The Resonance Hopping Effect in the Neptune-Planet Nine System

TL;DR

This paper investigates the resonance hopping phenomenon among distant Kuiper Belt objects influenced by Planet Nine, highlighting Neptune scattering's role and emphasizing secular interactions over resonances in their dynamics.

Contribution

It provides a detailed analysis of resonance hopping mechanisms and clarifies the dominant secular interactions governing TNO dynamics in the presence of Planet Nine.

Findings

Resonance hopping involves abrupt transitions between mean-motion commensurabilities.

Neptune scattering interactions cause diffusion in TNO semi-major axes.

Secular interactions primarily drive the dynamics of anti-aligned TNOs.

Abstract

The observed physical clustering of the orbits of small bodies in the distant Kuiper Belt (TNOs) has recently prompted the prediction of an additional planet in the outer solar system. Since the initial posing of the hypothesis, the effects of Planet Nine on the dynamics of the main cluster of TNOs - the objects anti-aligned with its orbit - have been well-studied. In particular, numerical simulations have revealed a fascinating phenomenon, referred to as "resonance hopping", in which these objects abruptly transition between different mean-motion commensurabilities with Planet Nine. In this work, we explore this effect in greater detail, with the goal of understanding what mechanism prompts the hopping events to occur. In the process, we elucidate the often underestimated role of Neptune scattering interactions, which leads to diffusion in the semi-major axes of these distant TNOs. In addition, we demonstrate that although some resonant interactions with Planet Nine do occur, the anti-aligned objects are able to survive without the resonances, confirming that the dynamics of the TNOs are predominantly driven by secular, rather than resonant, interactions with Planet Nine.