Electronic Telegram No. 5486 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 X4 (PANSTARRS) Y. Ramanjooloo, Institute for Astronomy, University of Hawaii, reports the discovery of another comet in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on Dec. 8 UT (discovery observations tabulated below); in 1".1 seeing, the comet showed a soft, diffuse head of size 1".8 (full-width-at-half-maximum) with no tail. 2024 UT R.A. (2000) Decl. Mag. Dec. 8.22197 22 37 05.68 +29 23 51.0 21.3 8.23272 22 37 06.13 +29 23 47.5 21.2 8.24333 22 37 06.60 +29 23 44.1 21.1 8.32028 22 37 10.01 +29 23 18.8 21.1 8.32092 22 37 10.03 +29 23 18.6 20.9 R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the three 60-s gri-band follow-up images taken on Dec. 25.23 UT with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (queue observer A. Acohido; queue coordinator H. Flewelling) show this to be clearly a comet; in 0".9 seeing, there was a very condensed head of diameter 1".1 FWHM with a broad tail about 4" long spanning p.a. 50-130 degrees. This object was independently found twice as an apparently asteroidal single-night object via the Mt. Lemmon Survey's 1.5-m reflector, on 2024 Sept. 30.2 UT at mag 21.8-22.3 and on Nov. 21.1 at mag 21.0-21.5, as found subsequently in the Minor Planet Center's "isolated tracklet file". The available astrometry appears on MPEC 2024-Y146. The following orbital elements by S. Nakano (Central Bureau) are from 32 observations spanning 2024 Sept. 30-2024 Dec. 25 (mean residual 0".4). There are no close approaches to major planets. Epoch = 1994 Mar. 29.0 TT T = 1994 Mar. 17.17105 TT Peri. = 153.56781 e = 0.6406606 Node = 259.02908 2000.0 q = 3.5803260 AU Incl. = 34.77906 a = 9.9636338 AU n = 0.03133844 P = 31.45 years Epoch = 2025 Sept. 2.0 TT T = 2025 Sept. 1.94371 TT Peri. = 153.29700 e = 0.6420081 Node = 258.94294 2000.0 q = 3.6047762 AU Incl. = 34.66828 a = 10.0694362 AU n = 0.03084582 P = 31.95 years Epoch = 2057 Aug. 25.0 TT T = 2057 Aug. 12.97126 TT Peri. = 153.27772 e = 0.6434077 Node = 258.67125 2000.0 q = 3.6151094 AU Incl. = 34.55766 a = 10.1379360 AU n = 0.03053372 P = 32.28 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 12 16 22 43.31 +28 45.4 3.922 4.054 90.7 14.0 20.8 2024 12 26 22 52.44 +28 06.5 4.012 4.023 83.6 14.1 20.9 2025 01 05 23 02.69 +27 39.6 4.104 3.993 76.6 13.9 20.9 2025 01 15 23 13.91 +27 24.5 4.194 3.963 69.8 13.5 20.9 2025 01 25 23 25.97 +27 20.6 4.280 3.935 63.1 12.9 20.9 2025 02 04 23 38.74 +27 27.1 4.361 3.907 56.7 12.2 20.9 2025 02 14 23 52.13 +27 42.7 4.434 3.880 50.4 11.3 20.9 2025 07 04 03 25.70 +36 33.2 4.259 3.631 46.2 11.7 20.6 2025 07 14 03 40.07 +36 55.4 4.157 3.623 52.1 12.8 20.6 2025 07 24 03 53.76 +37 12.4 4.045 3.616 58.3 13.8 20.5 2025 08 03 04 06.60 +37 24.0 3.924 3.611 64.8 14.7 20.4 2025 08 13 04 18.41 +37 29.9 3.796 3.608 71.6 15.5 20.4 2025 08 23 04 28.98 +37 30.0 3.663 3.606 78.8 16.0 20.3 2025 09 02 04 38.08 +37 24.0 3.526 3.605 86.3 16.2 20.2 2025 09 12 04 45.50 +37 11.7 3.388 3.606 94.3 16.2 20.1 2025 09 22 04 51.01 +36 52.4 3.252 3.608 102.7 15.8 20.0 2025 10 02 04 54.42 +36 25.2 3.121 3.611 111.6 14.9 19.9 2025 10 12 04 55.60 +35 49.0 3.000 3.616 121.0 13.7 19.9 2025 10 22 04 54.52 +35 02.5 2.892 3.623 131.0 12.0 19.8 2025 11 01 04 51.31 +34 04.3 2.802 3.631 141.4 9.8 19.7 2025 11 11 04 46.32 +32 53.8 2.735 3.640 152.2 7.3 19.7 2025 11 21 04 40.05 +31 31.3 2.695 3.651 163.0 4.5 19.7 2025 12 01 04 33.21 +29 58.9 2.685 3.663 171.7 2.2 19.7 2025 12 11 04 26.57 +28 20.1 2.706 3.677 168.6 3.0 19.7 2025 12 21 04 20.79 +26 39.8 2.760 3.692 158.3 5.7 19.7 2025 12 31 04 16.43 +25 02.9 2.842 3.708 147.3 8.2 19.8 2026 01 10 04 13.82 +23 33.4 2.951 3.725 136.4 10.5 19.9 2026 01 20 04 13.11 +22 13.8 3.082 3.744 125.8 12.3 20.0 2026 01 30 04 14.30 +21 05.4 3.230 3.764 115.7 13.6 20.2 2026 02 09 04 17.26 +20 08.0 3.391 3.785 106.1 14.5 20.3 2026 02 19 04 21.84 +19 20.5 3.559 3.807 96.9 14.9 20.4 2026 03 01 04 27.86 +18 41.5 3.732 3.831 88.2 15.0 20.5 2026 03 11 04 35.10 +18 09.0 3.905 3.855 79.8 14.7 20.6 2026 03 21 04 43.39 +17 41.4 4.075 3.881 71.8 14.1 20.8 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 December 28 (CBET 5486) Daniel W. E. Green