Dense and narrow rings around the Centaur object (10199) Chariklo

International audienceA stellar occultation observed on June 3, 2013 (Braga-Ribas et al., Nature 508, 72, 2014) revealed the unexpected presence of two dense rings around (10199) Chariklo, the largest Centaur object known to date with a radius of 119±5 km (Fornasier et al. A&A 2014, in press). The two rings (called respectively C1R and C2R hereby) have orbital radii a_C1R= 390.6±3.3 km and a_C2R= 404.8±3.3 km (1-sigma limits), and typical average optical depths of tau_C1R= 0.4 and tau_C2R= 0.06. They are separated by a gap of about 9 km with optical depth less than 0.004.The presence of those two rings was confirmed during four stellar occultations observed in 2014, on February 16 (Chile), March 16 (Thailand), April 29 (Southern Africa) and June 28 (Southern Africa).The occultation events imply a J2000 pole position of alpha= 151.25±0.50 and delta= 41.48±0.22 deg. The rings' changing geometry explains the long term variations of Chariklo's absolute magnitude and the spectral changes observed between 1997 and 2013. They imply a reflectance I/F of about 0.07 for C1R, and show that it contains about 20% of water ice, the latter remaining undetected on Chariklo's surface (Duffard et aL A&A 2014, in press).The April 29, 2014 occultation reveals a W-shaped structure for C1R, with the densest parts reaching an apparent optical depth of about 2. The width of C1R exhibits variations that are compatible with a m=1 mode, its value varying between ~5.5 and ~7.1 km over the full 360 degrees longitude range. The width of C2R is less constrained and lies between 2 and 4 km.This is the first ring system ever observed that does not pertain to a giant planet. The existence of such a system raises several questions as to the origin and evolution of rings around such a small object. This discovery also suggests that rings may be a more frequent feature than previously thought, in particular around small bodies.Possible models for the ring formation will be proposed. They can be classified into collisional scenarios that disrupted an impactor or a pre-existing satellite, tidal disruption of an inward-migrating satellite, or more exotic models in which material produced by a cometary activity of Chariklo was sent in orbit around the body