Habitable Zones in Binary Star Systems: A Zoology

TL;DR

This paper reviews various methods for determining habitable zones in binary star systems, comparing their assumptions and predictions, and provides simple analytic estimates for these zones.

Contribution

It offers a comprehensive overview of current habitable zone concepts in binary systems and introduces simple analytic estimates for these zones.

Findings

Different habitable zone concepts can yield varying predictions.

Stellar multiplicity generally does not exclude habitability.

Analytic estimates can aid in identifying promising systems.

Abstract

Several concepts have been brought forward to determine where terrestrial planets are likely to remain habitable in multi-stellar environments. Isophote-based habitable zones, for instance, rely on insolation geometry to predict habitability, whereas radiative habitable zones take the orbital motion of a potentially habitable planet into account. Dynamically informed habitable zones include gravitational perturbations on planetary orbits, and full scale, self consistent simulations promise detailed insights into the evolution of select terrestrial worlds. All of the above approaches agree that stellar multiplicity does not preclude habitability. Predictions on where to look for habitable worlds in such environments can differ between concepts. The aim of this article is to provide an overview of current approaches and present simple analytic estimates for the various types of habitable zones in binary star systems.