Earth will soon get a visit from not one asteroid, but two. The first radar images of asteroid 1998 QE2 have revealed that the incoming space rock has an unexpected companion – a small moon that may be the key to unlocking the asteroid's secrets.
Astronomers have been tracking the larger asteroid since it was discovered in 1998. Calculations of its orbit around the sun show that it will swing about 5.8 million kilometres from our home planet, or about 15 times the distance between Earth and the moon, at 2059 U.T.C (2159 British Summer Time, 1659 Eastern Standard Time) on 31May.
There is no risk of an impact, but it is getting close enough to take good images with telescopes on the ground. Asteroid enthusiasts from NASA to the White House have been gearing up to watch 1998 QE2 make its closest approach.
"We find something neat about every one that comes in like this," says Tim Spahr of the Minor Planet Center at Harvard University. "They're all different, and it's very cool what you can learn from close approaches."
Initial readings suggest that the main asteroid is 2.7-kilometres wide, and its bright companion is roughly 600 metres across.
Asteroid duos and even trios make up 15 per cent of near-Earth objects larger than200 metres. The discovery of the small moon around 1998 QE2 gives us a rare opportunity to weigh the larger object, and that can tell us what it is made of, says Spahr. 

 

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