  Observations in 2013 and 2014 of the Centaur 10199 Chariklo and its ring
system consistently indicated that the radial width of the inner, more massive
ring varies with longitude. That strongly suggests that this ring has a finite
eccentricity despite the fast differential precession that Chariklo's large
quadrupole moment should induce. If the inferred apse alignment is maintained
by the ring's self-gravity, as it is for the Uranian rings, we estimate a ring
mass of a few times 10^16 g and a typical particle size of a few meters. These
imply a short collisional spreading time of ~10^5 years, somewhat shorter than
the typical Centaur dynamical lifetime of a few Myrs and much shorter than the
age of the solar system. In light of this time constraint, we evaluate
previously suggested ring formation pathways including collisional ejection and
satellite disruption. We also investigate in detail a contrasting formation
mechanism, the lofting of dust particles off Chariklo's surface into orbit via
outflows of sublimating CO and/or N_2 triggered after Chariklo was scattered
inward by giant planets. This latter scenario predicts that rings should be
common among 100-km class Centaurs but rare among Kuiper belt objects and
smaller Centaurs. It also predicts that Centaurs should show seasonal
variations in cometary activity with activity maxima occurring shortly after
equinox.
