50000 Quaoar
Quaoar has one known moon, named Weywot. It also has a ring. Unexpectedly, the ring is at twice the distance of the Roche limit, which was thought to be the maximum distance of a ring: beyond the Roche limit, the particles in a ring should clump together and form a moon; yet this has not happened to Quaoar's ring. It is thought that the particles do not clump together because of tides created by Weywot. There may also be small shepherd moons on either side of the ring, as there are at Saturn's F Ring.