ALPO COMET NEWS FOR NOVEMBER 2024
A Publication of the Comets Section of the Association of Lunar and Planetary Observers
By Carl Hergenrother
The monthly Association of Lunar and Planetary Observers (ALPO) Comet News PDF can be found on the ALPO Comets Section website @ http://alpo-astr....org/Comets/ and in the Comets Section Image Gallery. A shorter version of this report is posted here (minus the magnitude estimates, images, and other figures contained in the full PDF). The ALPO Comets Section welcomes all comet-related observations, whether textual descriptions, images, drawings, magnitude estimates, or spectra. You do not have to be a member of ALPO to submit material, though membership is encouraged. To learn more about the ALPO, please visit us @ http://alpo-astronomy.org. We can also be reached at < comets @ alpo-astronomy.org >.
Summary
C/2023 A3 (Tsuchinshan-ATLAS) did not disappoint. After reaching a brilliant peak at magnitude -3 to -4, though it was only within a few degrees of the Sun at the time, the comet reappeared in the evening sky at around 0th magnitude. Though it quickly faded as it moved higher in the sky, a tail up to 20 degrees in length was visually observed. Imagers also detected the predicted anti-tail.
Tsuchinshan-ATLAS starts November in the evening sky at 6th magnitude. Since it is moving away from the Earth and Sun, it will continue to fade and should be around magnitude 9 at the end of the month.
The other comet that could have been bright this month did disappoint. Kreutz sungrazer C/2024 S1 (ATLAS) experienced a series of outbursts, presumably due to the break-up of its nucleus. Enough material survived to be imaged by the SOHO spacecraft as it closed in on perihelion, but unfortunately, nothing seems to have survived perihelion.
November will be the last month to see 13P/Olbers visually as it approaches solar conjunction. Northern hemisphere observers may be able to observe short-period comet 333P/LINEAR, which may reach 10th magnitude at the end of the month in the morning sky. While 333P/LINEAR will be a low-elevation object for southern hemisphere observers, they will have C/2024 G3 (ATLAS) to themselves. C/2024 G3 comes to perihelion in January at a close 0.09 au from the Sun. Though it will be located very close to the Sun when at its brightest, there is an outside chance that this could be a nice object from the southern hemisphere after its perihelion.
Last month, the ALPO Comets Section received 283 magnitude estimates and over 200 images of 26 comets: C/2024 S1 (ATLAS), C/2024 M1 (ATLAS), C/2024 G3 (ATLAS), C/2024 B1 (Lemmon), C/2023 A3 (Tsuchinshan-ATLAS), C/2022 QE78 (ATLAS), C/2022 N2 (PANSTARRS), C/2022 E2 (ATLAS), C/2020 V2 (ZTF), C/2020 K1 (PANSTARRS), C/2017 K2 (PANSTARRS), C/2014 UN271 (Bernardinelli-Bernstein), 487P/Siding Spring, 472P/NEAT-LINEAR, 276P/Vorobjov, 253P/PANSTARRS, 242P/Spahr, 208P/McMillian, 146P/Shoemaker-Levy, 130P/McNaught-Hughes, 89P/Russell, 54P/de Vico-Swift-NEAT, 49P/Arend-Rigaux, 43P/Wolf-Harrington, 33P/Daniel, and 13P/Olbers.
A big thanks to our recent contributors: Salvador Aguirre, Michael and Anthony Amato, Dan Bartlett, Denis Buczynski, José J. Chambó, Ed Chase, Dan Crowson, Michel Deconinck, Jose Guilherme de Souza Aguiar, Juan Jose Gonzalez Suarez, Christian Harder, Carl Hergenrother, Eliot Herman, Rik Hill, Michael Jäger, John Maikner, Gianluca Masi, Michael Mattiazzo, Ron May, Frank J. Melillo, Jim Melka, Martin Mobberley, Mike Olason, Timothy Parsons Andrew Pearce, Michael Rosolina, Gregg Ruppel, Chris Schur, Bob Soltys, Tenho Tuomi, and Christopher Wyatt.
