Electronic Telegram No. 5576 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/2025 M2 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in four 45-s w-band survey images taken in 1".3-1".4 seeing on June 22 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). The two best images show a very condensed head of size 1".6 (full- width-at-half-maximum) with no tail. Weryk writes that the set the PCCP flag to appear on the Minor Planet Center's PCCP webpage. 2025 UT R.A. (2000) Decl. Mag. June 22.53830 21 48 34.60 -15 00 43.5 20.6 22.54976 21 48 34.30 -15 00 44.9 20.5 22.56124 21 48 34.01 -15 00 46.3 20.6 22.57271 21 48 33.71 -15 00 47.8 20.6 Weryk and R. Wainscoat obtained three 60-s gri-band follow-up images of this object on June 25.52 UT with the 3.6-m Canada-France-Hawaii Telescope on Mauna Kea (queue observer L. Wells; queue coordinator V. Khatu); in 0".8 seeing, there was a very condensed coma of size about 1".1 (FWHM) with no tail. Weryk adds that, as a result of Palomar pre-discovery observations (from June 19-22) posted to the PCCP webpage (which the MPC received after Weryk's initial discovery report), he was able to identify the comet in four 45-s w-band Pan-STARRS2 survey images from May 29.6 taken in 1".4-1".6 seeing; stacked images show a very condensed head of size 1".7 (FWHM) with no tail. S. Deen (Simi Valley, CA, USA) reports that he has identified the comet at mag 20.6 in a V-band DECam image obtained in 1".6 seeing on May 29.41 UT with the 4-m reflector at Cerro Tololo; there was no apparent activity then. Deen was unable to find the object in Sept. 2024 images (assuming an orbit with perihelion date in the future) to limiting mag V = 24.0 (when an inverse- square brightness assumption would predict mag 21.4). The astrometry appears on MPEC 2025-M134. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 43 observations spanning May 29-June 27 (mean residual 0".4). The comet passed 2.39 AU from Saturn on 2024 Jan. 21 UT; it will pass 2.40 AU from Jupiter in 2028 April and 3.28 AU from Saturn in 2031 October. T = 2027 Nov. 26.19769 TT Peri. = 96.69161 Node = 305.52869 2000.0 q = 2.7320441 AU Incl. = 173.21937 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 7.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 06 14 21 51.80 -14 44.5 7.814 8.336 117.8 6.2 18.8 2025 06 24 21 47.96 -15 03.8 7.599 8.267 128.3 5.5 18.7 2025 07 04 21 43.19 -15 27.2 7.403 8.198 139.0 4.7 18.7 2025 07 14 21 37.59 -15 53.8 7.232 8.128 150.0 3.6 18.6 2025 07 24 21 31.24 -16 23.0 7.091 8.058 161.1 2.3 18.5 2025 08 03 21 24.32 -16 53.5 6.982 7.989 172.3 1.0 18.4 2025 08 13 21 17.05 -17 24.1 6.908 7.919 175.9 0.5 18.4 2025 08 23 21 09.68 -17 53.5 6.869 7.849 164.7 2.0 18.3 2025 09 02 21 02.47 -18 20.6 6.864 7.779 153.3 3.3 18.3 2025 09 12 20 55.67 -18 44.6 6.891 7.708 141.9 4.6 18.3 2025 09 22 20 49.53 -19 04.7 6.945 7.638 130.7 5.7 18.3 2025 10 02 20 44.21 -19 20.6 7.023 7.567 119.6 6.6 18.3 2025 10 12 20 39.85 -19 32.4 7.117 7.496 108.7 7.2 18.3 2025 10 22 20 36.51 -19 40.0 7.222 7.425 98.0 7.6 18.3 2025 11 01 20 34.21 -19 43.7 7.331 7.354 87.5 7.7 18.3 2025 11 11 20 32.92 -19 43.9 7.439 7.283 77.1 7.6 18.3 2025 11 21 20 32.58 -19 40.8 7.540 7.212 67.0 7.2 18.3 2025 12 01 20 33.12 -19 34.7 7.629 7.140 57.0 6.7 18.2 2025 12 11 20 34.42 -19 26.1 7.701 7.069 47.2 5.9 18.2 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 June 27 (CBET 5576) Daniel W. E. Green