'Comet of the century' visible tonight - it won't return for 80,000 years - how and when to see it

The bright comet, last visible from Earth when Neanderthals were alive, will be able to be seen with the naked eye tonight but will then start to fade and disappear - here's how to see it

Stargazers could be in for a rare treat tonight when a comet last visible from Earth when Neanderthals were alive will be crossing our skies. This weekend the Comet A3 - also known as Tsuchinshan-ATLAS - will be visible to the naked eye, according to scientists.

The comet, which was discovered early last year, has been called “the comet of the century” because of how bright and visible it could be, according to the Royal Astronomical Society (RAS). Astronomers say the come it would last have been visible from our planet around 80,000 years ago.

People living in the southern hemisphere have already glimpsed Comet A3 but it can now also be seen in the northern hemisphere, the society said. It is set to appear in the skies between October 12 and 30 when people may be able to view it with binoculars or potentially even with the naked eye.

In a video on the society’s website, deputy director Dr Robert Massey said taking photos of the comet may be possible, particularly if using a digital single-lens reflex (DSLR) camera. According to the RAS, the comet comes from the Oort Cloud – a giant spherical shell that surrounds our solar system and contains billions of objects including comets.

According to the BBC Sky at Night Magazine Long period comet C/2023 A3 (Tsuchinshan-ATLAS) was spotted in February 2023, during a sky survey performed by ATLAS – the Asteroid Terrestrial-impact Last Alert System – using the 0.5-m f/2 Schmidt reflector telescope operated at the Sutherland Observatory in South Africa. At that point it was an uninspiring 18th magnitude spot on a photo and was named 'A10SVYR'.

However when its orbit was calculated, it was noticed that it had already been spotted by the Purple Mountain Observatory in China on 9 January 2023. It quickly raised excitement as by looking at the data it showed its orbit would bring it close enough to both the Sun and the Earth in September/October 2024 which would make it visible to the naked eye.

It said: "As October began, it was hard to believe that the tiny, out-of-focus star we were all looking at on grainy, tracked and stacked images a few months ago had grown into a quite stunningly beautiful comet, with a fifteen-degree long tail shooting up from the horizon like a search beam… Although that glorious view of Comet C/2023 A3 was only available from the southern hemisphere, where the comet is a second magnitude, whip-tailed star shining in the twilight sky before sunrise and clearly visible to the naked eye, observers positioned in countries as far north as Spain, Italy and even France have been able to see the comet too.

"In the past week or so many of them have glimpsed the comet as a fuzzy star shining low in the marmalade orange pre-dawn sky. Unfortunately the comet was so low in the sky before sunrise from latitudes further north that only a handful of dedicated – and lucky! – imagers were able to capture it on camera from the UK and US states north of Florida.

"Now Comet A3 is moving up into the northern hemisphere’s evening sky. All those northern observers who have been desperate to see Comet C/2023 A3 will have their chance to gaze at it through their binoculars and telescopes, and turn their cameras towards it too – weather permitting, of course."

What will we see?

Depending on the weather people could be in for a real "treat" says the magazine. It says: "Comet C/2023 A3 shows no signs of falling apart, or fading, or springing any other nasty surprises on us before it claws its way out of the sunset glow.

So it looks like northern observers are in for a treat from around 12 October 2024: a naked-eye comet, with a tail long and bright enough to be visible to the naked eye, shining in the west as twilight deepens.

However it is unclear how bright it will be until it arrives. The length of its tail is not yet known but there has been a prediction of up to 30 degrees long. It could also grow a spike-like 'anti-tail' from the front of its coma, too, says the magazine.

How and where to view the comet

On 12 October, the comet may be visible in the sky during the evening in the UK and USA. At this time, it will be at its closest point to Earth but still be 44 million miles away. The comet will also be visible on the 13 and 14 October in the early evening.

To spot the comet passing by, look towards the western horizon straight after the Sun has set. Speed is important here as there is only a small window to catch it. The comet will disappear roughly 30 minutes after the Sun sets.