Rings Around Non-Spherical Worlds: Sub-mm Dust Retention Around Triaxial Small Bodies in the Solar System

TL;DR

This study models the evolution of narrow rings around small, non-spherical bodies in the Solar System, showing that triaxial shapes help rings retain sub-millimeter particles over relevant timescales.

Contribution

It introduces a GPU-accelerated simulation accounting for non-axisymmetric gravity and solar radiation effects, revealing how triaxial shapes influence ring stability and particle retention.

Findings

Triaxial shapes suppress radiation pressure-driven eccentricity growth.

Narrow rings can retain sub-millimeter particles for timescales shorter than Poynting-Robertson drag.

Ring widths are about 10 km for Chiron and Chariklo, and 40-70 km for Quaoar and Haumea.

Abstract

We investigated the millennial-scale evolution of narrow innermost rings composed of pebble-sized to sub-millimeter particles around the four known ring-bearing small bodies Chiron, Chariklo, Quaoar, and Haumea. Using a GPU-accelerated 8th-order Hermite integrator, we modeled the combined effects of solar radiation pressure (RP), shadowing of the rings by the host body, heliocentric motion, and the non-axisymmetric gravitational field of the rotating triaxial central body. The calculations compare spherical and triaxial-body models, as well as coplanar and inclined ring configurations. In spherical models, solar RP excites particle eccentricities, leading to accretion onto the central body above a critical RP parameter. This effect is strongest for the lower-mass systems, Chiron and Chariklo, where particles with relatively modest radiation forcing are rapidly removed. In contrast, when the triaxial shape of the host body is included, rapid apsidal precession suppresses RP-driven eccentricity growth and prevents material loss from the ring over the simulated interval. The triaxial models also suppress the previously identified Sun-facing reorientation of highly inclined rings and instead produce moderate vertical broadening. Strongly confined rings persist for RP parameters corresponding to particle sizes larger than about 7-40 micrometers, depending on composition. Their characteristic radial widths are about 10 km for Chiron and Chariklo and about 40-70 km for Quaoar and Haumea. The vertical thicknesses of the rings are estimated to be on the order of 1 km for Chiron and Chariklo, and only several hundred meters for Quaoar and Haumea. Our results suggest that narrow rings around triaxial small bodies in the Solar System can plausibly retain sub-millimeter particles over dynamically relevant timescales shorter than Poynting-Robertson drag.