When more is less: The P‐type binary habitability paradox.

In the case of single stars, larger stellar luminosities always entail larger habitable zones (HZs). If the stellar luminosity is increased, the HZs are established at larger stellar distances, and their widths are broader. However, studies have shown that this behavior is not necessarily the case for P‐type HZs of binary systems. In some of those systems, the width of the circumbinary HZ is smaller (or even nonexisting) than the width of the primary's HZ if they are considered a single star—an obvious paradox considering that the total luminosity of the binary is always larger than that of the system's primary. Here, we present a tutorial study of this behavior for theoretical main‐sequence stars with the combined masses of the stellar components equal to two solar masses. The planetary climate models are chosen in correspondence to the general HZ. The paradox is found to occur for systems of relatively unequal stellar masses (or luminosities) or in systems where the separation distances or eccentricities of the stellar components are relatively large. [ABSTRACT FROM AUTHOR]