The largest asteroid predicted to pass by Earth this year will be at its closest to the planet next week before being thrown back out into space, NASA has said.

While the interplanetary interloper will not come closer than 2 million kilometres (1.25 million miles) from Earth, it will present a scientific opportunity for astronomers.

Called 2001 FO32, the near-Earth asteroid will make its closest approach on 21 March at a distance that is equivalent to five-and-a-quarter times the distance from the Earth to the Moon. There is no threat of a collision with our planet now or for centuries to come, NASA said.

“We know the orbital path of 2001 FO32 around the Sun very accurately, since it was discovered 20 years ago and has been tracked ever since," said Paul Chodas, director of the Centre for Near Earth Object Studies (CNEOS), which is managed by NASA’s Jet Propulsion Laboratory. “There is no chance the asteroid will get any closer to Earth than 1.25 million miles.”

However, because the distance is close in astronomical terms, the rock has been designated a “potentially hazardous asteroid”.

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During its approach, 2001 FO32 will pass by at about 124,000km/h (77,000mph) – faster than the speed at which most asteroids encounter Earth.

The reason for the asteroid’s unusually fast, close approach is its highly inclined and elongated (or eccentric) orbit around the Sun – an orbit that is tilted 39° to Earth’s orbital plane. This orbit takes the asteroid closer to the Sun than Mercury at its closest point and twice as far from the Sun as Mars at its most distant.

As the asteroid makes its inner Solar System journey, it picks up speed like a skateboarder rolling down a ramp, and then slows after being flung back out into deep space and swinging back towards the Sun. It completes one orbit every 810 days.

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The asteroid, which analysis suggests is 440 to 680 metres wide, will not come this close to Earth again until 2052.

Reader Q&A: How many potentially hazardous asteroids are there?

Asked by: Jon Linbergh, Chester

A potentially hazardous asteroid (PHA) is an asteroid whose orbit comes nearer than 0.05AU (about 7.5 million km) to the Earth and whose brightness implies a size of the order of about 100m across or more. Such objects would have devastating consequences if they were to impact the Earth.

At the time of writing, the International Astronomical Union lists a total of 1,489 potential hazardous asteroids. This does not mean all these objects will eventually hit the Earth, just that they have the potential to do so. Of course, this number represents only the PHAs we know about. A survey by NASA’s WISE satellite suggested there are at least 4,700 such objects.

Although we are in no immediate danger, asteroids like this that are big enough to cause major destruction, particularly in heavily populated areas, have hit Earth every 200 to 300 years on average.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.