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(meteorobs) [IMO-News] Encounters with fresh Perseid trails - meteor storms?
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Lew Gramer <owner-meteorobs@jovian.com>
------- Forwarded Message
To: imo-news@imodot net
Cc: tvf@mindspring.com, fmbb@sci.fi, pjenniskens@mail.arc.nasadot gov
Date: Wed, 9 Feb 2000 16:10:14 +0200
Subject: [IMO-News] Encounters with fresh Perseid trails - Perseid meteor
storms?
From: Esko Lyytinen <Esko.Lyytinen@MINEDU.FI>
Encounters with fresh Perseid trails - Coming Perseid Meteor Storms?
The orbit of comet P/Swift-Tuttle has been passing outside the Earth's orbit
at least for the last 2000 years. The last return in 1992 was an exception.
Already during the previous return in 1862, the perihelion distance might
have had a lower value than during any of the previous history that can be
reliably calculated. Four revolutions back, the perihelion distance was
almost as low as in 1862. It is doubtful that the Earth has ever
encountered a fresh meteor trail from this comet. In 2004, the
one-revolution trail from 1862 will pass inside the Earth's orbit. At the
time of Perseids (the annual meteor shower associated with this comet), the
rE-rD has a value of about +0.0012 au. Earth passes the trail node at solar
longitude (2000.0) 139.441=B0. This occurs at 11 August 20:54 UT. If there
were a closer approach, a real meteor storm would be expected. But with
these conditions and no prior storms to judge by, it is uncertain what kind
of a shower this will give. The Moon will be a relatively narrow waning
crescent in 2004, with Europe and Western Asia in the most favorable viewing
locations. The principles I use in my unpublished Leonid ZHR-model would
give zenith hourly rates about 100 from this trail, if the numbers of
particles released were the same as for Leonid-parent-comet Tempel-Tuttle.
But since the Perseid parent comet is a lot bigger than the Leonid comet,
there may be a chance of storm level activity. Because the planet Jupiter
lowers the ecliptic crossing radii in general this year (2004), there may be
enhanced general activity as well. The one-revolution trail may give a short
shower with a half-strength duration of only about fifteen minutes. In the
year 2028, the Earth will pass within about -0.0004 au (rE-rD) of the
4-revolution trail from the year 1479, with a mean anomaly factor of about
0.15. I expect this to produce a real storm over the U.S., although under
unfavorable moonlight conditions.
Some further details with figures can be seen at the two websites:
http://www.metaresearch.org
(or directly: http://www.metaresearch.org/perseid/perseids.htm)
and
http://www.sci.fi/~fmbb/astro/meteorit.htm
Esko Lyytinen
esko.lyytinen@minedu.fi
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