Washington: NASA's planet-hunting Keplertelescope has confirmed a record-setting bonanza of 715 newly discovered planets outside our solar system, nearly doubling the count of exoplanets discovered to around 1,700.
These newly-verified worlds orbit 305 stars, revealing multiple-planet systems much like our own solar system. Nearly 95 per cent of these planets are smaller than Neptune, which is almost four times the size of Earth.
The discovery marks a significant increase in the number of known small-sized planets more akin to Earth than previously identified exoplanets, which are planets outside our solar system, said NASA.
"The Kepler team continues to amaze and excite us with their planet hunting results," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington.
Scientists used a statistical technique that can be applied to many planets at once when they are found in systems that harbour more than one planet around the same star.
To verify this bounty of planets, a research team co-led by Jack Lissauer, planetary scientist at NASA's Ames Research Center in California, analysed stars with more than one potential planet, all of which were detected in the first two years of Kepler's observations - May 2009 to March 2011.
The research team used a technique called verification by multiplicity, which relies in part on the logic of probability. Kepler observes 150,000 stars, and has found a few thousand of those to have planet candidates.
Kepler observed hundreds of stars that have multiple planet candidates. Through a careful study of this sample, these 715 new planets were verified. "We've now developed a process to verify multiple planet candidates in bulk to deliver planets wholesale, and have used it to unveil a veritable bonanza of new worlds," said Lissauer.
These multiple-planet systems are fertile grounds for studying individual planets and the configuration of planetary neighbourhoods. This provides clues to planet formation.
Four of these new planets are less than 2.5 times the size of Earth and orbit in their Sun's habitable zone – range of distance from a star where the surface temperature of an orbiting planet may be suitable for life-giving liquid water.
One of these new habitable zone planets, called Kepler-296f, orbits a star half the size and 5 per cent as bright as our Sun.
Kepler-296f is twice the size of Earth, but scientists do not know whether the planet is a gaseous world, with a thick hydrogen-helium envelope, or it is a water world surrounded by a deep ocean. The findings will be published in The Astrophysical Journal.
