The Influence of Planet 9 on the Orbits of Distant TNOs: The Case for a Low Perihelion Planet

TL;DR

This study explores how a hypothetical Planet 9 with a low perihelion could explain the observed orbital clustering of distant trans-Neptunian objects, using numerical simulations and statistical analysis.

Contribution

It demonstrates that a low perihelion Planet 9 can produce the observed orbital confinement of distant TNOs while preserving other known features of the outer Solar System.

Findings

Lower perihelion distances lead to stronger orbital confinement.

The proposed model retains the classical Kuiper Belt characteristics.

The ratio of detached to scattering objects matches observations.

Abstract

The hypothesis of an additional planet in the outer Solar System has gained new support as a result of the confinement noted in the angular orbital elements of distant trans-Neptunian objects. Orbital parameters proposed for the external perturber suggest semimajor axes between 500 and 1000 au, perihelion distances between 200 and 400 au for masses between 10 and 20 $M_{\oplus}$. In this paper we study the possibility that lower perihelion distances for the additional planet can lead to angular confinements as observed in the population of objects with semimajor axes greater than 250 au and perihelion distances higher than 40 au. We performed numerical integrations of a set of particles subjected to the influence of the known planets and the putative perturber during the age of the Solar System and compared our outputs with the observed population through a statistical analysis. Our investigations showed that lower perihelion distances from the outer planet usually lead to more substantial confinements than higher ones, while retaining the Classical Kuiper Belt as well as the ratio of the number of detached with perihelion distances higher than 42 au to scattering objects in the range of semimajor axes from 100 au to 200 au.