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C/2023 A3 (Tsuchinshan–ATLAS)

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C/2023 A3 (Tsuchinshan–ATLAS)
Comet C/2023 A3 (Tsuchinshan–ATLAS) on 28 September 2024
Discovery
Discovered byPurple Mountain Observatory
ATLAS South Africa
Discovery date9 January 2023[1]
Designations
C/2023 A3
A10SVYR
Orbital characteristics[4]
Observation arc1.37 years (502 days)
Earliest precovery date9 April 2022
Number of
observations		2060
Aphelion90000+ AU (inbound)[2]
Perihelion0.3914 AU (58.6 million km)[3]
Eccentricity0.999992 (epoch 1800)[2]
1.000008 (epoch 2200)
Orbital periodmillions of years (inbound)[2]
possible ejection (outbound)
Max. orbital speed67.33 km/s @ perihelion[3]
Inclination139.1°
21.56°
Argument of
periapsis		308.5°
Next perihelion27 September 2024 18:00 ± 20 minutes (3-sigma)[3][4]
Earth MOID0.275 AU (41.1 million km; 107 LD)[4]
Comet total
magnitude (M1)		4.3 ± 0.3[4]
Comet nuclear
magnitude (M2)		9.2 ± 0.3[4]

C/2023 A3 (Tsuchinshan–ATLAS) is a comet from the Oort cloud discovered by the Purple Mountain Observatory in China on 9 January 2023 and independently found by ATLAS South Africa on 22 February 2023. The comet passed perihelion at a distance of 0.39 AU (58 million km; 36 million mi) on 27 September 2024,[1][3] when it became visible to the naked eye.[5][6]

Observational history

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Discovery

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Images of comet C/2023 A3 (Tsuchinshan–ATLAS) obtained on 2023-02-24 at remote telescopes by amateur astronomer

During the search performed by the Asteroid Terrestrial-impact Last Alert System using the 0.5-m f/2 Schmidt reflector at the Sutherland Observatory in South Africa an asteroidal object with an estimated magnitude of 18.1 was detected in images taken on 22 February 2023, when the comet was about 7.3 AU (1.09 billion km; 680 million mi) from the Sun.[7] After the first orbit calculations it was noticed that it was the same as an 18.7 magnitude object reported to the Minor Planet Center by the Purple Mountain Observatory that was detected in images taken on 9 January 2023. It was entered in the objects awaiting confirmation list but after no follow up observations were reported, it was removed in 30 January 2023 and was considered lost.[7] Based on the naming conventions of comets, the comet received the name of both observatories.[7]

The object was subsequently detected in images taken by the Zwicky Transient Facility (ZTF) in Palomar Observatory on 22 December 2022, when it had a magnitude of 19.2–19.6. These images also revealed it had a very condensed coma and a small straight tail 10" in length, indicating it was a comet.[1] More evidence of cometary activity was reported by Hidetaka Sato, M. Mattiazzo, and Cristóvão Jacques.[7]

Towards perihelion

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A time-lapse of comet C/2023 A3 (Tsuchinshan–ATLAS) captured on 10 May 2024

The comet by January 2024 had brightened to an apparent magnitude of 13.6 and according to Bob King was visible through 15-inch telescopes at x142 magnification.[8] The comet was then moving through the constellations of Libra and Virgo.[8] By the end of April it had brightened to about magnitude 10 and could be observed through small telescopes, showing a short tail.[9] The spectrum of the comet on 31 May 2024, when the comet was 2.33 AU from the Sun, indicated strong cyanide emission and that the comet is carbon depleted.[10] The comet had a large dust to gas ratio.[11]

