Electronic Telegram No. 2507 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network ORIONID METEORS 2010 P. Jenniskens, SETI Institute, reports that the strong Orionid meteor shower activity of 2006-2009 may repeat this year, for a final year in this sequence, according to M. Sato and J.-I. Watanabe (2007, PASJ 59, L21); they ascribed the 2006-2009 activity to dust trails of comet 1P/Halley that were formed by meteoroids ejected in the years 1401 BC and 12 BC. The orbital evolution of the dust is affected by the 1:5 to 1:8 mean-motion resonances with Jupiter. This so-called "filament" component is expected to be in the earth's path again around Oct. 20-25 in 2010, giving rise to a higher-than-normal Orionid-shower activity that is relatively rich in bright meteors. Sato expects a peak ZHR of 40-50 /h, at the same level as in 2009. As case studies, Sato calculated peak times of Oct. 21 9h UT for the 1266 BC dust trail and Oct. 25 4h UT for the 911 BC trail, both having dust survive in the 1:6 resonance with Jupiter. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 October 19 (CBET 2507) Michael Rudenko