Electronic Telegram No. 5145 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/2021 QM_45 (PANSTARRS) An apparently asteroidal object found in images obtained with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on 2021 Aug. 17 -- and later linked by P. Veres (Minor Planet Center) with numerous other single-night observations in the MPC's "isolated tracklet file" as a single object in 2021 (and then announced with the minor-planet designation 2021 QM_45 on MPS 1473929, together with other observations through 2021 Sept. 25) -- has been found to show cometary appearance as it approaches perihelion. The tabulated observations below include the first five nights of observations now known (all from Pan-STARRS1, and most previously unpublished). 2021 UT R.A. (2000) Decl. Mag. Aug. 4.49384 0 00 56.08 - 2 29 23.2 23.0 4.50583 0 00 55.93 - 2 29 22.5 22.5 11.59301 23 59 08.67 - 2 19 50.3 21.7 12.49035 23 58 52.28 - 2 18 49.6 21.3 12.50280 23 58 52.06 - 2 18 48.4 22.5 12.51530 23 58 51.84 - 2 18 47.8 22.7 12.52781 23 58 51.56 - 2 18 46.9 22.1 17.51303 23 57 08.54 - 2 13 50.0 22.4 17.52492 23 57 08.24 - 2 13 49.5 22.5 17.53687 23 57 07.96 - 2 13 48.7 22.6 27.61288 23 52 43.49 - 2 07 09.8 21.4 R. Weryk, Department of Physics and Astronomy, University of Western Ontario, writes that his investigation now shows that the object appears clearly cometary on earlier Pan-STARRS exposures from last year (not noticed previously) -- drawn by a posting of the object (as an apparently independent 2022 discovery; cf. Bolin and Kelley, below) again recently on the MPC's NEOCP webpage that Weryk linked to the 2021 observations. Four 45-s w-band survey images obtained with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala on 2021 Oct. 4.4 UT in 1".2 seeing show a condensed coma of size 1".6 (full-width-at-half-maximum) and no tail. Four 45-s Pan-STARRS1 w-band survey images from 2021 Oct. 6.3 (previously unpublished astrometry) in 1".4 seeing show a condensed head of size 1".7 (FWHM) and no tail. Similarly, four more previously unpublished 45-s Pan-STARRS1 w-band survey observations from 2021 Oct. 27.3 in 1".25 seeing show a condensed coma of size 1".5 (FWHM) and no tail. B. T. Bolin, Infrared Processing and Analysis Center, California Institute of Technology; and M. S. P. Kelley, University of Maryland, on behalf of the "Zwicky Transient Facility (ZTF) Collaboration", report on observations of the distant object 2021 QM_45 taken with the 1.2-m Schmidt telescope at Palomar Observatory. The object was identified as an apparently new object with cometary appearance using automatic-detection software, and the cometary appearance was then confirmed by eye -- with a coma about 7" across and a broad tail about 10" in size in ZTF images taken on 2022 June 28.47 and 29.47 UT. ZTF r-band photometry (+/- 0.05 magnitude) measured in 5"-radius apertures and calibrated to the PS1 magnitude system are as follows: June 29.473, 17.86; 29.475, 17.77; 29.477, 17.91; 29.480, 17.90; 29.482, 18.11. The position angle of the comet's tail was consistently near about 270 degrees, roughly