Ring discovered around a dwarf planet.
In the early morning hours of January 21, 2017, the dwarf planet Haumea passed in front a star and cast a shadow across Europe. Twelve telescopes at 10 different observatories watched. European scientists hoped the transit would shed new light on a far-flung member of our solar system orbiting farther from the Sun than Pluto.
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.
The European observers discovered Haumea's rings by measuring the amount of light coming from the star the dwarf planet crossed. The light dips were consistent with a ringed world, and the
Nature paper describes the rings as being similar to those of Uranus and Neptune.