A lump of space rock some 6.9 million kilometres (4.3 million miles) away has been revealed to be an asteroid that’s quite rare in our Solar System, according to detailed images taken by the Arecibo Observatory.
To date, the asteroids that we have found seem to be comprised of smaller rocks held loosely by gravity. This asteroid, dubbed 2011 UW158, was found to have a shape not too dissimilar to an unshelled walnut. With a diameter of 300 by 600 metres (1000 by 2000 feet), UW158 is around the same size as two Arecibo telescopes. What’s more, the asteroid rotates very rapidly, once every 37 minutes. “Its size, shape and rotation suggest there is something more than gravity holding this object together or else the asteroid would break up due to its fast spin,” says Patrick Taylor, who led the observations.
There is one possibility that could explain the asteroid: it could be made of one single lump of rock, rather by many smaller pebbles held together by gravity. This type of asteroid is quite rare with only two others of this type observed before. “We expect that something this big should have been shattered into smaller pieces by collisions with other asteroids over the age of the Solar System,” explains Taylor. “It is interesting that something this large and apparently solid is still around.”
The asteroid passed just 1.5282 million miles (2.4594 million kilometres) from Earth yesterday and will not make a flyby of our Solar System until 2108. Taylor stresses that the asteroid is not considered as a potential threat to Earth.