Electronic Telegram No. 5659 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/2026 B1 (PANSTARRS) R. Weryk, Department of Physics and Astronomy, University of Western Ontario, reports the discovery of another comet in images obtained on Jan. 17 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below). Four 45-s w-band survey images taken in 1".7 seeing show a diffuse head of size 2".2 (full-width-at-half-maximum) with no obvious tail. 2026 UT R.A. (2000) Decl. Mag. Jan. 17.38313 8 31 40.74 +20 48 28.3 21.1 17.38505 8 31 40.63 +20 48 28.8 20.5 17.39541 8 31 40.16 +20 48 31.2 21.1 17.39736 8 31 40.05 +20 48 31.9 20.7 17.40776 8 31 39.57 +20 48 34.6 20.9 17.40971 8 31 39.47 +20 48 35.2 20.5 17.42032 8 31 38.95 +20 48 38.1 21.1 17.57439 8 31 31.62 +20 49 17.5 20.7 17.57521 8 31 31.58 +20 49 17.9 20.5 17.57603 8 31 31.55 +20 49 17.9 20.6 17.57685 8 31 31.50 +20 49 18.2 20.5 Weryk identified two pre-discovery single-night images of this comet in the Minor Planet Center's "isolated tracklet file": three images on Jan. 13.74- 13.77 UT at mag 20.1-20.5 obtained with a 1-m Schmidt telescope at Purple Mountain Observatory and four images obtained on Jan. 14.4 with the Mt. Lemmon survey's 1.5-m reflector (mag 20.3-20.6). Weryk then obtained two follow-up 60-s w-band Pan-STARRS2 observations on Jan. 18.41 in 1".3-1".4 seeing that show a condensed head of size 1".8 (FWHM) with a straight tail about 4" long in p.a. 340 degrees. These observations allowed him to identify pre-discovery Pan-STARRS2 from 2025 Nov. 23.5 (mag 22.2-22.8) and 30.5 (mag 21.2-22.4). Weryk was then able to use an orbit to find many Pan-STARRS2 images of the comet back to 2013 Apr. 15.5 (mag 21.9-22.2), including 2013 observations also on Apr. 21.4, 22.4, and May 3.4 (mag 21.0-22.0 throughout), as well as on 2018 Dec. 14.6 (mag 21.2-21.9), 2019 Jan. 3.53-3.55 (mag 21.2-21.3), 2019 Jan. 25.5 (mag 21.3), and on four nights in 2020: May 20.4 (mag 22.2-22.9), May 24.4 (mag 23.0-23.2), June 14.4 (mag 22.7-22.9), and June 23.35-23.37 (mag 22.7-23.2). Weryk was unable to discern cometary activity in those images. After these observations were all posted on the MPC's PCCP webpage, S. Deen (Simi Valley, CA, USA) used a three-apparition orbit to identify additional pre-discovery observations in archival images from January 2006 from the Sloan Digital Sky Survey, whre the comet appears essentially stellar in appearance (though there may have been a very short, 0".6 tail toward p.a. about 315 degrees in the r-band image from Jan. 7); Deen provides the following astrometry from the 2.5-m reflector at Apache Point Observatory. 2006 UT R.A. (2000) Decl. Mag. Jan. 6.50281 11 51 59.18 + 4 59 23.1 22.2 6.50364 11 51 59.20 + 4 59 22.9 21.8 6.50613 11 51 59.31 + 4 59 22.5 22.8 7.51667 11 52 43.70 + 4 57 18.8 21.4 7.51750 11 52 43.74 + 4 57 18.7 21.1 7.51999 11 52 43.85 + 4 57 18.4 22.0 Deen also identified pre-discovery archival images of this comet obtained by S. Sheppard, D. Tholen, and C. Trujillo with the 8.2-m Subaru telescope atop Mauna Kea on 2019 Jan. 6 and 8, as tabulated below. Deen notes that "the comet is notably streaked on account of the long exposure times (380 and 300 s) but nonetheless appears obviously cometary with a faint, short 4" tail." Deen also identified a pre-discovery image of this comet in a DECam exposure taken with the Cerro Tololo 4-m refletor on 2019 Mar. 2 by A. Zenteno, which shows an extremely condensed head with a faint, somewhat-broad 4"-long tail spanning p.a. 60-90 degrees. These 2019 observations are tabulated below. 