Low Spin-Axis Variations of Circumbinary Planets

TL;DR

This paper discovers that circumbinary planets tend to have low spin-axis variations due to the binary's quadrupole potential, which may enhance their habitability by stabilizing seasons.

Contribution

It introduces a new mechanism explaining low spin-axis variations in circumbinary planets, contrasting with the moon stabilization model for single planets.

Findings

Circumbinary planets exhibit low spin-axis variations.

Binary star quadrupole potential influences planetary precession.

Potential for more stable seasons on habitable zone planets.

Abstract

Having a massive moon has been considered as a primary mechanism for stabilized planetary obliquity, an example of which being our Earth. This is, however, not always consistent with the exoplanetary cases. This article details the discovery of an alternative mechanism, namely that planets orbiting around binary stars tend to have low spin-axis variations. This is because the large quadrupole potential of the stellar binary could speed up the planetary orbital precession, and detune the system out of secular spin-orbit resonances. Consequently, habitable zone planets around the stellar binaries in low inclination orbits hold higher potential for regular seasonal changes comparing to their single star analogues.