In May and June the brightening rate of the comet slowed, with the comet staying between magnitudes 10 and 11, while a dusty tail measuring 5 to 15 arcminutes long was observed visually to extend eastwards.[12] Czech-American astronomer Zdenek Sekanina suggested that this indicates that the comet nucleus has been fragmenting, with the fragmentation starting in late March, as indicated by an increase in the brightening rate and the subsequent decrease in dust production, the narrow teardrop-shaped dust tail, and non-gravitional changes in the orbit. He predicted that the comet would disintegrate before perihelion.[13] Observations of the comet with TRAPPIST robotic telescope indicate that dust production reached a minimum in May, when the comet was near a phase angle of zero, and started to increase again one month later, while gas production rates increased slowly throughout that period.[11] In mid June the comet entered the constellation of Leo, in the evening sky.[8] In early July a faint ion tail measuring about one and half degree in length was observed photographically.[14] After mid July the comet was lost in the Sun's glare until September.[8] In August the comet was observed by STEREO spacecraft to brighten steadily to an apparent magnitude of 7.[15][16]

Perihelion

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Photograph of the comet in twilight
C/2023 A3 taken from Murrays Bay, Auckland, New Zealand on 28 September 2024

The comet was recovered by Terry Lovejoy in the morning twilight on 11 September 2024, when it was located in the constellation of Sextans, at a magnitude of 5.5.[17] The comet was spotted with naked eye and photographed by astronaut Matthew Dominick on board the ISS on 20 September, followed by fellow astronaut Donald Pettit two days later.[18] The first naked eye observation of the comet from Earth was reported on 23 September, with the comet having an estimated magnitude of 3.3, while its tail was reported to be 2.5 degrees long when it was observed with binoculars.[19]

During the last week of September it was located in the dawn sky, better visible from the Southern Hemisphere, and it was predicted to have brightened to second magnitude. Perihelion took place on 27 September.[8] By 1 October the comet had brightened to magnitude 2[19] and its tail was estimated to be 10–12 degrees long.[20] After that it will move again in conjunction with the Sun.[8] On 9 October 2024 the comet will be 3.5 degrees from the Sun.[21] It will appear in the evening sky in mid-October.[8] Tsuchinshan–ATLAS is expected to make its closest approach to Earth on 12 October at a distance of 71 million km (44 million mi).[22]

Brightness predictions

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Upon discovery announcement the comet was estimated to reach a total magnitude of +3 during perihelion, assuming an absolute magnitude (H) of 7 and 2.5n = 8, when it will be in low solar elongation.[7] Better visibilty may occur about three weeks after perihelion, in mid October, when it is estimated to be of fourth magnitude.[7] Gideon van Buitenen estimated that the comet will reach a magnitude of 0.9 during perihelion and −0.2 at the time of closest approach to Earth, assuming H = 5.2 and 2.5n = 10, and will benefit from the effects of forward scattering.[23][24]

Revised data from June 2024 suggest the comet is going to brighten to an apparent magnitude of 2.2, assuming H = 6 and 2.5n = 7.5, which is the average brightening rate of long period comets in the inner solar system. However, the comet is expected to be at least one magnitude brighter due to the effects of forward scattering, which could boost the brightness by several magnitudes around the peak of the effect on 9.8 October 2024.[12] More calculations from early September indicate that accounting for forward scattering, the comet will be brighter than magnitude 0 between 5 and 13 October and could peak at over −4 on 9.4 October, when it is predicted that forward scattering could boost the comet's magnitude by up to 7 magnitudes.[25]

Orbit

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Animation of C／2023 A3 around Sun
  C/2023 A3 ·   Sun ·   Mercury ·   Venus ·   Earth ·   Mars

The comet has a retrograde orbit, lying at an inclination of 139°. Τhe comet has its perihelion on 27 September 2024, at a distance of 0.391 AU. Τhe closest approach to Earth will be on 12 October 2024, at a distance of 0.47 AU. The comet does not approach close to the giant planets of the Solar System.[7] The orbit is weakly bound to the Sun before entering the planetary region of the Solar System.[2] Due to planetary perturbations, the outbound orbit will have a greater eccentricity than the inbound orbit and is not bound to the Sun as it is weakly hyperbolic.[2] The weakly hyperbolic trajectory may or may not result in the comet being ejected from the Solar System. It is expected to be 200 AU from the Sun in the year 2237.[26]

