A collaboration of astronomers and observatories have discovered that the dwarf planet Haumea, which orbits out beyond Neptune, has a ring around it: Oddball dwarf planet Haumea has a ring | Science News
On January 21, [Jose-Luis Ortiz of the Institute of Astrophysics of Andalusia in Granada, Spain] and colleagues used 12 telescopes at 10 observatories to peer into the Kuiper Belt, a region of icy objects beyond the orbit of Neptune, and watch Haumea block the light of a distant star. That tiny eclipse let the team measure the dwarf planet’s size, shape and surrounding environment more accurately than ever before.
Haumea turned out to be larger — its long axis stretches at least 2,322 kilometers, a bit more than half the width of the contiguous United States — and less dense than previously thought, the team reports October 11 in Nature. To their surprise, the researchers also saw the background star flicker before and after its light was blocked by Haumea itself. That flicker is consistent with a 70-kilometer-wide ring about 1,000 kilometers above the dwarf planet’s surface.
The ring presumably consists of rocks and ice like planetary rings elsewhere: Planetary Society-funded telescopes help find ring around Haumea, a distant dwarf planet | The Planetary Society
We know giant planets like Jupiter, Saturn, Uranus and Neptune have rings, but thus far, we’ve only found them around two small worlds. Chariklo is about 250 kilometers wide, and has two rings, while Chiron, about the same size, is also suspected to have a ring. Both Chariklo and Chiron are Centaurs, small worlds orbiting the Sun between the asteroid belt and Kuiper belt, crisscrossing the giant planets’ orbits.
With today’s announcement, Haumea becomes the first, small, non-Centaur known to have a ring, and the farthest ring world we’ve found in our solar system.