Gliese 581g tops list of potentially habitable exoplanets

ISTANBUL

Gliese 581g is seen by many as the best candidate to host life beyond system.

Controversial exoplanet Gliese 581g has shot to the top of a list put out by researchers at Arecibo’s Planetary Habitability Laboratory at the University of Puerto Rico, after a new study encouraged support for its long-debated existence.

The controversial exoplanet Gliese 581g is the best candidate to host life beyond our own solar system, according to a new ranking of potentially habitable alien worlds, Scientific American has reported.

Gliese 581g shot to the top of the list — which was published on July 19 by researchers at the University of Puerto Rico at Arecibo’s Planetary Habitability Laboratory (PHL) — after a new study marshaled support for its long-debated existence.

The exoplanet was discovered in September 2010, but other astronomers began casting doubt on its existence just weeks later. Now Gliese 581g’s discoverers have rebutted their critics’ charges in a new paper, and have done so effectively enough to get the PHL onboard, according to the Scientific American article.

This rocky world — if it does indeed exist — is 20 light-years away from our solar system. It’s likely two to three times as massive as Earth and zips around its parent star, the red dwarf Gliese 581, every 30 days or so.

Habitable zone

This orbit places the planet squarely in the star’s “habitable zone” — that just-right range of distances where liquid water, and perhaps life as we know it, could exist.

Gliese 581g has at least four, and possibly five, planetary neighbors. The team that spotted Gliese 581g also detected another planet, known as 581f, circling much further away from the star. But scientists are still arguing about that world’s existence, too.

Gliese 667Cc, which was discovered in February 2012 by the same core team that spotted Gliese 581g, orbits a red dwarf 22 light-years away, in the constellation Scorpius (The Scorpion).

The alien world is a so-called “super Earth” that is at least 4.5 times as massive as our planet, and completes an orbit every 28 days.