BinHab allows for the calculation of S-type and P-type habitable regions in stellar binary systems. P-type orbits occur when the planet orbits both binary components, whereas in the case of S-type orbits the planet orbits only one of the binary components, with the second component considered a perturbator. The selected approach considers a variety of aspects, which include:
- Besides simple cases, the treatment of nonequal-mass systems and systems in elliptical orbits.
- The consideration of a joint constraint, including orbital stability and a habitable region for a putative system planet through the stellar radiative energy fluxes ("Radiative Habitable Zone"; RHZ), needs to be met.
- The provision of a combined formalism for the assessment of both S-type and P-type habitability; in particular, through the solution of a fourth-order polynomial, mathematical criteria are employed for the kind of system in which S-type and P-type habitability is realized.
- The consideration of classical or revised planetary climate models; in the latter case, the stellar RHZ may also depend on the planetary mass.
- The user-friendly option to choose different inner and outer limits for stellar RHZs. According to existing literature, those can be readily related to the Conservative Habitable Zone (CHZ), General Habitable Zone (GHZ), or Recent Venus / Early Mars (RVEM) for the various systems as defined for the Solar System and beyond.
In principle, five different cases of habitability are identified, which are: S-type and P-type habitability provided by the full extent of the RHZs; habitability, where the RHZs are truncated by the additional constraint of planetary orbital stability (referred to as ST and PT-type, respectively, for Truncated); and cases of no habitability at all. Regarding the treatment of planetary orbital stability, adequate analytical formulae are utilized.
