Planet Found that Could Support Life

 Skrevet av Alexander G. Rubio - Publisert 24.04.2007 kl. 21:46

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\"This is the most important discovery of its kind so far. But it didn\'t come as a complete surprise\", says the astronomer Malcolm Fridlund from the European Space Agency ESA.

The discovery was made by a team of French, Portuguese, Swiss astronomers using the High Accuracy Radial Velocity for Planetary Search­er spectrograph on the Europe­an Southern Observatory’s 3.6-meter telescope at La Silla, Chile, one of the most successful tools for detecting planets in other star systems to date. The instrument measures wiggles in the star\'s motion caused by the gravity of adjacent bodies in space. It is sensitive enough to detect velocity changes of just two to three meters per second, comparable to the speed of a brisk walk, according to the Geneva Observatory’s Michel Mayor, principal investigator for the instrument.The team announced their finds in a paper submitted to the journals of Astronomy and Astrophysics.

{img src=\'\' align=\'right\' desc=\'The arrow marks the approximate
loca­tion of the red dwarf star Gliese
581 with respect to the constellation
Libra visible in the southern sky.\' link=\'\'}The planet is a so called exoplanet, which just means that it orbits another star than our own Sun. The planet orbits its sun in a remarkably short 13 day year, in a path 14 times closer to Gliese 581 than the Earth\'s orbit around the sun. \"Red dwarfs are ideal targets for the search for such planets because they emit less light, and the habitable zone is thus much closer to them than it is around the Sun,\" said Xavier Bonfils, a co-researcher from Lisbon University. Planets near a star are easi­er to detect because their gravitational pull affects the parent star noticeably, inducing something of a wiggling motion.

Gliese 581 has only one third the mass of our Sun. Stars of this small size are referred to as red dwarfs, as they are at least 50 times fainter than the Sun, far cooler and emit light at a lower frequency, making them seem red. They are believed to be constitute the vast majority of stars in existence. Of 100 closest stars to the Sun, 80 belong to this class.

Due to the fusion process at the core of these red dwarfs being less intense, they actually have a far longer lifespan than larger stars. A star the size of Gliese 581 could be expected to shine for close to 130 billion years, some thirteen times longer than our sun. Scientists estimate that our sun is about halfway through its life cycle. But with billions of years of life still to go, we probably won\'t need to pack up and move to Gliese 581 any time soon.

Two years ago, Udry and his team found the first planet orbiting Gliese 581, a Neptune sized planet estimated to weigh as much as 15 Earths and orbiting the star in 5.4 days.

Their readings at the time made them suspect the presence of other bodies circling the star, Udry and col­leagues said. They thus took new measurements and found the new Earth like planet, as well as a likely third planet weighing eight Earths and orbiting in 84 days.

The average temperature on the planet is expected to lie between 0 and 40 degrees Celsius (32 to 104 degrees Fahrenheit), \"and water would thus be liquid,\" said Stéphane Udry of Switzerland’s Geneva Observatory, lead author of a paper reporting the result. \"Mod­els predict that the planet should be either rocky—like our Earth—or covered with oceans,\" he added. \"Liquid water is critical to life as we know it and because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X,\" noted Xavier Delfosse, a member of the team from Greno­ble University, France.

Nikolaj Piskunov, professor of observational astrphysics at Uppsala University in Sweden, says that the newly discovered exoplanet not only has the right temperature, but also probably has a gravity which could support the presence of life.

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