  With more and more extrasolar planets discovered in and around binary star
systems, questions concerning the determination of the classical Habitable Zone
arise. Do the radiative and gravitational perturbations of the second star
influence the extent of the Habitable Zone significantly, or is it sufficient
to consider the host-star only? In this article we investigate the implications
of stellar companions with different spectral types on the insolation a
terrestrial planet receives orbiting a Sun-like primary. We present time
independent analytical estimates and compare these to insolation statistics
gained via high precision numerical orbit calculations. Results suggest a
strong dependence of permanent habitability on the binary's eccentricity, as
well as a possible extension of Habitable Zones towards the secondary in close
binary systems.

Earth and Planetary Astrophysics