Nearby Exoplanet Is Best Candidate For Supporting Life

photo credit: Artistic representation of the potentially habitable Super-Earth Gliese 832 c against a stellar nebula background. Credit: PHL @ UPR Arecibo, NASA Hubble, Stellarium

Finding new exoplanets is always awesome, but discovering exoplanets within the star’s habitable zone are exponentially more exciting. A team led by Robert Wittenmyer of the University of New South Wales has announced the discovery of the Super-Earth Gliese 832 c, which could very well turn out to be the best candidate for extraterrestrial life discovered to date. It’s also fairly close, cosmologically speaking, which adds to the intrigue. The team’s paper has been accepted for publication in The Astrophysical Journal, but has been made available online in an open access format on arXiv.org.

Gliese 832 is a red dwarf star that is located 16.1 light-years away in the constellation Grus. Astronomers discovered a Jupiter analog orbiting the star back in 2009, but its orbit takes nine years to complete; far beyond the star’s habitable zone. Gliese 832 c looks much more promising. Though only two planets in the system are known, it appears to be organized quite similarly to our own solar system.

The planet is about 5.4 times more massive than Earth and has an Earth Similarity Index (ESI) of 0.81, which compares an exoplanet’s radius, escape velocity, surface temperature, and density to Earth. Other exoplanets with similar ESI values include Gliese 667 Cc (ESI 0.84, 22 light-years away) and Kepler-62e (ESI 0.83, 1,200 light-years away). ESI does not account for the planet’s potential habitability, which makes Gliese 832 c a little more of a priority for further analysis.

Gliese 832 c has an orbital period of only 36 days. While this does seem fairly short by our standards, the host star is much smaller and cooler than our Sun. This results in Gliese 832 c getting the same amount of solar energy as Earth. One aspect of Gliese 832 c that could make or break its likelihood of supporting life is its atmosphere. Researchers aren’t certain about the atmosphere’s composition or density. A dense atmosphere would make the planet much too hot for life, and Gliese 832 c would be more like a Super-Venus than Super-Earth. If the atmosphere is not quite as dense, it could have weather patterns somewhat similar to Earth, albeit with greater seasonal variations.

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