Habitability of Planets in Binary Star Systems

Recent results in exoclimatology suggest that double-star systems are capable of hosting habitable worlds. The presence of a second source of radiation as well as additional gravitational interactions can influence the location and extent of circumstellar and circumbinary habitable zones, however. In this chapter, several concepts such as isophote-based, radiative, and dynamically informed habitable zones are revisited. They help reveal where terrestrial planets can retain liquid water in such environments. Combining orbital dynamics with simple climate models we demonstrate that the size of circumstellar habitable zones depends on a planet's climate inertia. The higher a climate's resilience to variations in the incident light, the higher the chances for planets to remain in a habitable state. In systems like α Centauri, a low climate inertia shrinks the habitable zone by 50%. For circumbinary planets the mass-ratio of the stars and their distance to the habitable zone determine the impact of climate inertia on planetary habitability. Systems with similar stellar components akin to Kepler-35 turn out to be excellent places to search for potentially habitable worlds.