Chaotic Diffusion of Resonant Kuiper Belt Objects

TL;DR

This study uses numerical simulations to analyze the long-term chaotic dynamics and stability of Neptune's 3:2 and 2:1 resonances in the Kuiper belt, revealing differences in their stability and implications for primordial populations.

Contribution

It provides the first detailed comparison of the long-term stability and chaotic diffusion in Neptune's 3:2 and 2:1 resonances through extensive numerical integrations.

Findings

2:1 resonance has weaker stability than 3:2

Approximately 15% of Twotinos survive for 4 Gyr

Approximately 27% of Plutinos survive for 4 Gyr

Abstract

We carried out extensive numerical orbit integrations to probe the long-term chaotic dynamics of the two strongest mean motion resonances of Neptune in the Kuiper belt, the 3:2 (Plutinos) and 2:1 (Twotinos). Our primary results include a computation of the relative volumes of phase space characterized by large- and small-resonance libration amplitudes, and maps of resonance stability measured by mean chaotic diffusion rate. We find that Neptune's 2:1 resonance has weaker overall long-term stability than the 3:2 -- only ~15% of Twotinos are projected to survive for 4 Gyr, compared to ~27% of Plutinos, based on an extrapolation from our 1-Gyr integrations. We find that Pluto has only a modest effect, causing a ~4% decrease in the Plutino population that survives to 4 Gyr. Given current observational estimates, and assuming an initial distribution of particles proportional to the local phase space volume in the resonance, we conclude that the primordial populations of Plutinos and Twotinos formerly made up more than half the population of the classical and resonant Kuiper Belt. We also conclude that Twotinos were originally nearly as numerous as Plutinos; this is consistent with predictions from early models of smooth giant planet migration and resonance sweeping of the Kuiper Belt, and provides a useful constraint for more detailed models.