Space-watchers peering at the fly-by asteroid 2004 BL86 will have missed a detail that NASA caught: the flying mountain has its own moon.
As Space.com states, the rock is now receding from Earth at the respectable rate of 56,300 km/h (35,000 mph).
Using the 70 metre Deep Space Network antenna at Goldstone, NASA JPL scientists caught and animated the images of the 325-metre-across BL86 and its small-but-still-significant 70 metre moon.
NASA notes that about 16 per cent of asteroids bigger than 200 metres are binaries, with a handful living in a ménage-à-trois.
BL86 won't come this close to Earth again for “at least the next two centuries”, NASA reckons. ®