Consequences of a Distant Massive Planet on the Large Semi-major Axis Trans-Neptunian Objects

TL;DR

This study investigates how a hypothetical distant massive planet, Planet 9, influences the orbital evolution of distant Trans-Neptunian Objects, revealing effects like perihelion shepherding and inclination changes, but not matching observed clustering.

Contribution

It provides a detailed dynamical analysis of the impact of a distant giant planet on TNOs, highlighting the necessity of a massive TNO disk and the limitations in reproducing observed orbital clustering.

Findings

TNOs with semi-major axes >250 au experience perihelion shepherding.

Many TNOs evolve to larger pericenters and retrograde inclinations.

Distant giant planet scenarios do not reproduce observed orbital clustering.

Abstract

We explore the distant giant planet hypothesis by integrating the large semi-major axis, large pericenter Trans-Neptunian Objects (TNOs) in the presence of the giant planets and an external perturber whose orbit is consistent with the proposed distant, eccentric, and inclined giant planet, so called planet 9. We find that TNOs with semi-major axes greater than 250 au experience some longitude of perihelion shepherding, but that a generic outcome of such evolutions is that the TNOs evolve to larger pericenter orbits, and commonly get raised to retrograde inclinations. This pericenter and inclination evolution requires a massive disk of TNOs (tens of M$_\Earth$) in order to explain the detection of the known sample today. Some of the highly inclined orbits produced by the examined perturbers will be inside of the orbital parameter space probed by prior surveys, implying a missing signature of the 9th planet scenario. The distant giant planet scenarios explored in this work do not reproduce the observed signal of simultaneous clustering in argument of pericenter, longitude of the ascending node, and longitude of perihelion in the region of the known TNOs.