Distant dwarf planet near Pluto has a ring that no one expected

By Ken Croswell

A ring has been found around Haumea, a world more than 2 billion kilometres beyond Pluto. The ring is the most distant ever seen in our solar system.

“This is a landmark discovery,” says Alan Stern at the Southwest Research Institute in Boulder, Colorado. “It’s very exciting.”

Until recently, the only known rings circled giant planets such as Saturn. In 2013, however, astronomers found two rings around Chariklo, an odd little rock about 250 kilometres across between the orbits of Saturn and Uranus. Chiron, one of Chariklo’s neighbours, may also have a ring.

Now astronomers have found a ring beyond Neptune. José-Luis Ortiz and Pablo Santos-Sanz at the Institute of Astrophysics of Andalusia in Granada, Spain, and their colleagues watched the dwarf planet Haumea pass in front of a dim red star in the constellation Boötes on 21 January this year. A total of 12 telescopes in six European countries tracked the eclipse.

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