The gravitational braking of captured moons around ringed planets

TL;DR

This paper explores how the gravitational interaction between captured irregular moons and planetary ring systems can reveal details about moon capture processes and ring evolution, using computational simulations of Phoebe's capture by Saturn.

Contribution

It introduces a novel approach linking moon capture dynamics with ring system signatures, using simulations to constrain capture scenarios and understand ring-moon interactions.

Findings

Simulations of Phoebe's capture show distinctive ring signatures.

Gravitational braking influences ring structure and moon orbit parameters.

Method offers a new way to study moon origins and ring evolution.

Abstract

Irregular moons are a class of satellite found orbiting all of the Solar System's giant planets: as their orbits don't match those of their planets, they are theorised to have formed elsewhere in the Solar System and were subsequently captured into their observed orbits. Missions such as Cassini have contributed significant empirical data on irregular moons in the present day but this paper aims to develop our currently limited theoretical understanding of their origins and capture as it presents one of the first projects to connect moon capture with another feature common to all giant planets: ring systems. As a captured body gravitationally brakes around a ringed planet, it transfers orbital energy to the planetary system, a process which has been seen to leave distinctive signatures on the rings which may be used to constrain key parameters of this interaction, including the trajectory and timing. This paper presents a project which applies this technique to constrain scenarios for moon capture through conducting a series of computational simulations using the Python version of the astrophysical code REBOUND modelling the capture of the large irregular moon Phoebe by the planet Saturn and Phoebe's effect on Saturn's ring system. By helping to constrain scenarios for moon capture, this research will further our understanding of the moon systems of the giant planets while simulating the effects of a moon's interaction with a ring system will offer insight into the formation and evolution of planetary rings, whether within our own Solar System or orbiting exoplanets.