A comet that has not been visible from Earth since the era of Neanderthals has been spotted above London in a “once in a lifetime” sighting.
Comet C/2023 A3 – also known as Tsuchinshan-Atlas – is believed to orbit the Sun once every 80,000 years, making its current journey through our solar system the first since humans began leaving Africa.
It has now been spotted on the London skyline just after sunset yesterday, when it comes within 70 million kilometers of Earth.
And in the coming days it will pass by Earth so close that it should be visible to the naked eye – even without binoculars or a telescope.
A3 was last visible late last month, spotted by stargazers in San Francisco over the Golden Gate Bridge – but experts say tonight is the best chance for Brits to see it for themselves, before disappear for generations.
It was spotted on the London skyline just after sunset yesterday, when it comes within 44 million miles of Earth.
Comet C/2023 A3, also known as Tsuchinshan-ATLAS, is expected to pass through the skies of Great Britain in the coming days (photo in late September over Santa Fe, New Mexico)
The comet is in the midst of an 80,000-year journey through 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
This is because the comet has already passed the other side of the Sun – meaning it is expected to be visible in the UK next week.
A3 was discovered by researchers last year and first observed at China's Purple Mountain Observatory and an Atlas (Asteroid Earth Impact Last Alert System) telescope in South Africa. It is named after both observatories.
It is believed to have originated from the Oort cloud, a gigantic icy spherical shell that surrounds our solar system and dates back about 4.5 billion years and can measure up to 25 miles (40 km) in diameter.
Data from The Sky Live suggests that the comet is currently about 72 million kilometers away from Earth, traveling at approximately 240 thousand kilometers per hour.
Between tonight and tomorrow morning it will reach its closest point to Earth and shine with a magnitude of +1 or +2 – comparable to the North star Polaris and not far below the visibility of planets like Venus on clear nights.
The Sun's light will illuminate the double tail of dust and ice that follows it – in reality, gas and dust are released from the comet's ice as it melts in the vicinity of the Sun. This makes it even easier to detect the peak brightness.
Dr Gregory Brown, senior public astronomy officer at the Royal Greenwich Observatory, said: “The comet itself comes from an extremely distant part of our solar system, a place called the Oort cloud.
“It contains many pieces left over from the formation of the solar system. Every now and then, one of these bits will be pushed inward toward the solar system, where it could end up in a very, very long orbit.
'These 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 into the Solar System was around 80,000 years ago.
The comet is seen here looking like a dark streak in the Geneva sky on Friday. It will not be seen again for another 80,000 years when it leaves Earth's proximity
Images of comet C/2023 A3 (Tsuchinshan–ATLAS) obtained in February 2023, shortly after its discovery, in 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 (artistic rendering)
Experts say your best bet for spotting A3 is to find a hill or an area free of tall buildings or trees — away from streetlights and other sources of light pollution — about an hour after sunset, and look at it. west.
There are a number of astronomy apps available that should help you map the night sky and see exactly where the comet will be.
Having a telescope or pair of binoculars on hand can enhance your stargazing experience – but be prepared to spot a 'smudge' of light streaking across the sky rather than a twinkling shooting star.
It goes without saying that Britain's weather can make it difficult to see – so if there are clouds in the sky, you may have to use your imagination.
But if you don't come tonight, fear not. Dr Brown of the Royal Greenwich Observatory believes it will be visible in the skies over Britain next week, especially on Tuesday.
