First Potential Habitable Exoplanet in a Six-Planet Star System

First Potential Habitable Exoplanet in a Six-Planet Star System

posted Nov 7, 2012 6:59 PM by Abel Mendez Torres
HD 40307g is the closest habitable planet candidate around a Sun-like star.

A team of European-American astronomers announced the discovery of a new potential habitable exoplanet around the star HD 40307, a star slightly smaller than the Sun and 42 light years away in the constellation Pictor. HD 40307 is the third known star system with as many as six planets(1), and the first one of such with a potentially habitable planet.

The star HD 40307 was previously known to have three planets. The research team discovered three additional ones, including the one potentially habitable, HD 40307g. They used a novel statistical tool, the HARPS-TERRA software(2), to extract the faint signals of these objects from data from ESO's HARPS Instrument.

HD 40307g is a superterran(3) at least seven times more massive than Earth orbiting the star at the right distance to support liquid water. The planet could have a size between 1.9 and 2.5 Earth radii depending on composition, either rocky or water-rich, respectively. HD 40307g receives on average about 67% of the light Earth receives from the Sun.

There is no information about the type and composition of the atmosphere of HD 40307g. Average temperatures might be near 9°C (48°F) assuming a similar scaled-up terrestrial atmosphere. It might also experience strong seasonal surface temperature shifts between -17° to 52°C (1.4° to 126°F) due to its orbital eccentricity. Nevertheless, these extremes are tolerable by most complex life, as we know it.

HD 40307g has been added to the Planetary Habitability Laboratory’s Habitable Exoplanets Catalog(4). There are seven potentially habitable exoplanets now in the catalog with HD 40307g being the new fourth target of interest based on an Earth Similarity Index of 0.79(5). HD 40307g also is the closest planet orbiting a Sun-like star, and probably not tidally locked, unlike most of the other listed planets around red dwarf stars.

The detection of HD 40307g is remarkable example of the use a Bayesian Monte Carlo Markov Chain technique and HARPS-TERRA tools developed by the authors. However, this kind of detection needs independent confirmation by other methods, as also cautioned by the research team. Meanwhile, this discovery is considered a potentially habitable exoplanet candidate and an interesting target for future observations.

The international research team was led by Mikko Tuomi (Hertfordshire University) and Guillem Anglada-Escude (University of Goettingen). The study also contains significant contributions from E. Gerlach (Technical University of Dresden), Hugh R. A. Jones (University of Hertfordshire), A. Reiners (University of Goettingen), S. Vogt, E. Rivera (UCO-Lick Observatory) and R. P. Butler (Carnegie Institution for Science).

The research paper “Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307” was accepted for publication in Astronomy & Astrophysics.

Source:-
http://phl.upr.edu/press-releases/firstpotentialhabitableexoplanetinasix-planetstarsystem