An international team of astronomers has announced the discovery of a potentially-habitable Super-Earth around the nearby red dwarf star Gliese 832. Located 16 light-years from Earth, it's considered one of the closest and best habitable-world candidates so far.
Gliese 832-c features a brief orbital period of 36 days and a mass at least five times that of Earth's. This planet may be close to its red dwarf parent star, but it receives about the same average energy as Earth does from the Sun. According to lead astronomer Robert Wittenmyer from UNSW Australia, the planet might have Earth-like temperatures, though with large seasonal shifts (assuming it has an atmosphere similar to ours). More likely, however, is that it's a Super-Venus — an oversized terrestrial planet with a hot, dense atmosphere that's hostile to life.
"Gliese 832-c seems to have the right temperature for life but not necessarily the right size," Abel Méndez tells io9. "It could be a gas or water world instead of a rocky world but we simply don't know now. The orbital eccentricity of Gliese 832 c might cause large seasonal temperatures changes but not enough to preclude life. A dense CO2 atmosphere could make this planet too hot for life anyway."
Méndez, a planetary astronomer at the Planetary Habitability Laboratory at the University of Puerto Rico at Aricebo, was not involved in the study.
But Méndez still says it's a planet worth investigating. He tells io9:
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.
But in fact, there are other candidates that might turn out to be better bets. Earlier this month, astronomers discovered a potentially habitable planet around Kapteyn's star that's only 11 light-years away. There's also Gliese 581-d to consider, which is 20.2 light-years away.