Researchers at MIT have detected features around Chiron — a centaur in orbit between Saturn and Uranus — that indicate a ring system, or possibly jets or a shell of dust. If confirmed, it would only be the second minor planet in our Solar System known to host rings.
Chiron, more formally known as 2060 Chiron, represents a relatively new class of objects called centaurs. These minor planets, which are in orbit between the asteroid belt and the Kuiper belt, possess features indicative of both asteroids and comets. Astronomers estimate that there may be as many as 44,000 centaurs in the Solar System, mostly concentrated in a band between Jupiter and Pluto. Chiron, with its diameter of 144 miles (233 km), may actually qualify it as a dwarf planet.
Last year, another minor planet, Charliko, was found to have a pair of dense and narrow rings. Now, it appears that Chiron might have rings, too. Jennifer Chu from MIT News reports:
In November 2011, the group observed a stellar occultation in which Chiron passed in front of a bright star, briefly blocking its light. The researchers analyzed the star's light emissions, and the momentary shadow created by Chiron, and identified optical features that suggest the centaur may possess a circulating disk of debris. The team believes the features may signify a ring system, a circular shell of gas and dust, or symmetric jets of material shooting out from the centaur's surface.
"It's interesting, because Chiron is a centaur — part of that middle section of the solar system, between Jupiter and Pluto, where we originally weren't thinking things would be active, but it's turning out things are quite active," says Amanda Bosh, a lecturer in MIT's Department of Earth, Atmospheric and Planetary Sciences.
The researchers observed a pair of features, each about 186 miles (300 km) from Chiron's center. They appear to be 1.8 and 4.3 miles (3 and 7 km) wide, respectively. The going theory is that these features are rings, though the scientists haven't ruled out a shell or ring of gas and dust, or symmetrical jets of gas and dust.
As for the origin of these features, it's possible that Chiron captured the debris from another object that broke up. The rings could also be leftover material from the formation of the centaur itself.
"Another possibility involves the history of Chiron's distance from the sun," noted study co-author Jessica Ruprecht in MIT News. "Centaurs may have started further out in the solar system and, through gravitational interactions with giant planets, have had their orbits perturbed closer in to the sun. The frozen material that would have been stable out past Pluto is becoming less stable closer in, and can turn into gases that spray dust and material off the surface of a body. "
Regardless, it now appears that centaurs aren't always the dead, dormant objects they're often attributed to be.
Top image: ESO.