[vox] [fwd] Getting Pumped Up for the Leonids ?
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[vox] [fwd] Getting Pumped Up for the Leonids ?
Not Linux-related, but we're all such geeks, and there's been a lot
of talk on it on vox.
(And, umm.. hey! Pete can use his new Polaroid digital camera driver
he wrote to download photos of the meteor storm. There! Some Linux content!)
----- Forwarded message from firstname.lastname@example.org -----
Date: Fri, 16 Nov 2001 13:35:42 -0000
Subject: [MAWS General List] Getting Pumped Up for the Leonids ?
If the anticipation and forecasts in this article don't inspire you
to set an alarm, nothing will! .....
"It's time for a celestial shower"
... Meteors: This weekend's Leonid meteor display could be the most
spectacular in years. (Source: Baltimore Sunpapers, 11/16/01)
Astronomers say it could be the meteor shower of a lifetime, and
they're more sure of it this time than ever before. Where the skies
stay clear, they say, North Americans willing to roll out of bed
before dawn Sunday and drive to a dark place in the country should see
a starry sky streaked by hundreds -perhaps thousands - of meteors per
Even if you've been disappointed by past meteor predictions, crawl out
of bed this time, says Kelly Beatty, executive editor of Sky &
Telescope magazine: "You're going to see more meteors in those few
hours than you've probably seen in your whole life up to that point."
It's the annual Leonid meteor shower, an event that routinely produces
10 to 15 meteors an hour as Earth passes through the dusty orbital
path of the comet 55P/Tempel-Tuttle.
But three times a century, in the years around the comet's return,
meteor rates can soar into the thousands, and the shower becomes a
The Leonids have been storming each November since the comet's last
visit in 1998, especially in the Middle East and Europe. This year,
forecasters say, North Americans with the darkest skies might finally
be rewarded with up to 4,200 meteors an hour.
In the past, such forecasts have been notoriously unreliable. But
thanks to recent advances, "we seem to have it mastered now," says
Steve Maran, spokesman for the American Astronomical Society.
In the past two years forecasters "hit the Leonids bang-on, predicting
the right time of night and the right spot on the globe."
East Coast residents should be watching between 4 a.m. and 6 a.m. The
farther they get from urban lights, the more meteors they will see.
The weather forecast in <many locations> calls for clear skies, with
no moon to wash out the view.
The annual Leonid shower occurs when specks of dust and sand thrown
off by Tempel-Tuttle smack into Earth's atmosphere at 155,000 mph, or
43 miles per second. Friction burns them up, creating streaks of light
ranging from faint to fireball.
The great Leonid storm of 1833 terrified observers around the world.
It was witnessed by a young Abraham Lincoln and a Maryland slave named
Frederick Douglass, both of whom remembered the sight for the rest of
The 1998 Leonid shower startled observers with an unexpected barrage
of fireballs. NASA astronomer Tony Phillips said some were bright
enough to cast shadows.
"Some of the most startling left behind glowing trails of debris that
lingered in the sky, twisting and turning as they were sheared by
high-altitude winds," he said.
There is no risk to anyone on the ground. But satellite owners will be
shutting down vulnerable systems, rotating solar panels edge-on into
the meteor stream, and putting their most experienced controllers on
duty to reduce the risk of collisions and short-circuits, says Bill
Ailor, of the Aerospace Corp., which advises the operators of both
military and commercial satellites.
A meteor struck a European communications satellite during the Perseid
meteor shower one August several years ago, Ailor said. It sent a jolt
of electricity to the satellite's thrusters. By the time operators
realized it, the satellite had burned up all its maneuvering fuel,
putting it out of commission.
Even in a heavy Leonid shower, says Ailor, "the chances are still
pretty slight we will see any problems, but it pays to be aware."
Until about 20 years ago, scientists didn't know why annual meteor
showers were so unpredictably variable. Then Donald Yeomans, of the
NASA Jet Propulsion Laboratory, figured out that there were many
more-concentrated ribbons of dust embedded within the comet's broader
"Each time the comet went past the sun, every 33 years, it would dump
off a ribbon of this debris, which stayed pretty concentrated in
time," Beatty says.
Yeomans and others began mapping these dust lanes. They calculated how
they would be shoved around by the effects of solar radiation, and the
gravitational pull of the sun and the planets - especially giant
After the comet's return in 1998, they put their calculations to the
test. They found there were fewer meteors than they had forecast, and
the shower peaked several hours earlier than expected.
But the results helped them refine their models.
In 1999, astronomers David Asher, of the Armagh Observatory in
Northern Ireland, and Robert McNaught, of the Siding Spring
Observatory in Australia, predicted almost exactly when Earth would
move through one of the comet's ribbons of dust.
"The ribbons are so narrow" - 20,000 miles across - "that they
[forecasters] can pin down when the Earth is going to plow into it to
within a half-hour," says Beatty.
They can also predict how heavy the meteor shower will be and what
parts of the globe will have the best view. Astronomers have even
figured out when each trail was laid down by the comet. This year,
they say, Earth will pass through skeins of dust cast off by
Tempel-Tuttle in 1699, 1766 and 1866.
But the forecasters don't always agree.
For example, their computer models account in different ways for how
solar radiation and the gravity of the sun and Jupiter shove the dust
trails around. So, four teams of astronomers have made four different
forecasts for Sunday's Leonid shower.
Their North American predictions call for meteor rates ranging from
800 to 4,200 meteors per hour - under ideal seeing conditions -
between 4 a.m. and 6 a.m. EST as Earth charges through the comet's
1766 dust trail. Eight hours later, some forecasters say, Earth will
cross the 1699 and 1866 dust lanes, and people on the western Pacific
Rim could see rates up to 15,000 an hour. Others predict rates there
in the hundreds.
"This is a beautiful demonstration of how science works," Beatty says.
"You have these competing theories, and they make testable
predictions. Depending on what happens, one or the other of these
theories will emerge as a better method."
And if there are no meteor storms anywhere?
"It doesn't mean the astronomers screwed up," Beatty says. "It means
that our theories need to be reworked, and we've learned something."
This might be the last, best chance to see a big Leonid display until
the comet returns in 2030. Next year's shower is expected to be the
last of this series, but it will be obscured by a bright moon.
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