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ALPO Comet News for May 2024

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#1 Carl H.

Carl H.

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Posted 04 May 2024 - 07:11 PM

ALPO COMET NEWS FOR MAY 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://www.alpo-astr....org/cometblog/ 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://www.alpo-astronomy.org. We can also be reached at < comets @ alpo-astronomy.org >.

 

Summary

 

12P/Pons-Brooks reached its peak performance last month for northern hemisphere observers. The comet is still a 4th magnitude object as May begins but is only observable from the southern hemisphere, fading from 4th to 6th magnitude in the evening sky.

 

Northern observers currently have another Halley-type comet to themselves, as 13P/Olbers brightens from 8th to 7th magnitude in the evening sky. C/2023 A3 (Tsuchinshan-ATLAS) is observable by all in the evening sky as it continues brightening at 9th magnitude.

 

Two fainter objects between 10th and 12th magnitude are also visible. 479P/Elenin is having its best apparition in any of our lifetimes and should be at 10th to 11th magnitude in the evening sky. While in the morning sky, C/2021 S3 (PANSTARRS) is fading from 10th to 11th magnitude.

 

Last month, the ALPO Comets Section received 202 images and 109 magnitude estimates of 25 comets: C/2024 G1 (Wierzchos), C/2024 F2 (PANSTARRS), C/2024 C4 (ATLAS), C/2023 S3 (Lemmon), C/2023 A3 (Tsuchinshan-ATLAS), C/2022 L2 (ATLAS), C/2022 E2 (ATLAS), C/2021 S3 (PANSTARRS), C/2021 G2 (ATLAS), C/2020 S4 (PANSTARRS), C/2020 K1 (PANSTARRS), C/2019 U5 (PANSTARRS), C/2017 K2 (PANSTARRS), 479P/Elenin, 362P/(457175) 2008 GO98, 227P/Catalina-LINEAR, 144P/Kushida, 125P/Spacewatch, 65P/Gunn, 62P/Tsuchinshan, 37P/Forbes, 32P/Comas Sola, 29P/Schwassmann-Wachmann, 13P/Olbers, 12P/Pons-Brooks.

 

A big thanks to our recent contributors: Salvador Aguirre, Anthony Amato, Michael Amato, Dan Bartlett, Dan Crowson, Jose Guilherme de Souza Aguiar, J. J. Gonzalez Suarez, Christian Harder, Carl Hergenrother, Eliot Herman, Rik Hill, Michael Jäger, John Maikner, Gianluca Masi, Efrain Morales Rivera, Mike Olason, Uwe Pilz, Gregg Ruppel, Chris Schur, Greg T. Shanos, Willian Souza, Tenho Tuomi, and Chris 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 to digital observations. Though we try to keep these lightcurves up to date, observations submitted in the days 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 observations submitted directly to the ALPO and those submitted initially 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)

 

Apr 02 - Last Quarter Moon
Apr 08 - New Moon
Apr 15 - First Quarter Moon
Apr 23 - Full Moon

 

Comets at Perihelion

 

Apr 01 - 355P/LINEAR-NEAT [q = 1.71 au, 6.5-yr period, V ~ 17-18, discovered in 2004, missed at 2011 return, 4th observed return]
Apr 14 - 130P/McNaught-Hughes [q = 1.82 au, 6.2-yr period, V ~ 15, discovered in 1991, 6th observed return]
Apr 20 - 32P/Comas Sola [q = 2.02 au, 9.7-yr period, V ~ 13, discovered in 1926, seen at every return since discovery, 12th observed return, 1-4 mag outbursts well after perihelion in 1997 & 2006]
Apr 21 - 12P/Pons-Brooks [q = 0.78 au, 71-yr period, V ~ 4, discovered visually in 1812, visually rediscovered in 1883, also seen at returns in 1953, 1457, 1385 and perhaps 245 AD, known to experience multiple major outbursts including in the current return, more below]
Apr 22 - P/2023 X3 (PANSTARRS) [q = 3.03 au, 8.8-yr period, V ~ 21-22, first observed return]
Apr 24 - 267P/LONEOS [q = 1.34 au, 6.0-yr period, V ~ ??, discovered in 2006, will be 4th observed return]
Apr 25 - 212P/NEAT [q = 1.61 au, 7.7-yr period, V ~ 19-20, discovered in 2001, 4th observed return]
Apr 28 - C/2024 A2 (ATLAS) [q = 1.88 au, 184-yr period, V ~ 16-17]
Apr 30 - 299P/Catalina-PANSTARRS [q = 3.16 au, 9.2-yr period, V ~ 16, discovered in 2015, also seen at 1988 and 2006 returns, 4th observed return]

 

Photo Opportunities

 

Apr 08     - Will 12P/Pons-Brooks be observed or imaged during the Total Solar Eclipse?
Apr 10     - 12P/Pons-Brooks is close to 2-day old crescent moon
Apr 10-11  - C/2021 S3 (PANSTARRS) passes within 1 deg of 7th mag open cluster NGC 6834
Apr 13-14  - 12P/Pons-Brooks passes ~3 deg from Jupiter
Apr 19     - C/2021 S3 (PANSTARRS) passes within ~0.5 deg of 5th mag open cluster NGC 6871
Apr 23     - C/2021 S3 (PANSTARRS) passes within ~0.6 deg of the Crescent Nebula (NGC 6888)
Apr 30     - 13P/Olbers passes in front of the dark nebulosity (LBN 813) near the Little Flame Nebula (IC 2087)

 

Comets News

 

Looking Ahead to the Next 12 Months

 

The chart below shows those comets expected to become brighter than magnitude 10 in 2024. 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/2023 A3 (Tsuchinshan-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. Additionally, C/2023 A3 may be 1 or more magnitudes brighter than shown in early October due to forward scattering by dust.

