During a break from looking at planets around other stars, ESA’s CHaracterising ExOPlanet Satellite (Cheops) mission has observed a dwarf planet in our own Solar System and made a decisive contribution to the discovery of a dense ring of material around it.

The dwarf planet is known as Quaoar. The presence of a ring at a distance of almost seven and a half times the radius of Quaoar, opens up a mystery for astronomers to solve: why has this material not coalesced into a small moon?