Comet Tsuchinshan–ATLAS
What is Comet Tsuchinshan–ATLAS?
Comets· Nucleus ~2–3 km. The great comet of October 2024, found by China's Purple Mountain Observatory and the ATLAS survey. Passing between Earth and the Sun, forward-scattered sunlight briefly made it as bright as Venus. Replay its 80,000-year orbit and the October 2024 sky in the simulators.
Where Comet Tsuchinshan–ATLAS is in your sky right now: https://nowsky.org/solar/sky?sel=comet:tsuchinshan&loc=seoul&sd=2024-10-15T10:00Z — location and time set automatically, no login.
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 | ~80,000 yr |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- How close does Comet Tsuchinshan–ATLAS get to the Sun?
- 2024-09-27, 0.39 AU.
- How long is the orbital period of Comet Tsuchinshan–ATLAS?
- ~80,000 yr.
- In one line, what is Comet Tsuchinshan–ATLAS?
- Comets — The great comet of October 2024, found by China's Purple Mountain Observatory and the ATLAS survey.
- Where is Comet Tsuchinshan–ATLAS in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Possibly on its first visit from the Oort cloud
The orbit of Tsuchinshan–ATLAS has an eccentricity so close to 1 that its computed inbound aphelion lay thousands of AU out, inside the Oort cloud. Such "dynamically new" comets have never been near the Sun, so volatile ices survive at their surfaces; they tend to be active from far away and then fall short of expectations near perihelion, which was the background to the "it is disintegrating" reports of spring 2024.
This comet defied that worry, but Jupiter's perturbations during the passage changed its orbital energy and left its outbound path nearly hyperbolic — meaning it will not return, or not for hundreds of thousands of years. The Oort cloud is the edge of the solar system nobody has yet seen directly, and each comet like this one is a sample of the ices out there.
The comet in depth
Comet Tsuchinshan–ATLAS (C/2023 A3) was first caught in January 2023 by China's Purple Mountain (Tsuchinshan) Observatory and rediscovered a month later by the ATLAS asteroid survey in South Africa, hence the double name. It was 7.3 AU out, beyond Jupiter, at discovery; it passed perihelion at 0.39 AU on 27 September 2024 and came within 0.47 AU of Earth on 12 October.
Right after perihelion the comet slipped between Earth and the Sun, and forward scattering of sunlight by its dust spiked it to about magnitude −4 around 9 October — bright enough to be spotted in daylight. Through mid-October it hung in the western evening sky with a tail over 20 degrees long, and photographers also caught a faint anti-tail pointing toward the Sun. An Oort-cloud visitor, its orbit was altered by the passage and it will not return for around 80,000 years.
Track Tsuchinshan–ATLAS in the orbit view to see its steeply inclined path plunge inside Earth's orbit. In the Sky view, move to Seoul on the evening of 15 October 2024 to replay the comet standing tail-up in the west.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.