 

Attached File  Comet Observability.pdf   33.6KB   42 downloads

 

Last 10 Periodic Comet Numberings (from WGSBN Bull. 4, #6)

 

483P/2016 J1    = P/2020 Y6 = P/2010 G7 (PANSTARRS)   MPC 171409

482P/PANSTARRS  = P/2014 VF_40 (PANSTARRS)            MPC 171409

481P/2012 WA_34 = P/2024 C5 (Lemmon-PANSTARRS)        MPC 171409

480P/2014 A3    = P/2023 X6 (PANSTARRS)               MPC 169139

479P/2011 NO1   = P/2023 WM26 (Elenin)                MPC 169139
478P/2023 Y3    = P/2017 BQ100 (ATLAS)                MPC 169139
477P/2018 P3    = P/2023 V8 (PANSTARRS)               MPC 169139
476P/2015 HG16  = P/2023 W2 (PANSTARRS)               MPC 169139
475P/2004 DO29  = P/2023 V7 (Spacewatch-LINEAR)       MPC 169139
474P/2023 S4    = P/2017 O4 (Hogan)                   MPC 169139

 

New Discoveries

 

C/2024 G3 (ATLAS) – The "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program found a new 18th magnitude comet on 2024 April 5 at 18th magnitude deep in the southern sky at a declination of -74 degrees. ATLAS used their 0.5-m f/2 Schmidt reflector at Rio Hurtado, Chile. C/2024 G3 has attracted a little excitement due to its very small perihelion distance of 0.094 au on 2025 January 13. While an 8 log r rate of brightening results in a peak brightness of magnitude 1.5 to 2.0 at perihelion, the comet will be at a solar elongation of only 5 degrees at the time. Adding to the bad news, the comet will never be visible from the northern hemisphere, and even from the southern hemisphere will not be visible against a dark sky until a week after perihelion when it will be significantly fainter at 7th magnitude. And that’s assuming that it isn’t a dynamically new comet, at which point its survival may be in question. Luckily, we have time to follow its development. [MPEC 2024-H22, CBET 5384]

 

C/2024 G2 (ATLAS) – The ATLAS program also found a new 18th magnitude comet on 2024 April 8 with a 0.5-m f/2 Schmidt reflector at Rio Hurtado, Chile. C/2024 G2 passes perihelion on 2025 June 13 at a large distance of 5.34 au. At that time, it should be near a peak brightness of 17th magnitude. [CBET 5383, MPEC 2024-H20]

 

C/2024 G1 (Wierzchos) – Kacper Wierzchos (University of Arizona) discovered this 20th magnitude long-period comet on 2024 April 7 with the 2.3-m Bok telescope on Kitt Peak. C/2024 G1 arrives at perihelion on 2024 October 22 at 3.93 au. It should peak at 19th magnitude during the middle months of 2024. [CBET 5381, MPEC 2024-H10]

 

C/2024 F2 (PANSTARRS) – Yudish Ramanjooloo (University of Hawaii) reported the discovery of a new Halley-type comet at 20-21st magnitude by the Pan-STARRS1 1.8-m on 2024 in March 21. C/2024 F2 arrives at perihelion on 2024 August 3 at 3.96 au. It should reach a peak brightness of 19th magnitude when at opposition in May. It has an orbital period of 31 years. [CBET 5380, MPEC 2024-G103]

 

P/2024 F1 (PANSTARRS) - Rob Weryk ( University of Western Ontario) reported the discovery of a new short-period comet at 20-21st magnitude by the Pan-STARRS1 1.8-m on 2024 March 18. P/2024 F1 has an orbital period of 6.4 years and a perihelion distance of 1.86 au. With perihelion back on 2023 October 25, the comet is already fading. [CBET 5379, MPEC 2024-G102]

 

P/2022 U6 = P/2006 AH2 (Sheppard-Tholen) – Back on 2023 January 24, David Tholen of the University of Hawaii reported the discovery of a new comet made on images taken on 2022 October 28 with the Subaru 8.2-m telescope on Mauna Kea. The comet was 22nd magnitude at the time. The new object was linked by the Minor Planet Center with a Mount Lemmon Survey discovery from 2006, asteroid 2006 AH2, which was 20th magnitude. The comet is currently in orbit with an orbital period of 17.9 years and perihelion back on 2023 August 24, at 3.99 au. [CBET 5387]

 

Comets Brighter than Magnitude 6

 

12P/Pons-Brooks

 

Discovered visually on 1812 July 12 by Jean-Louis Pons and rediscovered visually on 1883 September 2 by William R. Brooks
Halley-type comet

 

Orbit (from Minor Planet Center, MPEC 2024-H91)

 

  12P/Pons-Brooks                                                              
Epoch 2024 Mar. 31.0 TT = JDT 2460400.5                                        
T 2024 Apr. 21.12393 TT                                 Rudenko                
q   0.7807796            (2000.0)            P               Q                 
n   0.01381015     Peri.  198.98909     +0.14510792     -0.32930067            
a  17.2056264      Node   255.85588     +0.98566267     +0.13016969            
e   0.9546207      Incl.   74.19152     +0.08609757     -0.93520956            
P  71.4                                                                        
From 7735 observations 2023 Feb. 27-2024 Apr. 19, mean residual 0".6.          

