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The dynamics of rings around irregular bodies

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Stellar occultations revealed the surprising presence of dense rings around (10199) Chariklo (1,2), a small Centaur object with diameter ~250 km that probably originates from the Trans-Neptunian region. Before that discovery, rings were known only around the four giant planets, and it now appears that those systems are more common in the universe than previously thought. Chariklo’s rings exhibits resemblance with their cousins of the giant planets, e.g. the narrow and sharply confined Uranus’ rings. This calls for some active confinement mechanisms, e.g. by nearly shepherd moonlets yet to be discovered. However, there is a noteworthy difference with the giant planets: the central body is small, hence much more irregular than the gaseous planets, which have esentially axisymmetric gravitational potentials. Here, we show that topographic features (e.g. mountains of a few km) or a slight elongation of the body may induce strong corotation and Lindblad mean motion resonances on the rings. I will discuss the strength of such resonances and show that an initial debris disk surrounding Chariklo should be pushed away from the corotation radius, so that the inner material falls onto the central body, while the outer material is pushed away at the present location of the rings. The time scales associated are short enough – some 10^5 years – to explain the current structure of Chariklo’s ring system: an empty region near the body, with rings residing in the outermost part of Chariklo’s Roche zone.

(1) F. Braga-Ribas et al., Nature 508, 72 (2014)

(2) B. Sicardy et al., arXiv 1612.03321 (2016)

This work receives funding from the ERC grant Agreement n°669416 “Lucky Star”

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