Electronic Telegram No. 5447 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 C/2024 Q4 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on Aug. 31 UT with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). 2024 UT R.A. (2000) Decl. Mag. Aug. 31.60923 6 38 07.38 +25 39 51.8 21.1 31.61450 6 38 07.62 +25 39 51.6 22.1 31.61975 6 38 07.88 +25 39 51.8 21.3 Follow-up observations were undertaken on Sept. 1.62 UT by Weryk and R. Wainscoat with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (queue observer J. Silva; queue coordinator V. Khatu); three 60-s gri-band exposures taken in 0".9 seeing show a diffuse coma of size 1".5 (full-width-at-half- maximum) with a broad tail about 5" long spanning p.a. 230-290 degrees. Weryk adds that two 60-s w-band Pan-STARRS2 exposures taken in 1".2 seeing on Sept. 4.62 show a condensed head of size 1".8 (FWHM) with a straight tail about 3" long in p.a. 260 degrees. Additional astrometry appears on MPEC 2024-S10. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 24 observations spanning 2024 Aug. 31-Sept. 15 (mean residual 0".3). These indicate that the comet passed 1.05 AU from Neptune in 2009 November and 1.95 AU from Jupiter on 2024 Apr. 12 UT. T = 2024 Nov. 8.30524 TT Peri. = 132.42624 Node = 324.46238 2000.0 q = 5.4220120 AU Incl. = 3.30437 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 10.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 09 07 06 43.14 +25 36.0 5.793 5.442 64.8 9.6 20.2 2024 09 27 06 56.67 +25 23.7 5.492 5.431 81.3 10.5 20.1 2024 10 17 07 06.17 +25 14.2 5.182 5.425 98.8 10.5 19.9 2024 11 06 07 10.85 +25 10.6 4.890 5.422 117.7 9.3 19.8 2024 11 26 07 10.38 +25 13.7 4.651 5.424 137.9 7.0 19.7 2024 12 16 07 05.36 +25 20.9 4.498 5.429 159.3 3.7 19.6 2025 01 05 06 57.69 +25 26.9 4.457 5.439 176.9 0.6 19.6 2025 01 25 06 50.23 +25 26.8 4.536 5.452 156.3 4.2 19.7 2025 02 14 06 45.75 +25 19.4 4.726 5.470 135.1 7.3 19.8 2025 03 06 06 45.92 +25 05.5 4.997 5.491 115.1 9.4 19.9 2025 03 26 06 51.14 +24 46.2 5.316 5.516 96.4 10.4 20.1 2025 04 15 07 00.89 +24 21.1 5.650 5.545 78.9 10.2 20.2 2025 05 05 07 14.26 +23 49.1 5.971 5.578 62.5 9.2 20.4 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 September 17 (CBET 5447) Daniel W. E. Green