[meteorite-list] Draconid Meteor Outburst

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 4 Oct 2011 14:16:13 -0700 (PDT)
Message-ID: <201110042116.p94LGDDr004768_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/science-news/science-at-nasa/2011/04oct_draconids/

Draconid Meteor Outburst
NASA Science News

Oct. 4, 2011: On October 8th Earth is going to plow through a stream
of dust from Comet 21P/Giacobini-Zinner, and the result could be an
outburst of Draconid meteors.

"We're predicting as many as 750 meteors per hour," says Bill Cooke of
NASA's Meteoroid Environment Office. "The timing of the shower favors
observers in the Middle East, north Africa and parts of Europe."

Every 6.6 years Comet Giacobini-Zinner swings through the inner solar
system. With each visit, it lays down a narrow filament of dust, over
time forming a network of filaments that Earth encounters every year in
early October.

"Most years, we pass through gaps between filaments, maybe just grazing
one or two as we go by," says Cooke. "Occasionally, though, we hit one
nearly head on--and the fireworks begin."

2011 could be such a year. Forecasters at NASA and elsewhere agree that
Earth is heading for three or more filaments on October 8th. Multiple
encounters should produce a series of variable outbursts beginning
around 1600 Universal Time (noon EDT) with the strongest activity
between 1900 and 2100 UT (3:00 pm - 5:00 pm EDT).

Forecasters aren't sure how strong the display will be, mainly because
the comet had a close encounter with Jupiter in the late 1880s. At that
time, the giant planet's gravitational pull altered the comet's orbit
and introduced some uncertainty into the location of filaments it has
shed since then. Competing models place the filaments in slightly
different spots; as a result, estimated meteor rates range from dozens
to hundreds per hour.

One respected forecaster, Paul Wiegert of the University of Western
Ontario, says the meteor rate could go as high as 1000 per hour -- the
definition of a meteor storm. It wouldn't be the first time. Close
encounters with dusty filaments produced storms of more than 10,000
Draconids per hour in 1933 and 1946 and lesser outbursts in 1985, 1998,
and 2005.

Meteors from Comet Giacobini-Zinner stream out of the northern
constellation Draco--hence their name. Draconids are among the slowest
of all meteors, hitting the atmosphere at a relatively leisurely 20
km/s. The slow pace of Draconid meteors minimizes their danger to
satellites and spacecraft and makes them visually distinctive.

"A Draconid gliding leisurely across the sky is a beautiful sight," says
Cooke.

Unfortunately, many of this year's Draconids will go unseen. Draconids
are faint to begin with, and this year they have to complete with an
almost-full Moon. Lunar glare will reduce the number of meteors visible
from Europe, Africa and the Middle East by 2- to 10-fold. The situation
is even worse in North America where the shower occurs in broad
daylight???completely obliterating the display.

That isn't stopping a group^1 of middle school and high school students
from Bishop, California, however. They plan to observe the shower from
the stratosphere where the sky is dark even at noontime.

Led by Science at NASA's Tony Phillips, the 15 students have been launching
helium balloons to the edge of space since May of 2011. With more than
95% of Earth's atmosphere below the balloon, the sky above looks almost
as black as it would from a spacecraft - perfect for astronomy.

"The students are going to attempt to fly one of our low-light meteor
cameras in the payload of their balloon," says Cooke. "I hope they catch
some Draconid fireballs for us to analyze. They could be the only ones
we get."

Stay tuned for results after Oct. 8th.


Author: Dr. Tony Phillips
Credit: Science at NASA
Received on Tue 04 Oct 2011 05:16:13 PM PDT