[IAUC] CBET 1543: 20081021 : ORIONID METEORS 2008

[IAUC mailing list]

                                                  Electronic Telegram No. 1543
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS en CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT en CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


ORIONID METEORS 2008
     Further to CBET 1518, P. Jenniskens, SETI Institute, reports that
K. Miskotte (Dutch Meteor Society) noticed unusual Orionid activity on
Oct. 20, mostly bright meteors between +1 and -2 magnitude.  According to
the International Meteor Organization, the Orionid meteor-shower rate had
increased to a zenith hourly rate (ZHR) of 34 +/- 3 meteors/hr on Oct. 20
(solar longitude 207.0 deg, equinox 2000.0) and to ZHR = 33 +/- 7 meteors/hr
on Oct. 21 (solar long. 208.2 deg), significantly above the normal peak
rate of ZHR = 23 meteors/hr (Jenniskens 2006, *Meteor Showers and Their
Parent Comets*, Cambridge University Press, p. 729).  Hence, the peak of the
outburst is later than the predicted date of 2008 Oct. 19d02h-19d08h UTC,
when the earth was to cross the dust trail of comet 1P/Halley material
ejected in the year -1265 (cf. CBET 1518).  Rates are expected to stay
higher than normal for at least another day or two.  A live update is
provided by the International Meteor Organization at the following website
URL:  http://www.imo.net/live/orionids2008/.  Jenniskens also forwards the
following report:
     J. M. Trigo-Rodriguez, Institute of Space Sciences, Consejo Superior
de Investigaciones Cientificas and Institut Estudis Espacials de Catalunya;
J. M. Madiedo, University of Huelva; and P. Pujols, Agrupacio Astronomica
Osona, report that the encounter with the -1265 dust trail on Oct. 19
coincided with a moderate ZHR rate of 20 meteors/hr from an apparent
radiant R.A. = 95 deg, Decl. = +15 deg, and a low population index of 1.5
+/- 0.4 (N = 40).  On Oct. 20, the ZHR was at the same level, but bright
bolides were detected between 2h and 5h UT, with a magnificent bolide of
magnitude -13 at Oct. 20d03h45m UT.  High meteor rates and fireballs were
also recorded over Europe on Oct. 21 when most Orionid meteors radiated
from R.A. = 93 deg, Decl. = +17 deg, and the ZHR increased to 40 +/- 8
(solar longitude 208.03 deg) with a population index of 1.6 +/- 0.4 (N = 52).


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

                         (C) Copyright 2008 CBAT
2008 October 21                  (CBET 1543)              Daniel W. E. Green