Request for Observations
As always, the Comet Section is happy to receive all comet observations, whether textual descriptions, images, drawings, magnitude estimates, or spectra. Please send your observations via email to the Comets Section < comets @ alpo-astronomy . org >, Comets Section Coordinator Carl Hergenrother < carl.hergenrother @ alpo-astronomy . org > and/or Comets Section Acting Assistant Coordinator Michel Deconinck < michel.deconinck @ alpo-astronomy . org >.
Photometric Corrections to Magnitude Measurements
We include lightcurves for the comets discussed in these reports and apply aperture and personal corrections to the visual observations and only personal corrections are applied to digital observations. Though we try to keep these lightcurves up to date, observations submitted just before publication may not be included in the lightcurves until next month’s News. All magnitude estimates are affected by many factors, including instrumental (aperture, focal length, magnification, type of optics), environmental (sky brightness due to moonlight, light pollution, twilight, aurora activity, zodiacal light, etc.), cometary (degree of condensation, coma color, strength and type of gas emission lines, coma-tail interface) and personal (sensitivity to different wavelengths, personal technique, observational biases). The first correction used here corrects for differences in aperture [Charles S. Morris, On Aperture Corrections for Comet Magnitude Estimates. Publ Astron Soc Pac 85, 470, 1973]. Visual observations are corrected to a standard aperture of 6.78 cm by 0.019 magnitudes per centimeter for reflectors and 0.066 magnitudes per centimeter for refractors. After applying the aperture correction and if a sufficient number of visual observations are submitted for a particular comet, we also determine personal corrections for each observer for each comet; for digital observations, only a personal correction is applied. A single observer submitting both visual and digital magnitude measurements may also have separate corrections for each observing method. If the magnitudes shown in the text don’t match those plotted in the lightcurves, it is because of the application of these corrections.
Acknowledgments
In addition to observations submitted directly to the ALPO, we occasionally use data from other sources to augment our analysis. Therefore, we acknowledge with thanks the observations submitted directly to the ALPO and those initially submitted to the International Comet Quarterly, Minor Planet Center, and COBS Comet Observation Database. In particular, we have been using observations submitted to the COBS site by Thomas Lehmann for our analysis and would like to thank Thomas for his COBS observations. We would also like to thank the Jet Propulsion Laboratory for making their Small-Body Browser and Orbit Visualizer available and Seiichi Yoshida for his Comets for Windows programs that produced the lightcurves and orbit diagrams in these pages. Last but not least, we’d like to thank Syuichi Nakano and the Minor Planet Center for their comet orbit elements, the asteroid surveys and dedicated comet hunters for their discoveries, and all of the observers who volunteer their time to add to our knowledge of these fantastic objects.
Thank you to everyone who contributed to the ALPO Comets Section!
Clear skies!
