The most Earth-like planet yet: Gliese 832c

 
Sarah Spickernell
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Gliese 832c is the most Earth-like planet (Source: PHL @ UPR Arecibo, NASA Hubble, Stellarium)

Could there be a planet supporting life beyond our solar system? Scientists from the University of New South Wales in Australia have discovered the most likely candidate yet.

16 light years away lies a planet called Gliese 832c. With a mass five times that of Earth's, it absorbs stellar energy from its central star, Gliese 832, and as a result has temperatures that are very similar to those found here.

It completes an orbit in just 35 days, but because its central star is a red dwarf, it releases less energy than the Sun does. The result is that the Earth and Gliese 832c receive similar amounts of energy and both are orbiting in the “habitable zone” when it comes to the potential for life.

This puts Gliese 832c in first place for Earth-likeness according to the Earth Similarity Index, which ranks planets by comparing them to Earth in terms of stellar flux and mass.

"If the planet has a similar atmosphere to Earth it may be possible for life to survive, although seasonal shifts would be extreme," said the University of South Wales' Professor Chris Tinney.

But some researchers think that the atmosphere may be much more similar to that of scorching-hot Venus than Earth, due to the extreme volatility in temperature: Its large mass means the atmosphere is far denser than on Earth, resulting in likely weather extremes.

"Given the large mass of the planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable," says Robert A. Wittenmyer, who led the study. "Indeed, it is perhaps more likely that Gliese 832c is a 'super-Venus'.”

Nonetheless, Gliese 832c is still the closest candidate when it comes to sustaining Earth-like life. "Gliese 832c is one of the most Earth-like planets we've ever encountered,” says Tinney.

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