Electronic Telegram No. 5658 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/2026 A1 (MAPS) Alain Maury, San Pedro de Atacama, Chile, reports his discovery of a diffuse comet with coma diameter 12" on CCD images obtained with a 0.28-m f/2.2 Schmidt astrograph on Jan. 13 in the course of the MAPS survey with Florian Signoret and Georges Attard (discovery observations tabulated below). 2026 UT R.A. (2000) Decl. Mag. Jan. 13.15195 5 15 14.02 -33 30 46.1 17.8 13.15817 5 15 12.59 -33 30 44.1 18.3 13.16435 5 15 11.22 -33 30 43.0 18.1 After the comet was posted to the Minor Planet Center's PCCP webpage, S. Deen (Simi Valley, CA, USA) reported that he identified pre-discovery apparently asteroidal images of the comet going back to 2025 Dec. 18 that were found on CCD images taken with 0.5-m f/2 Schmidt telescopes of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program, as tabulated below. The observations from 2025 Dec. 18/19, 21/22, 27, and 2026 Jan. 8 were obtained at Sutherland, South Africa; the 2025 Dec. 26 observations were obtained at Haleakala, Hawaii; the 2026 Jan. 10 observations were obtained at Rio Hurtado, Chile. 2025 UT R.A. (2000) Decl. Mag. Dec. 18.98467 6 37 40.35 -30 52 42.5 20.4 19.01883 6 37 35.34 -30 53 08.7 19.02530 6 37 34.32 -30 53 14.6 19.02710 6 37 34.02 -30 53 16.2 21.98182 6 29 51.33 -31 32 07.5 21.98461 6 29 50.93 -31 32 10.7 21.99033 6 29 50.06 -31 32 12.0 22.01838 6 29 45.41 -31 32 34.5 26.40612 6 17 10.64 -32 22 51.7 19.8 26.40792 6 17 10.40 -32 22 53.6 26.41202 6 17 09.63 -32 22 56.3 26.42117 6 17 07.97 -32 23 00.6 27.93690 6 12 29.17 -32 37 53.9 27.95914 6 12 25.01 -32 38 07.3 2026 UT R.A. (2000) Decl. Mag. Jan. 8.90525 5 31 13.84 -33 38 31.7 19.1 8.91509 5 31 11.68 -33 38 33.5 8.91832 5 31 10.85 -33 38 33.4 8.92376 5 31 09.74 -33 38 32.1 10.18739 5 26 26.90 -33 37 57.0 10.19013 5 26 26.17 -33 37 56.5 10.19298 5 26 25.42 -33 37 56.7 10.19841 5 26 24.36 -33 37 56.2 Deen also obtained nine 300-s liminance-filtered CMOS exposures on 2026 Jan. 15.1 UT with a 0.43-m f/6.8 CDK reflector that show a faint, 6"-long tail towards p.a. 45 degrees, with a much-fainter coma possibly about 25" in diameter surrounding it. M. Masek (Institute of Physica, Czech Academy of Sciences) writes that ninety-nine stacked 60-s images obtained on Jan. 14.14 UT with the 0.3-m f/6.8 reflector of the F/(Ph)otometric Robotic Atmospheric Monitor (FRAM) robotic observatory at the Pierre Auger Observatory in Malargue, Argentina, show a coma diameter of 11" and magnitude 18.8 with a 15"-long tail in p.a. 35 deg. He adds that twelve stacked 20-s R-filtered exposures taken on Jan. 17.09 by H. Kucakova with the 1.54-m Danish telescope at La Silla show a coma of size 6" and mag 18.9, and a broad tail 8" long spanning p.a. 30-85 degrees. R. Weryk, Department of Physics and Astronomy, University of Western Ontario, that three stacked 60-s gri-band images obtained on 2025 Jan. 14.3 UT with the 3.6-m Canada-France-Hawaii Telescope (queue observer L. Wells; queue coordinator V. Khatu) in 1".4-1".6 seeing show a diffuse head of size 1".9 (full-width-at-half-maximum) with a broad tail > 40" long spanning p.a. 10-50 degrees. Thirty-three stacked 60-s CMOS exposures taken by K. Yoshimoto (Kumage, Yamaguchi, Japan) with a 0.30-m f/4 reflector on Jan. 14.5 UT show a diffuse coma 13" in diameter of total mag 18.5 and no tail. Sixteen stacked 60-s CMOS exposures taken by Yoshimoto on Jan. 15.3 with a 0.25-m f/3.8 Newtonian astrograph located at Rio Hurtado, Chile, show an 18" coma that is extended northward, with total mag 18.4. Twenty stacked 60-s CCD exposures taken by Yoshimoto on Jan. 17.6 with a 0.51-m f/6.8 reflector located at Siding Spring, NSW, Australia, show a coma of diamter 16", total mag 18.7, and a faint tail in p.a. 20 deg. A. Pearce writes that stacked images obtained with the Perth Observatory 0.35-m reflector on Jan. 14.62 UT show a coma of size 0'.45 with total mag 18.0 and an 18"-long tail in p.a. 51 degrees. Three stacked 300-s CCD images obtained by A. Hale (Cloudcroft, NM, USA) on Jan. 14.9 with a 0.35-m f/3 Cassegrain reflector located at Sutherland, South Africa, show a strong condensation near the apex of a roughly fan-shaped coma of diameter 13"; there is a straight tail about 