Dynamical Environment and Stability around Centaur (2060) Chiron

Abstract A recent stellar occultation revealed that the Centaur (2060) Chiron hosts a broad disk extending beyond ∼200 km from its center, embedding three ring-like structures (Chi1R, Chi2R, and Chi3R), while a tenuous outer ring (Chi4R) lies beyond the Roche limit. Here, we present a first dynamical assessment of the system’s stability through numerical simulations of test particles, accounting for Chiron’s triaxial figure. For an equatorial ellipticity of C 22 ∼ 0.02, as inferred from the most recent shape estimates, our simulations reveal a chaotic inner zone extending to ∼260 km, where particle lifetimes reach up to a year, while particles beyond ∼260 km can remain stable for at least a decade. These results suggest that the innermost portion of the disk is ephemeral and can only persist if continuously replenished. For lower ellipticity values ( C 22 ≲ 0.012), however, the entire disk is located within the stable region, regardless of Chiron’s mass. Under the physical parameters currently available in the literature, Chi2R is possibly linked to the 1:3 spin-orbit resonance, while Chi1R cannot be linked to the 1:2 resonance, as previously proposed, since this resonance is unstable. Instead, Chi1R and Chi3R may be associated with the 2:5 and 1:5 spin–orbit resonances, respectively. Both the 1:3 and 1:5 resonances are bifurcated, generating chaotic zones that may explain the gap in Chi2R and the longitudinal asymmetry observed in Chi3R.