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2001 Leonid Meteor Shower

From: UFO UpDates - Toronto <ufoupdates@home.com>
Date: Fri, 16 Nov 2001 09:17:20 -0500
Fwd Date: Fri, 16 Nov 2001 09:17:20 -0500
Subject: 2001 Leonid Meteor Shower


SPECIAL REPORT: 2001 Leonid Meteor Shower

The 2001 Leonid meteor shower peaks early Sunday, Nov. 18 and
promises to be the best shooting star show in 35 years.


30 U.S. Cities & World Forecast

See Pictures & Submit Yours
How to Shoot Shooting Stars

Military Satellites Prepared
Odds of an Impact Soar

What Causes the Shower?

How it Stacks Up
Against History


Source: Space.com


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

By Robert Roy Britt
Senior Science Writer
posted: 07:00 am ET
16 November 2001

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).


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.


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'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.

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