Electronic Telegram No. 5471 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 U1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala, Hawaii, on Oct. 30 (discovery observations tabulated below). Four 45-s w-band survey images taken in 1".3-1".5 seeing show a condensed head of size 2".0 (full-width-at- half-maximum) with no tail. 2024 UT R.A. (2000) Decl. Mag. Oct. 30.55150 5 36 20.77 + 1 46 49.3 20.8 30.56424 5 36 20.01 + 1 46 40.7 20.4 30.57693 5 36 19.24 + 1 46 32.1 20.4 30.58963 5 36 18.45 + 1 46 23.8 20.7 Follow-up observations requested by Weryk and R. Wainscoat with the 3.6-m Canada-France-Hawaii Telescope on Mauna Kea were obtained by way of three 40-s gri-band images taken on 2024 Nov. 3.5 UT by queue observer A. Acohido (queue coordinator V. Khatu); the best image, taken in 0".9 seeing, shows a condensed head of size 1".4 (FWHM) with a broad trail 5" long spanning p.a. 0-60 deg. Weryk later identified pre-discovery images of the comet (all apparently stellar in appearance) taken with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala on 2023 Nov. 13.6 (mag 22.2-23.4) and 23.5 (mag 21.7- 22.2) and on 2023 Dec. 6.5 (mag 21.6-22.1) and 13.4 (mag 21.3-22.0), as well as with the Pan-STARRS1 telescope on 2023 Nov. 25 (mag 21.6-22.5), on 2024 Jan. 3.4 (mag 21.0-21.5), and on 2024 Oct. 24.6 (mag 20.4). After the comet was posted on the Minor Planet Center's NEOCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) reported that he noticed it having a comet-like orbit, but sixteen stacked 60-s CCD exposures taken remotely with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, on Oct. 31.74-31.75 show only a stellar appearance; the magnitude was 20.4 as measured within a circular aperture of radius 4".3. The available astrometry appears on MPEC 2024-V81. The following orbital elements by S. Nakano (Central Bureau) are from 66 observations spanning 2023 Nov. 13-2024 Nov. 5 (mean residual 0".3), with corresponding "original" and "future" values of 1/a being +0.001855 and +0.002188 (+/- 0.000007) AU**-1, respectively. The comet passed 1.44 AU from Jupiter on 2024 Sept. 25 UT Epoch = 2024 June 19.0 TT T = 2024 June 30.52707 TT Peri. = 188.04671 e = 0.9936143 Node = 270.22769 2000.0 q = 4.8359606 AU Incl. = 128.67250 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 10 17 05 48.28 +04 17.2 4.400 4.909 115.3 10.6 19.7 2024 10 27 05 39.79 +02 26.6 4.271 4.923 126.1 9.4 19.7 2024 11 06 05 29.57 +00 34.6 4.170 4.938 136.6 7.9 19.6 2024 11 16 05 17.89 -01 15.5 4.104 4.954 145.9 6.4 19.6 2024 11 26 05 05.18 -02 59.2 4.077 4.972 152.2 5.3 19.6 2024 12 06 04 52.00 -04 32.5 4.092 4.990 153.0 5.1 19.6 2024 12 16 04 38.99 -05 51.9 4.149 5.010 147.8 6.0 19.7 2024 12 26 04 26.76 -06 55.5 4.245 5.031 139.1 7.3 19.8 2025 01 05 04 15.81 -07 43.1 4.375 5.052 129.0 8.7 19.8 2025 01 15 04 06.48 -08 16.0 4.532 5.075 118.5 9.8 19.9 2025 01 25 03 58.92 -08 36.2 4.709 5.099 108.0 10.6 20.0 2025 02 04 03 53.17 -08 46.6 4.898 5.124 97.7 11.0 20.1 2025 02 14 03 49.15 -08 49.7 5.092 5.150 87.8 11.0 20.2 2025 02 24 03 46.71 -08 48.1 5.285 5.177 78.4 10.8 20.3 2025 03 06 03 45.66 -08 44.0 5.471 5.204 69.3 10.3 20.4 2025 03 16 03 45.83 -08 39.3 5.645 5.233 60.8 9.6 20.5 2025 03 26 03 47.01 -08 35.6 5.804 5.263 52.9 8.7 20.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 November 5 (CBET 5471) Daniel W. E. Green