Electronic Telegram No. 2019 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 LEONID METEORS 2009 P. Jenniskens, SETI Institute, reports that the earth is predicted to encounter the 1466 and 1533 dust ejecta of comet 55P/Tempel-Tuttle on 2009 Nov. 17d21h43m-50m UT. This may result in a brief (about 1 hr) duration outburst of Leonid meteors with peak Zenith Hourly Rate, ZHR, > 100 meteors per hour. The best viewing will be from sites in mid-Asia, including China, Indochina, India, Nepal, Mongolia, and Indonesia. Initial peak-rate predictions of ZHR = 5000 meteors per hour (Jenniskens 2006, *Meteor Showers and Their Parent Comets*, Cambridge Univ. Press, p. 631) have since been adjusted downward to reflect the results from more-recent observations of 55P's older dust trail encounters. However, peak rates critically depend on the exact position of the 1533 dust trail, which is uncertain because of the unknown orbit of the comet in 1533 and because the trail now moves rapidly by the earth at the time of the predicted Leonid meteor outburst. The forecast by (1) J. Vaubaillon and P. Atreya (I.M.C.C.E., Paris), Jenniskens, and J. Watanabe and M. Sato (National Astronomical Observatory of Japan) is summarized below and compared to results by (2) M. Maslov, Novosibirsk, Russia (two predicted peaks for each of the two trails); (3) by D. Moser and B. Cooke, NASA Meteoroid Enivronment Office; by (4) E. Lyytinen and M. Nissinen, Helsinki, Finland (2009, WGN 37, 122-124); and by (5) D. Asher, Armagh Observatory (also two predicted peaks for the 1466 trail). The miss distance is positive if the dust trail is outside the earth's orbit, and negative if inside the earth's orbit. 1533 trail (14 revolutions old, center just outside of the earth's orbit): Source: (1) (2) (3) (4) (5) Peak times Nov. 17d 21h50m 21h55m, 21h16m 22h30m 21h44m 21h15m Solar long., deg 235.550 235.550, 235.577 235.545 235.525 235.522 miss dist., AU +0.00053 +0.00044, -- -- +0.0005 +0.00039 ZHR, meteors/hr 80 65, 10 80 60 -- Duration, hr 1 -- < 1 4 -- R.A., deg 154.31 154.3 -- -- -- Decl., deg +22.93 +22.9 -- -- -- +++ 1466 trail (16 revolutions old, center just inside of the earth's orbit): Source: (1) (2) (3) (4) (5) Peak time Nov. 17d 21h43m 20h53m, 21h31m 20h53m 21h20m, 21h39m 22h00m Solar long., deg 235.545 235.506, 235.536 235.51 235.528, 235.538 235.556 miss dist., AU -0.00045 -0.00076 -- -- -0.0011, +0.0009 ZHR, meteors/hr 115 39 200 60 -- Duration, hr 1 -- 2 8 -- R.A., deg 153.92 -- -- -- -- Decl., deg +22.09 -- -- -- -- According to Vaubaillon, weaker activity may occur from the 1567 trail (Nov. 17d07h27m UT) at ZHR around 25 meteors/hr and from the 1102 trail (Nov. 18d03h29m UT) at ZHR = 10-50 meteors/hr. Maslov predicts the peak of the filament around Nov. 17d09h UT, with peak rates of ZHR = 25-30 meteors/hr. To calculate the expected rate from a specific location, go to website URL http://leonid.arc.nasa.gov/estimator.html. Online web sources are given below. (1) J. Vaubaillon et al.: http://www.imcce.fr/en/ephemerides/phenomenes/meteor/DATABASE/Leonids/2009/ (2) M. Maslov: http://feraj.narod.ru/Radiants/Predictions/Leonids2009eng.html (3) D. Moser and B. Cooke: http://www.nasa.gov/pdf/372657main_2009LeoVisibility_Public2.pdf (4) E. Lyytinen and M. Nissinen: http://lists.meteorobs.org/pipermail/meteorobs/2008-December/009634.html (5) D. Asher: http://www.arm.ac.uk/leonid/ NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2009 CBAT 2009 November 16 (CBET 2019) Daniel W. E. Green