[Iaude] CBET 5401: COMET P/2024 FG_9
quai at eps.harvard.edu
quai at eps.harvard.edu
Sat Jun 1 11:02:27 EDT 2024
Electronic Telegram No. 5401
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 P/2024 FG_9 (NANSHAN-HAHN)
An apparently asteroidal object that was discovered independently at
several different observatories was curiously assigned the minor-planet
designation 2024 FG_9 by the Minor Planet Center to a single-night set of Mt.
Lemmon Survey discovery observations from Mar. 21. The comet had been
discovered and followed on two nights at the Mt. Nanshan station of the
Xinjiang Astronomical Observatory (details provided by Xing Gao, who
participated in the observing and measurements, writing that Xio Liao first
noted this object) in the course of the Xingming Sky Survey on images taken
on Mar. 8 and 9 UT with a 1.0-m f/2.2 reflector. But the Xingming and Mt.
Lemmon observations were not linked as a single object until an independent
asteroidal discovery was made by Robson Henrique dos Santos Hahn (Moeckmuehl,
Germany) on images obtained remotely on Apr. 10 and 12 with his 0.36-m f/2
Celestron 14 (+ Hyperstar) reflector located near Valdin, Ourenses, Spain.
Hahn reported the object as potentially interesting, and it was placed at
that time on the MPC's NEOCP webpage. The discovery observations are
tabulated below. The Mt. Lemmon observations and Hahn's observationos first
appeared on MPS 2157401 (dated 2024 Apr. 18) together with many observations
obtained with the Pan-STARRS1 and Pan-STARRS2 1.8-m reflectors at Haleakala
on seven nights from 2023 Nov. 4 (mag 22.2-23.3) to 2024 Mar. 6 (mag
20.2-20.5); only the Pan-STARRS2 astrometry from 2023 Nov. 18 (mag 21.8-21.9)
had been reported to the MPC in real time (the rest reported as pre-discovery
observations after the posting on the NEOCP). The Mar. 8 Xingming
observations first appeared on MPS 2166265 (dated 2024 May 1), but curiously
without the Mar. 9 observations (which remained unpublished until now,
despite each set being reported the day that they made and under the same
preliminary designation; i.e., the Xingming observers recognized in real time
that the same object had been observed on Mar. 8 and 9). An orbit only for
2024 FG_9 was first published on Apr. 14 on MPEC 2024-G199 in a "Daily Orbit
Update".
2024 UT R.A. (2000) Decl. Mag. Observer
Mar. 8.57951 4 09 23.58 +20 14 55.6 19.7 Xingming
8.59395 4 09 25.41 +20 15 00.3 20.2 "
8.60840 4 09 27.23 +20 15 04.2 19.9 "
9.59481 4 11 31.49 +20 19 51.3 20.0 "
9.60617 4 11 32.86 +20 19 54.9 20.1 "
9.61710 4 11 34.30 +20 19 58.5 20.1 "
21.12415 4 37 17.98 +21 12 05.4 19.5 Mt. Lemmon Survey
21.12836 4 37 18.52 +21 12 06.9 19.5 "
21.13257 4 37 19.13 +21 12 07.3 19.8 "
21.13681 4 37 19.65 +21 12 08.5 "
21.14447 4 37 20.78 +21 12 09.9 20.1 "
21.15845 4 37 22.79 +21 12 13.6 19.4 "
21.16966 4 37 24.32 +21 12 16.4 19.7 "
Apr. 10.86547 5 30 02.06 +22 13 12.5 18.7 Hahn
10.88035 5 30 04.36 +22 13 13.2 18.1 "
10.89527 5 30 06.86 +22 13 14.1 18.7 "
11.86239 5 32 44.60 +22 14 38.5 19.0 "
11.87700 5 32 47.05 +22 14 39.6 19.0 "
11.89163 5 32 49.41 +22 14 40.8 18.3 "
Pre-discovery observations were later reported by S. Deen (Simi Valley, CA,
USA), who found cometary activity in 2024 FG_9. An image obtained with
the 4-m reflector (+ DECam) at the Cerro Tololo Interamerican Observatory (as
part of the DECam Legacy Survey) on 2018 May 16.97 UT shows the comet as a
diffuse object of size 1".8 (full-width-at-half-maximum) and magnitude z =
20.4 in 1".0 seeing, with a 3" tail toward p.a. 125 degrees. Deen also found
five images of the comet obtained with the 1.2-m Schmidt telescope at Palomar
taken on four nights in 2018 (Mar. 29, magnitude g = 20.8; Apr. 8, r = 20.0;
Apr. 11, r = 20.2; and Apr. 15, r = 20.5), with all of the "Zwicky Transient
Facility" survey images showing a "clearly hazy" and extended appearance.
Deen also observed this comet on 2024 Apr. 17.0 with a 0.43-m telescope
located at Rio Hurtado, Chile, when the object appeared diffuse with a size
of about 3" (FWHM) in 1".5 seeing, with a possible tail 4" long toward p.a.
90 degrees.
A. Hale, Cloudcroft, NM, USA, reports that 300-s exposures taken on 2024
Apr. 28.2 UT with a Las Cumbres Observatory 0.35-m f/3 Cassegrain reflector at
Haleakala, HI, USA, show the comet to be marginally diffuse (but relatively
condensed) when compared with stars of similar brightness; a coma size of 6"
with no tail was given. Similar exposures obtained by Hale on Apr. 15 show no
obvious cometary appearance. Additional images obtained by Hale on May 25.25
show a diffuse coma of size 24" with a prominent central condensation and no
tail; the magnitude was given as 17.4-17.5, and Hale noted that the comet was
then distinctly larger in size than during his previous observations.
