Electronic Telegram No. 5428 Central Bureau for Astronomical Telegrams Mailing address: 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/2024 O2 (PANSTARRS) Yudish Ramanjooloo, Institute for Astronomy, University of Hawaii, reports the discovery of another comet in images obtained on July 28 with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below); three 45-s w-band survey images taken in 1".6- 1".7 seeing show a diffuse ocma of size 2".1 (full-width-at-half-maximum) with a broad tail about 5" long and 2" wide spanning p.a. about 3450350 degrees. 2024 UT R.A. (2000) Decl. Mag. July 28.53543 23 50 18.04 -21 59 39.5 20.8 28.54729 23 50 17.81 -21 59 39.3 21.4 28.56723 23 50 17.44 -21 59 39.3 20.9 R. Weryk, Department of Physics and Astronomy, University of Western Ontario, writes that follow-up images were obtained in 1" seeing on July 29.51 UT with the 3.6-m Canada-France-Hawaii Telescope on Mauna Kea (R. Wainscoat's time; queue observer J. Silva; queue coordinator H. Flewelling); three 60-s gri-band exposures show a very condensed head of size 1".2 (FWHM) and a tail > 30" long towards p.a. 240 degrees. Three similar CFHT follow-up exposures taken by Weryk et al. (queue coordinator V. Khatu) on Aug. 1.6 in 0".7 seeing show a head of size 1".0 and a clear tail > 30" long in p.a. 240 deg. Pre-discovery images of the comet were subsequently found in exposures taken on June 30.6 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (magnitude 20.3-21.2). H. Sato (Bunkyo-ku, Tokyo, Japan) reported that he obtained eight stacked 120-s CCD exposures remotely on July 29.81 UT with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, that show a strongly condensed coma 6" in diameter with a 10" tail toward p.a. 255 degrees; the magnitude was 20.3 as measured within a circular aperture of radius 3".2. The available astrometry appears on MPEC 2024-P90. The following elliptical two-body orbital elements by S. Nakano (Central Bureau) are from 26 observations spanning 2024 June 30-Aug. 3 (mean residual 0".1). There are no close approaches to major planets. T = 2024 Apr. 19.90200 TT Peri. = 310.72573 e = 0.4997317 Node = 6.81062 2000.0 q = 3.6969238 AU Incl. = 28.96899 a = 7.3898817 AU n = 0.04906229 P = 20.1 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 12.0 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 07 29 23 50.16 -21 59.6 2.973 3.750 134.0 11.2 20.1 2024 08 08 23 46.21 -22 00.7 2.900 3.762 143.3 9.3 20.1 2024 08 18 23 40.63 -22 00.5 2.848 3.774 152.2 7.2 20.0 2024 08 28 23 33.78 -21 55.4 2.822 3.787 159.8 5.3 20.0 2024 09 07 23 26.18 -21 42.4 2.824 3.801 163.4 4.3 20.1 2024 09 17 23 18.45 -21 19.0 2.854 3.816 160.3 5.1 20.1 2024 09 27 23 11.23 -20 44.1 2.913 3.831 152.8 6.9 20.2 2024 10 07 23 05.05 -19 57.8 2.998 3.848 143.6 8.9 20.2 2024 10 17 23 00.33 -19 01.1 3.107 3.866 133.9 10.7 20.3 2024 10 27 22 57.30 -17 55.6 3.237 3.884 124.3 12.2 20.4 2024 11 06 22 56.04 -16 43.1 3.383 3.904 114.8 13.3 20.6 2024 11 16 22 56.51 -15 24.8 3.542 3.924 105.5 14.1 20.7 2024 11 26 22 58.58 -14 02.3 3.709 3.945 96.5 14.4 20.8 2024 12 06 23 02.09 -12 36.3 3.880 3.966 87.8 14.4 20.9 2024 12 16 23 06.86 -11 07.7 4.052 3.989 79.3 14.0 21.0 2024 12 26 23 12.71 -09 36.9 4.222 4.012 71.1 13.4 21.2 2025 01 05 23 19.46 -08 04.4 4.386 4.036 63.0 12.5 21.3 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 August 7 (CBET 5428) Daniel W. E. Green