In early 2023, the ATLAS survey and Purple Mountain Observatory detected a comet that was named C/2023 A3 (Tsuchinshan-ATLAS). It is expected to reach naked-eye visibility by October 2024 and become as bright as the most luminous stars! 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.

By the end of July 2023, C/2023 A3 (Tsuchinshan-ATLAS) will be 5.86 AU from the Sun and will be slowly approaching it, becoming brighter. It is predicted to reach maximum brightness in October 2024. According to the calculations by the SETI institute, the comet’s peak brightness can range from a magnitude of -0.1 to -6.6, which is comparable to the luminosity of the brightest stars. By comparison, the comet Hale-Bopp, one of the most widely observed comets of the 20th century, had a peak magnitude of -1.8. The so-called green comet C/2022 E3 (ZTF), which was trending at the beginning of 2023, reached a maximum magnitude of 5.4. The famous NEOWISE (C/2020 F3) peaked at 0.9.

What makes C/2023 A3 (Tsuchinshan-ATLAS) special?

First of all, C/2023 A3 (Tsuchinshan-ATLAS) is expected to grow a beautiful cometary tail; fainter comets usually don’t have prominent tails at all. After passing by the Sun at a distance similar to Mercury’s orbit, C/2023 A3’s coma of dust and ice will heat up considerably. As the ice particles evaporate, they will quickly escape into space, taking with them a large amount of dust that will extend into a long, bright tail. As history shows, comets that pass close to the Sun have the most impressive tails, formed soon after being “roasted” by the Sun’s heat. And this is the case with comet C/2023 A3!

In addition, C/2023 A3 (Tsuchinshan-ATLAS) will favor the Northern Hemisphere being perfectly visible there. The last time an exceptionally bright comet was visible from the northern latitudes was in 1997 when Comet Hale-Bopp lit up the sky.

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 – comets of this type originate from the Oort cloud and may pass through the Solar System only once or take from 200 to thousands of 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 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 September 27, 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 -4.0 magnitude.

After the perihelion, C/2023 A3 (Tsuchinshan-ATLAS) will disappear for a while and reappear in the evening sky in early October 2024. It will remain an evening object until the end of the month. On October 12, 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?

Currently, the comet stays within the 16th magnitude range and is visible through a big telescope. It rises in the daylight hours and sets around midnight local time. Northern Hemisphere observers can spot it after sunset in the constellation Virgo. You can track C/2023 A3 with the Sky Tonight free app. From August 2023, the comet will travel the sky during the daytime and, therefore, be almost invisible until next February.

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