Ring system around centaur Chariklo

Centauri - asteroids, orbiting Sun between Saturn and Uranus. Chariklo is the largest centaur in the class with sizes  334x266x172 km. It was discovered in 1997 and named after wife of centaur Chiron from Greek mythology.

The minor planet has its own ring system - just as Saturn. Two rings, one about seven and the other about three kilometers wide, separated by a gap of nine kilometers, are located at 396 and 405 kilometers from the centaur.

For now it is the smallest known object to have rings, and only the fifth body in the Solar System in the company of giant planets.

Image:  ESO/L. Calçada/M. Kornmesser/Nick Risinger (skysurvey.org)  Artist rendering of Chakiklo's rings

Image: JPL

Japanese research team modeled Chariklo system with rings, using realistic sizes for ther ring particles, while also taking into account collisions and gravitational interactions between the particles.  By considering both the detailed structure and the global picture for the first time, the team found that Chariklo's inner ring should be unstable without help. It is possible the ring particles are much smaller than predicted or that an undiscovered shepherd satellite around Chariklo is stabilizing the ring.

Image:  Shugo Michikoshi, Eiichiro Kokubo, Hirotaka Nakayama, 4D2U Project, NAOJ 

 Their results show that the density of the ring particles must be less than half the density of Chariklo itself. As observations from Earth show presence of water in Charicko composition, there is a probability that the rings are icy.

Their results also showed that a striped pattern, known as "self-gravity wakes," forms in the inner ring due to interactions between the particles. These self-gravity wakes accelerate the break-up of the ring. The team recalculated the expected lifetime of Chariklo's rings based on their results and found it to be only 1 to 100 years, much shorter than previous estimates. This is so short that it's surprising the ring is still there.

Image:  Shugo Michikoshi (Kyoto Women's University/University of Tsukuba) 

 Although Chariklo is only hundreds of kilometers in size, its rings are as opaque as those around Saturn and Uranus. Thus Chariklo offered an ideal chance to model a complete ring system.