Chunk of Space Rock Could Have Rings in Astronomical First

An illustration showing what Centaur 10199 Chariklo and its rings could look like.

Mary ManleyA centaur is a type of minor planet characterized by an asteroid-like body that orbits the Sun and is found between Jupiter and Neptune. Scientists have recently published their findings on a pair of gossamer rings that were discovered encircling an asteroid-like chunk of rock that is too small to be seen from Earth.The rock is named Chariklo, which is a minor planet known as a centaur. And the rings encircling that chunk of rock are believed to be shepherded by a tiny, unseen moonlet. The rings were first spotted in 2013, but it wasn’t until last year that scientists were able to capture the shadows of starlight cast by Chariklo’s thin rings.The find is an exciting one, as Chariklo—which is 250 kilometers (155 miles) in diameter—is the only known centaur or asteroid with stable rings.Chariklo is also the largest known Centaur, though it’s unclear if this is the reason for its rings.Centaurs are believed to originate in the Oort Cloud which lies far beyond Pluto. But after millions of years they begin to drift inward, and are either ejected from the solar system by the gravity of a giant planet, or they transition into Jupiter friendly comets.»Rings around minor planets have only been recently discovered, and only a small number of such systems are currently known,» said lead astronomer Amanda Sickafoose of the Planetary Science Institute.»There has been significant research into the dazzling rings around the giant planets; however, the mechanisms of ring formation and evolution around small objects are not well understood. We’ve shown that one of the possibilities for thin rings to exist around small bodies is that they are being sculpted by a small satellite.»Chariklo’s rings are located about 243 miles and 252 miles from its center, respectively. And the rings themselves are narrow, just 4.3 miles and 1.9 miles wide. The rings should have dispersed by now, but computer simulations revealed that the influence of a small moonlet—1 kilometer (0.62 miles) in diameter—could be what is keeping the rings thin and in place.»We’ve shown that one of the possibilities for thin rings to exist around small bodies is that they are being sculpted by a small satellite,» Sickafoose said.The rings are also placed close to the Roche limit: the distance from a central body within which gravity keeps the rings from clumping together and forming new moons, which could be further proof that a moonlet is playing a part in their stability.

Half of the planets in our Solar System have rings, as well as some dwarf planets. Astronomers have also been finding an increasing number of asteroids that have moons, so an asteroid with rings as well as a moon may not be impossible. But sadly, due to Chariklo’s size and distance, we won’t get any images of this rare object any time soon.


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