Exoplanet Kepler 22-b offers best hope yet for a new Earth
Nasa discovers planet which is about 2.4 times the size of our own and lies in the 'Goldilocks zone' of its solar system
A new planet outside of Earth's solar system has been identified with many similarities to our own – making it the latest best potential target for life.
Kepler 22-b, which is about 2.4 times the size of Earth and lies in the so-called "Goldilocks zone", has a relatively comfortable surface temperature of about 22C (72F) and orbits a star not unlike Earth's sun.
But while astronomers believe that it "probably" also possesses water and land, earthlings secretly harbouring hopes that such a planet could potentially host new colonies from our own increasingly overpopulated home may be in for a disappointment.
About 600 light-years from Earth, Kepler 22-b is a considerable trek away while experts are not yet sure if it is made mostly of rock, gas or liquid
The discovery was made by Nasa's Kepler planet-hunting telescope. It is the first time Kepler confirmed a planet outside Earth's solar system in the not-too-hot, not-too-cold habitable zone.
Twice before, astronomers have announced planets found in that zone, but neither was as promising. One was disputed; the other is on the hot edge of the zone.
More than 1,000 new planet candidates have been discovered by the Kepler telescope, nearly doubling the previously known count. Ten of the candidates are close to Earth's size while Kepler-22b is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun.
"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at Nasa headquarters in Washington.
"Kepler's results continue to demonstrate the importance of Nasa's science missions, which aim to answer some of the biggest questions about our place in the universe."
"Fortune smiled upon us with the detection of this planet," said William Borucki, Kepler principal investigator at Nasa's Ames Research Center at Moffett Field, California, who led the team that discovered Kepler 22-b. "The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season." Separately, a cosmic directory that lists the planets and moons most likely to harbour alien life was also launched by astronomers.
The online catalogue was created to make sense of the ever-rising number of distant worlds that researchers have spotted with modern telescopes.
More than 700 "exoplanets" have been spotted and verified outside our own solar system in recent decades, while thousands more await confirmation by missions such as Nasa's Kepler space telescope.
The Habitable Exoplanets Catalogue in essence ranks the habitability of planets and moons according to three criteria: their surface temperature, similarity to Earth, and capacity to sustain organisms at the bottom of the food chain.