Electronic Telegram No. 5419 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 M1 (ATLAS) An apparently asteroidal object discovered on CCD images taken on June 29 UT with a 0.5-m f/2 Schmidt reflector at Rio Hurtado, Chile, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program has been found to show cometary appearance by astrometrists elsewhere after it was posted on the Minor Planet Center's PCCP webpage. The discovery observations are tabulated below: 2024 UT R.A. (2000) Decl. Mag. June 29.42281 4 52 44.54 -39 09 57.6 17.8 29.42694 4 52 45.05 -39 09 54.4 17.6 29.43200 4 52 45.62 -39 09 50.9 17.9 29.44441 4 52 47.00 -39 09 41.7 18.3 K. Yoshimoto (Yamaguchi, Japan) writes that twenty stacked 30-s CCD exposures taken on July 8.4 UT with an iTelescope 0.51-m f/6.8 corrected Dall-Kirkham telescope at the "Deep Sky Chile" observatory at Rio Hurtado show a very condensed coma 8" in diameter (total mag 18.4) and a faint tail 6" long in p.a. 240 deg. A stacked CMOS image taken by T. Prystavski (Lviv, Ukraine) with a "Deep Sky Chile" 0.25-m f/3.8 Newtonian reflector at Rio Hurtado on July 18.4 shows a very condensed coma that is slightly elongated (total mag 18.0) with a possible tail 8".7 long in p.a. 272 degrees. S. Deen (Simi Valley, CA, USA) subsequently identified apparently stellar images of this comet in publicly available DECam observations obtained with the 4-m reflector at Cerro Tololo on 2022 May 10.4 UT (mag g = 23.0) and on 2023 June 6.3 (z = 20.9). The available astrometry appears on MPEC 2024-O16. The following orbital elements by S. Nakano (Central Bureau) are from 120 observations spanning 2022 May 10-2024 July 19 (mean residual 0".3). There are no close approaches to any major planets. Epoch = 2024 Nov. 26.0 TT T = 2024 Nov. 20.02750 TT Peri. = 345.59915 e = 0.9431014 Node = 76.21523 2000.0 q = 1.7033995 AU Incl. = 73.71017 a = 29.9374812 AU n = 0.00601702 P = 163.8 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 12.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2024 06 19 04 31.99 -41 25.2 2.753 2.541 67.4 21.7 17.9 2024 06 29 04 51.92 -39 15.3 2.674 2.457 66.7 22.3 17.8 2024 07 09 05 10.69 -37 14.4 2.595 2.375 66.2 23.1 17.6 2024 07 19 05 28.27 -35 23.4 2.513 2.295 66.0 23.9 17.4 2024 07 29 05 44.61 -33 42.1 2.425 2.218 66.1 24.7 17.2 2024 08 08 05 59.68 -32 10.3 2.330 2.143 66.8 25.8 17.0 2024 08 18 06 13.36 -30 46.8 2.226 2.072 68.0 26.9 16.8 2024 08 28 06 25.53 -29 29.7 2.112 2.006 70.0 28.3 16.5 2024 09 07 06 36.01 -28 16.4 1.986 1.944 72.8 29.7 16.3 2024 09 17 06 44.52 -27 02.9 1.848 1.887 76.5 31.2 16.0 2024 09 27 06 50.69 -25 43.6 1.699 1.837 81.2 32.6 15.8 2024 10 07 06 53.95 -24 10.2 1.540 1.793 87.1 33.8 15.5 2024 10 17 06 53.49 -22 09.3 1.374 1.758 94.4 34.4 15.1 2024 10 27 06 48.16 -19 20.2 1.204 1.731 103.5 33.9 14.8 2024 11 06 06 36.29 -15 09.5 1.039 1.713 115.0 31.6 14.5 2024 11 16 06 15.85 -08 48.3 0.892 1.704 129.8 26.5 14.1 2024 11 26 05 45.08 +00 31.6 0.783 1.705 148.6 17.5 13.8 2024 12 06 05 04.25 +12 30.3 0.737 1.716 169.5 6.0 13.7 2024 12 16 04 18.20 +24 33.5 0.771 1.735 162.5 9.8 13.9 2024 12 26 03 35.08 +33 54.6 0.878 1.764 142.8 19.7 14.2 2025 01 05 03 01.26 +40 08.7 1.033 1.801 126.6 26.0 14.6 2025 01 15 02 38.46 +44 16.3 1.216 1.846 113.7 29.2 15.1 2025 01 25 02 25.31 +47 15.1 1.412 1.897 103.2 30.3 15.5 2025 02 04 02 19.78 +49 40.1 1.613 1.955 94.5 30.2 15.9 2025 02 14 02 20.13 +51 50.1 1.811 2.018 87.1 29.3 16.2 2025 02 24 02 25.09 +53 53.9 2.005 2.086 80.6 27.9 16.6 2025 03 06 02 33.89 +55 56.2 2.191 2.158 75.0 26.4 16.9 2025 03 16 02 46.04 +57 58.9 2.367 2.233 70.0 24.8 17.2 2025 03 26 03 01.35 +60 02.1 2.534 2.311 65.7 23.2 17.4 2025 04 05 03 19.86 +62 05.2 2.690 2.391 62.1 21.7 17.7 2025 04 15 03 41.75 +64 06.8 2.835 2.473 59.0 20.4 17.9 2025 04 25 04 07.40 +66 04.4 2.970 2.557 56.6 19.2 18.1 2025 05 05 04 37.31 +67 55.1 3.095 2.643 54.7 18.1 18.3 2025 05 15 05 11.98 +69 34.7 3.210 2.729 53.3 17.3 18.5 2025 05 25 05 51.77 +70 58.4 3.318 2.816 52.4 16.6 18.7 2025 06 04 06 36.55 +72 00.5 3.417 2.904 52.0 16.0 18.9 2025 06 14 07 25.28 +72 36.0 3.510 2.993 51.9 15.5 19.0 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 July 20 (CBET 5419) Daniel W. E. Green