Libration of Pluto's argument of perihelion and the role of the major planets

TL;DR

This paper investigates how the major planets influence Pluto's argument of perihelion libration, focusing on the secular effects and resonance conditions that determine its behavior.

Contribution

It provides a quantitative analysis of the planetary perturbations affecting Pluto's perihelion libration, highlighting the role of the parameter k^2 and secular effects.

Findings

Neptune's mean motion resonance impacts libration behavior.

Secular perturbations from giant planets are significant.

Critical k^2 value determines libration occurrence.

Abstract

Pluto's argument of perihelion is known to librate around $90^\circ$. This libration is related to the secular phenomenon known as the von Zeipel-Lidov-Kozai (vZLK) oscillation. In this work, we make a quantitative assessment of the influence of Neptune's mean motion resonance and of the other giant planets' secular perturbations on the libration of Pluto's argument of perihelion. Here, a parameter $k^2 = (1-e^2) \cos^2 I$ is the key where $e$ is eccentricity and $I$ is inclination. When $k^2$ of a Pluto-like object is larger than a certain critical value, libration of its argument of perihelion would not occur. The secular effect of other disturbing planets (Jupiter, Saturn, Uranus) plays a significant role in determining the critical $k^2$. The non-zero oscillation amplitude of the critical resonant argument also plays a role, although not a dominant one.