The relationship between Centaur activity and ring formation

Abstract

Introduction: Centaurs are small bodies whose orbits lie between those of Jupiter and Neptune (Gehrels, 1999). They are thought to be transition objects that originate in the Kuiper belt and occupy the cis-Neptunian region before potentially becoming Jupiter-family or other short-period comets (Dones, Levison, & Duncan, 1996). Their short dynamical lifetimes are on the order of 106 years (Horner, Evans, & Bailey, 2004) due to their unstable, planet-crossing orbits (Horner, Evans, Bailey, & Asher, 2003). Some Centaurs have been observed to be active, and the bodies in the population of active Centaurs have perihelion distances that are statistically smaller than the median perihelion distance for all Centaurs, suggesting that Centaur activity is thermal in nature (Jewitt, 2009). Centaur activity may be observed through changes in the brightness of an object such as those exhibited by the Centaur Chiron (Parker et al., 1997). The presence of a coma around a Centaur may also provide evidence of activity, and dust comae have been detected around several bodies including Chiron (Meech & Belton, 1989; Luu & Jewitt, 1990) and Echeclus (Choi, Weissman, & Polishook, 2006). In addition to comae, other structures have been observed around Centaurs, such as the ring system that was discovered around Chariklo during a stellar occultation (Braga-Ribas et al., 2014). A symmetric feature was observed around Chiron during an occultation (Ruprecht et al., 2015), and some interpret this feature to be possible ring material (Ortiz et al., 2015). Similarly, the trans-Neptunian dwarf planet Haumea was revealed to have a ring during a stellar occultation (Ortiz et al., 2017). The collisional spreading time of Chariklo's rings was calculated to be on the order of 101 years, which is short in comparison to the estimated Centaur lifetime of approximately 106 years (Pan & Wu, 2016), yet Centaur rings are still observed despite this contradiction. Shepherd satellites may serve to increase the lifetime of a Centaur's rings (Pan & Wu, 2016) and maintain distinct ring edges such as those observed in Chariklo's ring system (Charnoz, Canup, Crida, Dones, 2017). Moreover, Centaur activity could supply material to an already present ring system, thus prolonging its lifetime. This study explores the potential connection between Centaur activity and Centaur ring systems by using the N-body integrator REBOUND to model outburst particle interactions and distributions.