Electronic Telegram No. 2249 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Room 209; Dept. of Earth and Planetary Sciences; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbat@iau.org; cbatiau@eps.harvard.edu URL http://www.cfa.harvard.edu/iau/cbat.html COMET P/2010 H2 Observations of an unusually bright asteroidal object (discovery observation below), only 15 deg from opposition, were reported to the Minor Planet Center yesterday by J. Vales, observing with the 0.60-m f/3.3 Deltagraph at Crni Vrh, Slovenia. The numerous follow-up observations reported after the discovery was announced on the NEOCP soon made it clear that the object was some 2.0-2.5 AU from the earth and therefore of absolute magnitude H = 8-9. It was also soon clear that there were no recent observations of the object in the MPC files, and R. A. Kowalski has confirmed that it was not present (down to magnitude V = 20) in frames of the relevant region obtained by the Catalina Sky Survey as recently as Apr. 15.4 UT. Several observers, beginning with W. Ryan on Apr. 16.2 at Magdalena Ridge (2.4-m f/8.9 reflector) and E. Guido and G. Sostero on Apr. 16.4 at Mayhill, NM (0.25-m f/3.4 reflector), have indicated that the new object has an FWHM consistently wider (by perhaps 10%) than nearby field stars of similar brightness. R. Miles reports that observations on Apr. 16.5 at the Faulkes Telescope South (2.0-m f/10.0 Ritchey-Chretien) gave colors g'-r' = 0.503, r'-i' = 0.113 and i'-z = 0.116, suggestive of a cometary dust coma. A. Maury, San Pedro de Atacama, Chile, reports the detection of a faint coma on a 60-min exposure (0.36-m f/2 reflector) centered on Apr. 17.3; and K. Kadota, Ageo, Saitama, Japan, remarks that, although the object appears starlike, 16 stacked 60-s exposures (0.25-m f/5.0 reflector) on Apr. 17.6 indicate a possible faint coma of diameter 1'.5. 2010 UT R.A. (2000) Decl. Mag. Observer Apr. 16.00831 13 39 25.17 +04 45 49.5 12.6 Vales The astrometry obtained so far (226 observations), the following still-very-preliminary elliptical orbital elements and an ephemeris are given on MPEC 2010-H12. While necessarily uncertain, this and other similar orbital solutions suggest that the object passed 1.2 AU (or perhaps significantly less) from Jupiter in 1976. T = 2010 May 21.605 TT Peri. = 144.469 e = 0.20730 Node = 64.548 2000.0 q = 3.07064 AU Incl. = 14.115 a = 3.87366 AU, n = 0.129277 deg/day, P = 7.62 years NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2010 CBAT 2010 April 17 (CBET 2249) Brian G. Marsden