Above: Artistic representation of the exoplanet Gliese 832 c as compared with Earth. Gliese 832 c is represented here as a temperate world covered in clouds. The relative size of the planet in the figure assumes a rocky composition but could be larger for a ice/gas composition. Credit: PHL @ UPR Arecibo.
According to a press release from the Planetary Habitability Laboratory, an international team of astronomers, led by Robert A. Wittenmyer from UNSW Australia, report the discovery of a new potentially habitable Super-Earth around the nearby red-dwarf star Gliese 832, sixteen light years away. This star is already known to harbour a cold Jupiter-like planet, Gliese 832 b, discovered on 2009. The new planet, Gliese 832 c, was added to the Habitable Exoplanets Catalog along with a total of 23 objects of interest. The number of planets in the catalog has almost doubled this year alone.
Gliese 832 c has an orbital period of 36 days and a mass at least five times that of Earth’s (≥ 5.4 Earth masses). It receives about the same average energy as Earth does from the Sun. The planet might have Earth-like temperatures, albeit with large seasonal shifts, given a similar terrestrial atmosphere. A denser atmosphere, something expected for Super-Earths, could easily make this planet too hot for life and a “Super-Venus” instead.
The Earth Similarity Index (ESI) of Gliese 832 c (ESI = 0.81) is comparable to Gliese 667C c (ESI = 0.84) and Kepler-62 e (ESI = 0.83). This makes Gliese 832 c one of the top three most Earth-like planets according to the ESI (i.e. with respect to Earth’s stellar flux and mass) and the closest one to Earth of all three, a prime object for follow-up observations. However, other unknowns such as the bulk composition and atmosphere of the planet could make this world quite different to Earth and non-habitable.