Electronic Telegram No. 5655 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 Y2 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on 2025 Dec. 27 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala. Four stacked 45-s w-band survey images taken in 1".1-1".4 seeing showed a very condensed head of size 1".7 (full-width-at-half-maximum) with a broad tail > 12" long spanning p.a. 260-310 degrees. The discovery observations are tabulated below. 2025 UT R.A. (2000) Decl. Mag. Dec. 27.58406 12 15 42.80 - 5 18 52.6 20.9 27.58739 12 15 42.95 - 5 18 53.0 20.4 27.59960 12 15 43.52 - 5 18 54.5 20.7 27.60289 12 15 43.68 - 5 18 55.0 20.3 27.61471 12 15 44.22 - 5 18 56.6 21.0 27.61800 12 15 44.36 - 5 18 56.9 20.4 27.62975 12 15 44.91 - 5 18 58.5 20.9 27.63306 12 15 45.06 - 5 18 59.0 20.4 Two stacked 60-s w-band follow-up images obtained in 1".2-1".3 seeing on Dec. 29.65 UT by Weryk with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala show a condensed head of size 1".5 (FWHM) with a broad tail about 4" long in p.a. 250-300 deg. After the comet was posted (by Weryk) to the Minor Planet Center's PCCP webpage, other CCD astrometrists reported on the cometary nature. Twelve stacked 60-s exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at Rio Hurtado, Chile, on 2025 Dec. 30.34 UT show a strongly condensed coma 7" in diameter with no tail; the magnitude was 20.0 as measured within a circular aperture of radius 3".6. Eighteen 60-s exposures taken remotely by T. Prystavski (Lviv, Ukraine) using an iTelescope 0.51-m f/6.8 "Corrected Dall-Kirkham" telescope (+ luminance filter) at Rio Hurtado on Dec. 31.3 show no clear sign of a coma but a clear tail 12".9 long in p.a. 298 degrees. The available astrometry appears on MPEC 2026-A121. The following orbital elements by S. Nakano (Central Bureau) are from 42 observations spanning 2025 Dec. 27-2026 Jan. 14. T = 2025 Dec. 9.21570 TT Peri. = 345.15796 e = 0.2402723 Node = 177.47312 2000.0 q = 3.0474197 AU Incl. = 16.59522 a = 4.0112002 AU n = 0.12268531 P = 8.03 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 12 31 12 18.33 -05 25.6 2.838 3.049 92.8 18.8 19.6 2026 01 10 12 24.99 -05 36.3 2.700 3.051 101.4 18.4 19.5 2026 01 20 12 29.99 -05 32.3 2.567 3.054 110.5 17.6 19.4 2026 01 30 12 33.12 -05 11.9 2.443 3.058 120.1 16.2 19.3 2026 02 09 12 34.29 -04 34.1 2.331 3.062 130.2 14.2 19.2 2026 02 19 12 33.45 -03 38.9 2.236 3.067 140.9 11.7 19.1 2026 03 01 12 30.75 -02 27.8 2.163 3.073 152.0 8.7 19.1 2026 03 11 12 26.54 -01 04.5 2.114 3.079 163.5 5.3 19.0 2026 03 21 12 21.32 +00 25.9 2.093 3.086 174.7 1.7 19.0 2026 03 31 12 15.78 +01 56.4 2.102 3.094 172.2 2.5 19.0 2026 04 10 12 10.63 +03 20.2 2.139 3.103 160.9 6.1 19.1 2026 04 20 12 06.48 +04 31.7 2.203 3.112 149.8 9.4 19.2 2026 04 30 12 03.82 +05 27.0 2.290 3.122 139.1 12.2 19.3 2026 05 10 12 02.90 +06 04.8 2.397 3.133 129.0 14.5 19.4 2026 05 20 12 03.82 +06 25.1 2.520 3.144 119.5 16.3 19.5 2026 05 30 12 06.53 +06 29.0 2.654 3.156 110.5 17.5 19.6 2026 06 09 12 10.89 +06 18.4 2.796 3.168 102.1 18.3 19.7 2026 06 19 12 16.74 +05 55.2 2.943 3.181 94.1 18.6 19.9 2026 06 29 12 23.91 +05 21.4 3.092 3.194 86.5 18.5 20.0 2026 07 09 12 32.20 +04 39.0 3.240 3.208 79.2 18.1 20.1 2026 07 19 12 41.47 +03 49.5 3.385 3.223 72.2 17.5 20.2 2026 07 29 12 51.58 +02 54.5 3.526 3.238 65.4 16.6 20.3 2026 08 08 13 02.40 +01 55.4 3.660 3.253 58.8 15.5 20.4 2026 08 18 13 13.84 +00 53.4 3.787 3.269 52.4 14.2 20.5 2026 08 28 13 25.81 -00 10.2 3.905 3.286 46.1 12.8 20.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 January 14 (CBET 5655) Daniel W. E. Green