Electronic Telegram No. 5510 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 P/2025 D2 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another faint comet in images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala on Feb. 22 UT (discovery observations tabulated below). Four 45-s w-band survey images taken in 1".0 seeing show a soft appearance (condensed head with size 1".5 (full-width-at-half-maximum) and no tail. 2025 UT R.A. (2000) Decl. Mag. Feb. 22.32709 9 27 04.60 + 9 11 26.2 22.0 22.33883 9 27 04.37 + 9 11 27.6 21.5 22.36227 9 27 03.88 + 9 11 29.9 21.8 Three 60-s gri-band follow-up images obtained on Feb. 23.52 UT by Weryk and R. Wainscoat (queue observer L. Wells; queue coordinator V. Khatu) with the 3.6-m Canada-France-Hawaii telescope at Mauna Kea in 0".9 seeing show a diffuse coma of size 1".2 (FWHM) and a broad tail about 6" long spanning p.a. 30-110 deg. The available astrometry appears on MPEC 2025-D149 and includes pre- discovery images (reported after the comet was posted on the Minor Planet Center's PCCP webpage by Weryk) taken with the Mt. Lemmon survey's 1.5-m reflector on Feb. 4.3 UT (mag 20.5-20.8) and Feb. 19.3 (mag 20.3-20.7). The following two-body elliptical orbital elements by S. Nakano (Central Bureau) are from 13 observations spanning Feb. 4-23; the formal error on the orbital period is +/- 2.0 yr, and T is still uncertain. There are no close approaches to major planets. T = 2028 Jan. 13.62360 TT Peri. = 303.61946 e = 0.2446639 Node = 255.20874 2000.0 q = 7.2327700 AU Incl. = 5.25682 a = 9.5755649 AU n = 0.03326270 P = 29.6 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 9.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 02 14 09 29.92 +08 57.6 6.947 7.929 173.6 0.8 20.4 2025 02 24 09 26.52 +09 14.2 6.959 7.918 164.7 1.9 20.4 2025 03 06 09 23.40 +09 30.8 7.000 7.906 154.3 3.1 20.4 2025 03 16 09 20.76 +09 46.3 7.069 7.894 143.8 4.3 20.4 2025 03 26 09 18.73 +09 59.8 7.163 7.883 133.5 5.3 20.4 2025 04 05 09 17.42 +10 10.8 7.278 7.872 123.3 6.1 20.5 2025 04 15 09 16.91 +10 18.5 7.408 7.860 113.4 6.7 20.5 2025 04 25 09 17.22 +10 22.8 7.549 7.849 103.7 7.2 20.5 2025 05 05 09 18.33 +10 23.3 7.697 7.838 94.3 7.4 20.6 2025 05 15 09 20.22 +10 20.0 7.847 7.827 85.2 7.4 20.6 2025 05 25 09 22.84 +10 13.0 7.995 7.816 76.2 7.2 20.7 2025 06 04 09 26.11 +10 02.1 8.137 7.805 67.5 6.9 20.7 2025 06 14 09 29.97 +09 47.8 8.269 7.794 58.9 6.4 20.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 February 24 (CBET 5510) Daniel W. E. Green