Comet Tsuchinshan–ATLAS
What is Comet Tsuchinshan–ATLAS?
Comets· Nucleus ~2–3 km. The great comet of October 2024, which trailed a long tail across the evening sky. As it passed between Earth and the Sun, sunlight scattered forward off its dust and made it briefly very bright.
Past visits and the next return
Orbit and period
| Nucleus | ~2–3 km |
|---|---|
| Perihelion | 2024-09-27, 0.39 AU |
| Closest to Earth | 2024-10-12, 0.47 AU |
| Period | none — leaving on a hyperbolic orbit |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Tsuchinshan–ATLAS, a visitor from the Oort cloud
Tsuchinshan–ATLAS came from the Oort cloud, the outermost part of the solar system. The Oort cloud is thought to be a vast shell of icy bodies surrounding the Sun at a great distance, though no one has ever seen it directly. Judging from its incoming orbit, this comet had never, or only very rarely, come close to the Sun before.
Comets like this still carry plenty of ice that turns to gas easily. They often shine brightly while still far away but then fail to brighten as much as expected near the Sun. In 2024 one astronomer even predicted that this comet would fall apart before reaching the Sun. Instead it survived and grew bright as forecast.
As it passed through the solar system, the planets' gravity changed its orbit. Calculations show that its outgoing path is a hyperbola that leads out of the solar system, so it is not expected to return. Each comet like this is a valuable sample that tells us what the ices of the unreachable Oort cloud are made of.
The comet in depth
Comet Tsuchinshan–ATLAS (C/2023 A3) was first spotted on 9 January 2023 by China's Purple Mountain (Tsuchinshan) Observatory. On 22 February the ATLAS survey telescope in South Africa found it independently, so it carries both names. When found, it was 7.3 AU away, beyond Jupiter. It passed 0.39 AU from the Sun on 27 September 2024 and came within 0.47 AU of Earth on 12 October.
Just after rounding the Sun, the comet lay between Earth and the Sun. Sunlight striking its dust was scattered forward toward Earth, making it suddenly brighter, much as dust glitters when you look toward a light behind it. It was brightest around 9 October in images from a Sun-watching satellite. In mid-October it hung in the western evening sky with a long tail, and cameras also caught a faint 'anti-tail' pointing the other way.
It is counted as the brightest comet seen from the northern hemisphere since Hale–Bopp in 1997. In the orbit view you can see its path cutting steeply across the plane of the planets and dipping inside Earth's orbit. In the Sky view, go to the evening of 15 October 2024 (10:00 UTC) to see the comet standing tail-up in the west.
Frequently asked
- How close does Comet Tsuchinshan–ATLAS get to the Sun?
- The perihelion of Comet Tsuchinshan–ATLAS is 2024-09-27, 0.39 AU.
- How long is the orbital period of Comet Tsuchinshan–ATLAS?
- The period of Comet Tsuchinshan–ATLAS is none — leaving on a hyperbolic orbit.
- In one line, what is Comet Tsuchinshan–ATLAS?
- Comets — The great comet of October 2024, which trailed a long tail across the evening sky.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.