This website is optimized to work with the Google Chrome web browser.

BHM Calculator 3
Binary Habitability and More

Bug Report

Welcome to the Binary Habitability (and More) Calculator, BHMcalc!

What do you want to do?

BHMcalc is a web application intended to explore the vast configuration space of Circumbinary Planetary System (aka. Tatooines).

You can use BHMcalc to calculate the evolution of stars and planets in binaries and the complex interactions between them. These interations affect any potential habitable environments around these systems.

If you want to use the calculator for more advanced purposes please select the BHMcalc Mode:

BHMcalc is the result of the fruitful collaboration between the group of Prof. Paul Mason in the University of Texas, El Paso and New Mexico State University and the group of Prof. Jorge I. Zuluaga, the Computational Physics and Astrophysics Group of the University of Antioquia (Medellín, Colombia). Other colleagues directly involved are Dr. Pablo Cuartas (FACom/UdeA) and Joni Clark (NMSU).

To cite BHMcalc please refer to one or all of the following papers:

  • [Zuluaga+2015] Zuluaga, J.I., Mason, P.A. & Cuartas-Restrepo, P. A. (2015). Constraining the Radiation and Plasma Environment of Kepler Circumbinary habitable zone planets. Submitted to the Astrophysical Journal (arXiv:1501.00296).

  • [Mason+2014] Mason, P. A., Zuluaga, J. I., Cuartas-Restrepo, P. A., & Clark, J. M. (2014). Circumbinary Habitability Niches. International Journal of Astrobiology. (ADS: 2014arXiv1408.5163M, arXiv:1408.5163)

  • [Mason+2013] Mason, P. A., Zuluaga, J. I., Clark, J. M., & Cuartas-Restrepo, P. A. (2013). Rotational Synchronization May Enhance Habitability for Circumbinary Planets: Kepler Binary Case Studies. The Astrophysical Journal Letters, 774(2), L26. (ADS: 2013ApJ...774L..26M, arXiv:1307.4624)

This is the second version of the BHMcalc. A previous and simpler version of the tool was released along the [Mason+2014] paper and it is presently unavailable.


BHMcalc is made possible thanks to the support and the direct as well as indirect participation of several institutions and colleagues.

Firstly we thank to W. Welsh, N. Haghighapor, G. Torres, S. Cranmer and A. Claret for useful discussions and insightful comments regarding the models applied in the calculator. I. Baraffe provided several key results for modeling the evolution of stellar rotation of low mass-stars.

Jorge I. Zuluaga thanks the Harvard-Smithsonian Center for Astrophysics for their hospitality during a 5 months stay in the fall/winter 2014-2015 where most of the major improvements of the calculator were achieved. Thanks to Prof. Dimitar Sasselov for the invitation.

The Calculator has been developed under the financial support of: Fulbright Commission, Colombia, the Vicerrectoria de Docencia / Facultad de Ciencias Exactas y Naturales / Instituto de Fisica of the University of Antioquia and the program of Sostenibilidad/CODI/UdeA.

Special thanks to Steffen Christensen for testing the tool and finding several major bugs.


This is version BHMcalc-v3.0.0
Version: 3.0.0
Last build: 563
Next patch: 3.0.1-b563
Next minor: 3.1.0-b563
Next major: 4.0.0-b563

Changes Log

Changes introduced in the most recent build/version:

Version 3.0

  • (Core) We have added two extra parameters to the HZ calculator: maximum time for a cold habitability start and minimum habitability time. These parameters allow user to configure properly the limits of the continuous Habitable Zone.
  • (Core) We have improved the algorithm to evaluate the interdependencies between the modules.
  • (Interface) We created a "Build your own system" mode that make the interface MUCH MORE SIMPLER. This is specially intended for not advanced users.

Version 2.1


Version 2.0


Help topics


Thousands of planets around other stars have been discovered so far (for an updated list see the Exoplanets Encyclopedia). Although nearly half of the stars in the Galaxy have one or more stellar companions (binary and multiple systems), most of these planets have been discovered around single stars.

In the last few years, the advent of very sensitive photometric and astrometric survey instruments (Kepler, Gaia), has finally allowed the discovery of the first planetary systems around multiple stellar systems. Today a dozen of them have been catalogued and well described (see the BHM Catalogue in this website).

Against all odds, planets can be formed and stay for billions of years around multiple stars. They can either orbit only one of the stars in the system in a so-called "s-type" orbit (see figure), or they can orbit two close stars in a "p-type" orbit (circumbinary planets).

Circumbinary Planets (planets orbiting two stars) or Tatooines as they are informally called, have proven to be the most interesting objects. Not only the dynamic of their orbits is much more complex but the conditions they could face while orbiting two stars lead to astrobiological relevant effects.

BHMcalc is a web tool intended to explore the complex parameter space of Circumbinary Planets in order to gain some insight about their properties and more specifically about their potential to host habitable environments. Beyond only helping to explore the properties of hypothetical systems, the calculator can also be used to constraint the conditions around already discovered circumbinary systems.

BHMcalc can be used to calculate/constraint:

  • The evolution of basic stellar properties, radius, luminosity, etc., using stellar evolutionary tracks provided by different groups (Star Mode).
  • Rotational evolution of single stars using different rotational evolutionary models (Star Mode).
  • Stellar activity as a function of time using the Cranmer & Saar solar-inspired model (Star Mode).
  • Basic properties of solid and ice/gas planets (Planet Mode).
  • Thermal evolution and magnetic properties of planets with masses from super-Earths to Jovian planets (Planet Mode).
  • Basic orbital properties of binary systems (Binary Mode).
  • Limits of the Circumbinary Habitable Zone (BHZ) and their evolution in time (Habitable Zone Mode).
  • limits of the Continuous Circumbinary Habitable Zone (CBHZ) and the habitability timespan of planets in binaries (Habitable Zone Mode).
  • Insolation and Photosynthetic Photon Flux Density (PPFD) in circumbinary planets (Habitable Zone Mode).
  • Rotational evolution of stars in binaries including the effect of tidal interaction (Interaction Mode).
  • Evolution of activity of stars in binary systems (Interaction Mode).
  • Stellar wind properties (flux and dynamic pressure) around moderately separated binaries (Interaction Mode).
  • X-ray luminosity of stars in binaries and its flux on circumbinary planets (Interaction Mode).