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

12P/Pons-Brooks                                                 Max El
                                                                 (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag  40N  40S
2024-May-01  04 01  +02 50   0.804   1.595    24E   Tau   4.5    0    7
2024-May-06  04 18  -00 43   0.830   1.587    27E   Eri   4.8    0   10
2024-May-11  04 34  -04 15   0.866   1.577    30E   Eri   5.0    0   13
2024-May-16  04 51  -07 45   0.910   1.568    33E   Eri   5.3    0   15
2024-May-21  05 08  -11 12   0.959   1.559    36E   Lep   5.7    0   17
2024-May-26  05 25  -14 37   1.014   1.552    40E   Lep   6.1    0   19
2024-May-31  05 43  -17 57   1.072   1.548    43E   Lep   6.4    0   21
2024-Jun-05  06 02  -21 14   1.132   1.548    46E   Lep   6.7    0   23

 

Comet Magnitude Formula (from ALPO and COBS data for the 1954 and 2023 returns)

 

m1 =  6.8 + 5 log d + 11.6 log r [between T-684 and T-275 days]
m1 =  4.2 + 5 log d +  7.2 log r [between T-275 days and perihelion]
m1 =  5.0 + 5 log d + 15.5 log r [between perihelion and T+30 days]
m1 =  5.1 + 5 log d + 11.4 log r [after T+30 days]
where “t” is date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au

 

12P_202405_LC.jpg

 

On April 21st, 12P/Pons-Brooks finally arrived at perihelion at a distance of 0.78 au from the Sun. Prior to this, its last perihelion was 69.9 years ago, in May 1954. It will next be at perihelion in August 2095, 71.3 years from now.

 

Pons-Brooks started April as an object observable from the northern hemisphere and ended the month only observable from the southern hemisphere. Though, Mike Olason was still able to dig deep into the twilight sky to image Pons-Brooks as late a May 1 from near Tucson, Arizona.

 

Though the comet was located close to the horizon in April, many observers were able to image, sketch, and obtain brightness measurements. Its peak brightness appears to have been between magnitude 4.0 and 4.5, with a few observations coming in a little brighter. All observers found the comet to be moderately condensed, and many reported a tail. The longest visual tail measurements in ALPO data were over a degree in length, with Chris Wyatt reporting a 3-degree tail on April 29.

 

On the imaging side, Pons-Brooks continues to experience large outbursts. One that occurred between April 2 and 3, displayed an expanding shell that was tracked by imagers over the following week.

 

As has been the case for the past few months, Pons-Brooks is an evening object this month as it moves southward through Taurus (May 1-4), Eridanus (4-20), and Lepus (20-31). While not observable from the northern hemisphere, it is increasingly better placed for those south of the equator. Now past perihelion, it should fade from around magnitude 4.5 to 6.4 in May. The fading is slightly offset by a slowly decreasing Earth-comet distance, with the minimum of 1.55 au being reached on June 2.

 

Photo Ops:
May 17-18 - 12P/Pons-Brooks crosses the Witch Head Nebula

 

Comets Between Magnitude 6 and 10

 

13P/Olbers

 

Discovered visually on 1815 March 6 by Heinrich Olbers in Bremen, Germany
Halley-type comet

 

Orbit (from Minor Planet Center, MPEC 2024-H91)

 

  13P/Olbers                                                                   
Epoch 2024 Mar. 31.0 TT = JDT 2460400.5                                        
T 2024 June 30.04758 TT                                 Rudenko                
q   1.1755818            (2000.0)            P               Q                 
n   0.01420581     Peri.   64.41099     -0.60849100     -0.37170348            
a  16.8846472      Node    85.84642     +0.18565977     -0.92567825            
e   0.9303757      Incl.   44.66583     +0.77153688     -0.07040106            
P  69.4                                                                        
From 1281 observations 2023 Oct. 8-2024 Apr. 23, mean residual 0".4.           
     Nongravitational parameters A1 = +2.92, A2 = +1.4453.                     

 

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-May-01  04 38  +26 31   1.479   2.243    31E   Tau   8.4   11    0
2024-May-06  04 51  +28 22   1.436   2.222    29E   Tau   8.1   10    0 
2024-May-11  05 04  +30 11   1.396   2.199    28E   Aur   7.9    9    0 
2024-May-16  05 18  +31 59   1.358   2.175    27E   Aur   7.7    8    0 
2024-May-21  05 34  +33 43   1.322   2.149    26E   Aur   7.5    7    0 
2024-May-26  05 51  +35 23   1.290   2.121    26E   Aur   7.3    7    0 
2024-May-31  06 09  +36 58   1.261   2.093    25E   Aur   7.1    7    0 
2024-Jun-05  06 28  +38 25   1.236   2.065    25E   Aur   6.9    7    0 

 

Comet Magnitude Formula (from 1956 ICQ and 2023 ALPO data)

 

m1 = -1.4 + 5 log d + 33.6 log r [Up through T-110 days]
m1 =  3.5 + 5 log d + 15.1 log r (T – 14) [After T-110 days]
where “T” is date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au

 

13P_202405_LC.jpg

 

With Pons-Brooks departing the northern sky, those of us north of the equator have two other brightening comets to watch in the evening. The first is, like 12P/Pons-Brooks, a returning Halley-type comet. 13P/Olbers was discovered in 1815 when it reached 5th magnitude. A peak of 6-7th magnitude was reached at the next two returns, in 1887 and 1956. In 1887 it was re-discovered by Brooks, which brings up the question of why Olbers and not Olbers-Brooks. This year, Olbers arrives at perihelion on June 30 at 1.18 au, though it will come no closer to the Earth than 1.90 au (on July 20).

 

As of late April, Olbers has been consistently brighter than expected based on its last return in 1956. If this continues, it may reach a peak brightness of 6th magnitude rather than the expected 7th magnitude. By taking its photometric index (15.1 log r) and seasonal offset (brightest 14 days after perihelion) and scaling it to its current brightness, we predict that Olbers will start May around magnitude 8.4 and brighten to around magnitude 7.1 by the end of May. Visual observers have reported a small 1-3’ coma with slight to moderate condensation (DC = 3 to 5.5). Images are already showing the development of a dust tail and an even longer and dynamic gas tail.

 

Like Pons-Brooks during the first half of April, Olbers will be an evening object at low elevations for northern observers. It won’t be visible in May to those in the southern hemisphere. Its path through Taurus (May 1-6) and Auriga (6-31) will also pass through some cluster and nebula-rich star fields in Auriga on May 17-22.

