A huge asteroid the size of a London bus will fly within 2,100 miles (3,400 km) of Earth tonight – the fourth closest approach on record.
Known as ‘2023 BU’, this space rock was only discovered by NASA scientists on Saturday, and is set to pass by our planet’s surface at about 00:30 GMT (19:30 ET).
It will race past at 33,000 mph at a distance of 6,500 miles (10,500 km) from the Earth’s centre.
A live stream of the event, hosted by the Virtual Telescope Project (VTP) in Italy, will begin at 19:15 GMT (14:15 ET), ensuring those without a telescope can still witness it.
The space rock, known as 2023 BU, was only discovered by NASA last weekend but is set to come within 2,100 miles (3,400 km) of Earth tonight at about 00:30 GMT (19:30 ET)
This orbital diagram from CNEOS shows 2023 BU’s trajectory (red) during its close approach with Earth tonight. The asteroid will pass about 10 times closer to Earth than the orbit of geosynchronous satellites (green)
What is a ‘potentially hazardous’ asteroid?
A potentially hazardous asteroid (PHA) is an asteroid whose orbit comes nearer than 0.05AU (about 7.5 million km) to the Earth.
It also is at least 100 metres (300 feet) in diameter.
The International Astronomical Union claims there are around 1,500 potential hazardous asteroids.
Although these are not a risk to Earth as of yet, asteroid this large have the potential to cause devastation if they were to land on our planet, especially in highly-populated areas.
It is believed one hits Earth once every 200-300 years.
2023 BU is so small that it will be too faint to be seen with the naked eye, shining at a maximum of 11.3 magnitude.
It measures about 12.4 by 27.8 feet (3.8 by 8.5 metres), which is around the same size as the original Routemaster London bus.
Therefore it has to be picked up by large, powerful telescopes, such as the VTP’s 14-inch and 17-inch robotic ones in Ceccano.
According to astronomer Jonathan McDowell, the ‘asteroidlet’ was within the orbit of the moon yesterday afternoon.
However, experts have calculated its orbit and insist there is no chance of 2023 BU hitting Earth on this particular approach.
Space rocks that are smaller than 82 feet (25 metres) across most likely burn up if they enter the Earth’s atmosphere, NASA says.
This would cause little to no damage on the ground, but some of the bigger debris may fall as small meteorites.
NASA’s Scout impact hazard assessment system, which is maintained by NASA’s Center for Near Earth Object Studies (CNEOS), quickly determined that 2023 BU would miss Earth.
Davide Farnocchia, a navigation engineer who developed Scout, said: ‘Scout quickly ruled out 2023 BU as an impactor, but despite the very few observations, it was nonetheless able to predict that the asteroid would make an extraordinarily close approach with Earth.
‘In fact, this is one of the closest approaches by a known near-Earth object ever recorded.’
Comparison: The space rock measures about 12.4 by 27.8 feet, which is around the same size as the original Routemaster London bus
NASA’s Scout system shows the deflection of asteroid 2023 BU’s trajectory (red) caused by Earth’s gravity. The orbit of geosynchronous satellites (green) and the orbit of the Moon are also depicted (grey)
A live stream, hosted by the Virtual Telescope Project (VTP) in Italy, will be made available for people to witness the event from 19:15 GMT (14:15 ET) tonight
Why has asteroid 2023 BU only just been seen?
Some asteroids can ‘sneak up’ on us thanks to a quirk of the Earth’s rotation that makes them seem like they are barely moving — making them hard to detect.
This is the warning of NASA-funded experts who investigated how telescopes nearly missed a 328-feet-wide asteroid that came within 43,500 miles of Earth back in 2019.
The space rock, dubbed ‘2019 OK’, was the first object of its size to get that close to our planet since 1908 — but it was only spotted 24 hours before its closest approach.
The reason, the team determined, is because it was moving towards us in such a way that its motion across the night sky was counteracted by the Earth’s spin.
Thus — to early warning systems like Pan-STARRS1 at Hawaii’s Haleakala Observatory — 2019 OK looked stationary, so did not set off the automated detection software.
In fact, the experts said, up to half of asteroids approaching Earth from a danger zone east of ‘opposition’ likely undergo periods of such apparent slow motion.
Although it won’t impact us, by some definitions the asteroid will technically pass through the uppermost region of our planet’s atmosphere, known as the ‘exosphere’.
This extends from around 6,000 miles (10,000 km) up to a maximum distance of 120,000 miles (193,000 km) above Earth.
However, most scientists don’t consider this region to be a true part of the Earth’s atmosphere because the air is so thin.
Nevertheless, asteroid 2023 BU will pass well within the orbit of geostationary satellites above South America, but still far away from the International Space Station at 250 miles (400 km) from the Earth.
This will be the fourth closest pass of our planet out of more than 35,000 past and future approaches, according to CNEOS, which holds data covering the period of 300 years from 1900 to 2200.
Most asteroids pass beyond the distance of the moon – which is 240,000 miles away – but this one is far closer.
The space rock was discovered by astronomer Gennadiy Borisov at the Crimean Astrophysical Observatory in Nauchnyi, Crimea on January 21.
He is famous for spotting the first comet ever seen that had travelled into the solar system from interstellar space, called 2I/Borisov.
2023 BU currently orbits the sun every 359 days, while its circular path occasionally intersects Earth’s orbital trajectory around our star.
NASA says its proximity to Earth during tonight’s fly-by will be close enough for our planet’s gravity to lengthen its orbit to 425 days, and make its path more elongated.
It will next pass relatively close to us on December 6, 2036, but on that occasion will be well beyond the orbit of the moon.
Known as 2023 BU, the object is about half the size of the famous Chelyabinsk meteor (pictured) that hit Earth 2013
NASA deems the asteroid a ‘near-Earth object’ (NEO) because its orbit sees it come within 120 million miles (195 million km) of the sun, but it is not a ‘potentially hazardous asteroid’ because it is not large enough to cause significant damage in the event of impact.
In February 2013, a meteor that blazed across southern Urals and came down in Chelyabinsk, Russia was the largest recorded meteor strike in more than a century.
More than 1,600 people were injured by the shock wave from the explosion, estimated to be as strong as 20 Hiroshima atomic bombs, as it landed near the city.
The fireball, measuring 60ft (19 metres) across, screamed into Earth’s atmosphere at 41,600 mph and much of it landed in a local lake called Chebarkul.
Last year, experts warned that some asteroids can ‘sneak up’ on us thanks to a quirk of the Earth’s rotation that makes them seem like they are barely moving — making them hard to detect.
In fact, they said up to half of asteroids approaching Earth from a danger zone east of ‘opposition’ likely undergo periods of such apparent slow motion.
The NASA-funded experts investigated how telescopes nearly missed a 328-feet-wide asteroid that came within 43,500 miles of Earth back in 2019.
Astronomers are hunting for asteroids larger than 450ft as they can cause ‘catastrophic damage’
Researchers have discovered most of the asteroids that are about a kilometers in size, but are now on the hunt for those that are about 459ft (140m) – as they could cause catastrophic damage.
Although nobody knows when the next big impact will occur, scientists have found themselves under pressure to predict – and intercept – its arrival.
Artist’s impression pictured
‘Sooner or later we will get… a minor or major impact,’ said Rolf Densing, who heads the European Space Operations Centre (ESOC) in Darmstadt
It may not happen in our lifetime, he said, but ‘the risk that Earth will get hit in a devastating event one day is very high.’
‘For now, there is little we can do.’