C/2023 A3 closest Earth approach on 12 October 2024[4]
Date and time of closest approach Earth distance
(AU) 		Sun distance
(AU) 		Velocity relative to Earth
(km/s) 		Velocity relative to Sun
(km/s) 		Uncertainty region
(3-sigma) 		Constellation Moon illumination Reference
2024 October 12 15:18 ± 15 min 0.47241 AU (70.672 million km; 43.913 million mi; 183.85 LD) 0.55619 AU (83.205 million km; 51.701 million mi; 216.45 LD) 80.5 56.5 ±7 thousand km Virgo 70% [27]
  • Positions of the comet C/2023 A3 near 2024 perihelion
  • The position of comet C/2023 A3 in August and September 2024 with the expected apparent magnitudes. The comet is located in the constellation Leo (Leo) between the two stars 55 and 57 Leonis about six degrees south of the ecliptic at the beginning of August and then moves towards the constellation Sextans. With increasing apparent brightness, it turns back toward the constellation Leo in the second half of September at maximum southern ecliptic latitude (just under 14 degrees of arc).
    The position of comet C/2023 A3 in August and September 2024 with the expected apparent magnitudes. The comet is located in the constellation Leo (Leo) between the two stars 55 and 57 Leonis about six degrees south of the ecliptic at the beginning of August and then moves towards the constellation Sextans. With increasing apparent brightness, it turns back toward the constellation Leo in the second half of September at maximum southern ecliptic latitude (just under 14 degrees of arc).
  • The position of comet C/2023 A3 in October 2024. The comet is located in the southernmost tip of the constellation Leo about ten degrees south of the ecliptic and moves in the first half of the month with decreasing apparent brightness across the constellation Virgo. It then moves into the western head of the constellation Serpens Caput, and then moves across the constellation Ophiuchus. By the end of the month, the comet reaches a northern ecliptic latitude of just over 27 degrees of arc. Therefore, in the second half of October the comet should be well visible on the western horizon after sunset.
    The position of comet C/2023 A3 in October 2024. The comet is located in the southernmost tip of the constellation Leo about ten degrees south of the ecliptic and moves in the first half of the month with decreasing apparent brightness across the constellation Virgo. It then moves into the western head of the constellation Serpens Caput, and then moves across the constellation Ophiuchus. By the end of the month, the comet reaches a northern ecliptic latitude of just over 27 degrees of arc. Therefore, in the second half of October the comet should be well visible on the western horizon after sunset.

