Two Dynamical Classes of Centaurs

TL;DR

This paper distinguishes two chaotic orbital behaviors in Centaurs—generalized diffusion and resonance-sticking—and links these behaviors to their dynamical lifetimes and potential evolution into comets.

Contribution

It quantitatively characterizes the two types of chaotic evolution in Centaurs and correlates them with their lifetimes and evolutionary outcomes.

Findings

Generalized diffusion describes short-lived Centaurs' orbital evolution.

Resonance-sticking dominates longer-lived Centaurs.

Centaurs in the diffusing class often become Jupiter-family comets.

Abstract

The Centaurs are a transient population of small bodies in the outer solar system whose orbits are strongly chaotic. These objects typically suffer significant changes of orbital parameters on timescales of a few thousand years, and their orbital evolution exhibits two types of behaviors described qualitatively as random-walk and resonance-sticking. We have analyzed the chaotic behavior of the known Centaurs. Our analysis has revealed that the two types of chaotic evolution are quantitatively distinguishable: (1) the random walk-type behavior is well described by so-called generalized diffusion in which the rms deviation of the semimajor axis grows with time t as ~t^H, with Hurst exponent H in the range 0.22--0.95, however (2) orbital evolution dominated by intermittent resonance sticking, with sudden jumps from one mean motion resonance to another, has poorly defined H. We further find that these two types of behavior are correlated with Centaur dynamical lifetime: most Centaurs whose dynamical lifetime is less than ~22 Myr exhibit generalized diffusion, whereas most Centaurs of longer dynamical lifetimes exhibit intermittent resonance sticking. We also find that Centaurs in the diffusing class are likely to evolve into Jupiter-family comets during their dynamical lifetimes, while those in the resonance-hopping class do not.