Electronic Telegram No. 2923 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 UH55 (SPACEWATCH) An apparently asteroidal reported by the Spacewatch survey (discovery observations tabulated below), and designated 2010 UH55 by the Minor Planet Center last year, has been found to show cometary activity. H. Sato (Tokyo, Japan) first reported the appearance of a condensed coma of size 6"-8" last year; his CCD images taken remotely on 2010 Nov. 17.4 UT taken with a 0.50-m f/6.8 reflector at the RAS Observatory near Mayhill, NM, U.S.A., suggest that the west side of the object appeared soft, with a hint of tail 12" long. Sato's report of cometary appearance remained unconfirmed until the past month, when he again found the object on 2011 Nov. 3.5 to be moderately condensed a faint coma of diameter 40" (and mag 18.8 within a circular aperture of radius 19".7) with a 55" tail in p.a. 290 degrees with a 0.51-m f/4.5 reflector at the same site. Luca Buzzi (Varese, Italy; 0.38-m f/6.8 relector) found a compact coma 8" wide that was faintly elongated out to 10"-15" in p.a. around 290 deg on stacked images obtained on Nov. 15.15-15.17 in good seeing but with moonlight interference. D. Chestnov and A. Novichonok report that 300-s unfiltered CCD images taken on Nov. 25.09 by V. Gerke with the 0.40-m telescope at the TAU Station of Ka-Dar Observatory (near Nizhny Arkhyz, North Caucasus, Russia) show that 2010 UH55 has a small coma of total mag 18.7 and a 0'.2 tail in p.a. about 295 deg; six stacked 240-s images taken on Nov. 28.03 show the same morphology except measuring the tail to be in p.a. 319 deg. G. Sostero, K. Rochowicz, N. Howes, and E. Guido write that five stacked 40-s R-band images taken remotely with the 2.0-m f/10 "Faulkes Telescope North" at Haleakala on Nov. 28.6 show a diffuse coma about 9" in diameter (mag 18.2-18.3) with a faint, broad tail nearly 20" long toward the west-northwest. 2010 UT R.A. (2000) Decl. Mag. Observer Oct. 29.21706 3 31 53.06 +20 24 43.4 19.4 Spacewatch 29.23481 3 31 52.58 +20 24 38.8 19.6 " 29.25255 3 31 52.08 +20 24 34.7 19.7 " S. Nakano notes that 2010 UH55 passed 0.58 AU from Jupiter on 1946 June 5 and 0.42 AU from Saturn on 1900 Jan. 1 UT. Revised orbital elements by G. V. Williams from MPEC 2011-W82: Epoch = 2011 Aug. 27.0 TT T = 2011 May 10.39701 TT Peri. = 221.62832 e = 0.5752275 Node = 235.26362 2000.0 q = 2.7680070 AU Incl. = 8.66233 a = 6.5164457 AU n = 0.05924994 P = 16.64 years NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2011 CBAT 2011 November 30 (CBET 2923) Daniel W. E. Green