Fifteen stacked 30-s CCD exposures obtained remotely by H. Sato (Bunkyo-ku,
Tokyo, Japan) with a 0.51-m f/6.8 astrograph located at Siding Spring, NSW,
Australia, on 2024 May 13.4 show a strongly condensed coma 15" in diameter
and a hint of tail eastward; the magnitude was 17.9 as measured within a
circular aperture of radius 7".6. Sixteen stacked additional 30-s exposures
taken by Sato on May 26.35-26.35 show a strongly condensed object with an
outer coma 1'.2 in diameter and no tail; the magnitude was 14.9 as measured
within a circular aperture of radius 37".8 (and Sato commented on the
increase in size/brightness). One-hundred-forty-five 30-s CCD exposures
taken by A. Aletti, F. Bellini, L. Buzzi, G. Galli, and M. Auteri with a
0.36-m f/8.4 reflector located at Hakos, Namibia, on 2024 May 21.74-21.77
in 3".6 seeing show a slightly condensed 7" coma.
Additional astrometry appears on MPEC 2024-L4. The following orbital
elements by S. Nakano (Central Bureau) are from 95 observations spanning 2018
Mar. 29-2024 May 26 (mean residual 0".5). The comet passed 0.20 AU from
Jupiter on 2021 Apr. 30 and will again pass 0.20 AU from Jupiter on 2033
Apr. 16 UT. Nakano was unable to find earlier observations of this comet in
astrometric archives.
Epoch = 1999 Jan. 22.0 TT
T = 1999 Jan. 4.81377 TT Peri. = 173.51077
e = 0.4084116 Node = 318.12254 2000.0
q = 2.0969019 AU Incl. = 10.34251
a = 3.5445283 AU n = 0.14769521 P = 6.67 years
Epoch = 2005 Sept.27.0 TT
T = 2005 Sept. 8.93263 TT Peri. = 173.71114
e = 0.4094045 Node = 318.05570 2000.0
q = 2.0912684 AU Incl. = 10.34940
a = 3.5409489 AU n = 0.14791921 P = 6.66 years
Epoch = 2012 Mar. 14.0 TT
T = 2012 Mar. 18.53711 TT Peri. = 184.30688
e = 0.4811829 Node = 311.51578 2000.0
q = 1.7129458 AU Incl. = 8.68876
a = 3.3016368 AU n = 0.16428962 P = 6.00 years
Epoch = 2018 Mar. 23.0 TT
T = 2018 Mar. 22.15412 TT Peri. = 184.47767
e = 0.4811437 Node = 311.45979 2000.0
q = 1.7134838 AU Incl. = 8.68671
a = 3.3024247 AU n = 0.16423083 P = 6.00 years
Epoch = 2024 May 10.0 TT
T = 2024 May 20.33931 TT Peri. = 245.90643
e = 0.5097333 Node = 253.04508 2000.0
q = 1.5963715 AU Incl. = 1.73108
a = 3.2561290 AU n = 0.16774581 P = 5.88 years
Epoch = 2030 Apr. 9.0 TT
T = 2030 Apr. 8.89452 TT Peri. = 246.16002
e = 0.5094058 Node = 252.89198 2000.0
q = 1.5980914 AU Incl. = 1.73047
a = 3.2574607 AU n = 0.16764295 P = 5.88 years
Epoch = 2036 July 6.0 TT
T = 2036 June 18.54697 TT Peri. = 351.94100
e = 0.4622931 Node = 148.08963 2000.0
q = 1.8177998 AU Incl. = 8.31473
a = 3.3806520 AU n = 0.15856356 P = 6.22 years
The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 14.0 and 2.5n = 10 for the
magnitudes.
Date TT R. A. (2000) Decl. Delta r Elong. Phase Mag.
2024 05 10 06 53.69 +21 39.5 1.990 1.600 53.0 30.3 17.5
2024 05 15 07 08.65 +21 16.3 2.014 1.597 51.6 29.8 17.6
2024 05 20 07 23.68 +20 47.8 2.039 1.596 50.4 29.2 17.6
2024 05 25 07 38.71 +20 14.1 2.064 1.597 49.1 28.7 17.6
2024 05 30 07 53.72 +19 35.3 2.090 1.599 47.9 28.1 17.6
2024 06 04 08 08.68 +18 51.5 2.118 1.603 46.7 27.4 17.7
2024 06 09 08 23.55 +18 03.0 2.146 1.608 45.6 26.8 17.7
2024 06 14 08 38.30 +17 10.0 2.175 1.614 44.4 26.1 17.8
2024 06 19 08 52.90 +16 12.9 2.205 1.622 43.3 25.4 17.8
2024 06 24 09 07.34 +15 12.1 2.236 1.631 42.1 24.7 17.9
2024 06 29 09 21.59 +14 07.9 2.268 1.642 41.0 23.9 17.9
2024 07 04 09 35.65 +13 00.7 2.302 1.654 39.8 23.2 18.0
2024 07 09 09 49.52 +11 50.9 2.336 1.667 38.6 22.4 18.1
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
(C) Copyright 2024 CBAT
2024 June 1 (CBET 5401) Daniel W. E. Green
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