An asteroid discovered last year is actually two objects, each about 900 metres in size and orbiting each other, new observations by three of the world’s largest radio telescopes have revealed.

Near-Earth asteroid 2017 YE5 was discovered with observations provided by the Morocco Oukaimeden Sky Survey in December last year, but no details about the asteroid’s physical properties were known until the end of June, NASA said in a statement.

This is only the fourth “equal mass” binary near-Earth asteroid ever detected, consisting of two objects nearly identical in size, orbiting each other.

The observations revealed two distinct lobes, but the asteroid’s orientation was such that scientists could not see if the two bodies were separate or joined. Eventually, the two objects rotated to expose a distinct gap between them.

The new observations obtained between June 21 and 26 indicate that the two objects revolve around each other once every 20 to 24 hours.

Radar imaging shows that the two objects are larger than their combined optical brightness originally suggested, indicating that the two rocks do not reflect as much sunlight as a typical rocky asteroid. 2017 YE5 is likely as dark as charcoal, NASA said..

Scientists estimate that among near-Earth asteroids larger than 200 metres in size, about 15 per cent are binaries with one larger object and a much smaller satellite. Equal-mass binaries like 2017 YE5 are much rarer.PTI


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