Electronic Telegram No. 5459
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 S1 (ATLAS)
A. Pearce, Nedlands, W. Australia, reports the following CCD total-
magnitude and coma-diameter measurements for C/2024 S1, using a 0.106-m
refractor at the Skygems Observatory in Namibia: Sept. 29.15 UT, 13.0, 3';
Oct. 5.15, 12.6, 3'; 9.15, 12.6, 3'.3; 10.13, 12.8, 3' (2'.2 tail in p.a. 261
deg); 11.15, 12.8, 2'.5 (1'.4 tail in p.a. 270 deg); 12.14, 13.1, 2'.6 (2'
tail in p.a. 260 degrees); 16.14, 11.8, 2'.5 (6'.7 tail in p.a. 258 deg);
17.14, 11.8, 2'.3); 18.14, 10.0, 2'.5; 3'.4 tail in p.a. 263 deg). Pearce
also reports the following total-magnitude and coma-diameter measures from
CCD images obtained with a 0.05-m refractor at Nedlands: Sept. 29.88, 13.1,
3'.2; 30.87, 12.9, 4'; Oct. 7.85, 13.3, 1'.6. Note that there is currently
a strong outburst in brightness that ocurred between Oct. 17 and 18, with
accompanying morphological changes in the comet's appearance, occurring in
the coma of C/2024 S1. Pearce adds that there was a smaller outburst that
occurred a few days earlier. Pearce also relates that T. Lovejoy imaged
this comet remotely using a 25-cm f/3.8 iTelescope in the Rio Hurtado valley
in Chile on Oct. 18.35 that yields total mag 9.4 with a 2'.4 coma and a 22'
tail in p.a. 259 degrees. M. Mattiazzo posted an image of C/2024 S1 on
the "ICQ Comet Observations" Facebook page that he took remotely on Oct.
16.38 with a 0.43-m f/6.8 iTelescope at Rio Hurtado showing the first
outburst (which saw an increase of 1.2 mag in V brightness in 24 hours).
Pearce's images appear on the same forum.
T. Prystavski (Lviv, Ukraine) reports that an unfiltered CCD exposure
taken remotely on Oct. 9.75 UT with a 43-cm Cassegrain reflector located at
Siding Spring, NSW, Australia, shows a 1'.8 coma of total mag 12.9 with a
3'.2 tail in p.a. 264 degrees. G. Pappa (Mascalucia, Sicily, Italy) writes
that he obtained the following total-magnitude and coma-diameter measurements
from CCD images taken using a 0.306-m Ritchey-Chretien reflector remotely in
Namibia: Oct. 09.13, 12.2, 1' (2' tail); 11.15, 12.7, 2'; 12.13, 13.1, 2'.5
(1' tail). K. Kadota (Ageo, Japan) reports the following total CCD magnitudes
for C/2024 S1: Oct. 1.81, 13.2; 9.81, 12.7.
Further to CBET 5453, the following updated orbital elements by S.
Nakano (Central Bureau) are from 193 observations spanning Sept. 27-Oct. 15
(mean residual 0".8). These elements yield a semi-major axis of 81.93 AU
and an orbital period of 742 years.
Epoch = 2024 Oct. 17.0 TT
T = 2024 Oct. 28.48663 TT Peri. = 69.26375
e = 0.9999026 Node = 347.27899 2000.0
q = 0.0079778 AU Incl. = 141.91881
Nakano also supplies these two-body orbital elements from 198 observations
spanning 2024 Sept. 27-Oct. 15 (also mean residual 0".8), which indicate
an orbital period of 759 yr. Nakano writes: "I think that this orbit of
C/2024 S1 without perturbations is slightly better than the former
perturbed orbit".
T = 2024 Oct. 28.48655 TT Peri. = 69.26150
e = 0.9999041 Node = 347.27998 2000.0
q = 0.0079809 AU Incl. = 141.91878
The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 12.0 and 2.5n = 8 for the
magnitudes (i.e., 1 mag fainter than given in the ephemeris on CBET 5453).
The comet is unlikely to survive perihelion passage due to its small size
(as ascertained by its faint absolute magnitude).
Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag.