References

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  1. ^ a b c "MPEC 2023-D77 : COMET C/2023 A3 (Tsuchinshan–ATLAS)". minorplanetcenter.net. Retrieved 1 March 2023.
  2. ^ a b c d e Horizons output. "Barycentric Osculating Orbital Elements for Comet C/2023 A3 (Tsuchinshan-ATLAS)". Retrieved 2023-09-01. (Solution using the Solar System's barycenter (Sun+Jupiter). Select Ephemeris Type:Elements and Center:@0)
    Epoch 1800 was PR= 3.6E+9 / 365.25 days = millions of years
  3. ^ a b c d "Horizons Batch for C/2023 A3 (Tsuchinshan–ATLAS) on 2024-Sep-27" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Archived from the original on 2023-04-04. Retrieved 2023-09-01. Perihelion as defined at epoch 2024-Sep-01 is QR= 3.91402E-01 (0.3914 AU).
  4. ^ a b c d e f "Small-Body Database: C/2023 A3 (Tsuchinshan–ATLAS)". ssd.jpl.nasa.gov. Archived from the original on 2023-03-01. Retrieved 1 September 2023.
  5. ^ "New comet – C/2023 A3 – could be bright in 2024". earthsky.org. 3 March 2023. Retrieved 8 April 2023.
  6. ^ King, Bob (16 March 2023). "Anticipating Comet Tsuchinshan-ATLAS (C/2023 A3)". Sky and Telescope. Retrieved 8 April 2023.
  7. ^ a b c d e f g "Electronic Telegram No. 5228". Central Bureau for Astronomical Telegrams. 28 February 2023. Retrieved 1 March 2023.
  8. ^ a b c d e f g King, Bob (31 January 2024). "The best comets in 2024". Sky and Telescope. Retrieved 3 February 2024.
  9. ^ Atkinson, Stuart (26 April 2024). "Have you seen Comet C/2023 A3 (Tsuchinshan-ATLAS) yet? We've been keeping an eye on it..." www.skyatnightmagazine.com. Retrieved 13 May 2024.
  10. ^ "ATel #16637: Molecular gas production rates of Comet C/2023 A3 (Tsuchinshan – ATLAS)". The Astronomer's Telegram. Retrieved 6 June 2024.
  11. ^ a b Jehin, E.; Vander Donckt, M.; Hmiddouch, S.; Manfroid, J. (12 July 2024). "ATel #16705: TRAPPIST bright comets production rates: 13P/Olbers, C/2023 A3 (Tsuchinshan – ATLAS) and C/2021 S3 (PanSTARRS)". The Astronomer's Telegram. 16705.
  12. ^ a b Green, Daniel (17 June 2024). "Electronic Telegram No. 5404: COMET C/2023 A3 (TSUCHINSHAN–ATLAS)". Central Bureau for Astronomical Telegrams. Retrieved 21 June 2024.
  13. ^ Sekanina, Zdenek (8 July 2024). "Inevitable Endgame of Comet Tsuchinshan-ATLAS (C/2023 A3)". arXiv:2407.06166 [astro-ph].
  14. ^ Kizer Whitt, Kelly; Eddie, Irizarry (10 July 2024). "Comet Tsuchinshan-ATLAS may be disintegrating". earthsky.org. Retrieved 18 July 2024.
  15. ^ Thomson, Jess (28 August 2024). "NASA reveals doomed comet survived—may become visible to the naked eye". Newsweek. Retrieved 28 August 2024.
  16. ^ "Spaceweather.com Time Machine: Wednesday, Aug. 28, 2024". www.spaceweather.com. Retrieved 28 August 2024.
  17. ^ King, Bob (12 September 2024). "Update: Comet Tsuchinshan-ATLAS Might Outshine Predictions". Sky&Telescope. Retrieved 13 September 2024.
  18. ^ Todd, Iain. ""Totally awesome to see a comet from orbit". Astronauts photograph Comet C/2023 A3 from the Space Station". www.skyatnightmagazine.com. Retrieved 25 September 2024.
  19. ^ a b "Observation list for C/2023 A3". cobs.si. COBS – Comet OBServation database. Retrieved 24 September 2024.
  20. ^ "Spaceweather.com Time Machine: Tuesday, Oct. 1, 2024". www.spaceweather.com. Retrieved 2 October 2024.
  21. ^ "Horizons Batch for C/2023 A3 (Tsuchinshan-ATLAS) Solar elongation on 2024-Oct-10". JPL Horizons. Retrieved 2023-03-03.
  22. ^ Plait, Phil (27 September 2024). "Will This Comet Be the Brightest of 2024?". Scientific American. Retrieved 2 October 2024.
  23. ^ "C/2023 A3 (Tsuchinshan–ATLAS)". astro.vanbuitenen.nl. Archived from the original on 1 March 2023. Retrieved 1 March 2023.
  24. ^ Seiichi Yoshida. "C/2023 A3 ( Tsuchinshan-ATLAS )". Seiichi Yoshida's Comet Catalog. Retrieved 2023-05-01.
  25. ^ Green, Daniel (10 September 2024). "Electronic Telegram No. 5445: COMET C/2023 A3 (TSUCHINSHAN–ATLAS)". Central Bureau for Astronomical Telegrams. Retrieved 11 September 2024.
  26. ^ C/2023 A3 outbound at 200 AU
  27. ^ Horizons
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