A ring has been discovered around one of the dwarf planets that orbits the outer reaches of the solar system.

Until now, ring-like structures had only been found around the four outer planets – Jupiter, Saturn, Uranus and Neptune.

“In 2014 we discovered that a very small body in the Centaurs region [an area of small celestial bodies between the asteroid belt and Neptune] had a ring and at that time it seemed to be a very weird thing,” explained Dr José Ortiz, whose group at the Instituto de Astrofísica de Andalucía in Granada made the discovery described in the journal Nature. “We didn’t expect to find a ring around Haumea, but we were not too surprised either.”

Thousands of so-called Neptunian objects are located in the outer solar system. In 2006, it was revealed that some of them could be as large as Pluto, which led the International Astronomical Union to create the category of dwarf planets.

Haumea was recognised by the International Astronomical Union in 2008 and is one of five dwarf planets, alongside Pluto, Ceres, Eris and Makemake. They are located beyond Neptune – 50 times farther away from the sun than Earth.

Haumea, named after the Hawaiian goddess of childbirth, is unusual because of its elongated shape, comparable to a rugby ball, and its rapid rotation, spinning around once every 3.9 hours. Its diameter is approximately a third of the size of Earth’s moon.

“Dwarf planets are unique by themselves but Haumea is even more special among them,” said Ortiz “It also has two moons, a large and a small one, and the larger one turns out to be in the same plane as the ring we found.”