New Comet With Great Potential — C/2023 A3 (Tsuchinshan-ATLAS)

Star Walk
5 min readMar 3, 2023
Image Credit: Vito Technology, Inc.

The ATLAS survey and Purple Mountain Observatory have recently detected a comet that may reach a magnitude of 0 by October 2024. Here is everything that is known about this comet so far.

What is the comet C/2023 A3 (Tsuchinshan-ATLAS)?

On February 22, 2023, the ATLAS telescope in South Africa detected a new faint object that was proven to be a comet. It was temporarily designated as A10SVYR. The comet was also independently captured by a telescope at Purple Mountain Observatory (Zijinshan Astronomical Observatory) on January 9, 2023. It was added to the list of objects awaiting confirmation, but after no follow-up observations were reported, it was removed on January 30, 2023, and was considered lost. Based on the comet naming system, the comet received the names of both observatories and was officially named C/2023 A3 (Tsuchinshan-ATLAS).

Shortly after its discovery, observations up to December 2022 were found in the archives of the Minor Planet Center, which gave us a little more information about the comet. Looks like it’s a long-period comet with an orbital period of 26,000 years. It also seems to have a fairly large nucleus.

C/2023 A3 (Tsuchinshan-ATLAS) is currently 7.3 AU from the Sun and is slowly approaching it, becoming brighter. It is predicted to reach maximum brightness at the end of 2024. According to current calculations by the Minor Planet Center, the comet will reach magnitude 0.3 on October 5–7, 2024. By comparison, the recently trending green comet C/2022 E3 (ZTF) reached a maximum magnitude of 5.4, and the famous NEOWISE (C/2020 F3) peaked at 0.9.

What does the name of the comet C/2023 A3 (Tsuchinshan-ATLAS) mean?

The name of the comet contains data about where and when the comet was first seen:

  • The letter C indicates a non-periodic comet (i.e., it passes through the Solar System only once, or it may take more than 200 years to orbit the Sun);
  • 2023 A3 means the comet was discovered in 2023, in the first half of January (this corresponds to the letter A in the IAU comet naming system), and was the third such object discovered in the same period;
  • Tsuchinshan-ATLAS means the discovery was made using telescopes of the Purple Mountain Observatory (Zijinshan Astronomical Observatory) and Asteroid Terrestrial-impact Last Alert System (ATLAS).

Best time to observe C/2023 A3 (Tsuchinshan-ATLAS)

C/2023 A3 (Tsuchinshan-ATLAS) favors the Northern Hemisphere, where it will be visible to the naked eye in mid-October 2024. It’s hard to predict the exact brightness of the comet — most tend to think it will be about 0–1 magnitude.

On October 10, the comet will make its closest approach to the Sun (0.39 AU), and there will be a chance to catch it during the day. Due to the effect of forward scattering, C/2023 A3 (Tsuchinshan-ATLAS) might brighten up to minus magnitude.

After perihelion, C/2023 A3 (Tsuchinshan-ATLAS) will disappear for a day and reappear in the evening sky on October 12, 2024. It will remain an evening object until the end of the month. On October 13, 2024, it will pass close to the Earth (0.48 AU) and should be easily visible around that time. Then the comet will fade rapidly, and by mid-November, it will no longer be visible to the naked eye. Observers will only be able to see it with binoculars and telescopes.

Is the comet C/2023 A3 (Tsuchinshan-ATLAS) visible now?

Right now, C/2023 A3 (Tsuchinshan-ATLAS) is a faint 18-magnitude object visible in the second half of the night in the constellation Serpens. In the future, the observation conditions will be gradually improving.

The comet will rise earlier and earlier until May 2023, when it will reach a magnitude of 17.5. However, the bright summer nights in the Northern Hemisphere will make observations difficult. In June 2023, C/2023 A3 (Tsuchinshan-ATLAS) will brighten up to magnitude 17 and move to the constellation Virgo. From August 2023, the comet will be almost invisible until next February.

C/2023 A3 (Tsuchinshan-ATLAS) visibility forecast for 2024

Here are some predictions for 2024 monthly visibility:

  • January: not visible
  • February: 14 magnitude, visible in the second half of the night;
  • March: 13 magnitude, visible from midnight;
  • April: 12 magnitude, visible in the evening;
  • May: 10–11 magnitude, visible in the evening;
  • June: 9–10 magnitude, favors the Southern Hemisphere. Bad observing conditions in the Northern Hemisphere due to bright summer nights and lower declination from the Sun;
  • July: 8–9 magnitude, still favoring Southern Hemisphere, evening visibility;
  • August: 4 magnitude by the end of the month, but too close to the Sun;
  • September: 3–4 magnitude, moves away from the Sun and begins to appear in the morning sky in the Southern Hemisphere. Short observation window, a good opportunity for capturing the comet’s tail. From September 27 to October 2, it appears in the morning in the Northern Hemisphere.
  • October: the best month for observations in the Northern Hemisphere.

After October, the comet will gradually fade.

Please note that comets are very unpredictable space objects, and data (especially apparent magnitude) can change quickly. However, we’ll do our best to keep you up to date.

How to find C/2023 A3 (Tsuchinshan-ATLAS) in the sky?

You can spot C/2023 A3 (Tsuchinshan-ATLAS) with the Sky Tonight app. Open the app, and tap the magnifier icon at the bottom of the screen. Then type “C/2023 A3” and tap the target icon next to the corresponding search result. The app will show you the comet’s current position in the sky for your location. Point your device at the sky and follow the white arrow to find it. But keep in mind that C/2023 A3 (Tsuchinshan-ATLAS) won’t become a notable object until July 2024.

Bottom line

The recently discovered comet C/2023 A3 (Tsuchinshan-ATLAS) has great potential and may become visible to the naked eye by mid-October 2024. According to some forecasts, it could reach 0 magnitude or brighter. Although the comet is not currently a prominent object and won’t be for at least a year, you can already use the Sky Tonight app to locate C/2023 A3 (Tsuchinshan-ATLAS) in the sky. You can also rewind time and see the comet’s position in your sky in the future.



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