Solar system 'centaur' might have rings like Saturn

MIT researchers think that Chiron might be the sixth body in our solar system to have rings. Take that, Saturn!

Michael Franco
Freelancer Michael Franco writes about the serious and silly sides of science and technology for CNET and other pixel and paper pubs. He's kept his fingers on the keyboard while owning a B&B in Amish country, managing an eco-resort in the Caribbean, sweating in Singapore, and rehydrating (with beer, of course) in Prague. E-mail Michael.
Michael Franco
2 min read

An artist's impression of what rings around a centaur -- in this case, Chariklo -- might look like. ESO/L. Calçada/Nick Risinger (skysurvey.org)

Think "rings" and "planet" and really only one thing comes to mind. That's right -- Green Lantern's Power Ring! No, that's not quite right. Oh yeah... Saturn.

The flashy planet that sits an average of 886 million miles away from the sun is the most famous ring-bearing body in our solar system, but it's actually not the only one. Astronomers have found five in all -- and a new report published last month in the journal Icarus by MIT scientists indicates that there might now be a sixth.

In addition to Saturn, the planets Jupiter, Uranus and Neptune also have rings around them, albeit much fainter than those that swirl around Saturn. Then, just last year, astronomers made the discovery that a centaur named Chariklo also had rings. Centaurs are solar system bodies somewhere between a comet and an asteroid and are typically found between Jupiter and Pluto. Their dual personality earned them their name from the mythic half-man, half-horse figure.

Now, MIT lecturer Amanda Bosh and her colleagues believe that Chiron, the first centaur ever discovered (1977), might also have a ring system. The team analyzed data from NASA's Infrared Telescope Facility and the Las Cumbres Observatory Global Telescope Network (both in Hawaii) from 2011 when Chiron passed in front of a bright star. By observing the kind of shadow they were able to see when Chiron was backlit, the researchers figured out that there were features measuring about 3-7 kilometers wide (about 2-4 miles) jutting out about 300 kilometers (about 186 miles) from its center.

While the researchers feel most confident with the ring theory, they say it's also possible that the features extending from Chiron could be a shell or jets spraying material off the surface of the centaur.

"If we want to make a strong case for rings around Chiron, we'll need observations by multiple observers, distributed over a few hundred kilometers, so that we can map the ring geometry," Jessica Ruprecht, a team member from MIT's Lincoln Laboratory, said in a statement. "But that alone doesn't tell us if the rings are a temporary feature of Chiron, or a more permanent one. There's a lot of work that needs to be done."

Whether they're jets, a shell, or rings -- which are typically made from dust and ice -- the mere fact that we're learning about these distant bodies is encouraging for Matthew Knight, an astronomer at the Lowell Observatory in Flagstaff, Ariz., who wasn't involved in the research.

"We have a pretty good feel for what most of the inner solar system is like from spacecraft missions, but the small, icy worlds of the outer solar system are still mysterious," Knight told MIT News. "At least to me, being able to picture a centaur having a ring around it makes it seem more tangible."