Discovery of new planets by Kepler telescope raises hopes of 'another Earth'

Astronomers have confirmed the discovery of 1,284 new planets by the Kepler space telescope, including nine Earth-like worlds that potentially could harbour life.

The announcement, made by scientists from the American space agency Nasa, more than doubles the tally of "verified" Kepler planets orbiting distant stars.

Of the nearly 5,000 total planet candidates found to date, more than 3,200 have now been confirmed as genuine worlds and of these 2,325 were discovered by Kepler.

The new finds belong to a catalogue of 4,302 potential planet candidates identified by Kepler, which was launched in March 2009 and orbits the Earth at a distance of 100 million miles.

Before confirming the discovery of a new "exoplanet", astronomers have to make sure the candidate is not another object such as a companion star or brown dwarf.

Dr Ellen Stofan, chief scientist at Nasa headquarters in Washington, said: "This announcement more than doubles the number of confirmed planets from Kepler. This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth."

Kepler scientist Dr Natalie Batalha said nine new worlds had been added to the exoplanet "hall of fame" - those Earth-like planets that could conceivably support life. A total of 21 exoplanets are now believed to be belong to this exclusive group.

All the new planets are less than 1.6 times the size of Earth, and all orbit within the "habitable" zones of their stars, the narrow region where temperatures are mild enough to allow the existence of liquid surface water.

Speaking at a broadcast press conference, Dr Batalha said she was "intrigued" by two new planets in particular. One, Kepler 1229B, is Earth-sized but closer to the middle of its habitable zone than our own planet. The other, Kepler 1638B, is 50% larger than the Earth and orbiting a star slightly warmer than the sun.

Based on the discoveries made so far, calculations indicated that "tens of billions" of potentially life-supporting planets could exist among the 100 billion stars in our galaxy, the Milky Way, Dr Batalha added.

Dr Paul Hertz, astrophysics division director at Nasa headquarters, said: "Before the Kepler space telescope launched, we did not know whether exoplanets were rare or common in the galaxy.

"We now know that exoplanets are common, that most stars in our galaxy have planetary systems, and that a reasonable fraction of the stars in our galaxy have potentially habitable planets. Knowing this is the first step to addressing the question: are we alone in the universe?"

Kepler searches for planets by measuring the tiny dip in brightness that occurs when an object passes in front of, or transits, a star.

Scientists have devised a much faster automated way of verifying planets using computer simulations rather than long, detailed observations using Earth-based telescopes.

The technique, which produces results that tally with those from telescope observations, combines data on the shape of the detected signal and a statistical analysis of how common planet "imposters" are likely to be.

Prior to the announcement, the tight lid Nasa kept on the news fuelled wild speculation about the likely findings.

One rumour was that Kepler had found evidence of intelligent alien life, such as a "megastructure" built around a star.