Electronic Telegram No. 2874 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 COMET P/2011 U1 (PANSTARRS) Larry Denneau, Richard Wainscoat, and Henry Hsieh, Institute for Astronomy, University of Hawaii, report the discovery of a comet on CCD images taken with the "Pan-STARRS 1" 1.8-m Ritchey-Chretien telescope at Haleakala (discovery observations tabulated below); stacked discovery frames show FWHM for the comet of 1".5, compared with 1".1 for nearby stars. Confirming images taken with the Canada-France-Hawaii Telescope by M. Micheli (measured by Hsieh) show a diffuse, low-level coma with a slight extension (about 3"-4" long) to the west. After posting on the Minor Planet Center's NEOCP webpage, Shinsuke Abe (Institute of Astronomy, National Central University, Jhongli, Taoyuan, Taiwan) writes that stacked images taken by J. K. Guo, N. Panwar, W. P. Chen, and himself on Oct. 26.4 UT (with a 0.81-m f/7 Ritchey-Chretien telescope at the Tenagra II Observatory near Nogales, AZ, U.S.A.) show a tail-like structure around p.a. 270 deg, though it is difficult to see clearly due to bad seeing (about 2".2). 2011 UT R.A. (2000) Decl. Mag. Oct. 23.45242 5 06 41.93 + 2 46 50.5 21.0 23.46729 5 06 41.87 + 2 46 46.2 21.2 23.48218 5 06 41.80 + 2 46 42.3 21.4 23.49712 5 06 41.72 + 2 46 38.1 21.3 The available astrometry, the following preliminary elliptical orbital elements by G. V. Williams, and an ephemeris appear on MPEC 2011-U84. T = 2012 June 29.230 TT Peri. = 0.710 e = 0.47609 Node = 133.997 2000.0 q = 2.22570 AU Incl. = 15.380 a = 4.24827 AU n = 0.112560 P = 8.76 years NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 October 26 (CBET 2874) Daniel W. E. Green