April 24, 2007 — Astronomers have found the first Earth-sized world circling its mother star at a distance suitable for life. It also has good prospects for liquid surface water — believed to be a key ingredient for life.
"This planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life," said Xavier Delfosse, with Grenoble University in France.
It will be years before more sensitive instruments are developed to glean additional clues about whether life exists on the planet.
"It is not possible with current telescopes and instruments yet," Xavier Bonfils, an astronomer with the Lisbonne Observatory in Portugal, wrote in an e-mail to Discovery News. "But in the next decade, we may have the tools to answer this question."
The planet, which is about 50 percent larger than Earth, circles a star in the constellation Libra known as Gliese 581, about 20.5 light-years away. Light travels in a vacuum at about 187,000 miles per second.
Astronomers previously have found a Neptune-sized world circling Gliese 581, as well as strong evidence for a third planet about eight times the mass of Earth.
The new planet, which is the smallest planet beyond our solar system found to date, circles its star 14 times closer than Earth orbits the sun. But because Gliese 581 is smaller and colder than our sun, the system's so-called habitability zone, where liquid water and thus life is possible, is closer to the mother star than in our solar system.
