[meteorite-list] ESA's Shortcut To A Comet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:15 2004
Message-ID: <200211142145.NAA24702_at_zagami.jpl.nasa.gov>

ESA Science News

14 Nov 2002

ESA's shortcut to a comet

Night owls across Europe, get ready. On the night of 18-19
November 2002, you may see a spectacular sky show. As tiny
particles in Comet 55/P Tempel-Tuttle's tail enter Earth's
atmosphere, they will pierce through it, heating up, and
finally explode. Welcome to one of the most spectacular
natural fireworks displays of the year: a meteor shower
called the Leonids.

Unlike in 2001, this year the Leonids will be very well
visible from Europe. The meteor showers are expected every
night between 13 and 21 November 2002. Scientists expect
the Leonids meteor shower to reach its peak at 04:00 CET,
in Europe, and 10:30 on the night of 18-19 November 2002.

Die-hards willing to travel each year all around the planet
look for the best location to witness the shooting-star
show. Some years that can be in the middle of a desert.
This year, that will be on top of a cold mountain close to
Pico Veleta in Granada, Spain. The scientists aim to obtain
information about the meteor shower, the structure of our
own atmosphere, and comets.

"It's like a cheap comet mission," says Detlef Koschny, a
member of the ESA team. "The behaviour of the particles
left in past orbits tells us things about comets, even
without having to go there."

Koschny has led the ESA Leonids campaigns since 1998. The
team has observed the meteors in The Netherlands, Spain,
Germany, and Australia. This year the location is once
again Spain. Why? Statistically it is one of the places
where there are higher chances of good weather. Secondly,
scientists can use a professional observatory, from which
the visibility conditions are optimal. Lastly, technicians
are at hand to help these Leonid-chasers solve possible
engineering problems.

Scientific models predict the intensity and the maxima
of the storms, and this year's shower appears promising.
Scientists are expecting about 3000 events per hour in
the stronger, first peak. However, the light of the near
full moon will make observations more difficult and may
reduce the apparent number by 10%.

The 2002 Leonids show could be the last one for many years
to come. Calculations of the comet's path predict that the
next perihelions, or closest points of approach, of the
comet in 2031 and 2065 could be significantly less
dramatic. Jupiter's gravitational pull is pushing the
orbit of the comet further away from Earth's orbit.

The path of our planet intersects the comet's trails twice
this year. Firstly, Earth's atmosphere will encounter the
trail the comet left in 1767, seven comet journeys ago.
These particles will create a shower storm visible from
Europe. A few hours later, a second trail Comet Tempel-
Tuttle left in 1866, about four cycles ago, will cause
another shower. North American sky-watchers will benefit
from this second shower.

Koschny is also involved in the Rosetta mission, the ESA
spacecraft to Comet Wirtanen due for launch in January
2003. "The composition of the particles belonging to the
two different trails can tell us a lot about the structure
of the comet. If we observe different chemical properties,
we can conclude that the particles are coming from
different parts of its surface." Knowing whether a comet
is homogenous or not is very useful since scientists have
to decide on a landing site for the Rosetta lander
touchdown on the comet in 2011.

The Leonids enter Earth's atmosphere at a speed around 70
kilometres per second -- nearly twice as fast as other
meteors. Why? Comet Tempel-Tuttle orbits the Sun roughly
in the opposite direction than the Earth's orbit of the
Sun. There are therefore almost head-on collisions between
Earth and comet-trail debris. However, this is much less
dangerous than it sounds.

"The biggest pieces can't exceed 0.5 metres in diameter,"
says Koschny. "The gases vaporising from the nucleus of
the comet would not be able to lift anything bigger than
that. These rocks are small enough to be vaporised by the
Earth's atmosphere and really do not constitute a risk
for the observers. More worrying is the effect they may
have on satellites, which could be seriously damaged by
such collisions."

For video animations, see:



* Meet the team
* Typical Leonids puzzles
* Previous Leonids campaigns
* Listening to the Leonids
* Video animations
* Chasing meteors on-board airplanes
* More about Rosetta


[Image 1:
The Leonids as seen in 2001. Copyright 2001 Shigemi
Numazawa, Japan Planetarium Laboratory; courtesy Sky &

[Image 2:
Spanish radio telescope ready for the Leonids. Copyright
"Observers", AlltheSky.com
Received on Thu 14 Nov 2002 04:45:45 PM PST

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