Earth has a mysterious second moon - here's what we know about it

Earth's moon isn't alone out there.

It turns out that a second large rocky body is orbiting our world, and has been for about a hundred years now.

The object, called asteroid 2016 HO3, was first spotted by NASA this April and follows Earth in a long, wobbly orbit around the Sun, drifting ahead of and behind our planet.Here's what else we know about it so far: