put things in the proper presepective.

Glad for ya'll! ;-)
When I went outside around 2 a.m., the clouds had rolled in. ;-(

Oh, well. Like I e-mailed my good buddy: I guess I'll have to wait for the '99 "Really Big Shew!"

66 posted on 11/18/2001 7:45:00 AM PST by MeekOneGOP
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To: FR_addict
Here in the western suburbs of Philadelphia, it was great. I got my eldest daughter out of bed at a little past 5am( the predicted optimum viewing time) and we saw quite a bit in the next hour. It was a clear, cold night, optimum viewing conditions
67 posted on 11/18/2001 7:57:50 AM PST by SauronOfMordor
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To: All
(((PING))))))

Here's A/P article about the shower last night!:

Leonid Meteor Shower Delights Many

68 posted on 11/18/2001 9:28:56 AM PST by MeekOneGOP
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Just adding this to the GGG catalog, not sending a general distribution.
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest
-- Gods, Graves, Glyphs (alpha order)

69 posted on 05/19/2005 8:34:32 AM PDT by SunkenCiv (FR profiled updated Tuesday, May 10, 2005. Fewer graphics, faster loading.)
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