Electronic Telegram No. 5247 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/2022 JK_5 (PANSTARRS) [Editor's note: This text replaces that on CBET 5246 (observatory name).] An apparently asteroidal object discovered on images obtained in May 2022 with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (discovery observations tabulated below from MPS 1612933) has been found to show cometary appearance in CCD images taken on 2023 Apr. 3 UT with a 0.5-m f/2 Schmidt reflector at Rio Hurtado, Chile, in the course of the "Asteroid Terrestrial- Impact Last Alert System" (ATLAS) search program, the observations of which were thought to be a new discovery reported by P. Veres, L. Denneau, and A. Fitzsimmons, who note a condensed 12" coma and a straight 14" tail in p.a. 260 degrees, with the comet now much brighter (mag 17.6-18.2) as it neared perihelion. Before it was identified with 2022 JK_5 by H. Sato of Tokyo, the comet was posted to the Minor Planet Center's PCCP webpage for confirmation. 2022 UT R.A. (2000) Decl. Mag. May 9.43358 15 14 16.85 -13 55 23.8 21.0 9.44579 15 14 16.41 -13 55 23.7 20.8 9.45803 15 14 15.94 -13 55 23.8 20.9 23.39482 15 05 34.52 -13 59 24.0 20.9 23.39545 15 05 34.52 -13 59 23.7 21.2 23.40629 15 05 34.10 -13 59 24.1 21.1 23.41781 15 05 33.65 -13 59 24.8 21.1 23.41844 15 05 33.63 -13 59 24.4 21.2 23.42931 15 05 33.22 -13 59 24.6 21.1 23.42994 15 05 33.19 -13 59 24.7 21.1 S. Deen (Simi Valley, CA, USA) identified the comet on publicly available images taken with the 4-m reflector (+ DECam) at Cerro Tololo on 2022 Sept. 15.0 (at g magnitude 21.4) and 16.0 UT (g mag 21.3), with the comet appearing somewhat condensed with a 1".0 coma (full-width-at-half-maximum) in 0".8 seeing on both night; there was a short 2".5 tail in p.a. 105 deg on Sept. 15.0 but no visible tail visible in quite hazy conditions on Sept. 16. Twenty-four stacked 60-s CCD exposures taken remotely on 2023 Apr. 9.8 by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.51-m f/6.8 astrograph at Siding Spring, NSW, show a strongly condensed coma 18" in diameter with no tail; the magnitude was 17.2 as measured within a circular aperture of radius 9".8. A. Hale, Cloudcroft, NM, USA, finds a marginally diffuse object of mag 17.5-17.7 when compared to nearby stars in CCD images obtained on 2023 Apr. 11.37 with a Las Cumbres Observatory 0.4-m f/10 Schmidt-Cassegrain reflector located at Cerro Tololo. The available astrometry appears on MPEC 2023-H180. The following elliptical orbital elements by S. Nakano (Central Bureau) are from 63 observations spanning 2022 May 9-2023 Apr. 24 (mean residual 0".3), with corresponding original and future values of 1/a being +0.023210 and +0.023334 (+/- 0.000019) AU**-1, respectively. The comet will pass 2.48 AU from Jupiter on 2024 June 14 and 2.91 AU from Uranus on 2031 July 10 UT. Epoch = 2023 May 16.0 TT T = 2023 Apr. 28.81812 TT Peri. = 247.15931 e = 0.9377059 Node = 59.65241 2000.0 q = 2.6869356 AU Incl. = 16.83089 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 11.5 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2023 04 16 21 56.92 -26 55.6 2.970 2.690 64.2 19.6 17.3 2023 04 26 22 15.48 -26 14.5 2.866 2.687 69.7 20.6 17.2 2023 05 06 22 33.09 -25 36.3 2.763 2.688 75.2 21.3 17.1 2023 05 16 22 49.60 -25 02.7 2.661 2.693 80.9 21.8 17.1 2023 05 26 23 04.87 -24 35.8 2.562 2.701 86.8 22.0 17.0 2023 06 05 23 18.73 -24 17.2 2.466 2.713 92.9 21.9 16.9 2023 06 15 23 30.99 -24 08.3 2.374 2.729 99.3 21.5 16.9 2023 06 25 23 41.44 -24 10.2 2.288 2.749 106.0 20.8 16.8 2023 07 05 23 49.88 -24 23.1 2.210 2.772 113.1 19.7 16.8 2023 07 15 23 56.11 -24 46.2 2.142 2.798 120.5 18.2 16.7 2023 07 25 23 59.97 -25 17.8 2.085 2.828 128.1 16.4 16.7 2023 08 04 00 01.39 -25 54.4 2.043 2.861 135.9 14.3 16.7 2023 08 14 00 00.46 -26 31.5 2.019 2.896 143.5 12.0 16.7 2023 08 24 23 57.44 -27 03.4 2.014 2.935 150.2 9.9 16.8 2023 09 03 23 52.87 -27 24.3 2.032 2.976 154.8 8.3 16.8 2023 09 13 23 47.41 -27 29.4 2.073 3.020 155.8 7.8 16.9 2023 09 23 23 41.85 -27 15.6 2.139 3.066 152.7 8.6 17.0 2023 10 03 23 36.96 -26 42.3 2.229 3.114 146.7 10.2 17.2 2023 10 13 23 33.30 -25 50.9 2.341 3.165 139.2 11.9 17.3 2023 10 23 23 31.24 -24 43.9 2.474 3.217 131.1 13.5 17.5 2023 11 02 23 30.97 -23 24.7 2.625 3.271 122.8 14.8 17.7 2023 11 12 23 32.46 -21 56.2 2.791 3.326 114.5 15.7 17.9 2023 11 22 23 35.59 -20 21.2 2.970 3.383 106.4 16.3 18.1 2023 12 02 23 40.20 -18 41.8 3.157 3.442 98.4 16.5 18.3 2023 12 12 23 46.08 -16 59.8 3.351 3.502 90.6 16.3 18.5 2023 12 22 23 53.04 -15 16.4 3.548 3.563 82.9 15.9 18.7 2024 01 01 00 00.88 -13 32.7 3.746 3.625 75.4 15.2 18.8 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2023 CBAT 2023 April 26 (CBET 5247) Daniel W. E. Green