[Iaude] CBET 4896: COMET C/2020 X2

quai at eps.harvard.edu quai at eps.harvard.edu
Mon Dec 14 02:23:18 EST 2020


                                                  Electronic Telegram No. 4896
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/2020 X2 (ATLAS)
     A comet discovery was reported to the Minor Planet Center on Dec. 10 by
the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program
(discovery observations tabulated below) from CCD images taken on Dec. 10.5
UT with a 0.5-m f/2 Schmidt reflector at Mauna Loa, Hawaii (with no details
given about appearance); a day later, A. Heinze told the MPC that the comet
showed a condensed 4".5 coma.

     2020 UT             R.A. (2000) Decl.       Mag.
     Dec. 10.50409    6 58 30.87   +19 19 55.0   18.2
          10.50701    6 58 30.85   +19 19 55.7   18.7
          10.54240    6 58 30.02   +19 20 05.2   18.7
          10.54516    6 58 29.87   +19 20 05.5   18.9

After the comet was posted on the MPC's PCCP webpage, other CCD astrometrists
have also commented on the cometary appearance.  Four stacked 60-s CCD
exposures taken remotely on Dec. 12.35 UT by H. Sato, Tokyo, Japan, with a
0.43-m f/6.8 astrograph located near Mayhill, NM, USA, show a strongly
condensed and elongated coma of size 6" x 12" with no tail; the magnitude was
18.4 as measured within a circular aperture of radius 7".6.  A. Valvasori,
Padulle, Italy, writes that fifteen stacked unfiltered 120-s exposures taken
remotely by E. Guido and himself on Dec. 13.2 with an iTelescope 0.32-m f/7.9
reflector at Nerpio, Spain, show a diffuse coma about 7".5 in diameter and of
magnitude 18.9-19.1.
     Four nights of apparently asteroidal pre-discovery observations of this
comet, from three different observatories and spanning 2020 Oct. 14-Dec. 8,
were identified by the Minor Planet Center in its "isolated tracklet file"
(with Mt. Lemmon Survey observations on Oct. 14.4 UT giving mag 19.1-19.7);
in addition, pre-discovery Mt. Lemmon Survey observations reported after the
ATLAS discovery was reported date to Sept. 25.5 (mag 19.7-19.9), Oct. 29.4
(mag 19.0-19.3), and Nov. 23.5 (mag 18.6-18.8).  The available astrometry
appear on MPEC 2020-X156.
     The following elliptical orbital elements by S. Nakano (CBAT) are from
50 observations spanning Sept. 25-Dec. 13 (mean residual 0".4).  These
elements indicate that the comet passed 1.19 AU from Jupiter in 1955 Oct. and
2.54 AU from Neptune in 1985 June, and that the comet will pass 2.99 AU from
Saturn in 2083 Nov.

                    Epoch = 2020 Nov.  7.0 TT
     T = 2020 Nov. 16.11268 TT        Peri. = 347.39646
     e = 0.7659816                    Node  = 105.45808 2000.0
     q = 3.8283698 AU                 Incl. =  18.19220
       a = 16.3592685 AU   n = 0.01489561   P =  66.17 years

                    Epoch = 2087 Nov. 16.0 TT
     T = 2087 Nov.  8.39301 TT        Peri. = 347.72636
     e = 0.7676293                    Node  = 105.14563 2000.0
     q = 3.8449245 AU                 Incl. =  18.10448
       a = 16.5465107 AU   n = 0.01464348   P =  67.31 years

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.
2020 11 27    07 02.34   +18 25.7    3.021    3.829   139.9     9.5  18.6
2020 12 02    07 01.24   +18 44.5    2.979    3.830   145.3     8.4  18.5
2020 12 07    06 59.76   +19 04.9    2.942    3.832   150.7     7.2  18.5
2020 12 12    06 57.94   +19 26.5    2.912    3.834   156.2     5.9  18.5
2020 12 17    06 55.83   +19 49.3    2.888    3.836   161.8     4.6  18.5
2020 12 22    06 53.48   +20 13.1    2.872    3.838   167.5     3.2  18.5
2020 12 27    06 50.97   +20 37.5    2.863    3.841   173.1     1.8  18.5
2021 01 01    06 48.38   +21 02.3    2.862    3.845   177.9     0.5  18.5
2021 01 06    06 45.76   +21 27.2    2.868    3.848   174.8     1.3  18.5
2021 01 11    06 43.20   +21 52.0    2.882    3.852   169.3     2.7  18.5
2021 01 16    06 40.78   +22 16.3    2.903    3.857   163.6     4.1  18.5
2021 01 21    06 38.56   +22 40.1    2.932    3.862   158.0     5.5  18.5
2021 01 26    06 36.62   +23 03.2    2.967    3.867   152.5     6.8  18.6
2021 01 31    06 35.00   +23 25.3    3.009    3.873   147.0     8.0  18.6
2021 02 05    06 33.76   +23 46.5    3.057    3.878   141.6     9.1  18.6
2021 02 10    06 32.92   +24 06.5    3.111    3.885   136.3    10.1  18.7
2021 02 15    06 32.51   +24 25.4    3.170    3.892   131.2    11.0  18.7
2021 02 20    06 32.56   +24 43.2    3.233    3.899   126.1    11.8  18.8
2021 02 25    06 33.07   +24 59.7    3.301    3.906   121.2    12.5  18.8
2021 03 02    06 34.03   +25 15.1    3.372    3.914   116.3    13.1  18.9
2021 03 07    06 35.44   +25 29.3    3.446    3.922   111.6    13.6  18.9
2021 03 12    06 37.29   +25 42.3    3.523    3.930   107.0    14.0  19.0
2021 03 17    06 39.57   +25 54.1    3.601    3.939   102.6    14.3  19.0
2021 03 22    06 42.25   +26 04.8    3.681    3.948    98.2    14.5  19.1
2021 03 27    06 45.32   +26 14.2    3.763    3.958    93.9    14.6  19.2
2021 04 01    06 48.74   +26 22.4    3.844    3.968    89.7    14.6  19.2
2021 04 06    06 52.50   +26 29.4    3.927    3.978    85.6    14.5  19.3
2021 04 11    06 56.57   +26 35.2    4.009    3.988    81.6    14.4  19.3
2021 04 16    07 00.94   +26 39.8    4.091    3.999    77.7    14.2  19.4
2021 04 21    07 05.57   +26 43.1    4.172    4.010    73.9    13.9  19.4
2021 04 26    07 10.45   +26 45.2    4.251    4.021    70.1    13.6  19.5
2021 05 01    07 15.55   +26 46.1    4.330    4.033    66.4    13.2  19.5
2021 05 06    07 20.85   +26 45.8    4.407    4.045    62.7    12.8  19.6
2021 05 11    07 26.33   +26 44.3    4.482    4.058    59.1    12.3  19.6
2021 05 16    07 31.98   +26 41.5    4.556    4.070    55.6    11.8  19.7
2021 05 21    07 37.77   +26 37.6    4.626    4.083    52.1    11.3  19.7
2021 05 26    07 43.68   +26 32.5    4.695    4.097    48.6    10.7  19.8


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

                         (C) Copyright 2020 CBAT
2020 December 14                 (CBET 4896)              Daniel W. E. Green



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