First 'habitable zone' exoplanet found

WASHINGTON, Sept. 30 (UPI) -- U.S. astronomers say they've detected a rocky planet in another solar system with the basic and essential conditions needed to support extraterrestrial life.

Scientists for years have predicted the existence of Earth-like exoplanets in what is called the "habitable zone" around a star, but the identification and measurement of one has been called the beginning of a new era in the search for life beyond Earth.

"This is our first Goldilocks planet -- just the right size and the right distance from its sun," astronomer Paul Butler with the Carnegie Institution of Washington told The Washington Post.

"A threshold has been crossed," he said.

The new exoplanet, called Gliese 581G, is quite close at 20 light years from Earth.

Because of its size and its distance from its sun, it is considered to be in its star's habitable zone.

Its distance from the star that it orbits means any water on the planet will be in liquid form, scientists say, and the planet is large enough to have the gravitational pull to hold an atmosphere around it.

The star Gliese 581 is now known to have six and perhaps seven planets orbiting it in circular paths and lined up by type in a way similar to our solar system.

"As we collect more data, we can see the system looks like our own -- with an inner clutch of rocky, terrestrial planets and then a big loner like Jupiter further out," Steven Vogt of the University of California at Santa Cruz said.