Binary Star Habitable Zone Calculator

Updated to Account for New Planetary Climate Models

Two suns over an ocean and mountains

1. Background

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:
  1. Besides simple cases, the treatment of nonequal-mass systems and systems in elliptical orbits.
  2. 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.
  3. 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.
  4. The consideration of classical or revised planetary climate models; in the latter case, the stellar RHZ may also depend on the planetary mass.
  5. 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 (CHZ), general (GHZ), or extended zone (EHZ) of habitability 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, the formulae of Holman & Wiegert (1999) [AJ 117, 621] are utilized.

2. Calculating the Habitable Zone - Enter Binary System Parameters

A. System Parameters (binary star system)   (Click here for System Parameter Limits.)
      Semi-major axis (AU) 

B. Stellar Parameters   (Click here for Stellar Parameter Limits.)
    Primary Star
          Temperature (K)  
          Luminosity (L)  
          Mass (M)  
    Secondary Star
          Temperature (K)  
          Luminosity (L)  
          Mass (M)  

C. Planetary Parameter   (Click here for Planetary Parameter Limits.)
      Mass (ME) (only used in New Climate Models)

D. Habitable Zone Limits
    Choose your climate model and inner and outer habitable zone limits
    Classical Climate Models   (Click here for References.)
           Inner Habitable Zone
             Recent Venus
             Runaway Greenhouse
             Moist Greenhouse
           Outer Habitable Zone
             First CO2 Condensation
             Maximum Greenhouse
             Early Mars
             Extreme CO2-Cloud Coverage
    New Climate Models   (Click here for References.)
           Inner Habitable Zone
             Recent Venus
             Runaway Greenhouse (depends on the planetary mass)
             Moist Greenhouse (not implemented for planetary masses other than 1 ME)
           Outer Habitable Zone
             Maximum Greenhouse
             Early Mars

If you use any of the results or materials from this page, please consider citing the following papers (which also have further information):
  * Cuntz, M.: 2014, ApJ, 780, 14 (arXiv: 1303.6645v2)
  * Cuntz, M.: 2015, ApJ, 798, 101 (arXiv: 1409.3796v3)

The material on this page is based on the work of Prof. Dr. Manfred Cuntz.
This website was created by Dr. Robert Bruntz.
For further information on the implementation of BinHab, see: Cuntz, M., & Bruntz, R.: 2014, "BinHab: a numerical tool for the calculation of S/P-type habitable zones in binary systems", in Cool Stars, Stellar Systems, and the Sun, Proc. 18th Cambridge Workshop, eds. G. van Belle and H. Harris (Flagstaff: Lowell Observatory), p. 831.
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Page last updated: 22 Jan. 2015