[meteorite-list] Leonid Meteor Shower Could Be One Of Best In History

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:47:09 2004
Message-ID: <200111081622.IAA04269_at_zagami.jpl.nasa.gov>

Astronomical Society of the Pacific
San Francisco, California

November 1, 2001

Leonid Meteor Shower Could Be One Of Best In History
By Robert Naeye

In the wee morning hours of Sunday, November 18, the Leonid meteor shower
might intensify into a dazzling meteor storm, with "shooting stars"
continuously blazing trails across the night sky. Viewers across the
United States are perfectly positioned to take advantage of the storm,
which could be among the most spectacular sky events of the 21st century
according to the latest scientific predictions.

The peak in shower activity will occur between 4:00 and 6:00 a.m. EST, or
1:00 and 3:00 a.m. PST on Sunday morning, November 18. "During the peak,
people viewing under clear and dark skies could see meteors shooting
across the sky at a rate of 1,000 to 2,000 per hour, with flurries of one
meteor per second at the peak of the storm," says Robert Naeye, Editor of
Mercury magazine, which is published in San Francisco by the Astronomical
Society of the Pacific (ASP).

During the predicted storm, Earth will plow through a trail of tiny dust
particles left behind by Comet Tempel-Tuttle during its passage through
the inner solar system in the year 1767. This comet rounds the Sun every
33.25 years, shedding dust particles as it is warmed by sunlight. Meteor
showers occur when Earth passes through debris left behind by comets.
But meteor storms occur when Earth passes through particularly dense
ribbons of comet debris.

"During a typical Leonid meteor shower, an experienced observer might see
about 10 to 15 meteors per hour. But during a storm, that rate climbs to
1,000 or more meteors per hour," says Naeye. "This year's Leonid storm
might peak at a rate of up to 2,000 per hour, although it's difficult to
pin down a precise number. The rates will rise and fall over a period of
two hours."

"Of course, these numbers depend on the accuracy of our predictions. But
the predictions have been remarkably accurate in recent years," says ASP
member Dr. Peter Jenniskens, an astronomer and meteor researcher at the
SETI Institute in Mountain View, California, and author of an in-depth
article about meteor science in the November/December 2001 issue of
Mercury magazine.

This year's Leonid display has two added bonuses. The Moon will rise
during daylight and set six hours before the peak, so the Moon's glare
will not obscure fainter meteors. In addition, the peak will occur on
a Sunday morning, so many people can sleep in after a long night of
skygazing.

If one mentally traces back the trajectory of Leonid meteors, they
appear to originate in the constellation Leo (the Lion). Leo rises
around midnight, so the shower will be minimal in the hours immediately
after sunset. But it will pick up considerably as the night progresses.

The entire United States should enjoy a good shower. Peak meteor rates
should occur around 5:00 a.m. EST, 4:00 a.m. CST, 3:00 a.m. MST, and
2:00 a.m. PST. Observers in eastern Asia and the Western Pacific will
also enjoy a storm approximately 8 hours later (in the morning hours
of November 19, local time), according to the forecasts. For the
latest predictions for your local area, visit this website from NASA's
Ames Research Center
     http://www-space.arc.nasa.gov/~leonid/estimator.html

Earth will encounter another dense ribbon of Comet Tempel-Tuttle debris
in 2002, but under a full Moon. After that, it's over for nearly a
century. "It's now or never," stresses Naeye. "People should take
advantage of this year's Leonid storm, because astronomers don't think
we'll see another storm like this one until the year 2099. We will
probably never see a better meteor shower in our lifetimes."

When you see meteors, popularly known as "shooting stars," you're seeing
interplanetary dust particles burning up in the atmosphere at altitudes
of about 60 to 70 miles. A typical comet dust particle -- known as a
meteoroid -- is only about the size of a grain of sand or a pebble when
it enters the atmosphere. Larger chunks of comet debris, perhaps up to
the sizes of basketballs, sometimes light up the sky as they burn up,
which are events called fireballs or bolides. Leonids enter the
atmosphere at 160,000 miles per hour, making them the fastest meteors
of the year.

"Shooting stars are for every man, woman, and child to see, and it
doesn't take any special equipment to see them," says Jane Houston Jones,
a member of the ASP Board of Directors and an experienced meteor observer.
"Most Leonid meteors are faint, so you'll see more of them if you are far
away from city light pollution. If you can't get to a dark site, then
control your own light pollution by turning out as many lights as you
can control. Then sit back in a lawn chair, bundle up in a blanket,
and at a little before midnight local time, face east. You'll see the
backwards question-mark shape of Leo's mane rising, and that's where the
meteors will appear to radiate over the next few hours."

Meteors are beautiful sky events for skygazers. But for scientists,
meteors are fascinating in their own right. "Meteor science involves more
than just predicting storms. We also want to learn about the meteoroids
themselves, which in turn tell us a great deal about the parent comet,"
says Jenniskens. "We also want to learn more how meteors may have brought
critical organic material to Earth, perhaps leading to the origin and
prevalence of life on our planet."

Related Articles:

* Ready for the Storm, by Peter Jenniskens
  http://www.astrosociety.org/pubs/mercury/1101pr/leonids.html
* How to Enjoy the Meteor Show, by Jane Houston Jones
  http://www.astrosociety.org/pubs/mercury/1101pr/leonidsidebar.html
Received on Thu 08 Nov 2001 11:22:26 AM PST