Rings Around Non-Spherical Worlds: Sub-mm Dust Retention Around Triaxial Small Bodies in the Solar System
Zs. Regaly, V. Frohlich, Cs. Kalup, Cs. Kiss
TLDR
Triaxial shapes of small solar system bodies enable the long-term retention of sub-millimeter dust rings by suppressing radiation pressure effects.
Key contributions
- Modeled millennial-scale evolution of sub-mm rings around Chiron, Chariklo, Quaoar, and Haumea using a GPU integrator.
- Demonstrated that triaxial body shapes suppress radiation pressure-driven ring dispersal via rapid apsidal precession.
- Found triaxial shapes prevent reorientation of inclined rings, instead causing moderate vertical broadening.
- Calculated stable ring dimensions: ~10-70 km radial width and ~hundreds of meters to 1 km vertical thickness.
Why it matters
This research explains how narrow rings around non-spherical small bodies can persist over long timescales, despite solar radiation pressure. It provides a crucial mechanism for retaining sub-millimeter particles, which was previously difficult to account for. This significantly advances our understanding of ring stability in the outer Solar System.
Original 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.
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