Tsuchinshan-ATLAS: the comet of the century?
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Comet C/2023 A3 (Tsuchinshan-ATLAS) photographed on September 24, 2024, at 9:13 UTC, from SpaceObs, in San Pedro de Atacama (Chile). The image was taken with a 110 mm refractor telescope, with an exposure time of 1.2 minutes.
Credit: Patrick Ditz, SAFGA & commission des comètes de la SAF
The C/2023 A3 (Tsuchinshan-ATLAS) comet was discovered in January 2023 in China by the Purple Mountain Observatory, and then again the following month by the South African telescope of the ATLAS program. Immediately named after the two discovering observatories, the comet had a visual magnitude of 18 at the time.
C/2023 A3 (Tsuchinshan-ATLAS) is a long-period comet with a highly elongated orbit. Following its progress, researchers at IMCCE, based at the Paris Observatory - PSL, modeled its trajectory. It is currently within the inner Solar System, following a journey lasting millions of years, originating from the Oort cloud.
The trajectory model established by IMCCE at the Paris Observatory - PSL indicates that the Tsuchinshan-ATLAS comet follows an elliptical orbit, with a maximum distance (or aphelion) estimated at around 400,000 astronomical units (AU).
This distance of 400,000 AU represents the maximum distance it could have reached. However, this figure should be taken cautiously, as it is very difficult to predict what kind of encounters the comet may have had with its environment at such a distance from the Sun.
Orbit of the C/2023 A3 (Tsuchinshan-ATLAS) comet within the inner Solar System at the date of its perihelion passage, on 09/27/2024. The comet passes between the orbits of Mercury and Venus.
Credit: Lucie Maquet / Observatoire de Paris - PSL / IMCCE
Its orbit was likely disturbed by the gravitational influence of neighboring stars or other massive objects located in the Oort cloud: a trajectory deviation that caused it to plunge into the Solar System, paying us a visit.
Candidate for the title of "comet of the century"?
It's not easy to predict, but a comet's visibility in the sky depends on its composition, the physical characteristics of its surface and interior. As the comet approaches the Sun, it becomes more illuminated and thus brighter; it also heats up more, which increases its activity.
The visibility of its cloud of ice and dust (the coma) surrounding the nucleus, as well as the dust and gas tails that emerge from it, depends on the comet's activity, i.e., the rate at which various volatiles are released at its surface.
The Tsuchinshan-ATLAS comet could reach a maximum magnitude of 2.4 at its closest approach to Earth on October 12, 2024, according to an estimate from IMCCE.
This celestial object has serious potential for claiming the title of "comet of the century." It might even briefly reach a negative magnitude, around its conjunction with the Sun on October 9.