consistent with the anti-sun and anti-heliocentric velocity vectors (both at 280 degrees and 250 degrees, respectively, on 2022 June 28-29). The available astrometry appears on MPEC 2022-N12. The following nearly parabolic orbital elements by S. Nakano (Central Bureau) are from 82 observations spanning 2021 Aug. 4-2022 June 29 (mean residual 0".4), with corresponding "original" and "future" values of 1/a with respect to the solar system's barycenter being +0.002546 and +0.002966 AU**-1, respectively (+/- 0.000002 AU**-1). The comet passed 4.87 AU from Saturn on 2020 Feb. 17 UT and 2.06 AU from Jupiter on 2021 July 18. Epoch = 2022 Aug. 9.0 TT T = 2022 Aug. 13.43365 TT Peri. = 72.80403 e = 0.9920883 Node = 354.58864 2000.0 q = 2.7732653 AU Incl. = 22.82236 The following ephemeris by the undersigned from the above orbital elements uses photometric power-law parameters H = 12.0 and 2.5n = 8 for the magnitudes. Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag. 2022 06 20 03 34.49 +34 15.5 3.639 2.829 32.0 11.0 18.4 2022 06 30 03 55.49 +36 00.1 3.561 2.811 36.6 12.4 18.3 2022 07 10 04 17.07 +37 37.6 3.480 2.796 41.1 13.8 18.3 2022 07 20 04 39.13 +39 07.2 3.396 2.785 45.8 15.2 18.2 2022 07 30 05 01.53 +40 28.3 3.310 2.777 50.5 16.4 18.1 2022 08 09 05 24.07 +41 40.6 3.222 2.774 55.4 17.5 18.1 2022 08 19 05 46.52 +42 44.1 3.132 2.774 60.3 18.5 18.0 2022 08 29 06 08.64 +43 39.5 3.042 2.778 65.4 19.3 18.0 2022 09 08 06 30.10 +44 27.5 2.951 2.786 70.7 20.0 17.9 2022 09 18 06 50.61 +45 09.7 2.860 2.797 76.3 20.4 17.9 2022 09 28 07 09.82 +45 47.8 2.769 2.812 82.1 20.7 17.8 2022 10 08 07 27.37 +46 23.7 2.680 2.831 88.2 20.7 17.8 2022 10 18 07 42.92 +46 59.1 2.594 2.854 94.7 20.4 17.7 2022 10 28 07 56.09 +47 35.9 2.512 2.879 101.5 19.8 17.7 2022 11 07 08 06.51 +48 14.9 2.436 2.908 108.6 18.8 17.6 2022 11 17 08 13.85 +48 55.8 2.368 2.941 116.1 17.6 17.6 2022 11 27 08 17.80 +49 37.3 2.311 2.976 123.8 16.0 17.6 2022 12 07 08 18.23 +50 15.7 2.269 3.014 131.6 14.2 17.6 2022 12 17 08 15.28 +50 46.3 2.243 3.055 139.0 12.2 17.6 2022 12 27 08 09.41 +51 03.2 2.238 3.098 145.3 10.4 17.7 2023 01 06 08 01.57 +51 00.9 2.256 3.144 149.5 9.1 17.7 2023 01 16 07 52.97 +50 36.5 2.299 3.192 150.5 8.7 17.8 2023 01 26 07 44.88 +49 49.9 2.367 3.242 147.7 9.3 18.0 2023 02 05 07 38.41 +48 44.0 2.459 3.294 142.2 10.6 18.1 2023 02 15 07 34.22 +47 23.6 2.574 3.348 135.2 12.0 18.3 2023 02 25 07 32.59 +45 53.9 2.710 3.404 127.4 13.4 18.4 2023 03 07 07 33.48 +44 19.3 2.864 3.461 119.4 14.5 18.6 2023 03 17 07 36.64 +42 43.3 3.033 3.520 111.4 15.3 18.8 2023 03 27 07 41.75 +41 07.9 3.213 3.580 103.5 15.7 19.0 2023 04 06 07 48.48 +39 34.1 3.402 3.641 95.8 15.9 19.1 2023 04 16 07 56.49 +38 02.5 3.596 3.704 88.3 15.7 19.3 2023 04 26 08 05.51 +36 33.1 3.792 3.767 80.9 15.3 19.5 2023 05 06 08 15.30 +35 05.7 3.989 3.832 73.8 14.6 19.7 2023 05 16 08 25.63 +33 40.0 4.183 3.897 66.8 13.8 19.8 2023 05 26 08 36.37 +32 15.8 4.373 3.963 59.9 12.8 20.0 2023 06 05 08 47.34 +30 52.8 4.556 4.030 53.2 11.6 20.1 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2022 CBAT 2022 July 2 (CBET 5145) Daniel W. E. Green