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(meteorobs) Leonids Peak Earlier Than Expected
ESA Science News
http://sci.esa.int
18 Nov 1998
Leonids peak earlier than expected
This year's Leonids shower was a wonderful event for those who finally enjoyed
clear skies and stayed up long after midnight on 16 November, or got up early
on the 17th. All indications are now that the peak of the Leonids shower was
well ahead of the predicted time for the maximum rates (predicted time 19:15
to 20:00 UTC 17 November). Preliminary results indicate that the Earth passed
the maximum about 16 hours earlier.
This is, however, well within the uncertainties. Besides the threat meteor
storms pose to spacecraft, there is also a significant interest in their
scientific study. Meteors provide us with information about the larger grains
(size of a grain of sand to a few centimetres) emitted from the nucleus of
comets and about their dynamics, i.e. orbits in space. The study of their
trails when they burn up in the upper atmosphere gives us information on the
composition of the grains.
Our poor understanding of how the dust grains are emitted from comets and of
their density and shape -- all factors that influence their dynamics -- is
responsible for the large uncertainties that exist when predicting the
occurrence of storms.
But here Rosetta, ESA's mission to comet Wirtanen, will provide the crucial
information. Besides studying in detail the composition of a cometary nucleus,
the spacecraft will follow the comet along its path from its most distant
point from the Sun through perihelion (about the Sun).
It will provide detailed information of the dust emission process -- the
emission speeds as a function of grain size -- and study if the emission is
continuous or in outburst, (so-called jets).
All this will contribute to a significantly better understanding of cometary
processes and to a more accurate prediction of phenomena like meteor showers
and storm.
G. Schwehm
Rosetta project scientist
USEFUL LINKS FOR THIS STORY
ESA's John Zarnecki speaking on BBC (RealAudio)
http://news.bbc.codot uk/olmedia/215000/audio/_216474_zarnecki.ram
Rosetta project
http://sci.esa.int/rosetta/
BBC news report
http://news.bbc.codot uk/hi/english/special_report/1998/11/98/the_leonids_98/
newsid_216000/216446.stm
Leonids Live
http://www.LeonidsLive.com/
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