It turns out Uranus has a cosmic companion as it circles the sun from nearly 1.8 billion miles away. Scientists have detected a Trojan - an asteroid-like object that shares a planet's orbit - moving ahead of the ice giant.
The discovery of 2011 QF99 was reported this week in the journal Science. And it was found almost by accident.
Mike Alexandersen, a doctoral student in astronomy at the University of British Columbia in Vancouver, Canada, wasn't looking for a Trojan. Nor was he studying Uranus.
He and his colleagues were surveying the transneptunian region of the outer solar system, hoping to see what kinds of orbits the objects there followed. (The transneptunian region is more or less the same thing as the Kuiper Belt. Studying the patterns of objects' orbits in the region helps scientists understand how the solar system formed some 4.5 billion years ago.)