 

Photo Op:
May 17-22 - 13P/Olbers passes through a crowded deep space field in Auriga that contains the Flaming Star and other nebula as well as open star clusters M36 and NGC 1893

 

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-H91)

 

    C/2023 A3 (Tsuchinshan-ATLAS)                                              
Epoch 2024 Mar. 31.0 TT = JDT 2460400.5                                        
T 2024 Sept. 27.74025 TT                                Rudenko                
q   0.3914539            (2000.0)            P               Q                 
z  -0.0002889      Peri.  308.48919     +0.36137961     +0.90086013            
 +/-0.0000056      Node    21.55942     +0.91855592     -0.29963956            
e   1.0001131      Incl.  139.11291     -0.16018677     +0.31411329            
From 3446 observations 2022 Apr. 9-2024 Apr. 29, mean residual 0".4.           
1/a(orig) = -0.000231 AU**-1, 1/a(fut) = -0.000203 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-May-01  13 22  -00 50   2.765   1.807   157E   Vir   9.9   49   51
2024-May-06  13 08  -00 06   2.696   1.777   149E   Vir   9.8   50   50
2024-May-11  12 55  +00 34   2.628   1.760   141E   Vir   9.7   50   50
2024-May-16  12 41  +01 11   2.558   1.754   133E   Vir   9.6   51   49
2024-May-21  12 28  +01 43   2.488   1.758   125E   Vir   9.5   51   48
2024-May-26  12 16  +02 10   2.416   1.771   117E   Vir   9.4   49   48
2024-May-31  12 04  +02 31   2.344   1.790   110E   Vir   9.3   45   48
2024-Jun-05  11 54  +02 47   2.271   1.815   103E   Vir   9.2   41   47

 

Comet Magnitude Formula (from ALPO, COBS, and MPC data)

 

m1 = -16.6 + 5 log d + 35.0 log r [Through T-650 days]
m1 =   3.6 + 5 log d + 11.3 log r [Between T-650 and T-150 days]
m1 =   5.1 + 5 log d +  8.0 log r [After T-150 days, assumed]
where “t” is the date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au

 

C2023A3_202405_LC.jpg

 

With 12P/Pons-Brooks now past perihelion and invisible from northern skies, the attention of many is shifting to the next comet with a reasonable chance of becoming a bright object. C/2023 A3 (Tsuchinshan-ATLAS) is a little less than 5 months from its September 27 perihelion at 0.39 au. It is currently at 10th magnitude and should brighten to 9th this month. It will be observable in the evening sky till mid-July in the northern hemisphere (at 8th mag) and mid-August in the southern hemisphere (at 6-7th mag). We will then lose sight of it, at least from the ground against a dark sky, until early October, when it will pass nearly between the Earth and the Sun, possibly resulting in a few magnitudes of increased brightness due to forward scattering by dust in its tail and coma. After that, it rockets higher into the evening sky as it fades.

 

Tsuchinshan-ATLAS is a dynamically new long-period comet, presumably making its first pass through the inner solar system. This fact raises a number of red flags. Dynamically new comets are usually observed to be bright when far from the Sun as supervolatile ices sublimate, resulting in a large release of dust. As a result of this “head fake,” predictions based on their brightness when far from the Sun result in a brightness at perihelion that is too bright. These comets also have a habit of brightening at a slow rate as they get closer to perihelion or, in the worst case, completely disintegrating. History is full of examples of dynamically new comets that disappointed, like C/1973 E1 (Kohoutek), C/1989 X1 (Austin), and C/2012 S1 (ISON).

 

The lightcurve above is based on total magnitude photometry submitted to the ALPO as well as digital photometry submitted to the COBS site by Thomas Lehmann. Between early 2023 and late April, Tsuchinshan-ATLAS has been brightening at a healthy rate of 11.3 log r. This is unlikely to continue to perihelion, and many comets, like ISON and Austin, experienced episodes of slower brightening or even intrinsic fading. As if on cue, as I was working on this write-up, Thomas Lehmann and Nick James reported in comets-ml that photometry of the inner coma is showing a decrease in brightness (see this BAA lightcurve).

 

This doesn’t mean the comet is falling apart, at least not yet, but as was the case with other dynamically new comets, it has entered a period of decreased dust and gas production. Since the Lehmann and BAA photometry measures the region near the nucleus, it is much more sensitive to short-term changes than measurements that involve the entire coma, like visual observations. The reason is that dust may only take hours or days to leave a small photometric aperture, while measurements of the entire coma are detecting dust that was released days to weeks or even months ago. If its production continues to decrease, then eventually, the brightness of the total coma will increase at a slower rate or even fade. For now, the predicted magnitudes in the above ephemerides assume an 8 log r rate of brightening.

 

This month, Tsuchinshan-ATLAS is in the evening sky in Virgo. The 8 log r rate has it brightening from around magnitude 9.9 on May 1 to 9.3 on June 1.

 

Comets Between Magnitude 10 and 12

 

479P/Elenin

 

Discovered digitally on 2011 July 7 by Leonid Elenin and I. Molotiv with a remote telescope in Mayhill, NM, USA

Short-period comet

 

Orbit (from Minor Planet Center, MPEC 2022-H91)

 

479P/Elenin                                                                   
Epoch 2024 Mar. 31.0 TT = JDT 2460400.5                                        
T 2024 May 5.24421 TT                                   Rudenko                
q   1.2437077            (2000.0)            P               Q                 
n   0.07392503     Peri.  263.52483     -0.91135992     +0.33512619            
a   5.6226587      Node   295.83397     -0.18492596     -0.85207958            
e   0.7788043      Incl.   15.39787     -0.36773018     -0.40205824            
P  13.3                                                                        
From 831 observations 2011 June 12-2024 Apr. 27, mean residual 0".5.           

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

479P/Elenin                                                     Max El
                                                                 (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag  40N  40S
2024-May-01  08 46  -14 55   1.245   0.621    96E   Hya  10.5   25   64 
2024-May-06  09 01  -16 32   1.244   0.621    96E   Hya  10.5   23   66
2024-May-11  09 17  -18 10   1.246   0.622    96E   Hya  10.5   20   68
2024-May-16  09 35  -19 48   1.252   0.624    97E   Hya  10.6   17   69
2024-May-21  09 54  -21 22   1.262   0.629    97E   Hya  10.7   15   71
2024-May-26  10 14  -22 53   1.275   0.636    98E   Hya  10.8   13   73
2024-May-31  10 36  -24 16   1.292   0.647    99E   Hya  11.0   11   74
2024-Jun-05  10 59  -25 31   1.311   0.661   100E   Hya  11.2   10   76

 

Comet Magnitude Formula (from Seiichi Yoshida)

 

m1 =  9.5 + 5 log d + 21.7 log r
where “t” is date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au

 

479P_202405_LC.jpg

 

Here is an example of a relatively obscure short-period comet. 479P/Elenin was a CCD discovery by Leonid Elenin and I. Molotov at 19th magnitude in July 2011 with the ISON-NM 0.45-m f/2.8 astrograph near Mayhill, New Mexico. Since the comet was found nearly 7 months after perihelion, it was never observed at its brightest in 2011.

 

479P/Elenin is the discoverer of six comets, the other five comets were the disintegrated C/2010 X1 (Elenin), P/2014 X1 (Elenin), P/2015 PD229 (Cameron-ISON), C/2015 X4 (Elenin), and C/2017 A3 (Elenin).

 

2024 marks 479P’s second observed return on its 13.3-year orbit, with the closest approach to Earth on May 4 at 0.62 au and perihelion on May 5 at 1.24 au. The comet has an interesting orbit. While its inclination isn’t very large at 15 degrees, the orbit is aligned in such a way that its perihelion is near its furthest point below the ecliptic (the plane of the planets), and its aphelion is near its furthest point above the ecliptic. As a result, approaches within 0.9 au of Jupiter are not possible, at least between 1900 and 2100. As a result, 479P has been in a similar orbit for many decades now. Surprisingly, though it can come within 0.38 au of Earth, it has had few good apparitions, with the last return better than 2024 back in 1903 (0.47 au from Earth).

 

This month, Elenin should be a diffuse, gassy 10th-magnitude comet in the evening sky. Though the ephemeris above shows the comet staying within the constellation of Hydra all month, remember that Hydra is the longest constellation at over 100 degrees long. Elenin will be moving along the length of Hydra for the next few months. With no better apparitions predicted before 2100, this may be our only chance to see 479P in a small aperture telescope.

 

C/2021 S3 (PANSTARRS)

 

Discovered 2021 September 24 by PANSTARRS with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala
Long-period comet

 

Orbit (from Minor Planet Center, MPEC 2024-H91)

 

    C/2021 S3 (PANSTARRS)                                                      
Epoch 2024 Mar. 31.0 TT = JDT 2460400.5                                        
T 2024 Feb. 14.71121 TT                                 Rudenko                
q   1.3202167            (2000.0)            P               Q                 
z  -0.0002143      Peri.    6.85469     -0.77078804     +0.39887556            
 +/-0.0000009      Node   215.62123     -0.61750354     -0.65961195            
e   1.0002829      Incl.   58.53303     -0.15676470     +0.63703246            
From 1584 observations 2020 Dec. 6-2024 Apr. 29, mean residual 0".5.           
1/a(orig) = +0.000143 AU**-1, 1/a(fut) = +0.000058 AU**-1.

 

Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

C/2021 S3 (PANSTARRS)                                           Max El
                                                                 (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag  40N  40S
2024-May-01  20 19  +42 60   1.726   1.542    82M   Cyg  10.7   63    6 
2024-May-06  20 24  +45 43   1.772   1.585    83M   Cyg  10.8   64    4
2024-May-11  20 29  +48 14   1.819   1.628    83M   Cyg  10.9   65    1
2024-May-16  20 32  +50 32   1.866   1.672    84M   Cyg  11.0   66    0
2024-May-21  20 35  +52 38   1.915   1.716    84M   Cyg  11.1   67    0
2024-May-26  20 36  +54 32   1.964   1.760    85M   Cyg  11.2   68    0
2024-May-31  20 36  +56 15   2.014   1.804    86M   Cyg  11.4   68    0
2024-Jun-05  20 35  +57 46   2.065   1.847    87M   Cyg  11.5   69    0

 

Comet Magnitude Formula (from ALPO and COBS data)

 

m1 =  8.0 + 5 log d +  5.6 log r (T + 32)[pre-T]
Where “t” is the date of perihelion, “d” is Comet-Earth distance in au, and “r” is Comet-Sun distance in au.

 

C2021S3_202405_LC.jpg

 

Most of the recent action has been in the evening sky, and May will be no different. Still, there has been one relatively bright comet in the morning sky: C/2021 S3 (PANSTARRS). Discovered nearly three years ago with observations going back to December 2020, C/2021 S3 has been an odd comet. Its lightcurve has been fairly steady for almost two years but brightened at an extremely slow rate. It will be interesting to see if it will fade at a slow rate as well.

 

This month, it will be a northern object in Cygnus in the morning sky, fading from around magnitude 10.7 to 11.4. With an orbit plane crossing at the end of April, imagers have been following the development of a neckline and long straight tail.

