Electronic Telegram No. 5381 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/2024 G1 (WIERZCHOS) Kacper W. Wierzchos, Lunar and Planetary Laboratory, University of Arizona, reports his discovery of a comet on mosaic CCD images obtained with the 2.25-m "Bok" reflector at Kitt Peak as part of a collaborative program (cf. CBET 5103) on Apr. 7 UT (discovery observations tabulated below). Four 30-s exposures showed a diffuse 6" coma and a broad 9" tail spanning p.a. 260-290 degrees. 2024 UT R.A. (2000) Decl. Mag. Observer Apr. 7.47946 19 33 30.68 +61 20 39.2 Wierzchos 7.48639 19 33 30.25 +61 20 44.5 20.6 " 7.49326 19 33 29.84 +61 20 49.4 20.3 " 7.50013 19 33 29.42 +61 20 54.5 20.2 " After the comet was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists also confirmed the cometary appearance. Fourteen stacked 60-s exposures taken remotely by H. Sato (Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl Junction, UT, USA) show a strongly condensed coma 8" in diameter with no tail; the magnitude was 20.2 as measured within a circular aperture of radius 4".9. R. A. Mastaler (University of Arizona) reports that 60-s exposures taken in 2".0 seeing on Apr. 12.4 UT with the Spacewatch 1.8-m f/2.7 reflector at Kitt Peak show a faint coma but no definite tail; the magnitude was measured to be R = 19.7. The available astrometry appears on MPEC 2024-H10. The following parabolic orbital elements by S. Nakano (Central Bureau) are from 39 observations spanning 2024 Apr. 7-15 (mean residual 0".5). The comet passed 2.77 AU from Uranus in 2017. T = 2024 Oct. 22.85117 TT Peri. = 128.65364 Node = 30.27974 2000.0 q = 3.9280018 AU Incl. = 95.44068 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. 2024 03 31 19 39.37 +59 52.4 4.390 4.309 78.8 13.1 19.8 2024 04 10 19 30.96 +61 50.9 4.314 4.275 81.1 13.4 19.7 2024 04 20 19 17.52 +63 50.1 4.238 4.242 83.4 13.6 19.7 2024 04 30 18 57.84 +65 41.1 4.167 4.211 85.6 13.8 19.6 2024 05 10 18 30.99 +67 11.3 4.103 4.181 87.4 14.0 19.5 2024 05 20 17 57.24 +68 05.9 4.048 4.152 88.8 14.1 19.5 2024 05 30 17 18.95 +68 10.5 4.006 4.125 89.6 14.2 19.4 2024 06 09 16 40.45 +67 17.0 3.979 4.100 89.6 14.3 19.4 2024 06 19 16 06.14 +65 27.1 3.967 4.076 88.9 14.4 19.4 2024 06 29 15 38.55 +62 51.0 3.972 4.054 87.3 14.5 19.4 2024 07 09 15 18.01 +59 41.7 3.993 4.034 85.0 14.5 19.4 2024 07 19 15 03.71 +56 12.0 4.029 4.015 81.9 14.5 19.4 2024 07 29 14 54.40 +52 32.4 4.079 3.998 78.3 14.4 19.4 2024 08 08 14 48.98 +48 50.6 4.139 3.983 74.1 14.2 19.4 2024 08 18 14 46.54 +45 12.6 4.207 3.969 69.6 13.8 19.4 2024 08 28 14 46.35 +41 42.3 4.280 3.958 64.9 13.4 19.4 2024 09 07 14 47.90 +38 22.4 4.354 3.948 60.0 12.8 19.5 2024 09 17 14 50.77 +35 14.8 4.425 3.940 55.3 12.1 19.5 2024 09 27 14 54.63 +32 20.4 4.491 3.934 50.8 11.4 19.5 2024 10 07 14 59.24 +29 39.6 4.548 3.930 46.7 10.7 19.5 2024 10 17 15 04.38 +27 12.7 4.594 3.928 43.3 10.0 19.6 NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2024 CBAT 2024 April 17 (CBET 5381) Daniel W. E. Green