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What is the occasion all about?
LEONIDS: RARE EARTH ENCOUNTER WITH COMET DUST TRAILS
In 1999, we saw the first meteor storm of the space age. Even now,
the societal and physical effects of meteor storms remain unclear.
Will a particularly intense meteor storm cause satellites to malfunction some time in the future?
What chemical reactions will occur as the meteors incinerate? Might cometary debris have influenced the development of life on Earth?
The current episode of Leonid storms is a unique chance to study these issues.
The figures show how the showers have manifested itself in the past years
and how our understanding has gradually improved with new observations.
The graphs in the middle are a map of where the dust is located, according to calculations
by
David Asher of Armaugh Observatory. Each colorfull elipse is the point where a
trail of dust, from one of comet
55P/Tempel-Tuttle's returns to the Sun,
crosses the Earth's orbital plane. The blue trails are the onces closest to
Earth's orbit. Those are detected as Leonid showers.
The year of origin of each trail is marked. The path of Earth is shown as an orange line.
The observed Leonid shower rates in the years
1998, 1999 and 2000 during Leonid MAC missions and from data gathered by the
International Meteor Organisation
are shown on the right. The rates are in unit of "Zenith Hourly Rate", the count of
meteors seen by a visual observer
when the sky conditions are ideal and the shower radiant is in the zenith. The horizontal
axis shows the time in hours
since November 18 at 0h UT of a given year. The graphs for 2001 and 2002
are predicted rates by one of several dust models, in particular that of
Esko Lyytinen and Tom Van Flandern (which is sort of in the
middle of predicted levels of activity). Note that the encounter with each blue
trail resulted in a peak of Leonid shower activity.
Each encounter is unique and provides important information about the exact location
of the dust trails and the dust properties of different ages. From precise measurements,
Leonid MAC PI Dr. Peter Jenniskens derived such properties as the meteoroids density,
how much dust is ejected by the comet in each return. More information here.
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