Largest asteroid to pass by Earth whips past as Nasa celebrates near encounter

Andrew Griffin@_andrew_griffin
Monday 22 March 2021 14:13
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Earth has been visited by the largest asteroid that will pass nearby all year.

The object known as 2001 FO32 came about 1.25 million miles from Earth – more than five times as close as the Moon is – on 21 March.

Though that may sound far, it is relatively close in astronomical terms. The object is designated a “potentially hazardous asteroid” by Nasa, though experts caution there is no chance that it will hit our planet, either this time or in the future.

They can be confident about our safety because the object has been known for 20 years – the 2001 in its name refers to the year it was discovered – and its orbit has been precisely tracked and projected into the future.

The asteroid flew by at just under 80,000mph, unusually fast and sped up by its long orbit around the Sun. That just over two years each time, and its journey means that it will not come as close to Earth again until 2052.

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Though scientists are not sure of the asteroid’s exact size – it is probably between 440 and 680 meters wide – it is almost certainly the biggest asteroid to come by so close this year. The last comparible visit happened in April of last year, when an object known as 1998 OR2 visited, which was bigger than the latest object but also three times as far away.

The close proximity gives Nasa and other researchers a valuable chance to study a rock that formed at the very beginning of early solar system.

Researchers will use data gathered during the pass to learn more about its size, how reflective it is and what it might be made of. Researchers do so by watching for the wavelengths of light that are reflected back when the asteroid is hit by the Sun, and comparing that spectrum with similar objects on Earth.

Researchers will also scan it using radar observations. That will give more detailed information on how big it might be, its orbit – and even whether it is carrying its own moon, as 15 per cent of similar-sized asteroids do.

Such research is valuable in part because it allows scientists to better understand the threat any such asteroids may pose to Earth. Nasa says that it has found 95 per cent of near-Earth asteroids of a similar size to 2001 FO32, and that none of those found pose any danger to Earth.

But Nasa and other agencies continue to look for those remaining asteroids, and getting more information about them would help inform any response if such an object were to pose a threat – helping design missions that would aim to deflect them elsehwere in space, for instance.

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