- Carl Hergenrother
Comets Calendar
Lunar Phases (UTC)
Nov 01 - New Moon
Nov 09 - First Quarter Moon
Nov 15 - Full Moon
Nov 23 - Last Quarter Moon
Comets at Perihelion
Nov 11 - 33P/Daniel [q = 2.24 au, 8.3-yr period, V ~ 17, discovered in 1909, observed at 12 returns, reached 9th magnitude in 1909, the comet was brighter back then due to a smaller perihelion distance of 1.38 au, ~3 mag outburst about 9 months after perihelion in 2001, 2 more 3-4 magnitude outbursts 7-8 months after perihelion in 2009]
Nov 13 - 363P/Lemmon [q = 1.72 au, 6.8-yr period, V ~ 20, discovered in 2011, observed at 2 returns, not seen yet this time]
Nov 16 - C/2023 C2 (ATLAS) [q = 2.37 au, V ~ 12]
Nov 17 - 305P/Skiff [q = 1.42 au, 10.0-yr period, V ~ 16, discovered in 2004, 2024 is the 3rd observed return]
Nov 20 - C/2024 M1 (ATLAS) [q = 1.70 au, 163-yr period, V ~ 13-14]
Nov 28 - C/2023 H1 (PANSTARRS) [q = 4.45 au, V ~ 17]
Nov 29 - 333P/LINEAR [q = 1.11 au, 8.7-yr period, V ~ 9-10, discovered in 2007, this is third observed return, reached 11th magnitude in 2016]
Photo Opportunities
Nov 13 - C/2023 (Tsuchinshan-ATLAS) passes ~1.5 degrees from large open cluster IC 4756
Nov 14 - 333P/LINEAR passes within 1.5 deg of Leo Triplet of galaxies (NGC 3623, 3627, 3628]
Nov 27 - 333P/LINEAR passes over 12th mag galaxy NGC 3994
Nov 29 - 333P/LINEAR passes 40’ from 10th mag galaxy NGC 4244
Nov 29 - 333P/LINEAR passes 1.5 deg from 11th mag galaxy NGC 4151
Comets News
Looking Ahead to the Next 12 Months
The chart below shows those comets expected to become brighter than magnitude 10 over the next 18 months. The number in each date bin is the expected brightness for that date. Magnitudes are only shown for dates when the comet is above the horizon during the dark of night (between the end of astronomical twilight in the evening and the start of astronomical twilight in the morning). The only exceptions are the dates bolded in red for C/2024 G3 (ATLAS) when the comet will only be above the horizon in bright twilight but may still be bright enough to be observed.
All brightness predictions are just that—predictions and may be off by many magnitudes.
Comet Observability.pdf 31.63KB
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Last 10 Periodic Comet Numberings (from WGSBN Bull. 4, #13)
493P/2005 SB216 = P/2004 Q2 (LONEOS)
492P/2010 WK = P/2010 PB57 = P/2024 O3 (LINEAR)
491P/2014 MG4 = P/2024 K2 (Spacewatch-PANSTARRS)
490P/2019 M2 = P/2024 C6 (ATLAS)
489P/1894 F1 = P/2007 HE4 (Denning)
488P/2024 N6 = P/2002 QU151 (NEAT-PANSTARRS)
487P/2012 US27 = P/2024 N5 (Siding Spring)
486P/2018 L5 = P/2024 H1 (Leonard)
485P/2022 U6 = P/2006 AH2 (Sheppard-Tholen)
484P/2005 XR132 (Spacewatch)
New Recoveries & Discoveries
P/2024 T4 = P/2011 UA134 (Spacewatch-PANSTARRS) – P/2011 UA134 (Spacewatch-PANSTARRS) was accidentally recovered on 2024 October 5 by J. K. Hogan with the Mount Lemmon 1.5-m and on October 9 and 10 by the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala. The comet was 21st magnitude at recovery. Perihelion will be on 2025 February 15, at 2.08 au, when the comet reaches 19-20th magnitude. [CBET 5464, MPEC 2024-U43]
C/2024 T3 (PANSTARRS) – This 20th magnitude comet was found with the Pan-STARRS2 telescope on 2024 October 10. C/2024 T3 is not expected to become brighter than magnitude 19. It is on an orbit with a perihelion on 2025 March 15 at 3.71 au and an orbital period of ~783 years. [CBET 5461, MPEC 2024-U17]
