It’s the kind of show that we sometimes wait decades for. Comet Tsuchinshan-Atlas is expected to appear in the sky of the northern hemisphere this Friday, October 11, 2024.
The last event of this kind was offered to us by comet Neowise, in July 2020. But the diameter of comet Tsuchinshan-Atlas is estimated between 20 and 40 km, compared to 5 km for Neowise and 11 km for Halley’s comet.
A comet is a celestial body composed of icy rocks which, approaching our star, shine and “melt” leaving behind particles reflecting sunlight. This is called comet hair, or coma.
It was observed for the first time in January 2023 by the Chinese Tsuchinshan Observatory as it crossed Saturn’s orbit, then a few months later by the South African Atlas program. Hence its name, Tsuchinshan-Atlas. Here’s what you need to know about its passage near the blue planet.
Read also: “Barnard b”, a new exoplanet detected very close to us
It will be visible this evening
No need to set your alarm for an ungodly hour to watch the show. “It will be enough to wait for the sun to set on the western horizon. And if it is clear, we will first see it low on the horizon, then as the days go by it rises a little in the sky. advises Nicolas Andre, professor of planetary science at Isae-SUPAERO in Toulouse, to 20 Minutes .
Tsuchinshan-Atlas was already visible in the southern hemisphere last week. She was then heading towards the sun, which she went around to come back towards us this Friday. As the days go by, it will become less and less luminous while remaining visible. “for a good week, with small binoculars and small telescopes”specifies the specialist to our colleagues.
It also entered the field of vision of the Soho solar observation satellite a few days ago, almost saturating its receivers.
She comes from far away
The journey of Tsuchinshan-Atlas is measured in millions of years. It probably saw the light of day in the Oort cloud, a hypothetical and gigantic assembly of tiny planets and celestial bodies, at the edge of the solar system.
Models suggest that it could have been up to 400,000 times the Earth-Sun distance before reaching us.
When comets approach our star, the ice contained in their core sublimates and lets out a long trail of dust, reflecting sunlight.
This characteristic hair, the coma, is also the sign that the object “degas”. For Tsuchinshan-Atlas, the risk was to know whether this degassing would not be too significant, at the risk of disintegrating the comet. A priorithis did not happen, but the show this weekend could vary depending on the weight loss treatment she has undergone.
“It’s a bit of a surprise at the last moment, but in any case it’s going to be a bright comet, that’s for sure,” according to Lucie Maquet, astronomer at the Institute of Celestial Mechanics and Ephemeris Calculation (IMCCE), located within the Paris-PSL Observatory.
She might never come back
It follows an orbit “which is not closed”, explains Lucie Maquet. Its future course is unpredictable. The models used predict, without any commitment, that it could be “ejected from the solar system, to get lost between the stars”, according to the September IMCCE newsletter.
Everything will depend in fine encounters that C/2023 A3 will have during its journey through the Oort cloud, a few thousand years from now. It would be enough, remarks the astronomer, that it “encounters a body which deflects it enough for it to return for a spin in the solar system.”