2019 UT R.A. (2000) Decl. Mag. Jan. 6.30051 7 11 28.19 +22 22 02.7 21.0 8.28594 7 09 42.72 +22 27 52.4 21.0 Mar. 2.06308 6 43 01.26 +24 12 18.6 22.6 Sixteen stacked 60-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, Chile, show only a stellar appearance; the magnitude was 21.1 as measured within a circular aperture of radius 2".9. Additional astrometry appears on MPEC 2026-B202. The following linked orbital elements by S. Nakano (Central Bureau) are from 94 observations spanning 2006 Jan. 6-2026 Jan. 27 (mean residual 0".4). The comet will pass 0.17 AU from Jupiter on 2057 Dec. 18 UT; due to this close approach, the orbit will change significantly as indicated below. Epoch = 1999 May 22.0 TT T = 1999 May 30.32144 TT Peri. = 69.49539 e = 0.3301287 Node = 106.98296 2000.0 q = 2.4088235 AU Incl. = 4.08059 a = 3.5959498 AU n = 0.14453854 P = 6.82 years Epoch = 2006 Mar. 6.0 TT T = 2006 Mar. 21.93340 TT Peri. = 69.52902 e = 0.3319542 Node = 106.95466 2000.0 q = 2.3978932 AU Incl. = 4.08237 a = 3.5894144 AU n = 0.14493346 P = 6.80 years Epoch = 2012 Dec. 19.0 TT T = 2012 Dec. 22.79702 TT Peri. = 69.60530 e = 0.3399242 Node = 106.67334 2000.0 q = 2.3504316 AU Incl. = 4.09220 a = 3.5608511 AU n = 0.14668083 P = 6.72 years Epoch = 2019 Oct. 4.0 TT T = 2019 Sept.16.71137 TT Peri. = 69.87947 e = 0.3400392 Node = 106.62532 2000.0 q = 2.3497080 AU Incl. = 4.09227 a = 3.5603753 AU n = 0.14671023 P = 6.72 years Epoch = 2026 Aug. 28.0 TT T = 2026 Aug. 14.73678 TT Peri. = 72.72386 e = 0.3140116 Node = 104.65950 2000.0 q = 2.5122001 AU Incl. = 4.02117 a = 3.6621614 AU n = 0.14063643 P = 7.01 years Epoch = 2033 Aug. 31.0 TT T = 2033 Aug. 22.39365 TT Peri. = 72.81637 e = 0.3120162 Node = 104.62067 2000.0 q = 2.5239793 AU Incl. = 4.01925 a = 3.6686608 AU n = 0.14026288 P = 7.03 years Epoch = 2040 Sept. 3.0 TT T = 2040 Aug. 23.74282 TT Peri. = 72.55608 e = 0.3139562 Node = 104.60604 2000.0 q = 2.5135253 AU Incl. = 4.02001 a = 3.6637973 AU n = 0.14054225 P = 7.01 years Epoch = 2047 Sept. 7.0 TT T = 2047 Aug. 20.67088 TT Peri. = 72.09212 e = 0.3136263 Node = 104.56580 2000.0 q = 2.5141949 AU Incl. = 4.02106 a = 3.6630116 AU n = 0.14058748 P = 7.01 years Epoch = 2054 Sept.10.0 TT T = 2054 Aug. 26.29951 TT Peri. = 72.33391 e = 0.3150054 Node = 104.52042 2000.0 q = 2.5061927 AU Incl. = 4.02201 a = 3.6587043 AU n = 0.14083581 P = 7.00 years Epoch = 2062 Nov. 27.0 TT T = 2062 Nov. 30.54869 TT Peri. = 158.70737 e = 0.0657871 Node = 355.69079 2000.0 q = 4.5089303 AU Incl. = 7.93900 a = 4.8264483 AU n = 0.09295282 P = 10.60 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 14.0 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2025 12 31 08 42.64 +19 38.9 1.940 2.842 151.3 9.6 20.0 2026 01 10 08 36.96 +20 17.1 1.862 2.817 162.9 5.9 19.8 2026 01 20 08 29.65 +20 59.8 1.811 2.792 174.6 1.9 19.7 2026 01 30 08 21.60 +21 42.3 1.789 2.769 172.5 2.7 19.7 2026 02 09 08 13.86 +22 20.0 1.795 2.745 160.7 6.8 19.7 2026 02 19 08 07.44 +22 49.9 1.827 2.723 149.1 10.8 19.7 2026 03 01 08 03.16 +23 10.0 1.883 2.702 138.0 14.2 19.7 2026 03 11 08 01.51 +23 20.0 1.957 2.681 127.6 17.1 19.7 2026 03 21 08 02.64 +23 20.2 2.045 2.661 117.9 19.3 19.8 2026 03 31 08 06.51 +23 11.0 2.144 2.643 108.9 20.9 19.9 2026 04 10 08 12.86 +22 52.9 2.250 2.625 100.6 22.0 20.0 2026 04 20 08 21.39 +22 26.2 2.359 2.609 92.8 22.6 20.0 2026 04 30 08 31.80 +21 50.8 2.469 2.593 85.6 22.8 20.1 2026 05 10 08 43.75 +21 07.0 2.579 2.579 78.8 22.6 20.2 2026 05 20 08 56.98 +20 14.7 2.686 2.566 72.3 22.1 20.2 2026 05 30 09 11.24 +19 14.1 2.789 2.555 66.2 21.3 20.3 2026 06 09 09 26.30 +18 05.6 2.888 2.545 60.4 20.3 20.4 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2026 CBAT 2026 January 29 (CBET 5659) Daniel W. E. Green