 

Fainter Comets of Interest

 

29P/Schwassmann-Wachmann

 

Discovered 1927 November 15 by Arnold Schwassmann and Arno Arthur Wachmann at the Hamburg Observatory in Bergedorf, Germany
Centaur comet with orbital period of ~14.9 years

 

Orbit (from Minor Planet Center, MPEC 2024-H50)

 

  29P/Schwassmann-Wachmann                                                     
Epoch 2024 Mar. 31.0 TT = JDT 2460400.5                                        
T 2019 May 2.75161 TT                                   Rudenko                
q   5.7859627            (2000.0)            P               Q                 
n   0.06618423     Peri.   51.95355     +0.98936628     -0.08207065            
a   6.0529402      Node   312.40588     +0.01231221     +0.86988468            
e   0.0441071      Incl.    9.35915     +0.14492332     +0.48637953            
P  14.9                                                                        
From 19004 observations 2018 June 18-2024 Apr. 20, mean residual 0".6.        
 
                                                                               
Ephemerides (produced with Seiichi Yoshida’s Comets for Windows program)

 

29P/Schwassmann-Wachmann                                         Max El
                                                                  (deg)
    Date      R.A.   Decl.     r       d    Elong  Const  Mag   40N  40S
2024-May-01  08 10  +20 34   6.198   6.303    79E   Cnc  12-14  47   28
2024-May-06  08 11  +20 25   6.199   6.383    75E   Cnc  12-14  42   27
2024-May-11  08 13  +20 15   6.201   6.461    70E   Cnc  12-14  37   26
2024-May-16  08 16  +20 05   6.202   6.536    66E   Cnc  12-14  32   25
2024-May-21  08 18  +19 54   6.203   6.610    62E   Cnc  12-14  28   24
2024-May-26  08 21  +19 42   6.204   6.680    58E   Cnc  12-14  23   23
2024-May-31  08 24  +19 29   6.206   6.748    53E   Cnc  12-14  18   21
2024-Jun-05  08 27  +19 16   6.207   6.812    49E   Cnc  12-14  14   20

 

Large Centaur comet 29P/Schwassmann-Wachmann is an object in a class of its own. While 12P/Pons-Brooks has experienced several multi-magnitude outbursts over the past few months, 29P has several multi-magnitude outbursts almost every year. What is even more amazing is that it currently never gets closer to the Sun than 5.79 au, that’s just beyond Jupiter.

 

The BAA Comet Section is coordinating a monitoring program called Mission 29P ( https://britastro.org/node/18562 & https://britastro.org/node/25120 ). Mission 29P reported 5 new outbursts in April. Four minor ones on April 6, 14, 17, and 30, and a moderate one on April 20.

 

29P is nicely placed in the constellation of Cancer in the evening sky this month.

 

 

 


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#2 h2ologg

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Posted 04 May 2024 - 10:07 PM

My favorite periodical!  Read it line by line. Thank you Carl!


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#3 Carl H.

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Posted 06 May 2024 - 05:57 PM

My favorite periodical!  Read it line by line. Thank you Carl!

Thanks for the kind words, Dan!

 

And thanks to everyone who has sent words of encouragement and observations over the past few years.

 

I'll have to admit it can be difficult to find the time and energy to write these, so your encouraging words and observations are very much appreciated.


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#4 Krish123

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Posted 08 May 2024 - 07:33 AM

I love this summery!!! I am new here and to astronomy (with a telescope, I love reading on astronomy and astrophysics) in general

but honestly I'm kind of expecting C/2024 G3 (ATLAS) to be a dud. It has a very small nucleus size and would probably disintegrate at around 0.5 AU or more but it could be like the comet NEAT in 2003 so I have low expectations but still expectations the one I am most excited about is tsuchinshan-ATLAS with perihelion at 0.39 AU and a somewhat large neucleus Do you agree?



#5 happylimpet

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Posted 08 May 2024 - 07:56 AM

Thanks for the kind words, Dan!

 

And thanks to everyone who has sent words of encouragement and observations over the past few years.

 

I'll have to admit it can be difficult to find the time and energy to write these, so your encouraging words and observations are very much appreciated.

It's much appreciated. While Im generally aware of the cometary headlines, to have such a thorough and yet concise wrap-up is invaluable. Thanks Carl!


Edited by happylimpet, 08 May 2024 - 07:56 AM.


#6 Octans

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Posted 08 May 2024 - 08:53 PM

I suspect 8 log r is probably a bit too high for C/2023 A3 for the next few months as a visually dusty dynamically new comet, which tend to be closer to ~5 log r as they approach ~1 au after correcting for phase angle/backscattering. A good comparison I've been drawing attention to since discovery is comet Arend-Roland, which is dynamically new like C/2023 A3 and had very similar viewing geometry over its entire apparition. As it turns out, C/2023 A3 is now looking fairly similar in intrinsic brightness to Arend-Roland, so we should get a reasonable idea of C/2023 A3 may look like by just looking through observation reports of Arend-Roland.

 

At its discovery at r=2.8 au near opposition (equivalent to C/2023 A3 in mid-late April), it was reported at mag ~10, but the first follow up observations a couple weeks later at r~2.6 au (comparable to C/2023 A3 right now in early May) had the comet a little fainter at mag ~11 (possibly due to moving away from opposition/to higher phase angle). Brightness was pretty much flat for the next couple months, inching back up slightly to mag ~10 at r~1.8 au (C/2023 A3 in late June/early July), with a gradual brightening to mag ~8 when it disappeared into evening twilight at r~1.0 au (C/2023 A3 in mid-August). It then reappeared in the morning sky at mag ~2-3 near perihelion (C/2023 A3 in late September), but brightened to mag ~1 in twilight thanks to forward scattering (C/2023 A3 in mid-October) as it swung back into the evening sky to make its famous display.

 

The usual caveats with comet predictions still apply as different comets vary in their behavior, but Arend-Roland brightened fairly typically for a dynamically new comet, quite similarly in fact to other, less impressive examples like Kohoutek and the more recent C/2011 L4 (which had relatively unfavorable orbits compared to Arend-Roland and C/2023 A3), so I'd regard the summary of Arend-Roland's brightening above should serve as a reasonable nominal case for C/2023 A3's brightness in the months ahead, and likely much closer to reality than a simple power law extrapolation. Note, however, that Arend-Roland's perihelion was ~19% closer to the Sun, so C/2023 A3 may not be quite as bright near perihelion in late September; however, C/2023 A3 also reaches much higher phase angles and stays there for longer in the evening sky while closer to Earth, which I expect will more than compensate for its slightly more distant perihelion.

