A ring system detected around the Centaur (10199) Chariklo Journal-ref: Braga-Ribas et al., Nature, Volume 508, Issue 7494, pp. 72-75 (2014) DOI: 10.1038/nature13155 (original) (raw)

Until now, rings have been detected in the Solar System exclusively around the four giant planets 1. Here we report the discovery of the first minor-body ring system around the Centaur object (10199) Chariklo, a body with equivalent radius 2 124±9 km. A multi-chord stellar occultation revealed the presence of two dense rings around Chariklo, with widths of about 7 km and 3 km, optical depths 0.4 and 0.06, and orbital radii 391 and 405 km, respectively. The present orientation of the ring is consistent with an edge-on geometry in 2008, thus providing a simple explanation for the dimming of Chariklo's system between 1997 and 2008 3 , and for the gradual disappearance of ice and other absorption features in its spectrum over the same period 4, 5. This implies that the rings are partially composed of water ice. These rings may be the remnants of a debris disk, which were possibly confined by embedded kilometre-sized satellites. Chariklo is the largest known Centaur object orbiting in a region between Saturn and Uranus with orbital eccentricity 0.171 and semi-major axis 15.8 astronomical units (1AU is the Earth-Sun distance). It may be a former transneptunian object that has been recently (less than 10 Myr) scattered by gravitational perturbations from Uranus 6. No clear detection of Chariklo's rotation has been made so far. Its surface is very dark with a geometric albedo 2 0.035±0.011, and it is subject to long-term spectral and photometric variabilities 3, 4, 5 , although no cometary activity has ever been reported. An occultation of an R=12.4 magnitude star by Chariklo was predicted 7 to cross South America on June 3, 2013; see Extended Data Figures 1 and 2. We obtained data from sites distributed in Brazil, Argentina, Uruguay and Chile (Extended Data Table 1). While the occultation by Chariklo itself was recorded at three sites in Chile, seven sites detected a total of thirteen rapid stellar flux interruptions (secondary events), two of them being resolved into two sub-events by the Danish 1.54m telescope at the European Southern Observatory (ESO) at La Silla (Figure 1).