Electronic Telegram No. 5546 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/2010 KG_43 = P/2010 PT_8 [Editor's note: this text replaces that on CBET 5545 (2010 PT_8).] In Oct. 2012, A. Waszczak (California Institute of Technology) and E. O. Ofek (Weizmann Institute of Science) reported slight apparent cometary appearance of the Centaur-type minor planet 2010 KG_43, which had been found in infrared images obtained on 2010 May 20 with the Wide-field Infrared Survey Explorer (the WISE earth-orbiting satellite; discovery observations tabulated below from MPS 329447). 2010 UT R.A. (2000) Decl. May 20.53650 22 13 36.73 -15 55 35.7 20.53663 22 13 36.80 -15 55 35.6 20.66880 22 13 43.70 -15 54 38.7 20.66893 22 13 43.72 -15 54 39.0 20.80110 22 13 50.77 -15 53 43.0 20.86732 22 13 54.39 -15 53 14.4 20.93341 22 13 57.83 -15 52 45.4 20.99962 22 14 01.29 -15 52 18.6 21.13193 22 14 08.35 -15 51 23.8 21.19802 22 14 11.83 -15 50 51.7 21.52884 22 14 29.23 -15 48 34.1 21.66114 22 14 36.30 -15 47 37.4 It was re-discovered on 2010 Aug. 3 via the LINEAR survey (LINEAR astrometry is tabulated below), whence it was assigned the provisional minor-planet designation 2010 PT_8 because it was not immediately identified with the one-day arc from WISE more than two months previously. 2010 UT R.A. (2000) Decl. Mag. Aug. 3.40670 22 28 36.22 - 9 53 33.7 19.4 3.41855 22 28 35.80 - 9 53 31.0 19.9 3.44216 22 28 35.06 - 9 53 27.4 19.0 3.45392 22 28 34.69 - 9 53 25.5 19.2 4.33429 22 28 06.11 - 9 51 30.8 19.1 4.35801 22 28 05.23 - 9 51 28.0 20.2 4.38304 22 28 04.43 - 9 51 22.9 19.9 Waszczak and Ofek reported that archived CCD images obtained in 2010 with the 1.2-m f/2.44 Oschin Schmidt telescope during the "Palomar Transient Factory" (PTF) survey (Law et al. 2009, PASP 121, 1395; Rau et al. 2009, PASP 121, 1334) showed a head of size 3".3 +/- 0".8 (full-width-at-half-maximum) in 2".2 +/- 0".3 seeing on 2010 Aug. 28.4 UT (magnitude r = 18.7), 2010 Sept. 1.2 (r = 18.6), 2010 Sept. 8.2 (r = 18.6-18.7), and 2010 Sept. 12.3 (r = 18.6- 18.8). On one of the Sept. 8 images, the object appears to have a faint tail approximately 1' long toward p.a. 135 degrees; the PTF astrometry was published on MPS 434201. A one-opposition orbit with a 13-yr period appeared on MPEC 2012-T02. Eight stacked 120-s CCD exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW, Australia, on 2023 July 16.6 UT showed only a stellar appearance; the magnitude was 19.5 as measured within a circular aperture of radius 4".3. Eight stacked 60-s CCD exposures taken by Sato with a "Deep Sky Chile" 0.51-m f/6.8 astrograph located at Rio Hurtado, Chile, on 2023 Nov. 15.04 show a strongly condensed coma 7" in diameter with a fan-like tail 10" long spanning p.a. 45-135 degrees; the magnitude was 18.8 as measured within a circular aperture of radius 3".6. K. Kobayashi identified the following observations of this comet obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala last year in the Minor Planet Center's "isolated tracklet file": 2024 UT R.A. (2000) Decl. Mag. Sept. 1.54171 2 48 09.85 +31 23 43.0 22.3 1.55228 2 48 09.87 +31 23 46.1 22.3 1.56282 2 48 09.89 +31 23 49.2 22.4 1.57353 2 48 09.91 +31 23 51.9 22.1 All remaining astrometry has been collected on MPEC 2025-H90. The following linked orbital elements by S. Nakano (Central Bureau) are from 286 observations spanning 2010 May 20-2024 Sept. 1 (mean residual 0".5). The comet passed 1.21 AU from Saturn in 1977 November and 1.35 AU from Jupiter in 1981 October. Epoch = 2010 July 23.0 TT T = 2010 July 11.35950 TT Peri. = 353.53811 e = 0.4849555 Node = 327.82200 2000.0 q = 2.9116726 AU Incl. = 13.50035 a = 5.6532451 AU n = 0.07332589 P = 13.44 years Epoch = 2023 Sept.13.0 TT T = 2023 Aug. 25.55743 TT Peri. = 353.89340 e = 0.4823952 Node = 325.84131 2000.0 q = 2.8783554 AU Incl. = 13.65706 a = 5.5609132 AU n = 0.07515968 P = 13.11 years Epoch = 2036 Nov. 3.0 TT T = 2036 Oct. 27.91640 TT Peri. = 354.88211 e = 0.4819655 Node = 325.52190 2000.0 q = 2.8794286 AU Incl. = 13.68982 a = 5.5583718 AU n = 0.07521123 P = 13.10 years Epoch = 2049 Nov. 15.0 TT T = 2049 Nov. 9.59105 TT Peri. = 354.84342 e = 0.4826266 Node = 325.40098 2000.0 q = 2.8595138 AU Incl. = 13.71754 a = 5.5269828 AU n = 0.07585285 P = 12.99 years The comet is currently predicted to be fainter than mag 22. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2025 CBAT 2025 April 26 (CBET 5546) Daniel W. E. Green