Electronic Telegram No. 5508 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 A6 (LEMMON) An apparently asteroidal object discovered on CCD images obtained on Jan. 3 by D. C. Fuls with the Mt. Lemmon survey's 1.5-m reflector has been found to show cometary appearance by observers elsewhere. The discovery observations are tabulated below. 2025 UT R.A. (2000) Decl. Mag. Jan. 3.34215 7 52 21.68 +15 16 09.8 21.6 3.34727 7 52 21.28 +15 16 11.1 21.7 3.35240 7 52 20.93 +15 16 13.3 21.1 3.35754 7 52 20.48 +15 16 14.8 21.6 After the object was posted to the Minor Planet Center's NEOCP webpage, R. Weryk (Department of Physics and Astronomy, University of Western Ontario) measured three 60-s follow-up CCD images obtained by J. Fairlamb with the University of Hawaii 2.2-m reflector at Mauna Kea on Jan. 6.5 UT in 1".3 seeing that show a very condensed head of size 2".2 (full-width-at-half- maximum and no tail. Weryk adds that three 60-s gri-band images were taken on Feb. 21.25 with the 3.6-m Canada-France-Hawaii Telescope on Mauna Kea (queue observer L. Wells; queue coordinator H. Flewelling) in 0".5 seeing, showing a very condensed head of size 0".6 (FWHM) with a short tail about 2" long toward p.a. 95 degrees. Weryk also subsequently identified the comet in pre-discovery images from exposures taken on 2024 Nov. 12.6 (at mag 22.3-23.3), Dec. 2.5 (mag 22.1-22.2), Dec. 6.5 (mag 22.0-23.1), and Dec. 22.6 (mag 22.2-23.0) with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala, as well as in images taken on 2024 Nov. 28.5 (at mag 23.6), Dec. 6.5-6.6 (mag 23.1), Dec. 23.44-23.48 (mag 21.7-22.2), and Dec. 30.6 (mag 21.3-21.9) with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala. The Pan-STARRS images are not good enough to definitively show cometary appearance. The available astrometry appears on MPEC 2025-D55. The following orbital elements by S. Nakano (Central Bureau) are from 95 observations spanning 2024 Nov. 12-2025 Feb. 21 (mean residual 0".3), with corresponding "original" and "future" values of 1/a being +0.008213 and +0.009113 (+/- 0.000039) AU**-1, respectively. The comet will pass 2.33 AU from Jupiter on 2025 Apr. 16 and 0.60 AU from the earth on 2025 Oct. 21 UT. These suggest an orbital period of somewhat over 1300 years. Epoch = 2025 Nov. 21.0 TT T = 2025 Nov. 8.53941 TT Peri. = 132.97265 e = 0.9956258 Node = 108.09833 2000.0 q = 0.5298497 AU Incl. = 143.66192 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 02 14 06 54.38 +19 04.0 3.304 4.087 137.5 9.4 20.5 2025 02 24 06 42.09 +19 52.9 3.329 3.975 124.6 11.8 20.4 2025 03 06 06 31.72 +20 37.3 3.378 3.862 112.1 13.8 20.3 2025 03 16 06 23.55 +21 17.3 3.441 3.747 100.2 15.1 20.3 2025 03 26 06 17.64 +21 53.8 3.511 3.631 88.9 15.9 20.2 2025 04 05 06 13.93 +22 27.5 3.580 3.513 78.1 16.2 20.1 2025 04 15 06 12.25 +22 59.0 3.641 3.393 67.9 15.9 20.1 2025 04 25 06 12.40 +23 29.0 3.689 3.272 58.2 15.1 20.0 2025 05 05 06 14.18 +23 57.8 3.720 3.149 48.8 14.0 19.8 2025 09 02 08 00.21 +32 01.4 2.003 1.472 44.9 28.9 15.9 2025 09 12 08 20.93 +33 57.1 1.684 1.310 51.0 36.7 15.1 2025 09 22 08 51.13 +36 38.7 1.350 1.146 56.0 46.6 14.1 2025 10 02 09 43.98 +40 13.9 1.013 0.979 58.2 60.3 13.0 2025 10 12 11 35.55 +42 10.0 0.718 0.816 53.8 80.9 11.6 2025 10 22 14 34.11 +27 56.9 0.598 0.667 40.6 103.7 10.5 2025 11 01 16 23.56 +02 47.6 0.778 0.559 34.1 94.4 10.4 2026 01 20 17 07.82 -45 44.5 2.089 1.550 44.6 26.5 16.1 2026 01 30 17 01.96 -49 18.8 2.067 1.706 55.1 28.3 16.4 2026 02 09 16 51.28 -53 05.5 2.028 1.858 65.9 29.0 16.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 February 22 (CBET 5508) Daniel W. E. Green