Electronic Telegram No. 1987
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


ORIONID METEORS 2009
     P. Jenniskens, SETI Institute, reports that the current elevated rate of
Orionids above their normal 23 meteors/hr zenith hourly rate (ZHR), and a
higher-than-normal abundance of relatively bright meteors (magnitude -2 to
-7), is likely to continue for another 1-2 days.
     The International Meteor Organization reports rates of ZHR = 32
meteors/hr on Oct. 21.5 UT, possibly still climbing.  Y. K. Chia, observing
from Singapore, first noticed high rates of bright Orionids on Oct. 19.8.
Javor Kac, observing from Veliki Raven in Slovenia, reported high Orionid
rates on Oct. 20.1, the brightest of which was of magnitude -7.  The next
night, Kac photographed eleven Orionids in 3 hours; his brightest meteor
that night was a Orionid of magnitude -4 that left a 50-s persistent train.
Koen Miskotte and Carl Johannink (Dutch Meteor Society), observing from
Wismar in Germany, report mean magnitudes of 2.65 for 31 Orionids and 4.00
for 22 sporadic meteors around Oct. 20.9.
     As noted on CBET 1976, this outburst was predicted by M. Sato and J.-I.
Watanabe (2007, PASJ 59, L21) and is thought to be due to dust particles
ejected by comet 1P/Halley in the years prior to -11 and now moving in the
1:5 to 1:8 mean-motion resonances with Jupiter, creating a "filament" dust
cloud typical of Halley-type comets.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2009 CBAT
2009 October 22                  (CBET 1987)              Daniel W. E. Green