Electronic Telegram No. 5102 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/2020 B4 (SHEPPARD) Scott S. Sheppard, Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, reported in September 2020 his discovery of a comet on CCD images taken on 2020 Jan. 26 and 27 UT by C. Trujillo and himself with the Cerro Tololo 4-m Blanco telescope (discovery observations tabulated below), the comet noted as having a faint tail about 8" from the nuclear condensation in p.a. 80 degrees in 400-s exposures taken with a very-broad-band VR filter. The tail is fairly obvious on Jan. 27 (less so on the Jan. 26 image because the comet was near a bright star). 2020 UT R.A. (2000) Decl. Mag. Observer Jan. 26.18195 8 23 06.93 + 7 16 08.8 22.5 Sheppard 27.22491 8 22 41.90 + 7 18 04.8 22.5 " Following a request from the Central Bureau, S. Deen (Simi Valley, CA, USA) was able to identify an image of the comet with a vague hint of haziness on an i-band DECam image taken on 2020 Feb. 11.23 with the CTIO 4-m reflector. 2020 UT R.A. (2000) Decl. Mag. Feb. 11.23069 8 16 54.41 + 7 49 26.9 22 After the object was posted on the Minor Planet Center's PCCP webpage, Sheppard also contacted R. Weryk (Department of Physics and Astronomy, University of Western Ontario) to ask him to search Pan-STARRS images for the comet. Weryk identified images obtained on two nights with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (2020 Mar. 23 and 2021 Feb. 7) and on five nights with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala (2019 Nov. 5, 25, and 29; 2020 Feb. 4 and May 12), as tabulated below. Eight 45-s w-band survey images taken on 2021 Feb. 7 show the comet overlapping a star, but masking and stacking shows an apparently diffuse coma of size about 2" (full-width-at-half-maximum) in seeing around 1".4 with no obvious tail. 2019 UT R.A. (2000) Decl. Mag. Nov. 5.61947 8 37 24.27 + 7 27 41.3 23.7 25.62328 8 39 02.86 + 6 55 03.1 23.7 29.63260 8 38 54.75 + 6 50 30.0 21.4 2020 UT R.A. (2000) Decl. Mag. Feb. 4.39649 8 19 28.42 + 7 34 25.2 21.6 Mar. 23.35033 8 07 54.83 + 9 23 57.7 21.8 May 12.26263 8 17 58.20 +10 23 51.1 23.4 2021 UT R.A. (2000) Decl. Mag. Feb. 7.44143 10 04 28.41 + 3 12 17.6 22.2 7.46151 10 04 27.95 + 3 12 20.2 22.4 7.46539 10 04 27.85 + 3 12 21.2 22.7 7.47354 10 04 27.67 + 3 12 22.5 21.9 7.47743 10 04 27.58 + 3 12 23.0 22.1 The following orbital elements by S. Nakano (CBET) are from 14 observations spanning 2019 Nov. 5-2021 Feb. 7 (mean residual 0".2), which indicate that the comet passed 0.52 AU from Saturn in 1968 July. Nakano found no other identifications in archival astrometry files, but he notes that the comet passed close to minor planet 2010 RQ_8 on 2010 Sept. 2 and 3. Epoch = 1999 Apr. 12.0 TT T = 1999 Mar. 23.51784 TT Peri. = 341.26197 e = 0.1914998 Node = 186.06651 2000.0 q = 6.4400609 AU Incl. = 11.59832 a = 7.9654417 AU n = 0.04384189 P = 22.48 years Epoch = 2021 Dec. 12.0 TT T = 2021 Nov. 22.82663 TT Peri. = 342.30722 e = 0.1917884 Node = 185.98045 2000.0 q = 6.4399508 AU Incl. = 11.60737 a = 7.9681496 AU n = 0.04381954 P = 22.49 years Epoch = 2044 July 4.0 TT T = 2044 June 27.91784 TT Peri. = 342.98034 e = 0.1913550 Node = 185.94184 2000.0 q = 6.4347996 AU Incl. = 11.61232 a = 7.9575086 AU n = 0.04390747 P = 22.45 years The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 10.0 and 2.5n = 10 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2022 01 21 11 55.27 -02 46.1 5.886 6.442 120.5 7.6 21.9 2022 02 10 11 52.50 -02 17.5 5.641 6.444 141.6 5.5 21.8 2022 03 02 11 46.77 -01 25.5 5.491 6.447 163.3 2.5 21.8 2022 03 22 11 39.63 -00 20.2 5.458 6.450 174.0 0.9 21.8 2022 04 11 11 33.08 +00 44.3 5.547 6.453 152.7 4.1 21.8 2022 05 01 11 28.85 +01 35.1 5.741 6.457 131.9 6.7 21.9 2022 05 21 11 27.99 +02 03.7 6.011 6.462 112.2 8.3 22.0 2022 06 10 11 30.73 +02 07.6 6.323 6.467 93.6 9.0 22.1 2022 06 30 11 36.81 +01 48.0 6.642 6.473 76.1 8.8 22.2 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 February 17 (CBET 5102) Daniel W. E. Green