Statisticallikelihood ExoPlanetary Habitability Index (SEPHI)
Abstract
A new index, the Statisticallikelihood ExoPlanetary Habitability Index (SEPHI), is presented. It has been developed to cover the current and future features required for a classification scheme disentangling whether any exoplanet discovered is potentially habitable compared with life on Earth. SEPHI uses likelihood functions to estimate the habitability potential. It is defined as the geometric mean of four subindexes related to four comparison criteria: Is the planet telluric? Does it have an atmosphere dense enough and a gravity compatible with life? Does it have liquid water on its surface? Does it have a magnetic field shielding its surface from harmful radiation and stellar winds? SEPHI can be estimated with only seven physical characteristics: planetary mass, planetary radius, planetary orbital period, stellar mass, stellar radius, stellar effective temperature and planetary system age. We have applied SEPHI to all the planets in the Exoplanet Encyclopaedia using a Monte Carlo method. Kepler1229b, Kepler186f and Kepler442b have the largest SEPHI values assuming certain physical descriptions. Kepler1229b is the most unexpected planet in this privileged position since no previous study pointed to this planet as a potentially interesting and habitable one. In addition, most of the tidally locked Earthlike planets present a weak magnetic field, incompatible with habitability potential. We must stress that our results are linked to the physics used in this study. Any change in the physics used implies only an updating of the likelihood functions. We have developed a web application allowing the online estimation of SEPHI (http://sephi.azurewebsites.net/).
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 November 2017
 DOI:
 10.1093/mnras/stx1910
 arXiv:
 arXiv:1707.07986
 Bibcode:
 2017MNRAS.471.4628R
 Keywords:

 methods: data analysis;
 methods: statistical;
 planets and satellites: fundamental parameters;
 planets and satellites: terrestrial planets;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 10 pages, 4 figures, 6 tables. Accepted for publication in MNRAS