Haumea, a Dwarf Planet in the Kuiper Belt, Has Its Own Ring

Scientists have identified a ring circling Haumea, an egg-shaped dwarf planet (relatively) near Pluto shown in this artist's illustration. JM Madiedo, JL Ortiz/IAA-CSIC

There's a lot going on just outside of our solar system, planet-wise. Sure, there's the dwarf planet Pluto lurking out there beyond Neptune. But there's more than that one, demoted little former planet hanging out in the Kuiper Belt, the disc of space rubble that orbits our sun. In fact, in addition to an unfathomable number of asteroids and chunks of frozen gasses, Pluto has a couple of dwarf planet friends out there in the Kuiper belt called Haumea and Makemake. There may, of course, be more mini worlds out there, but for now it's great to find out what we can about the ones we know.

Which is why astronomers are pumped about discovering a ring around Haumea.

Planets, as we know, sometimes have rings made out of chunks of rock and ice — Saturn's got the most famous one, but Jupiter, Uranus and Neptune have them, too. But Haumea, a little oblong chunk of rock that lies 50 times farther away from the sun than Earth, is the only official dwarf planet ringed by its own collection of orbiting space particles. It's also the only trans-Neptunian object — a planet-like object that orbits the sun from a distance equal or greater to that of the planet Neptune — known to have a ring.

A new study published in the October 2017 journal Nature reports the discovery of Haumea's ring. In January, 2017, a team of researchers from the Spain's Institute of Astrophysics of Andalusia (IAA-CSIC) wanting to find out more about the celestial body trained 12 telescopes from 10 different European observatories at a star they knew Haumea would pass in front of. When the dwarf planet moved in front of the star, they expected to be able to get a good look at Haumea's size, shape and rotational speed, which they did, but they also spotted a ring.

"There are different possible explanations for the formation of the ring," said lead author José Luis Ortiz, a researcher at the IAA-CSIC, in a press release. "It may have originated in a collision with another object, or in the dispersal of surface material due to the planet's high rotational speed."

The scientists also found Haumea to be much bigger, less dense and less reflective than they suspected. The egg-shaped Haumea, when measured along its largest axis, is about as long as Pluto is round, and has at least two of its own moons: Hiʻiaka and Nāmaka. But unlike Pluto, the dwarf planet lacks the global atmosphere of that erstwhile ninth (non-)planet. And the researchers think that presence of a ring, which circles Haumea about 1,421 miles (2,287 kilometers) from its equator at a speed three times slower than the planet's own rotation, might mean similar rings could be much more common in our solar system than previously thought.

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