 

Note that one interesting fact about Arend-Roland's famously long and sharp antitail is that it was what's called a neck-line structure made up of dust grains released months earlier while the comet was on the opposite side of the Sun that were focused back into the comet's orbital plane by the Sun's gravity. That means as long as C/2023 A3 keeps up with Arend-Roland's brightening through August, we are essentially guaranteed an Arend-Roland-class antitail because basically all the dust making up that antitail will have already been released by then, and nothing the comet does afterward will make a significant difference to that antitail.


Edited by Octans, 08 May 2024 - 09:35 PM.

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#7 happylimpet

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Posted 09 May 2024 - 03:46 AM

Note that one interesting fact about Arend-Roland's famously long and sharp antitail is that it was what's called a neck-line structure made up of dust grains released months earlier while the comet was on the opposite side of the Sun that were focused back into the comet's orbital plane by the Sun's gravity. That means as long as C/2023 A3 keeps up with Arend-Roland's brightening through August, we are essentially guaranteed an Arend-Roland-class antitail because basically all the dust making up that antitail will have already been released by then, and nothing the comet does afterward will make a significant difference to that antitail.

Will we be close to the comet's orbital plane though? Thats a very specific requirement for a good anti-tail isnt it?



#8 Octans

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Posted 09 May 2024 - 02:13 PM

Will we be close to the comet's orbital plane though? Thats a very specific requirement for a good anti-tail isnt it?

Yes, we will cross the orbital plane on October 14, so that will be a date to mark your calendar for. On that date, the dust tail will actually be pointed almost directly at Earth, so the upward-pointing "normal" tail will actually appear fairly short/stubby (up to ~2-3 degrees), which might give the comet a bit of an odd appearance with a long, sharp, antitail pointing downward toward the Sun. It's fairly unlikely the ion tail will be bright enough to be visible at this point, but on the off chance it somehow is, it'll also be pointed almost straight at Earth (Earth may actually cross through, or at least graze the edge of the tail around this time, depending on the behavior of the solar wind), so could look quite interesting and potentially even appear to point toward the Sun. However, if the comet brightens similarly to Arend-Roland and most other bright dynamically new comets, the "normal" dust tail will very rapidly grow out to ~20-30 degrees by October 19-20 just in time for the Moon to go away, so that's another date to mark your calendar for. The main tail will have substantially dropped in surface brightness and the antitail won't be quite as sharp by that point, but both may still be decently visible, and possibly even more so with the darker skies than during the actual orbital plane crossing a few days earlier (at least if observing far from city lights). Due to the dust tail curving toward Earth during this post-perihelion evening apparition, the comet should appear considerably more impressive than an average comet of its magnitude, whatever its magnitude turns out to be.


Edited by Octans, 09 May 2024 - 02:40 PM.

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#9 Krish123

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Posted 10 May 2024 - 07:42 AM

Who here is very excited for tsuchinshan atlas; I know, everyone, I ran through all the parameters and calculated that yes, It Is most likely to become great, here is why

 

 

"New" comets typically display lots of activity far from the sun, becoming bright at the orbit of like, Jupiter and then fail to deliver during and after perihelion C/2023 A3 is displaying activity ( tsuchinshan-ATLAS is just 1 AU out of mars orbit and is only mag 10 ), but not as much, I feel that this comet is a returning visitor or has an interstellar origin

 

Also, Lets talk about the orbit, This comets path is clearly stated and not hyperbolic ( it may only turn weakly hyperbolic because of gravitational disturbances )  but this comet seems to  have a clearly defined path and not something like C/2021 S3 where it is a new comet is getting a orbit just now, It came below the solar plane and now spends most of it's time above it ( also, this comet is hyperbolic but under non-Hyperbolic parameters it gets a completely new orbit).

 

Hope this contributes!



#10 columbidae

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Posted 10 May 2024 - 04:02 PM

Love the report too, but the comet calendar is still showing April dates.

 

As for C/2023 A3, "we will be watching your career with great interest."



#11 Carl H.

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Posted 11 May 2024 - 02:49 PM

Love the report too, but the comet calendar is still showing April dates.

 

As for C/2023 A3, "we will be watching your career with great interest."

Thanks for catching that. Here's the correct info.

 

Lunar Phases (UTC)

 

May 01 - Last Quarter Moon
May 08 - New Moon
May 15 - First Quarter Moon
May 23 - Full Moon
May 30 - Last Quarter Moon

 

Comets at Perihelion
 

May 01 - 478P/ATLAS [q = 2.39 au, 7.0-yr period, V ~ 17, discovered in 2017, this is its 2nd observed return]
May 05 - 479P/Elenin [q = 1.24 au, 13.3-yr period, V ~ 10-11, discovered in 2011, this is also its 2nd observed return]
May 10 - 133P/Elst-Pizarro [q = 2.67 au, 5.6-yr period, V ~ 20, Main-Belt Comet, discovered in 1996, seen back to 1979, usually inactive but can show activity at and after perihelion]
May 12 - 50P/Arend [q = 1.92 au, 8.3-yr period, V ~ 17, discovered in 1951, seen at every return after perihelion, 10th observed return]
May 12 - 222P/LINEAR [q = 0.78 au, 4.8-yr period, V ~ 16, discovered in 2004, will be 5th observed return]
May 17 - 202P/Scotti [q = 3.07 au, 8.4-yr period, V ~ 20, discovered in 2001, also seen back in 1930, 5th observed return]
May 19 - 46P/Wirtanen [q = 1.05 au, 5.4-yr period, V ~ 10 though located to close to the Sun for observation, discovered in 1947, seen at every return since discovery except at 1980 return, 13th observed return, ~3 mag outburst in 2002, reached 4th mag during very close approach to Earth in 2019]
May 22 - P/2023 T1 (PANSTARRS) [q = 2.82 au, 8.7-yr period, V ~ 20, first observed return]
May 24 - 192P/Shoemaker-Levy [q = 1.46 au, 16.4-yr period, V ~ 14, discovered in 1990, 3rd observed return]
May 24 - C/2023 X4 (Hogan) [q = 3.66 au, V ~ 19]
May 27 - 349P/Lemmon [q = 2.51 au, 6.8-yr period, V ~ 17-18, discovered in 2010, 3rd observed return]
May 30 - C/2023 V4 (Camarasa-Duszanowicz) [q = 1.12 au, V ~ 12]

