The Ring System Discovered Around the Centaur Object (10199) Chariklo

Thursday, 18 December 2014: 1:40 PM
Felipe Braga-Ribas1, Bruno Sicardy2, Jose L Ortiz3, Roberto Vieira Martins1, Francois Colas4, Rene Duffard3, Julio I.B. Camargo1, Josselin Desmars1, Amanda Gulbis5,6, Marcelo Assafin7, Lucie Maquet2, Wolfgang Beisker8, Gustavo Benedetti-Rossi1, Frederic Vachier4, Christophe Dumas9, Valentin D. Ivanov9, Stefan Renner4,10, Karl-Ludwig Bath11, Alain Klotz12 and Joseph T. Pollock13, (1)Observatorio Nacional, GPA, Rio de Janeiro, Brazil, (2)Paris Observatory Meudon, LESIA, Meudon, France, (3)Instituto de Astrofisica de Andalucia, Granada, Spain, (4)Observatoire de Paris, IMCCE, Paris, France, (5)Massachusetts Institute of Technology, Cambridge, MA, United States, (6)South African Astronomycal Observatory, Cape Town, South Africa, (7)Observatório do Valongo, Rio de Janeiro, Brazil, (8)Internetional Occultation Timing Associatios, European Section, Munich, Germany, (9)European Southern Observatory, Santiago, Chile, (10)Université de Lille, Villeneuve d'Ascq, France, (11)Internationale Amateursternwarte, Heidelberg, Germany, (12)Universite de Toulouse, Toulouse, France, (13)Appalachian State University, Boone, NC, United States
Observations of a stellar occultation on 03 June 2013 led to the discovery of the first ring system around a small Solar System object, the Centaur (10199) Chariklo (Braga-Ribas et al. 2014, Nature, 508, 72). The object has a radius of about 125 km and moves on an unstable orbit between Saturn and Uranus, with lifetime of about 10 Myr.

The fifth ring system ever discovered (after those around the four giant planets) is made of two dense and narrow rings with respective widths of 7 and 3 kilometers, normal optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometers, respectively (see figure). They are separated by an empty gap of about 9 km (see Figure 1). Their current configuration may be explained by the presence of putative kilometric-sized satellites. By means of the shepherd mechanism, satellites can confine and open the gap between the rings, otherwise they would spread out in few thousand years.

From 1997 to 2008, the Chariklo system exhibited an unexplained behavior. It dimmed by 0.6 in absolute magnitude and the water-ice band in its spectrum, formerly observed, could not be detected in 2008. All this is simply explained by the rings' pole orientation, which implies that they were seen edge-on in 2007-2008. We can also calculate their reflectivity I/F ~ 0.1. Spectroscopic and photometric observations of the system allowed us to calculate the amount of water ice and silicate elements in the rings as well as on the main body. No water ice is detectable on the surface of Chariklo. 

New stellar occultations by the Chariklo system were observed in 2014, and they show the fine structure of the rings as well confirm the preferred pole position from the 2013 event. These findings will be presented and possible formation scenarios will be discussed.