P/2024 T2 (Rankin) – P/2024 T2 is one of three comets discovered by David Rankin of the University of Arizona’s Catalina Sky Survey in recent weeks. David has 14 comets bearing his name. This one was found on 2024 October 4, at 20th magnitude with the Mount Lemmon 1.5-m. It arrives at perihelion on 2024 December 7, at 1.98 au, and is expected to peak at 19th magnitude. Its orbital period is 15.9 +/- 1.6 years. [CBET 5460, MPEC 2024-U16]
P/2024 T1 (Rankin) – P/2024 T1 was also a David Rankin find with discovery observations on October 2 at 19th magnitude with the Mount Lemmon 1.5-m. The comet has already passed its 2024 September 30 perihelion at 2.29 au. It should peak at 18th magnitude in December when it is close to opposition. It has an orbital period of 17.4 +/- 0.3 years. [CBET 5455, MPEC 2024-T181]
P/2024 S3 = P/2010 A3 (Hill) – The Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala independently recovered P/2010 A3 (Hill) on 2024 October 7 at 20th magnitude. With an orbital period of 15.1 years, this is this comet’s first return since its discovery apparition. It should peak at 17th magnitude as it approaches perihelion on 2025 March 10 at 1.62 au. [CBET 5466]
P/2024 S2 (Rankin) – David Rankin made this discovery not as part of the Catalina Sky Survey or one of their telescopes but with his private observatory and 0.28-m f/2.2 astrograph. P/2024 S2 was 17th magnitude when discovered on 2024 September 30. Perihelion was on 2024 September 15, at 2.05 au. The comet will only get a little brighter this return. It has an orbital period of ~11.7 years. [CBET 5457, MPEC 2024-T259]
Comets Between Magnitude 6 and 10
C/2023 A3 (Tsuchinshan-ATLAS)
Discovered on 2023 January 9 at the Purple Mountain Observatory's XuYi Station and on February 22 by ATLAS
Dynamically new long-period comet
Orbit (from Minor Planet Center, MPEC 2024-U268)
C/2023 A3 (Tsuchinshan-ATLAS)
Epoch 2024 Oct. 17.0 TT = JDT 2460600.5
T 2024 Sept. 27.74204 TT Rudenko
q 0.3914290 (2000.0) P Q
z -0.0002518 Peri. 308.49210 +0.36143372 +0.90083585
+/-0.0000003 Node 21.55932 +0.91853248 -0.29968132
e 1.0000986 Incl. 139.11072 -0.16019907 +0.31414309
From 5865 observations 2022 Apr. 9-2024 Oct. 30, mean residual 0".6.
1/a(orig) = -0.000237 AU**-1, 1/a(fut) = -0.000209 AU**-1.
Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)
C/2023 A3 (Tsuchinshan-ATLAS) Max El
(deg)
Date R.A. Decl. r d Elong Const Mag 40N 40S
2024-Nov-01 18 00 +03 44 0.926 0.978 56E Oph 6.1 34 9
2024-Nov-06 18 18 +03 52 1.022 1.152 56E Oph 6.8 35 7
2024-Nov-11 18 32 +03 58 1.115 1.324 55E Ser 7.4 35 4
2024-Nov-16 18 43 +04 04 1.207 1.491 53E Ser 8.0 34 1
2024-Nov-21 18 53 +04 11 1.297 1.653 51E Ser 8.5 33 0
2024-Nov-26 19 01 +04 19 1.386 1.808 49E Aql 8.9 31 0
2024-Dec-01 19 08 +04 29 1.472 1.958 46E Aql 9.3 29 0
2024-Dec-06 19 14 +04 41 1.557 2.101 44E Aql 9.7 27 0
Comet Magnitude Formula (from ALPO, COBS, and MPC data)
m1 = -16.6 + 5 log d + 35.0 log r + dust phase_function [Through T-650 days]
m1 = 0.2 + 5 log d + 15.7 log r + dust phase_function [Between T-650 and T-309 days]
m1 = 5.3 + 5 log d + 8.4 log r + dust phase_function [Between T-309 and T-70 days]
m1 = 5.7 + 5 log d + 6.7 log r + dust phase_function [Between T-70 days and perihelion]
m1 = 6.4 + 5 log d + 8.5 log r + dust phase_function [After perihelion]
where “t” is the date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au
C/2023 A3 (Tsuchinshan-ATLAS) did not disappoint and became the best comet since C/2020 F3 (NEOWISE) in 2020.
