Astronomers May Be on Brink of Finding Habitable 'second Earth'

Astronomers may be on the brink of discovering a second Earth-like planet, a find that would add fresh impetus to the search for extraterrestrial life, according to a leading science journal.

Planet hunters have spotted more than 200 planets beyond our solar system, but the vast majority are hot, Jupiter-sized planets that would dwarf the Earth and are almost certainly lifeless.

Writing in the US journal Science, astronomers from six major centers, including Nasa, Harvard and the University of Colorado, outline how advances in technology suggest scientists are on the verge of being able to detect the presence of small, rocky planets, much like our own, around distant stars for the first time. The planets are considered the most likely havens for extraterrestrial life.

One technique relies on observing the shift in light coming from a star as a planet swings around it. Until recently, this "radial velocity" method has only been sensitive enough to pick up planets far more massive than Earth, but improvements now make the discovery of a second Earth highly likely, said Dave Latham, a co-author on the paper at the Harvard-Smithsonian Center for Astrophysics.

"It could happen almost any time now. We have the technological capability to identify Earth-like planets around the smallest stars even now," he said.

Nasa's mantra of "follow the water" has defined the search for extraterrestrial life on Mars and other planets. If water is crucial for life, then the most likely sanctuaries will be planets which lie in a "habitable zone" just the right distance from a star, so that it is neither so hot that water evaporates, or so cold that it remains permanently frozen.

Dr Latham said missions such as Nasa's planned Kepler space observatory, which is due to launch in early 2009, would have a high chance of finding Earth-like planets if they are out there.

"These are the biggest questions. Are there habitable abodes? Are we alone?" he said. "Put it like this. If we don't find anything, I'll have to rethink my agnosticism."