A new analysis of the system of planets in the star Gliese 581, a red dwarf star about twenty light years from Earth, shows that besides the already known (and controversial) Gliese 581g, another of the six worlds, Gliese 581d, seem able to hold liquid water on its surface, and perhaps life. The study appears in the latest issue of the Astrophysical Journal Letters.
Less than a year, a team of astronomers from the University of California, Santa Cruz and the Carnegie Institution of Washington announced the discovery of the first planet "really living" beyond our solar system. It was the planet "g", one of six known worlds around the star Gliese 581, about twenty light years from Earth.
Just weeks later, however, another group of astronomers questioned the discovery, because they were not able to detect the planet with its instruments. Since then, the question remained in suspense, waiting for new data to confirm or disprove the spectacular discovery.
A new possibility
Now all eyes turn to head towards the red dwarf Gliese 581, but not the planet "g" but another of their worlds, the "d", a planet discovered in 2007 and was initially dismissed as potential recipient of life . A new model developed by Robin Wordsworth and Francois Forget, climatologists from the French CNRS (Centre national de la recherche scientifique) shows indeed that Gliese 581d has an amazing potential. Enough to snatch his neighbor planet (the "g"), the title of first habitable planet detected by the man outside the Solar System.
In fact, the new calculations indicate that its thick atmosphere rich in CO2, is perfectly capable of retaining the heat of the planet through the greenhouse effect. At the same time, which is essential to allow the passage of red light rays from the star, they heat the surface. "In any case, the researchers say, the temperatures allow the presence of liquid water."
Gliese 581d, also is on the edge of the "habitable zone" of its star, the orbital narrow or too cold or too hot, allowing the existence of liquid water on the surface, a condition that is considered essential to the pursuit of one type of life we know.
Twice the size of Earth
The planet "d" is several times larger than its neighbor, "g". It is a rocky world that has doubled in size and seven times more massive than Earth. "With a dense atmosphere of carbon dioxide, a likely scenario in a world so large, the atmosphere of Gliese 581d is not only stable, but warm enough to have oceans, clouds and rain."
Gliese 581d receives less than one third of solar radiation the Earth and, like his younger brother "g", it always shows the same face to its sun. That is, half the planet is always day, while the other half is mired in perpetual darkness.
In the words of the researchers, "Gliese 581 d would be a very strange place to visit. The high density of the air and the thick clouds keep the surface under a perpetual murky reddish light. And its large mass means that gravity would experience there would be about twice that on Earth. "
However, despite the star Gliese 581 is one of the "neighbors" are closest to the Sun, with today's media would take forever to save twenty light years that separate us from it (each light year is about 9 , 6 billion km.). The fastest of our ships, in effect, would have to travel for more than 300,000 years to get there.
Find
In April, a team of astronomers announced in Astronomy & Astrophysics the discovery of two planets orbiting the M star Gliese 581 (a red dwarf), with masses of at least 5 and 8 Earth masses. Given their distance from the parent star, these new planets (now known as Gliese 581 c Gliese 581 d) are considered possible candidates for the first habitable planets.
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