Third Rock From Distant Sun Might Suit Life
Sydney Morning Herald
Saturday May 20, 2006
THE possibility that other Earth-like worlds exist has been boosted by the discovery of the smallest planet ever found circling inside the "habitable zone" around another star.
The planet is one of three orbiting a star 41 light years away. Two are too close to their star, and thus too hot, for life as we know it. One has a year lasting less than six Earth days, while the second goes around the star in under 32 Earth-days.But the third planet, with a year of 197 days, is further out, in what astronomers call the "habitable zone", where temperatures might be right for water. About 18 times more massive than Earth, scientists suspect it may resemble Neptune in our solar system.But it "appears to be located near the inner edge of the habitable zone, where liquid water can exist at the surface of rocky/icy bodies," astronomers from the European Southern Observatory said. The planet "is likely to be made of a rocky/ice core surrounded by a quite massive [gas] envelope".The two inner planets, 10 times more massive than Earth, are also Neptunian-sized. "For the first time," said Christophe Lovis, from the Geneva Observatory, "we have discovered a planetary system composed of several Neptune-mass planets". NASA's Spitzer space telescope recently spotted a possible asteroid belt circling the same star. The asteroids may be close to the path of the third planet. So it might be pounded by collisions.But an Australian planet-hunter, Chris Tinney, from the Anglo-Australian Observatory near Coonabarabran, said that may not be a major problem for any life on the planet. "Mars is the planet nearest the asteroid belt in our solar system," said Dr Tinney. "I don't believe there is evidence Mars has been more pounded to bits than our moon or Earth."
© 2006 Sydney Morning Herald