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(meteorobs) IMO Press Release: Leonid Meteor Shower on Nov 16/17
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I M O S h o w e r C i r c u l a r
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LEONID Activity 2000
Observers saw no unusual activity during the nights of
November 15/16 and 16/17, though certains variations in the
activity level require further scrutiny.
Zenithal hourly rates (ZHRs) seem to have risen from about
10 +/- 5 around Nov 16, 0h UT, to about 45 +/- 5 by 4h UT.
After that, the picture becomes less clear. Observers at the
Canary Islands report high rates at the beginning of their
observations, resulting in a peak with ZHR around 110 +/- 20
at 6h00m +/- 5m UT. Activity drops again down to about
65 +/- 20 afterwards, but American observers report average
activity around 100 +/- 10 between 6h45m and 8h30m UT, with
a possible peak around 8h10m +/- 10m of 150 +/- 20. Afterwards,
activity drops again significantly to 45 +/- 10 by 9h00m UT.
Due caution is needed in interpreting these activity
variation, for the following reasons:
1) Only a few observations contributed to each
peak. Unexperienced or very perceptive observers can
"inflate" ZHRs. On the other hand, the peaks cannot be
explained away by averaging effects alone, as they are
also noticeable in the individual observations of the
observers involved.
2) The bright Last Quarter Moon is a disturbing factor in
the observations which is not easy to account for
exactly. Several observers, both in Europe and North
America, report to have seen their best activity during
the beginning of their observation. One may speculate the
continuous hindrance from the bright light of the Moon
made observers less perceptive for fainter meteors after
a while, resulting in a "decreasing peak branch" at the
beginning of their observations.
If the above-mentioned variations in activity are real,
however, the Nov 16, 6h45m-8h30m UT enhancement in activity
with a possible peak around 8h10m UT may be associated with the
Earth passing the outer regions of the 1932 (2 revolutions
old) dust trail of the parent comet, 55P/Tempel-Tuttle, for
which a possible activity enhancement was predicted at 7h53m
UT by (among others) Asher and McNaught.
The following observers have contributed data immediately
after the event, from which the ZHR profile given below
has been derived:
Birger Andresen, Joseph Assmus, Neil Bone, Andreas Buchmann,
Marc de Lignie, Petros Georgopoulos, Robin Gray, Rosely
Gregio, Valentin Grigore, Wayne Hally, Zoltan Hevesi, Janne
Pyykkoe, Robert Lunsford, Alastair McBeath, Gilberto Klar
Renner, Josep Trigo, Vishnu Vardhan, Cis Verbeeck, Jean-Marc
Wislez, Ju Zhao, Jin Zhu, Xiaojin Zhu.
Date Time (UT) Sol. long. Intervals Leonids ZHR +-
(2000.0)
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Nov 15 22h05m 243.848 2 11 13 4
Nov 16 03h33m 234.067 1 7 8 3
Nov 16 21h16m 234.820 6 44 20 3
Nov 17 3h23m 235.076 5 37 40 7
Nov 17 4h47m 235.136 9 74 47 5
Nov 17 6h00m 235.187 3 30 108 20
Nov 17 6h16m 235.198 3 16 66 17
Nov 17 6h30m 235.208 3 11 63 19
Nov 17 7h22m 235.244 11 91 98 10
Nov 17 9h19m 235.322 5 31 45 8
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ZHRs are computed with a population index of 2.0, zenithal
exponent of 1.0.
---
Marc Gyssens, 2000 November 17, 16h UT.
wgn@imodot net
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