27" long in p.a. 35 degrees (though there are hints that it could be up to twice that long), with a possible second tail perhaps 13" long in p.a. approximately 330 degrees (though this might be the outer edge of the coma). Twenty stacked 20-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at Rio Hurtado on Jan. 15.3 show a strongly condensed coma with an outer coma 12" in diameter and a broad tail 15" long toward p.a. 20 degrees; the magnitude was 19.2 as measured within a circular aperture of radius 6".5. A. Valvasori, Padulle, Italy, writes that twelve stacked 40-s unfiltered CCD exposures taken on Jan. 15.5 by E. Guido and himself with an iTelescope 0.51-m f/6.8 reflector located at Siding Spring show a compact coma about 7" in diameter (mag 17.7-17.9) and a tail 8" long in p.a. 24 degrees. M. Jaeger, Vienna, reports that twelve 120-s exposures obtained on Jan. 16.91 UT with a 0.30-m f/3.6 reflector at Tivoli, Namibia, by G. Rhemann and himself show a 2' coma and a 85"-long tail in p.a. 41 degrees, with a total mag 16.5. Twelve 120-s exposures taken on Jan. 17.88 between clouds in less-good conditions show a 1'.5 coma, a 45" tail, and total mag 17.0. Additional imaging from Jan. 18.80 show a coma of size 2'.5 and mag 16.1 with a 45" tail in p.a. 47 degrees. Images posted by Jaeger at the "ICQ Comet Observations" forum on Facebook show a strong greenish-blue color to the coma, even at mag 16-17. A. Aletti reports that one-hundred-twenty stacked 30-s CMOS exposures taken on Jan. 17.9 UT at Hakos, Namibia, with a 0.36-m reflector show a condensed coma of size 4" with a faint, straight tail 20" long in p.a. 41 deg. The available astrometry appears on MPEC 2026-B129. The following orbital elements by S. Nakano (Central Bureau) are from 177 observations spanning 2025 Dec. 18-2026 Jan. 17 (mean residual 0".6), with corresponding "original" and "future" values of 1/a being +0.006950 and +0.006255 (+/- 0.000145) AU**-1, respectively. These are the elements of a Kreutz sungrazer, and the indicated orbital period is around 1935 years with semi-major axis 155.3 AU. Epoch = 2026 Mar. 21.0 TT T = 2026 Apr. 4.59831 TT Peri. = 86.34876 e = 0.9999631 Node = 7.89274 2000.0 q = 0.0057261 AU Incl. = 144.49280 This appears to be the furthest from the sun pre-perihelion that a Kreutz sungrazer has been observed. Photometry on as many nights as possible are therefore urged by experienced observers. The faint absolute magnitude of C/2026 A1 (H = 14-15 at r = 2.0) does not bode well for the comet's survival past perihelion. Recent Kreutz sungrazers observed from the ground include C/2011 W3 (Lovejoy) and C/2024 S1 (ATLAS), both of which had pre-perihelion absolute magnitudes, H, around 7.5-11, and both of which fell apart near perihelion. Kreutz sungrazers observed from the ground that survived perihelion in the past 65 years include C/1963 R1 (Pereyra) and C/1970 K1 (White-Ortiz-Bolelli), both of which were found after perihelion and both with H = 6-7; the only Kreutz sungrazer seen from the ground on both sides of perihelion in that time span was C/1965 S1 (Ikeya-Seki), which had H = 6.5 on both sides of perihelion (2.5n = 8-9). The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 12 31 06 02.65 -33 03.7 1.584 2.275 123.1 21.2 17.9 2026 01 10 05 27.15 -33 38.1 1.466 2.112 117.8 24.3 17.4 2026 01 20 04 49.08 -32 41.8 1.383 1.942 109.0 28.6 17.0 2026 01 30 04 12.50 -30 13.4 1.331 1.764 98.1 33.6 16.6 2026 02 09 03 40.39 -26 32.2 1.302 1.576 85.9 38.6 16.2 2026 02 14 03 26.36 -24 22.6 1.293 1.478 79.6 41.1 15.9 2026 02 19 03 13.65 -22 04.4 1.286 1.377 73.2 43.4 15.7 2026 02 24 03 02.09 -19 40.1 1.279 1.272 66.8 45.7 15.4 2026 03 01 02 51.42 -17 11.1 1.270 1.162 60.3 47.8 15.0 2026 03 06 02 41.33 -14 38.0 1.259 1.046 53.8 49.9 14.7 2026 03 11 02 31.44 -12 00.1 1.244 0.924 47.2 52.0 14.2 2026 03 16 02 21.19 -09 15.8 1.224 0.794 40.3 54.1 13.6 2026 03 21 02 09.79 -06 21.8 1.196 0.651 33.0 56.3 12.9 2026 03 26 01 55.76 -03 11.3 1.160 0.491 24.9 58.7 11.9 2026 03 31 01 35.62 +00 30.9 1.109 0.299 15.2 60.9 10.0 2026 04 05 01 21.45 +03 56.6 1.112 0.169 6.9 45.4 8.1 2026 04 10 15 05.07 +13 27.5 0.872 1.787 145.0 18.7 15.7 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 January 20 (CBET 5658) Daniel W. E. Green