Electronic Telegram No. 5022
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 P3 (PANSTARRS)
     R. Weryk, Department of Physics and Astronomy, University of Western
Ontario, reports the discovery of another comet in images obtained with the
Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on Aug. 11.  Weryk
and R. Wainscoat obtained three 60-s gri-band follow-up exposures on Aug.
12.5 UT with the Canada-France-Hawaii Telescope on Mauna Kea (queue observer
H. Januszewski; queue coordinator T. Burdullis) that show this to be clearly
a comet, with a very condensed coma of size 1".2 (full-width-at-half-maximum)
in 0".7 seeing; there was a very broad tail about 5" long spanning p.a.
100-230 degrees.  The discovery observations are tabulated below, along with
pre-discovery Pan-STARRS1 observations from Aug. 3.

     2021 UT             R.A. (2000) Decl.       Mag.
     Aug.  3.58406    0 27 06.01   - 4 18 54.9   21.2
           3.59232    0 27 05.90   - 4 18 52.4   21.1
           3.60051    0 27 05.77   - 4 18 49.5   21.3
           3.60870    0 27 05.64   - 4 18 47.0   21.2
          11.58454    0 24 32.59   - 3 38 48.0   20.6
          11.59701    0 24 32.28   - 3 38 44.7   20.5
          11.60944    0 24 31.95   - 3 38 40.6   20.6

After the object was posted to the Minor Planet Center's PCCP webpage, H.
Sato (Tokyo, Japan) reported that sixteen stacked 60-s CCD exposures taken
remotely with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW,
Australia, on Aug. 12.79 UT show a strongly condensed coma 8" in diameter with
no tail; the magnitude was 19.7 as measured within a circular aperture of
radius 4".9.
     The available astrometry appears on MPEC 2021-Q29.  The following orbital
elements by S. Nakano (CBAT) are from 34 observations spanning 2021 Aug. 3-15
(mean residual 0".4); he notes that the period is still rather uncertain, and
a search for previous observations in archival data was unsuccessful.

     T = 2021 May  28.97038 TT        Peri. = 333.71631
     e = 0.3422152                    Node  = 358.24295 2000.0
     q = 2.9124675 AU                 Incl. =  27.10851
       a =  4.4276906 AU   n = 0.10578843   P =   9.32 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 13.0 and 2.5n = 10 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2021 08 14    00 23.48   -03 27.4    2.126    2.947   136.9    13.6  19.3
2021 08 19    00 20.84   -03 04.9    2.087    2.952   142.1    12.2  19.3
2021 08 24    00 17.66   -02 43.6    2.054    2.957   147.5    10.6  19.3
2021 08 29    00 13.99   -02 23.4    2.026    2.962   153.1     8.9  19.2
2021 09 03    00 09.88   -02 04.2    2.005    2.968   158.8     7.1  19.2
2021 09 08    00 05.42   -01 45.9    1.990    2.973   164.6     5.2  19.2
2021 09 13    00 00.70   -01 28.2    1.982    2.979   170.5     3.2  19.2
2021 09 18    23 55.83   -01 10.8    1.982    2.986   176.4     1.2  19.2
2021 09 23    23 50.94   -00 53.7    1.989    2.992   177.7     0.8  19.3
2021 09 28    23 46.12   -00 36.5    2.004    2.999   171.7     2.8  19.3
2021 10 03    23 41.51   -00 19.2    2.025    3.006   165.8     4.7  19.3
2021 10 08    23 37.19   -00 01.4    2.055    3.013   160.0     6.5  19.4
2021 10 13    23 33.26   +00 17.0    2.091    3.020   154.2     8.3  19.4
2021 10 18    23 29.80   +00 36.3    2.133    3.028   148.6     9.9  19.5
2021 10 23    23 26.86   +00 56.5    2.181    3.036   143.1    11.4  19.5
2021 10 28    23 24.47   +01 17.8    2.235    3.044   137.7    12.7  19.6
2021 11 02    23 22.66   +01 40.3    2.295    3.053   132.4    13.9  19.7
2021 11 07    23 21.44   +02 04.1    2.358    3.061   127.2    14.9  19.7
2021 11 12    23 20.80   +02 29.2    2.426    3.070   122.2    15.8  19.8
2021 11 17    23 20.74   +02 55.8    2.497    3.079   117.4    16.6  19.9
2021 11 22    23 21.22   +03 23.8    2.570    3.089   112.7    17.2  19.9
2021 11 27    23 22.23   +03 53.3    2.647    3.098   108.1    17.6  20.0
2021 12 02    23 23.72   +04 24.2    2.725    3.108   103.6    18.0  20.1
2021 12 07    23 25.69   +04 56.6    2.804    3.118    99.2    18.2  20.2
2021 12 12    23 28.09   +05 30.5    2.885    3.128    94.9    18.3  20.3
2021 12 17    23 30.89   +06 05.7    2.966    3.138    90.8    18.3  20.3
2021 12 22    23 34.06   +06 42.3    3.048    3.148    86.7    18.2  20.4
2021 12 27    23 37.57   +07 20.3    3.129    3.159    82.7    18.0  20.5
2022 01 01    23 41.39   +07 59.5    3.210    3.170    78.8    17.7  20.5
2022 01 06    23 45.50   +08 39.9    3.290    3.181    75.0    17.4  20.6
2022 01 11    23 49.88   +09 21.5    3.369    3.192    71.3    17.0  20.7
2022 01 16    23 54.50   +10 04.2    3.446    3.203    67.6    16.5  20.7
2022 01 21    23 59.33   +10 47.9    3.522    3.215    64.0    16.0  20.8


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

                         (C) Copyright 2021 CBAT
2021 August 20                   (CBET 5022)              Daniel W. E. Green