[Iaude] CBET 4959: COMET C/2021 G1 (LEONARD)

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 4959
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2021 G1 (LEONARD)
     Gregory J. Leonard reports his discovery of a comet with a moderately
condensed coma about 10" across (and no discernible tail) in four co-added
30-s CCD exposures taken on Apr. 11.3 UT (discovery observatinos tabulated
below) with the Mt. Lemmon 1.5-m reflector in seeing around 1".7.

     2021 UT             R.A. (2000) Decl.       Mag.   Observer
     Apr. 11.32667   14 19 13.62   +55 04 30.2   21.7   Leonard
          11.33188   14 19 12.57   +55 04 35.9   21.0     "
          11.33710   14 19 11.56   +55 04 41.8   22.0     "
          11.34231   14 19 10.46   +55 04 46.2   20.8     "
          11.36843   14 19 05.24   +55 05 13.2   20.8     "
          11.38509   14 19 01.87   +55 05 31.2   21.4     "
          11.39353   14 19 00.07   +55 05 39.9   21.0     "

D. Rankin found a condensed 6" coma with no tail on images obtained with the
1.5-m Catalina Sky Survey reflector on Apr. 20.2 UT; he noted "while faint,
object shows clear activity".
     The available astrometry appear on MPEC 2021-J72.  The following orbital
elements by S. Nakano (CBAT) are from 44 observations spanning Apr. 11-30;
they suggest an orbital period around 650 yr, and it appears that this comet
passed 0.52 AU from Saturn on 2018 Mar. 30 and passed 2.02 AU from Jupiter on
2019 Aug. 7 UT.

     T = 2021 July 22.00063 TT        Peri. = 107.42567
     e = 0.9545176                    Node  = 270.68321 2000.0
     q = 3.4242886 AU                 Incl. = 131.56623

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 14.0 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2021 04 16    14 03.10   +56 17.7    3.014    3.535   113.4    15.1  20.8
2021 04 21    13 44.94   +57 18.8    3.039    3.524   110.9    15.4  20.8
2021 04 26    13 26.31   +58 01.2    3.072    3.514   107.9    15.8  20.8
2021 05 01    13 07.76   +58 25.3    3.112    3.504   104.6    16.2  20.8
2021 05 06    12 49.80   +58 32.1    3.160    3.495   100.9    16.5  20.8
2021 05 11    12 32.89   +58 23.4    3.213    3.486    97.1    16.7  20.9
2021 05 16    12 17.37   +58 01.6    3.272    3.478    93.2    16.9  20.9
2021 05 21    12 03.42   +57 29.2    3.334    3.470    89.2    17.0  20.9
2021 05 26    11 51.11   +56 48.6    3.399    3.463    85.1    16.9  21.0
2021 05 31    11 40.43   +56 01.9    3.465    3.457    81.1    16.8  21.0
2021 06 05    11 31.28   +55 11.2    3.533    3.451    77.1    16.7  21.0
2021 06 10    11 23.54   +54 17.8    3.601    3.445    73.1    16.4  21.1
2021 06 15    11 17.09   +53 23.2    3.669    3.441    69.2    16.0  21.1
2021 06 20    11 11.77   +52 28.2    3.735    3.437    65.3    15.6  21.2
2021 06 25    11 07.46   +51 33.8    3.799    3.433    61.6    15.1  21.2
2021 06 30    11 04.01   +50 40.4    3.860    3.430    57.9    14.5  21.2
2021 07 05    11 01.33   +49 48.5    3.918    3.428    54.4    14.0  21.2


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2021 CBAT
2021 May 6                       (CBET 4959)              Daniel W. E. Green