It is the most promising candidate of 17 "extrasolar" planets discovered by various techniques over the past few years. Most of those are gas giants like Jupiter, or else too remote from a star to have any chance of supporting life. The new planet appears to be both the right size and distance to give life a chance.
Ian Bond, of Auckland University, said the new planet, which lies about 30,000 light years away, would probably be a little bit heavier than the Earth. "It has a probable mass range between that of the Earth and that of the planet Neptune [which has 17 times the Earth's mass]".
No pictures exist of the distant planet, which was detected last July by the team at Mount John Observatory on New Zealand's South Island with Japanese, American and Australian astronomers.
Crucially, the new planet is about the right distance from its star to sustain life, if it contains the correct mixture of elements. The distance from the Earth to the Sun (93 million miles) is defined as one "astronomical unit", or AU: Mr Bond said the so-far unnamed planet "will be something like between one to four astronomical units, which places it in a promising region".
The planet was discovered using a relatively new technique called gravitational microlensing, which employs supersensitive equipment to detect a dark object's movement in front of a far more distant star. "This is the first discovery using the microlensing technique. It's the only technique that is sensitive to Earth-size planets," Mr Bond said.
The microlensing method's power is not sufficient, however, to help scientists to tell whether there is any water or other elements thought of as essential to life, for example.
Most of the extrasolar planets discovered so far have been detected because they are so massive that they induce a "wobble" in the motion of their parent star as they orbit around it.
However, such planets are unlikely candidates to support life because of their enormous surface gravities, wildly varying temperatures and the preponderance of elemental gases in their atmospheres. Gravitational microlensing, by comparison, can detect much smaller planets at greater distances.Reuse content