How to spot comet not seen for 80,000 years in night sky across UK in October

An comet that may have been witnessed by Neanderthals will make its first close pass by Earth in mid-October – and won’t be back for another 80,000 years.

The Oort Cloud comet, called C/2023 A3 Tsuchinshan-ATLAS, was discovered in 2023, approaching the inner solar system on its highly elliptical orbit for the first time in documented human history.

But if you want to see this ancient celestial body in all its glory, there are a few things you need to know. First, locate the Plough, the seven bright stars of the constellation Ursa Major, then follow an arc to Arcturus, the fourth brightest star in the night sky. The comet will be slightly west of it.

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BBC Sky At Night states: "Clear skies and a flat western horizon will be key from mid-October.

"Those that are lucky enough to have that may pick the comet up on 11 October, but it will be extremely low as darkness falls and difficult to see. The comet’s closest approach to Earth, at 43.9 million kilometres, occurs on 12 October. On 13 October at 20:00 BST , the comet will be 4° above the western horizon under deep twilight as seen from the centre of the UK. This increases to 6° at the same time on 14 October and 9° up on 15 October, again at 20:00 BST."

The comet successfully made its closest transit past the sun last month but scientists predicted it could break up because its volatile and icy composition would be unable to withstand the intense heat, but it survived more or less intact and is now on track to come within approximately 44 million miles of Earth on October 12.

“Comets are more fragile than people may realise, thanks to the effects of passing close to the sun on their internal water ice and volatiles such as carbon monoxide and carbon dioxide,” said NASA astronomer Bill Cooke, who leads the Meteoroid Environment Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “Comet Kohoutek, which reached the inner solar system in 1973, broke up while passing too close to the Sun. Comet Ison similarly failed to survive the Sun’s intense heat and gravity during perihelion in 2013.”

It’s highly unlikely Tsuchinshan-ATLAS will be visible in daylight hours, except perhaps at twilight, Cooke said. In the past 300 years of astronomical observation, only nine previous comets have been bright enough to spot during the day. (The last were Comet West in 1976 and, under ideal conditions, Comet Hale-Bopp in 1997.)

“Savour the view,” Cooke advised. "Because by early November, the comet will be gone again for the next 800 centuries."

It is expected to be visible from the UK from Saturday, October 12 until Wednesday, October 30 in the West just after sunset. The Royal Astronomical Society saw it on Wednesday, October 2 just before sunrise but there are plenty of days left to catch a glimpse. However Earth Sky is now suggesting it may not be visible on some of those dates, with October 14 to 24 the most likely days it'll be visible.