Electronic Telegram No. 5152 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/2021 R9 (SHEPPARD-THOLEN) David J. Tholen, University of Hawaii, reports the discovery of a comet by Scott S. Sheppard and himself in SuprimeCam images obtained on 2021 Sept. 5.6 and 6.6 UT with the 8.2-m f/2.2 Subaru reflector at Mauna Kea (astrometry tabulated below). The comet then showed a narrow tail extending at least 14" in p.a. 240 deg (possibly much further). 2021 UT R.A. (2000) Decl. Mag. Observer Sept. 5.61526 0 19 30.06 +10 53 27.0 22.4 Tholen 6.62152 0 19 04.19 +10 52 05.3 22.8 " Following a request by Tholen, R. Weryk (Department of Physics and Astronomy, University of Western Ontario) identified the comet in images obtained with the Pan-STARRS1 and the Pan-STARRS2 1.8-m Ritchey-Chretien reflectors at Haleakala. On poor-quality Pan-STARRS2 images from 2021 Sept. 5.4 UT, stacked images suggest it may have had a tail toward p.a. 240 degrees. In four stacked 45-s w-band Pan-STARRS1 survey images from 2021 Oct. 31.2, additional_comments:4x45 second w-band survey images, there was a condensed coma of size 1".5 (full-width-at-half-maximum) in 1".2 seeing with no obvious tail. In four stacked 45-s w-band Pan-STARRS2 survey images from 2021 Nov. 7.2, there was a condensed coma of size 1".4 (FWHM) in 1".0 seeing with no obvious tail. Other Pan-STARRS1 and Pan-STARRS2 astrometry from 2021 June 22 to 2022 Jan. 25 appear on MPEC 2022-O19 (as well as other astrometry spanning 2008 Dec. 4-2021 Nov. 7 not described elsewhere here). After Tholen's and Weryk's astrometry were posted on the Minor Planet Center's PCCP webpage, S. Nakano (Central Bureau) identified CCD observations with separate preliminary designations in the MPC's "isolated tracklet file" from 2008 Oct. 9.4 and Oct. 29.4 that had been made with the Mt. Lemmon Survey's 1.5-m reflector. S. Deen (Simi Valley, CA, USA) then identified in publicly available data a poor-quality single observation that had been made by C. Willott with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on 2007 June 6. These astrometic observations are tabulated below. 2007 UT R.A. (2000) Decl. Mag. Observer June 6.55674 23 16 18.00 + 0 00 28.4 22.8 Willott 2008 UT R.A. (2000) Decl. Mag. Observer Oct. 9.35032 1 42 23.58 +20 37 49.9 22.6 Mt. Lemmon 9.35615 1 42 23.32 +20 37 48.7 21.7 " 9.36197 1 42 23.14 +20 37 48.3 21.7 " 9.36776 1 42 23.00 +20 37 47.6 21.5 " 29.37935 1 31 46.56 +19 42 41.0 20.9 " 29.38719 1 31 46.27 +19 42 39.9 20.9 " 29.39498 1 31 46.02 +19 42 38.4 21.9 " 29.40272 1 31 45.80 +19 42 36.6 21.6 " The following linked orbital elements by Nakano are from 46 observations spanning 2007-2022 (mean residual 0".3). The comet passed 0.45 AU from Jupiter on in 1931 Jan., 3.98 AU from Saturn on 2018 May 6, and 2.89 AU from Jupiter on 2020 Nov. 18 UT; the comet will pass 0.46 AU from Jupiter on 2037 Mar. 7. Epoch = 2009 Jan. 9.0 TT T = 2009 Jan. 3.51732 TT Peri. = 94.39829 e = 0.1824453 Node = 302.89942 2000.0 q = 4.6306172 AU Incl. = 7.42388 a = 5.6639846 AU n = 0.07311744 P = 13.48 years Epoch = 2022 Aug. 9.0 TT T = 2022 Aug. 18.01297 TT Peri. = 97.52837 e = 0.1804494 Node = 302.69606 2000.0 q = 4.6269639 AU Incl. = 7.43286 a = 5.6457330 AU n = 0.07347229 P = 13.42 years Epoch = 2035 Feb. 2.0 TT T = 2035 Jan. 27.05451 TT Peri. = 83.34197 e = 0.2489151 Node = 292.73047 2000.0 q = 4.6439109 AU Incl. = 7.18753 a = 6.1829373 AU n = 0.06410794 P = 15.37 years Epoch = 2047 Feb. 19.0 TT T = 2047 Mar. 5.01360 TT Peri. = 73.17494 e = 0.1424450 Node = 274.18345 2000.0 q = 4.8342943 AU Incl. = 8.85688 a = 5.6372993 AU n = 0.07363723 P = 13.38 years 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. 2022 06 30 02 42.23 +22 43.2 5.169 4.630 53.1 10.1 21.9 2022 07 10 02 50.34 +23 28.3 5.044 4.629 60.5 11.0 21.8 2022 07 20 02 57.76 +24 10.3 4.909 4.628 68.2 11.8 21.8 2022 07 30 03 04.33 +24 49.0 4.766 4.627 76.0 12.3 21.7 2022 08 09 03 09.92 +25 24.1 4.619 4.627 84.2 12.6 21.6 2022 08 19 03 14.39 +25 55.3 4.470 4.627 92.6 12.6 21.6 2022 08 29 03 17.57 +26 22.0 4.322 4.627 101.3 12.4 21.5 2022 09 08 03 19.35 +26 43.8 4.179 4.628 110.4 11.8 21.4 2022 09 18 03 19.63 +26 59.9 4.045 4.628 119.9 10.9 21.4 2022 09 28 03 18.39 +27 09.6 3.924 4.629 129.7 9.6 21.3 2022 10 08 03 15.66 +27 12.0 3.821 4.630 139.8 8.0 21.2 2022 10 18 03 11.64 +27 06.7 3.740 4.632 150.2 6.1 21.2 2022 10 28 03 06.61 +26 53.5 3.685 4.633 160.4 4.1 21.2 2022 11 07 03 00.99 +26 32.9 3.658 4.635 169.1 2.3 21.1 2022 11 17 02 55.24 +26 06.4 3.661 4.637 169.6 2.2 21.1 2022 11 27 02 49.87 +25 35.8 3.695 4.640 161.1 3.9 21.2 2022 12 07 02 45.33 +25 03.9 3.757 4.642 150.8 5.9 21.2 2022 12 17 02 41.97 +24 33.3 3.846 4.645 140.2 7.8 21.3 2022 12 27 02 40.02 +24 06.3 3.958 4.648 129.7 9.4 21.3 2023 01 06 02 39.59 +23 44.6 4.088 4.651 119.5 10.6 21.4 2023 01 16 02 40.70 +23 29.2 4.232 4.655 109.6 11.5 21.5 2023 01 26 02 43.30 +23 20.6 4.385 4.659 100.0 12.0 21.6 2023 02 05 02 47.28 +23 18.8 4.543 4.663 90.8 12.2 21.6 2023 02 15 02 52.52 +23 23.0 4.702 4.667 81.9 12.1 21.7 2023 02 25 02 58.88 +23 32.6 4.857 4.671 73.4 11.7 21.8 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 July 22 (CBET 5152) Daniel W. E. Green