At the start of October, Tsuchinshan-ATLAS was 2nd magnitude with a 10-20 degree long tail. By the 5th, it was being reported as bright as 0th magnitude, but due to a rapidly shrinking solar elongation, it was soon lost to visual observation. Images continued to pick up the comet as it neared solar conjunction, but the best view was from the SOHO LASCO coronagraph, which watched the comet pass 3 degrees from the Sun on the 9th. Due to a large phase angle and dust forward scattering causing several magnitudes of enhanced brightness, the comet peaked between -3 and -4 magnitude. After conjunction, the comet rocketed into the evening sky, where it was again picked up as bright as 0th magnitude. Even in a bright moonlit sky, a long ghostly tail up to 20 degrees was again observed.
At the end of October, Tsuchinshan-ATLAS dimmed to 6th magnitude, though still displaying several degrees of tail. As has been the case since it reappeared in the evening sky, further dimming is expected as the comet moves away from the Sun (0.93 to 1.42 au) and Earth (0.98 to 1.96 au). Our prediction has the comet at magnitude 6.1 on the 1st, magnitude 7.0 on the 6th, 8.0 on the 14th, 9.0 on the 25th, and 9.3 at the end of the month.
The comet remains well placed for northern hemisphere observers in the evening sky as it moves through Ophiuchus (Nov 1-10), Serpens (10-24), and into Aquila (24-30). It hasn’t been as well placed for southern hemisphere observers, and it only gets worse in November, with the comet having set by the end of astronomical twilight by mid-month.
Photo Opportunities
Nov 13 - C/2023 (Tsuchinshan-ATLAS) passes ~1.5 degrees from large open cluster IC 4756
13P/Olbers
Discovered visually on 1815 March 6 by Heinrich Olbers in Bremen, Germany
Halley-type comet
Orbit (from Minor Planet Center, MPEC 2024-U268)
13P/Olbers
Epoch 2024 Oct. 17.0 TT = JDT 2460600.5
T 2024 June 30.05013 TT Rudenko
q 1.1754760 (2000.0) P Q
n 0.01422889 Peri. 64.41676 -0.60853297 -0.37163087
a 16.8663839 Node 85.84712 +0.18555913 -0.92570139
e 0.9303066 Incl. 44.66594 +0.77152799 -0.07048000
P 69.3
From 2141 observations 2023 Oct. 8-2024 Oct. 13, mean residual 0".5.
Nongravitational parameters A1 = +0.66, A2 = -0.1612.
Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)
13P/Olbers Max El
(deg)
Date R.A. Decl. r d Elong Const Mag 40N 40S
2024-Nov-01 15 46 -05 09 2.117 3.007 21E 9.9 4 0
2024-Nov-06 15 55 -06 24 2.170 3.078 19E 10.1 2 0
2024-Nov-11 16 04 -07 34 2.223 3.148 17E 10.2 0 0
Comet Magnitude Formula (from 2023-2024 ALPO data)
m1 = -0.9 + 5 log d + 32.9 log r [Up through T-115 days]
m1 = 3.9 + 5 log d + 17.5 log r [Between T-115 days and perihelion]
m1 = 4.4 + 5 log d + 9.6 log r [After perihelion]
where “T” is date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au
The 2024 apparition of Halley-type comet 13P/Olbers is coming to a close for most visual observers. Not only is the comet dropping below magnitude 10.0 this month, but it will soon be located too close to the Sun to be observed. It is already too close to the Sun for southern hemisphere observers, and northern observers will lose sight of it early in November, if not already, due to its low elevation. After solar conjunction, Olbers will reappear in the morning sky in January when it may still be as bright as 11-12th magnitude.
Comets Between Magnitude 10 and 12
333P/LINEAR
Discovered on 2007 November 4 by the Lincoln Laboratory Near-Earth Asteroid Research program
Jupiter-family comet
Orbit (from Minor Planet Center, MPEC 2024-U268)
333P/LINEAR
Epoch 2024 Oct. 17.0 TT = JDT 2460600.5
T 2024 Nov. 29.29918 TT Rudenko
q 1.1129402 (2000.0) P Q
n 0.11366829 Peri. 26.01798 -0.12521098 +0.73230090
a 4.2206224 Node 115.70564 +0.73013498 -0.38878626
e 0.7363090 Incl. 132.02166 +0.67173292 +0.55908911
P 8.67
From 629 observations 2016 Jan. 1-2024 Oct. 31, mean residual 0".6.
Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)
333P/LINEAR Max El
(deg)
Date R.A. Decl. r d Elong Const Mag 40N 40S
2024-Nov-01 10 52 +04 26 1.180 1.400 56M Leo 13.0 34 8
2024-Nov-06 10 59 +07 12 1.159 1.262 60M Leo 12.1 39 7
2024-Nov-11 11 07 +10 41 1.142 1.121 65M Leo 11.5 45 5
2024-Nov-16 11 17 +15 14 1.128 0.980 69M Leo 11.0 51 2
2024-Nov-21 11 31 +21 17 1.119 0.844 74M Leo 10.6 57 0
2024-Nov-26 11 50 +29 31 1.114 0.720 79M UMa 10.2 62 0
2024-Dec-01 12 23 +40 34 1.113 0.618 84M CVn 9.9 64 0
2024-Dec-06 13 24 +53 55 1.117 0.554 88M UMa 9.7 57 0
Comet Magnitude Formula (from Seiichi Yoshida)
H = 15.0, G = 0.15 [Through T-55 days]
m1 = 6.5 + 5 log d + 80.0 log r [Between T-55 days and T-20 days]
m1 = 9.5 + 5 log d + 30.0 log r [Between T-20 days and T+108 days]
H = 15.0, G = 0.15 [After T+108 days]
where “T” is date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au
333P/LINEAR is one odd-ball object. With an orbital inclination of 132 degrees and an orbital period of 8.7 years, it holds the title of retrograde comet with the shortest orbital period. After adding asteroids in the mix, only one asteroid is retrograde with a shorter orbital period, (343158) Marsyas, which coincidently is also at perihelion this month (T = 2024 November 29 at 0.49 au).
333P was discovered by the Lincoln Laboratory Near-Earth Asteroid Research (LINEAR) survey on 2007 November 4, about 4 months after perihelion when the comet was 17-18th magnitude. During its next return in 2016, 333P rapidly brightened from 20th magnitude 3 months before perihelion to a peak brightness 11th magnitude before dropping back to 19th magnitude 4 months after perihelion.
Assuming it follows the same brightness trend at the current apparition, the comet will only remain bright for a short while (brightening from around 13th magnitude on November 1 to about magnitude 10 at the end of the month before peaking around magnitude 9.7 in early December). Observations submitted to the Minor Planet Center suggest a current brightness of 14.5, so 333P may be running fainter than the prediction above. Then again, it is also possible that this low-activity comet has a low surface brightness gas coma that isn’t being adequately measured. In short, there is some uncertainty about how bright it will get.
During this return, 333P/LINEAR will be a morning object. Since it will be heading north through Leo (Nov 1-25), Ursa Major (25-28), and Canes Venatici (28-30), it is much better placed for observers in the northern hemisphere. Southern hemisphere observers will lose sight of it by mid-month. Even if the comet reaches 10th magnitude this month, it may be difficult to observe due to a large low-surface brightness coma.
Perihelion occurs on November 29 at 1.11 au and closest approach to Earth on December 9 at 0.54 au. Before its discovery, it made closer approaches (0.25 au in 1903, 0.38 au in 1929, 0.49 au in 1955, 0.22 au in 1973, and 0.43 au in 1998). In the future, it will pass 0.18 au from Earth in 2068.
