Signatures of a Distant Planet on the Inclination Distribution of the Detached Kuiper Belt

TL;DR

This study uses simulations and survey data to investigate how a hypothetical ninth planet influences the inclination distribution of distant, detached Kuiper Belt objects, potentially explaining observed features not accounted for by the known planets.

Contribution

It demonstrates that a ninth planet can produce low-inclination detached TNOs, offering a new way to test the existence of Planet Nine through observational constraints.

Findings

A ninth planet creates low-inclination detached TNOs absent in the 8-planet model.

Kozai-Lidov oscillations in Neptune resonances do not produce low-inclination detached TNOs.

Differences in TNO inclination distributions can constrain the existence of Planet Nine.

Abstract

A distant, massive planet in the outer solar system has recently been proposed to explain some observed features of extreme trans-Neptunian objects (TNOs). Here we use N-body simulations of the formation of the Kuiper belt and Oort cloud as well as a survey simulator to compare models of the solar system with and without a 9th planet to one another as well as to observations. The main mechanism for TNOs to be deposited into the distant ($a$ > au), detached ($q$ > au) region of the Kuiper Belt in the 8-planet model is Kozai-Lidov oscillation of objects in mean motion resonances (MMR) with Neptune. This effect does not deposit low-inclination ($i \lesssim$ 20{\deg}) objects into this region. However, we find that the 9th planet generates a group of distant, detached TNOs at low inclinations that are not present in the 8-planet model. This disparity between the 8-planet and the 9-planet models could provide a strong constraint on a possible planet 9 with further detections of TNOs in the distant, detached region of the Kuiper Belt.