 

Photo Opportunities
May 17-18 - 12P/Pons-Brooks crosses the Witch Head Nebula
May 17-22 - 13P/Olbers passes through a crowded deep space field in Auriga that contains the Flaming Star and other nebula as well as open star clusers M36 and NGC 1893

 

The pdf at https://alpo-astrono...Comet-News/2024 also has the correct dates.



#12 emh52

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Posted 11 May 2024 - 08:01 PM

Kind of a different comet photo op not expected  I set my Vixen VSD for comet 13P and would have never thought an epic aurora would squelch the green comet but it did and in Tucson Arizona fading light !  Given how rare seeing an aurora in AZ, this is likely a once in a lifetime image.

 

May 10, 2024

 

 

https://flic.kr/p/2pQA3FF

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  • redo comet and aurora for CN ES etc.jpg

Edited by emh52, 11 May 2024 - 10:32 PM.

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#13 emh52

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Posted 15 May 2024 - 10:09 AM

13P plus minus aurora

 

https://flic.kr/p/2pQwjoE

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#14 Octans

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Posted 17 May 2024 - 02:08 AM

Also of note is we're rapidly approaching the orbital plane of 12P, and will cross it on June 7. As 12P is now well post-perihelion, that means a substantial amount of its pre-perihelion dust has had the chance to be focused into a flat sheet on the orbital plane as what's called a neck-line structure, which looks like it's already starting to appear in recently posted images as a sunward-pointing stripe lagging behind the comet (as opposed to its main dust tail that keeps pointing away from the Sun). As we approach June 7, this stripe will become sharper and sharper until it turns into a long, thin spike (quite possibly much longer than the main dust tail) pointing straight toward the Sun on that date when we view it perfectly edge on, after which it will again become increasingly diffuse and fade away. This will not be a diffuse (and in my opinion, rather unimpressive) antitail like that of C/2022 E3 where the orbital plane crossing was too early for much pre-perihelion dust to be focused back onto the orbital plane, but a far more prominent/sharper feature closer in appearance to (but likely not quite as bright as) that of C/2011 L4 in May of 2013, with which 12P shares somewhat similar observing geometry. This event (though largely limited to southern observers) should provide a nice preview of the equivalent (but likely brighter) structure of C/2023 A3 on/around October 14.


Edited by Octans, 17 May 2024 - 02:20 AM.

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#15 BrooksObs

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Posted 19 May 2024 - 10:38 AM

Who here is very excited for tsuchinshan atlas; I know, everyone, I ran through all the parameters and calculated that yes, It Is most likely to become great, here is why

 

 

"New" comets typically display lots of activity far from the sun, becoming bright at the orbit of like, Jupiter and then fail to deliver during and after perihelion C/2023 A3 is displaying activity ( tsuchinshan-ATLAS is just 1 AU out of mars orbit and is only mag 10 ), but not as much, I feel that this comet is a returning visitor or has an interstellar origin

 

Also, Lets talk about the orbit, This comets path is clearly stated and not hyperbolic ( it may only turn weakly hyperbolic because of gravitational disturbances )  but this comet seems to  have a clearly defined path and not something like C/2021 S3 where it is a new comet is getting a orbit just now, It came below the solar plane and now spends most of it's time above it ( also, this comet is hyperbolic but under non-Hyperbolic parameters it gets a completely new orbit).

 

Hope this contributes!

 

I would strongly urge observers to curtail any excessive excitement concerning this object. Both visual and CCD photometric data of C/2023 A3 shows that over the course of the past 4-5 weeks the comet's total and inner condensation magnitude has essentially stabilized, then slowly but steadily decreased. Such a situation is common among dynamically 'new' comets near the "waterline' point in their orbits as they approach the Sun. The decline in visual brightness currently amounts to just about one full magnitude when corrected for shrinking geocentric distance, while that of the CCD data is essentially twice the amount.

 

Whether this trend continues will govern both the comet's heliocentric total magnitude (Ho) as well as the degree in the activity (less than n=3, instead of n=4 or better) will affect the comet's ultimate display later this year. However, while the latest assumed value of Ho still seems sufficient to allow the comet to easily survive perihelion passage, even considering potential forward scattering near perihelion (itself dependent on actual dust particle size), the comet may well be significantly fainter than presently projected during mid to late October to something far less than a highly spectacular display. We should hopefully have a better handle on what is likely to be the case by late August or early September..

 

BrookObs


Edited by BrooksObs, 19 May 2024 - 10:50 AM.

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#16 Zorbathegeek

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Posted 26 May 2024 - 05:31 PM

Well, 12P has certainly shown me how little I know about comets. I was in the southern hemisphere (where I live) when 12P was in the north. Then I had to go to the northern hemisphere as 12P became a southern hemisphere object. I'm now back home, and last night was my first chance to observe 12P. With observations around 5.7 to 6.0 magnitude, I didn't think my prospects would be at all good from my city center home. However, I was extremely pleased that, not only was it an easy find, but I was able to locate the comet during civil twilight. Very happy here.


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