Abstract

Contributed Talk - Splinter MinorBodies

Tuesday, 10 September 2024, 16:00   (S21)

A Stellar Flyby Connects Irregular Moons and Trans-Neptunian Objects: Implications for the Early Solar System

Susanne Pfalzner, Amith Govind, and Frank Wagner
Forschungszentrum Jülich

The giant planets' irregular moons are characterised by distant, inclined, and eccentric trajectories that are in sharp contrast to the regular moons' coplanar and nearly circular orbits. Despite their mysterious origins, these irregular moons share striking similarities with trans-Neptunian objects (TNOs). Our research shows that a close stellar flyby may be the key to unlocking this mystery. Using numerical simulations, we modelled the effects of a stellar flyby and found that such an event can replicate the complex dynamics of TNOs while simultaneously explaining the origin of the irregular moons and the colour distributions of both populations. The stellar flyby provides a plausible explanation for several unexplained features of the irregular moons. Specifically, it would result in a greater number of moons around Saturn than Jupiter, and retrograde orbits would be more common around both planets. Additionally, the stellar flyby would have injected TNOs from beyond 60 AU into the planetary region, which could explain why there are no very red irregular moons. This event would have also sent a significant portion of the original TNO population into the inner Solar System. However, most of these TNOs would have been either ejected from the Solar System or fallen into the Sun, while a substantial number would have impacted on terrestrial planets, potentially delivering prebiotic molecules.