Constraining the magnitude of climate extremes from time-varying instellation on a circumbinary terrestrial planet

TL;DR

This paper investigates how the periodic variation in stellar illumination of circumbinary planets affects their surface temperatures, showing that ocean coverage constrains temperature swings and impacts habitability.

Contribution

It introduces an analytic and numerical model to quantify temperature variations driven by binary star orbits, highlighting the role of ocean-land ratios in climate stability.

Findings

Ocean-rich planets have modest temperature variations.

Land-dominated planets can experience extreme temperature swings.

Habitability is influenced by the planet's surface composition.

Abstract

Planets that revolve around a binary pair of stars are known as circumbinary planets. The orbital motion of the stars around their center of mass causes a periodic variation in the total instellation incident upon a circumbinary planet. This study uses both an analytic and numerical energy balance model to calculate the extent to which this effect can drive changes in surface temperature on circumbinary terrestrial planets. We show that the amplitude of the temperature variation is largely constrained by the effective heat capacity, which corresponds to the ocean-to-land ratio on the planet. Planets with large ocean fractions should experience only modest warming and cooling of only a few degrees, which suggests that habitability cannot be precluded for such circumbinary planets. Planets with large land fractions that experience extreme periodic forcing could be prone to changes in temperature of tens of degrees or more, which could drive more extreme climate changes that inhibit continuously habitable conditions.