2024 10 17 11 17.53 -18 17.3 0.945 0.552 32.9 78.7 9.8
2024 10 18 11 28.98 -18 31.5 0.929 0.519 31.0 81.7 9.6
2024 10 19 11 41.10 -18 42.6 0.914 0.485 29.0 84.9 9.3
2024 10 20 11 53.89 -18 50.0 0.902 0.450 26.8 88.3 9.0
2024 10 21 12 07.37 -18 52.7 0.892 0.413 24.5 92.0 8.7
2024 10 22 12 21.55 -18 49.9 0.884 0.375 22.0 95.9 8.3
2024 10 23 12 36.42 -18 40.5 0.880 0.335 19.3 100.2 7.9
2024 10 24 12 52.00 -18 23.0 0.879 0.292 16.5 104.8 7.4
2024 10 25 13 08.29 -17 55.9 0.883 0.245 13.4 110.1 6.8
2024 10 26 13 25.38 -17 16.5 0.893 0.194 10.1 116.2 6.1
2024 10 27 13 43.49 -16 19.8 0.911 0.136 6.5 124.3 4.9
2024 10 28 14 03.59 -14 49.1 0.946 0.061 2.3 139.8 2.2
2024 10 29 13 59.73 -13 17.8 1.015 0.063 3.4 68.4 2.4
2024 10 30 13 45.75 -14 17.9 1.015 0.137 7.7 76.9 5.1
2024 10 31 13 35.70 -15 14.1 1.013 0.195 11.1 78.5 6.4
2024 11 01 13 27.39 -16 07.1 1.011 0.246 14.1 78.7 7.2
2024 11 02 13 20.11 -16 57.8 1.009 0.292 16.8 78.4 7.7
2024 11 03 13 13.54 -17 46.8 1.007 0.335 19.3 77.9 8.2
2024 11 04 13 07.48 -18 34.5 1.005 0.375 21.7 77.2 8.6
2024 11 05 13 01.81 -19 21.1 1.003 0.414 23.9 76.5 8.9
2024 11 06 12 56.44 -20 06.7 1.001 0.450 26.1 75.7 9.2
2024 11 07 12 51.31 -20 51.7 0.999 0.486 28.2 75.0 9.5
2024 11 08 12 46.38 -21 35.9 0.997 0.520 30.3 74.2 9.7
2024 11 09 12 41.60 -22 19.6 0.995 0.553 32.3 73.4 9.9
2024 11 10 12 36.94 -23 02.7 0.993 0.585 34.3 72.6 10.1
2024 11 11 12 32.39 -23 45.4 0.991 0.616 36.2 71.8 10.3
2024 11 12 12 27.90 -24 27.7 0.989 0.646 38.1 71.0 10.5
2024 11 13 12 23.48 -25 09.6 0.987 0.676 40.0 70.2 10.6
2024 11 14 12 19.09 -25 51.1 0.985 0.705 41.8 69.4 10.8
2024 11 15 12 14.72 -26 32.3 0.983 0.733 43.6 68.6 10.9
2024 11 16 12 10.37 -27 13.1 0.981 0.761 45.5 67.8 11.0
2024 11 17 12 06.01 -27 53.6 0.979 0.789 47.2 67.0 11.1
2024 11 18 12 01.64 -28 33.7 0.977 0.816 49.0 66.2 11.2
2024 11 19 11 57.24 -29 13.5 0.975 0.842 50.8 65.4 11.3
2024 11 20 11 52.81 -29 52.9 0.973 0.868 52.5 64.6 11.5
2024 11 21 11 48.33 -30 32.0 0.972 0.894 54.3 63.8 11.5
2024 11 22 11 43.80 -31 10.6 0.970 0.919 56.0 63.0 11.6
2024 11 23 11 39.21 -31 48.8 0.968 0.944 57.7 62.2 11.7
2024 11 24 11 34.55 -32 26.5 0.966 0.969 59.5 61.3 11.8
2024 11 25 11 29.82 -33 03.7 0.965 0.993 61.2 60.5 11.9
2024 11 26 11 25.00 -33 40.3 0.963 1.017 62.9 59.7 12.0
2024 11 27 11 20.10 -34 16.3 0.962 1.041 64.6 58.9 12.1
2024 11 28 11 15.09 -34 51.6 0.961 1.065 66.3 58.0 12.1
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
(C) Copyright 2024 CBAT
2024 October 18 (CBET 5459) Daniel W. E. Green