Electronic Telegram No. 5503
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/2025 C1 (ATLAS)
An apparently asteroidal object discovered on CCD images taken on Feb. 2
UT with a 0.5-m f/2 Schmidt reflector at Haleakala, Hawaii, in the course of
the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program has
been found to show cometary appearance by CCD astrometrists elsewhere. The
discovery observations are tabulated below.
2025 UT R.A. (2000) Decl. Mag.
Feb. 2.63291 14 12 21.01 -14 13 30.7 18.4
2.63475 14 12 21.09 -14 13 31.2 18.4
2.65138 14 12 21.86 -14 13 37.5 18.1
2.67255 14 12 22.81 -14 13 46.0 18.1
Eight stacked 60-s exposures taken on Feb. 3.3 UT by H. Sato (Tokyo, Japan)
using an iTelescope 0.51-m f/6.8 astrograph located at Rio Hurtado, Chile,
show a strongly condensed disk-like coma 8" in diameter with no tail; the
magnitude was 16.5 as measured within a circular aperture of radius 5".0,
and he comments that this appears to have experienced a recent outburst.
A. Hale (Cloudcroft, NM, USA) writes that images obtained on Feb. 7.2 UT
with a 0.35-m f/3 Cassegrain reflector at Tenerife show a moderately strong
condensation located near the apex of an asymmetric coma of size 12" x 9",
extended toward p.a. approximately 280 degrees; the magnitude was given as
16.7-16.8. (Hale adds that images obtained with multiple 0.35-m f/3
Cassegrain reflectors at Tenerife on Feb. 3.2 and 4.2 show only a stellar
appearance.)
Thirty-five stacked 60-s exposures taken remotely by F. D. Romanov
(Yuzhno-Morskoy, Nakhodka, Russia) using an iTelescope 0.51-m f/6.8 reflector
(+ Luminance filter) located at the Rio Hurtado Valley in Chile on Feb. 8.26
UT show a condensed coma 15" in diameter of total mag 16.8 (nearby reference-
star G-band magnitudes from the Gaia DR2 catalogue); the coma appears extended
toward p.a. 305 degrees.
R. Weryk, Department of Physics and Astronomy, University of Western
Ontario, reports that follow-up images obtained on Feb. 8.61 by J. Fairlamb
with the University of Hawaii 2.2-m reflector in 1".6 seeing show a condensed
head of size about 3" (full-width-at-half-maximum) with a broad tail 12" long
spanning p.a. 230-330 degrees.
The available astrometry appears on MPEC 2025-C158. The following
two-body elliptical orbital elements by S. Nakano (Central Bureau) are from
187 observations spanning Feb. 2-10 (mean residual 0".4). These indicate that
the comet passed 0.29 AU from Jupiter on 2010 Feb. 3 UT, and it will pass 0.33
AU from Jupiter in 2045. The formal uncertainty on the orbital period at this
point is a third of a year.
T = 2025 Feb. 3.76777 TT Peri. = 186.09557
e = 0.3588665 Node = 9.17529 2000.0
q = 2.7548200 AU Incl. = 7.52523
a = 4.2967966 AU n = 0.11065903 P = 8.91 years
The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 10.5 and 2.5n = 10 for the
magnitudes.
Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag.
2025 02 25 14 24.45 -16 20.2 2.162 2.758 117.1 18.6 16.6
2025 03 07 14 26.27 -17 02.8 2.054 2.762 126.5 16.8 16.5
2025 03 17 14 25.65 -17 35.7 1.960 2.767 136.4 14.4 16.4
2025 03 27 14 22.65 -17 58.3 1.884 2.773 146.8 11.4 16.3
2025 04 06 14 17.56 -18 10.0 1.830 2.781 157.6 7.9 16.3
2025 04 16 14 10.97 -18 11.6 1.800 2.790 168.2 4.2 16.2
2025 04 26 14 03.71 -18 04.8 1.797 2.800 174.8 1.9 16.2
2025 05 06 13 56.68 -17 52.8 1.820 2.812 166.8 4.7 16.3
2025 05 16 13 50.77 -17 39.7 1.870 2.825 156.3 8.3 16.4
2025 05 26 13 46.59 -17 29.4 1.943 2.839 145.8 11.6 16.5
2025 06 05 13 44.54 -17 25.1 2.037 2.854 135.9 14.3 16.6
2025 06 15 13 44.75 -17 29.0 2.148 2.870 126.5 16.5 16.7
2025 06 25 13 47.17 -17 41.7 2.272 2.888 117.7 18.2 16.9
2025 07 05 13 51.65 -18 03.3 2.407 2.907 109.3 19.3 17.0
2025 07 15 13 57.98 -18 33.1 2.550 2.926 101.4 19.9 17.2
2025 07 25 14 05.94 -19 09.9 2.698 2.947 93.9 20.1 17.3
2025 08 04 14 15.34 -19 52.4 2.848 2.968 86.7 20.0 17.5
2025 08 14 14 26.00 -20 39.3 2.999 2.990 79.8 19.5 17.6
2025 08 24 14 37.74 -21 29.2 3.148 3.013 73.1 18.7 17.8
2025 09 03 14 50.44 -22 20.8 3.294 3.037 66.5 17.7 17.9
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
(C) Copyright 2025 CBAT
2025 February 10 (CBET 5503) Daniel W. E. Green