BHMcalc is specifically designed to calculate these and other properties in the particular case of binaries with moderate separations and orbital periods, i.e. 5 days < Pbin < 60 days. Although some of the tools available here (stellar and planetary evolution models) apply irrespectively binary separations, the most important modules are only designed for these particular systems.

Quick Start

BHMcalc works as a regular windows application. Its usage is intuitive and easy to master.

The calculator can be used in different ways (modes): you can browse the BHM catalogue (Catalogue Mode), calculate the properties of a single star (Star Mode) or a planet (Planet Mode) or simply proceed to do the full thing (Interaction Mode), ie. calculate the property of stars in a binary system and their interaction with a planet.

The Calculator Modes

So, why don't you try the calculator while reading this guide. Click here to open it in a new browser tab.

Catalogue Mode

BHMcalc comes along with a selection of real binary systems to play with. We call this selection the BHM Catalogue. The catalogue includes those binaries where real planetary systems have been discovered, a set of moderately separated binaries (4 days < Pbin < 60 days) selected from different spectroscopic and eclipsing binaries catalogues and last but not least, a list of what we have called Binary Habitability Niches, ie. binaries with properties well suited for the action of what we have called the BHM mechanism [Mason+2014].

In the Catalogue Mode a dynamic table with the basic properties of the binary systems will be displayed. You will be able to sort, filter and search into the catalogue using the form controls at the top of the table.

The BHM Catalogue dynamic table

Beside browsing and filtering the binaries in the catalogue, you will also be able to load each star, planet or the whole system into the calculation modes.

All the objects in the catalogue has been already load into the BHMcalc. As a result, all their properties have been already calculated and available to explore in depth. This is the right place to start playing with the calculation modes.

We encorauge you to load your preferred system into the calculator before going through the next sections. Click here to load the catalogue and select a binary system to play with.

Calculation Modes

When an object is load from the catalogue, a calculation mode is activated. If you click in the binary system link the Interaction Mode will be activated. If instead, you click the link of the star, the Star Mode will be load.

Each mode has its own set of tabs depending on its purpose. The Star Mode, for example, is just intended for exploring the properties and evolution of single stars. So, only the Star tab will be open in this mode. On the other hand, if the Binary Mode is load, four instead of one tabs will be available: Star 1, Star 2, Planet and Binary itself.

Each tab have the same structure: two panels, one cointanining an input form and the other one the result panel.

The common structure of a calculation tab.

The calculator use a technology called AJAX (Asyncrhonous JavaScript And XML). This allows you to calculate something on backgorund without reloading the page or while you are doing something else in the calculator. This is precisely the purpose of the Update button. This button will let you to commit a calculation after changing some value in the input form. You do not need to reload the page or expect for the calculation to end, to continue exploring or changing other fields in the calculator.

By default, when you load an already existing object (an object from the catalogue or a configuration you have saved in your session directory), a new tab, the Summary tab, will be available. In the summary tab, a panel with the results already calculated and stored in the server, will be loaded.

The summary tab.

Using the summary tab you will be able to: Download files related to the system (configuration, data, images). Generate a link to the system; you will be able to "bookmark" this link or send it to a collaborator. Generate the command line required to calculate the properties of the system using the offline calculator. Save and load stored configurations; saved configurations will be available only in the same session of the browser. If you use another browser or clean the cookies the session information will change.

The calculator uses a scheme of dependencies on which a given object can only be calculated after other one has been calculated. Thus, for instance, when you try to calculate the rotation and activity evolution of a binary system, the properties of their stars should be first updated. Thus, when changing something in a system, we recommend to update first the more complex object first. This will probably impact the time you need to wait for a result but will ensure you the least clicks possible. If you want to proceed safer you can better update each object at a time.

This site is under construction.

Snapshots and Gallery

BHMcalc screenshot. The Calculation Modes.

BHMcalc screenshot. The summary tab.

BHMcalc screenshot. The Star module tab.

BHMcalc screenshot. The BHM Catalogue.

BHMcalc screenshot. The BHM Catalogue sorted by binary semimajor axis.

BHMcalc screenshot. The Habitable Zone module.

BHMcalc screenshot. The Bug Report form

Stellar rotation evolution for the primary of Kepler-34.

Evolution of rotation for the components of Kepler-34.

Mass-loss from gas giants in the Habitable Zone of Niche-02 planet.

Flux of XUV radiation in the HZ of Niche-02.

Magnetospheric standoff distance calculated for Kepler-35b.

Evolution of KIC-9632895 using the closest PARSEC evolutionary track.

Magnetospheric standoff radius as a function of time for an Earth-like planet in the middle of the BHZ of Niche-08

Habitable Zone of Kepler-16.

Continuous Habitable Zone of KIC-9632895.

Schematic diagram of the size and interior structure of the ice/gas giant Kepler-47c.

Schematic representation of the Earth interior as calculated with the Planet module.

Sunset in a Circumbinary Planet. Credit: Paramount Pictures/CBS Studios. Source

"Is there any life around single stars?". Credit: Alejandro Rua, Medellin, Colombia.