A comet that hasnt been visible from Earth since the era of the Neanderthals is set to make the closest pass to our planet in millenia tonight.
Comet C/2023 A3 - also known as Tsuchinshan-Atlas - is believed to orbit the Sun once every 80,000 years, making its current trip through our solar system the first since humans began to move out of Africa.
Later tonight it will travel past the Earth at such close proximity it should be visible to the naked eye - even without binoculars or a telescope.
A3 was last visible at the end of last month, spotted by stargazers in San Francisco streaking over the Golden Gate Bridge - but experts say tonight is the best chance for Brits to see it for themselves before it vanishes for generations.
This is due to the fact the comet has now passed around the other side of the sun - meaning it is now visible in the evening in the UK.
Comet C/2023 A3, also known as Tsuchinshan-ATLAS, is set to pass over Britains skies in the coming days (pictured at the end of September over Santa Fe, New Mexico)
The comet is in the midst of an 80,000 year round trip to the solar system - seen here on September 22, captured from space by NASA astronauts Don Petit and Matthew Dominick
Comet C/2023 A3 (Tsuchinshan-Atlas) was last seen when Neanderthals walked the Earth, experts say
A3 was discovered by researchers last year and first observed at Chinas Purple Mountain Observatory and an Atlas (Asteroid Terrestrial-impact Last Alert System) telescope in South Africa. It is named after both observatories.
It is thought to have originated from the Oort cloud, a giant spherical icy shell that surrounds our solar system and dates back some 4.5billion years and may measure as much as 25 miles (40km) across.
Data from The Sky Live suggests the comet is currently around 44million miles away from Earth, travelling at approximately 150,000 miles an hour.
Between tonight and tomorrow morning it will reach its closest point to the Earth and will shine at a +1 or +2 magnitude - comparable to the north star, Polaris, and not far below the visibility of planets such as Venus on clear nights.
Light from the sun will illuminate the two-pronged tail of dust and ice that follows it - in reality gas and dust being released from the ice of the comet as it thaws in close proximity to the Sun. This makes it even easier to spot at peak brightness.
Dr Gregory Brown, senior public astronomy officer at the Royal Observatory Greenwich, said: The comet itself comes from an extremely distant part of our solar system, a place called the Oort cloud.
It contains lots of bits left over from the formation of the solar system. Every so often, one of those bits will be nudged inwards in towards the solar system, where it could end up in a very, very long orbit.
Those orbits can take extraordinarily long periods of time - thousands of years. The estimate on this particular comet is that if it is in a stable orbit, its last path to the inner solar system was about 80,000 years ago.
The comet is seen here as a dark streak across the sky in Geneva on Friday. It will not be seen again for another 80,000 years as it leaves the Earths proximity
Images of comet C/2023 A3 (Tsuchinshan–ATLAS) obtained in February 2023, shortly after it was discovered, on remote telescopes by an amateur astronomer
Comets are large objects made of dust and ice that orbit the sun. NASA describes them as leftovers from the formation of the solar system 4.6 billion years ago (artists depiction)
Experts say your best bet at spotting A3 is to find a hill or an area free of tall buildings or trees - away from street lamps and other sources of light pollution - about an hour after sunset, and to look west.
There are a host of astronomy apps available that should be able to help you map out the night sky and see exactly where the comet will be.
Having a telescope or a pair of binoculars to hand may enhance your star-spotting experience - but be prepared to spot a smudge of light crossing the sky rather than a glimmering shooting star.
It goes without saying that Britains weather might hamper your view - so if there are clouds in the sky, you may have to resort to using your imagination.
But if you dont see it tonight, fear not. Dr Brown, of the Royal Observatory Greenwich, believes it will be visible in the skies over Britain into next week, especially on Tuesday.