Donald Savage/Nancy Neal
Headquarters, Washington November 14, 2002
(Phone: 202/358-1547)
RELEASE: 02-221
NASA PREPARES FOR "LAST CHANCE" METEOR SHOWER
The early morning hours of Nov. 19 may be your last
chance to see the spectacular Leonid meteor shower in its
full glory, according to astronomers.
"Even with the full moon, this year's Leonids will probably
be better than any other for the next hundred years," said
Dr. Don Yeomans, an astronomer at NASA's Jet Propulsion
Laboratory, Pasadena, Calif. "If you're ever going to see
them, this might be the year to try," he said. NASA is taking
advantage of the event for several research efforts around
the world.
The shower is predicted to have two peaks, each a couple of
hours long, during which the most meteors can be seen. The
shower's second peak, most prominent in North American skies,
is expected at around 5:30 a.m. EST Nov. 19, and promises the
rare spectacle of a few meteors every minute or even more.
"Observers in good locations away from city lights might see
a few hundred per hour. You'll only get to see the bright
ones because the moonlight will wash out the ones that aren't
as bright," said Yeomans. Last year, observers did not have
to contend with the Moon and saw meteors at a pace of several
hundred per hour.
An earlier peak is expected over Europe and Africa the night
of Nov. 18, and observers in North America might see a few
grazers -- meteors skimming the top of the atmosphere -- from
this first peak starting around 11:30 p.m. EST Nov. 18.
The Leonids are grains of dust from comet Tempel-Tuttle
colliding into the Earth's atmosphere. Most Leonid particles
are tiny and will vaporize very high in the atmosphere due to
their extreme speed (about 44 miles per second, or almost 71
km/sec), so they present no threat to people on the ground or
even in airplanes. As it progresses in its 33-year orbit, the
comet releases dust particles every time it comes near the
Sun. Earth intersects the comet's debris trail every year in
mid-November, but the intensity of each year's Leonid meteor
shower depends on whether Earth ploughs through a
particularly concentrated stream of dust within the broader
debris trail.
The dust that Tempel-Tuttle shed in 1866 forms the stream
predicted to give Americans a good show this year. Last year,
people in Asia saw the plentiful collisions within that
stream. A dust stream from 1767 provided last year's peak
hour of viewing in North America and will provide this year's
peak hour of viewing in Europe. After 2002, Earth won't hit
either of those streams again for decades to come, and is not
predicted to encounter a dense Leonid stream until 2098 or
2131.
The golden rule for watching the Leonids -- or any meteor
shower -- is to be comfortable. Be sure to wrap up warmly --
a sleeping bag placed atop a lawn chair facing east is a good
way to enjoy the show. Put your chair in a clear, dark place
with a view of as much of the sky as possible. Don't stare at
any one place -- keep your eyes moving across the sky. Most
Leonids will appear as fleeting streaks of light, but watch
for the bigger ones that produce fireballs and trails -- some
trails will remain visible for several minutes or more.
The Leonids get their name from the constellation where they
appear to originate; the meteors will be radiating from the
Sickle pattern in the constellation Leo the Lion, which will
be rising out of the east-northeast sky. Don't look directly
at the constellation, but at the area above and around it.
And, though you don't need them to see the Leonids, a pair of
binoculars could come in handy.
Researchers think meteors might have showered the Earth with
the molecules necessary for life's origin. A two-aircraft
campaign, led by astronomer Dr. Peter Jenniskens of the SETI
Institute and NASA's Ames Research Center, Moffett Field,
Calif., will investigate this possibility. "We are looking
for clues about the diversity of comets and their impact on
the chemistry of life's origin on Earth," Jenniskens said.
"We are eager to get another chance to find clues to two
puzzling questions: What material from space rains down on
Earth, and what happens to the (meteor's) organic matter when
it interacts with the atmosphere?" said Dr. Michael Meyer,
senior scientist for astrobiology at NASA Headquarters in
Washington.
On Nov. 15, a team of 42 astrobiologists from seven countries
will depart from southern California's Edwards Air Force Base
on a mission to Spain to observe this year's two Leonid storm
peaks. The DC-8 Airborne Laboratory, operated by NASA's
Dryden Flight Research Center, Edwards, Calif., will carry
high-speed cameras; a radio receiver to listen to upper
atmosphere molecules; and a team of meteor observers, who
will keep track of the meteor activity for satellite
operators concerned about impact hazards.
"This final deployment of the Leonid Multi-instrument
Airborne Campaign program promises an important and unique
database for the development of instruments targeted at in
situ sampling of cometary materials and for the future
definition of comet missions," said Dr. John Hillman, lead
scientist for planetary astronomy at NASA Headquarters. "It
is hoped that these scientific data will provide new insights
for the comparative studies of comets," he said.
Although the meteors are harmless to people, there is a
slight chance that a satellite could be damaged if it was hit
by a Leonid meteoroid. The meteoroids are too small to simply
blow up a satellite. However, the Leonids are moving so fast
they vaporize on impact, forming a cloud of electrified gas
called plasma. Since plasma can carry an electric current,
there is a risk that a Leonid-generated plasma cloud could
cause a short circuit in a satellite, damaging sensitive
electronic components.
NASA's Goddard Space Flight Center, Greenbelt, Md., is
responsible for controlling a large number of satellites for
NASA and other organizations and is taking precautions to
mitigate the risk posed by the Leonids. These include
pointing instrument apertures away from the direction of the
Leonid stream, closing the doors on instruments where
possible, turning down high voltages on systems to decrease
the risk of a short circuit, and positioning satellites to
minimize the cross-section exposed to the Leonids.
Minimizing the threat meteoroids pose to satellites is the
second major area of NASA's Leonid research. From five key
points on the globe and from the International Space Station,
NASA researchers will use special cameras to scan the skies
and report activity around the clock during the Leonid
shower. Led by Dr. Rob Suggs of the Engineering Directorate
at NASA's Marshall Space Flight Center in Huntsville, Ala.,
the research is part of a long-term goal to protect
spacecraft from potentially damaging meteoroids.
Using "night-vision" image-intensifier video systems and sky-
watchers outfitted with Palm computer software developed to
record visual counts, NASA engineers and astronomers will
record their observations for later analysis. Another tool at
Marshall's disposal is "forward-scatter radar" -- an early
warning system built by Suggs, Dr. Jeff Anderson, also of
Marshall's Engineering Directorate, and Dr. Bill Cooke, an
astronomer at Marshall.
"Our system is pretty simple," said Suggs. "We use an antenna
and a computer-controlled shortwave receiver to listen for 67
MHz signals from distant TV stations." The transmitters are
over the horizon and normally out of range. When a meteor
streaks overhead, the system records a brief ping -- the echo
of a TV signal bouncing off the meteor's trail. Like the
image-intensified cameras, this system is capable of
detecting meteors too dim to see with the unaided eye.
The research data from the Leonids shower will be analyzed to
help NASA engineers refine their forecasts for spacecraft; by
better determining where, when and how the meteors will
strike, NASA can improve protective measures to prevent or
minimize damage to spacecraft.
For more information, including predicted peak times for
major cities and NASA media contacts, refer to:
http://www.gsfc.nasa.gov/topstory/2002/1114leonid.html
-end-
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