Astronomers have spotted a ring around a dwarf planet called Quaoar in the outer reaches of the solar system.
Dwarf planet:
A dwarf planetis a small planetary-mass object that is in direct orbit of the Sun, smaller than any of the eight classical planets but still a world in its own right. The prototypical dwarf planet is Pluto.
The dwarf planet, which is about half the size of Plutoand orbits beyond Neptune, is too distant and the ring too narrow to be seen directly.
Rings and Roche Limit
The observations, by a powerful telescope on La Palma, reveal the ring to be much further away from the planet.
The ring was outside the theoretical maximum for where a ring can survive according to classical theory.
The ring is located at a distance of more than seven planetary radii, twice as far out as what was previously thought to be the maximum radius, known as the Roche limit. Inside the Roche limit, the planet exerts strong tidal forces that prevent debris in the ring amalgamating into a moon.
