Milankovitch Cycles for a Circumstellar Earth-analog within $\alpha$ Centauri-like Binaries

TL;DR

This study investigates how Milankovitch cycles influence climate and habitability of an Earth-like planet orbiting within the habitable zone of α Centauri B, considering large obliquity variations and their effects on ice distribution.

Contribution

It introduces a detailed analysis of climate variability driven by obliquity changes in a binary star system using an energy balance model with ice sheets.

Findings

Large obliquity variations can induce snowball states.

Moderate variations can sustain ice caps or an ice belt.

Orbital and spin dynamics critically affect habitability.

Abstract

An Earth-analog orbiting within the habitable zone of $\alpha$ Centauri B was shown to undergo large variations in its obliquity, or axial tilt, which affects the planetary climate by altering the radiative flux for a given latitude. We examine the potential implications of these obliquity variations for climate through Milankovitch cycles using an energy balance model with ice sheets. Similar to previous studies, the largest amplitude obliquity variations from spin-orbit resonances induce snowball states within the habitable zone, while moderate variations can allow for persistent ice caps or an ice belt. Particular outcomes for the global ice distribution can depend on the planetary orbit, obliquity, spin precession, binary orbit, and which star the Earth-analog orbits. An Earth-analog with an inclined orbits relative to the binary orbit can periodically transition through several global ice distribution states and risk runaway glaciation when periods of ice caps and an ice belt overlap. When determining the potential habitability for planets in stellar binaries, more care must be taken due to the orbital and spin dynamics.