Photo Opportunities
Nov 14 - 333P/LINEAR passes within 1.5 deg of Leo Triplet of galaxies (NGC 3623, 3627, 3628]
Nov 27 - 333P/LINEAR passes over 12th mag galaxy NGC 3994
Nov 29 - 333P/LINEAR passes 40’ from 10th mag galaxy NGC 4244
Nov 29 - 333P/LINEAR passes 1.5 deg from 11th mag galaxy NGC 4151
C/2024 G3 (ATLAS)
Discovered visually on 1812 July 12 by Jean-Louis Pons and rediscovered visually on 1883 September 2 by William R. Brooks
Dynamically old long-period comet
Orbit (from Minor Planet Center, MPEC 2024-U268)
C/2024 G3 (ATLAS)
Epoch 2024 Oct. 17.0 TT = JDT 2460600.5
T 2025 Jan. 13.42898 TT Rudenko
q 0.0935252 (2000.0) P Q
z -0.0000952 Peri. 108.12535 -0.04069055 +0.81534820
+/-0.0000034 Node 220.33878 +0.14761168 +0.57658088
e 1.0000089 Incl. 116.84643 +0.98820801 -0.05255281
From 271 observations 2024 Apr. 5-Oct. 28, mean residual 0".4.
1/a(orig) = +0.000335 AU**-1, 1/a(fut) = +0.000163 AU**-1.
Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)
C/2024 G3 (ATLAS) Max El
(deg)
Date R.A. Decl. r d Elong Const Mag 40N 40S
2024-Nov-01 14 53 -44 29 1.841 2.624 30E Lup 12.0 0 9
2024-Nov-06 15 02 -43 57 1.752 2.562 28E Lup 11.8 0 7
2024-Nov-11 15 11 -43 24 1.662 2.494 26E Lup 11.5 0 4
2024-Nov-16 15 21 -42 49 1.569 2.418 24M Lup 11.3 0 3
2024-Nov-21 15 31 -42 12 1.473 2.336 22M Lup 11.0 0 2
2024-Nov-26 15 42 -41 32 1.375 2.247 21M Lup 10.7 0 2
2024-Dec-01 15 54 -40 46 1.273 2.150 20M Lup 10.3 0 2
2024-Dec-06 16 06 -39 54 1.167 2.045 19M Lup 9.9 0 2
Comet Magnitude Formula (from ALPO and COBS data for the 1954 and 2023 returns)
m1 = 7.2 + 5 log d + 13.7 log r [Until T-120 days]
m1 = 3.5 + 5 log d + 22.2 log r [between T-120 days and T-85 days]
m1 = 7.8 + 5 log d + 8.0 log r [after T-85 days, assumed]
where “t” is date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au
2025 is looking to be a slow year for comet observers. One of the only comets expected to get bright is C/2024 G3 (ATLAS). Making matters even worse, G3 will be located very close to the Sun when bright and only visible from one hemisphere (the southern) when far enough from the Sun to be observed.
C/2024 G3 (ATLAS) was discovered on 2024 April 5 by the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program with one of their 0.5-m f/2 Schmidt reflector at Rio Hurtado, Chile. The comet was 4.6 au from the Sun at discovery and 18th magnitude. Perihelion will be on 2025 January 13, at a small distance of 0.09 au from the Sun. Usually, with such a small perihelion distance, we are concerned with the possibility of disintegration. While that is always a possibility, this comet appears to be dynamically old so it has likely made past close perihelia passages in the past.
Observations in late October show a rapidly brightening comet that is now around magnitude 12.0. Going forward, we are using a conservative 8 log r brightening rate, which brings the comet up to magnitude 10.3 at the end of the month. If it continues to brighten at a faster rate, it may be even brighter than the predictions here.
As mentioned above, G3 is only visible to southern hemisphere observers. Even then, it will be a low-elevation object in the evening sky until November 13, when it moves into the morning sky. All month long, its solar elongation drops from 31 degrees on the 1st to 20 degrees at the end of the month.
Looking forward to its January 13 perihelion, the comet will be at a small solar elongation of 5 degrees. Even though it may be as bright as 0th magnitude at the time, it will be much too close to the Sun to be observed from Earth. But luckily, we have the SOHO spacecraft and its coronagraph. G3 will be within the SOHO LASCO C3 coronagraph field of view from January 11 to 15.
