The planet WASP-12b, discovered in 2008, is so close to its host star that it completes a full orbit in just 26 hours. ((ESA/C. Carreau))

NASA's Kepler orbiting telescope has found more than 700 objects in a far-off region of our galaxy that could be planets, the space agency has announced.

In the first release of data since the mission began 15 months ago, the Kepler team said it has discovered 706 "viable exoplanet candidates with sizes as small as that of the Earth to larger than that of Jupiter." The majority of the planetary candidates are the size of Neptune or smaller, they said.

Some of the planetary candidates will no doubt turn out to be something other than planets, such as binary stars. But further observation will likely confirm many as planets.

The Kepler data was gathered in just the first 43 days of the mission. The Kepler mission is aimed at finding orbiting planets — especially Earth-like planets — in a region near the Cygnus and Lyra constellations that includes about 156,000 stars that are up to 3,000 light years from Earth.


This artist's rendition provided by NASA shows the Kepler space telescope. Kepler is designed to search for Earth-like planets in the Milky Way galaxy. ((AP/NASA))

Kepler locates potential planets by spotting tiny decreases in the amount of light emitted by a star — something that could be evidence of an orbiting planet passing between the star and Earth.

Data on only 306 of the potential planets was released Tuesday. Identity and characteristics for the other 400 — the most promising candidates — are being held back until February 2011 to allow scientists to carry out more observations to confirm their planetary status or identify them as false positives.

5 potential multi-planet systems

The scientists also announced they had found five potential multi-planet systems.

"I look forward to the scientific community analyzing the data and announcing new exoplanet results in the coming months," said NASA spokeswoman Lia LaPiana in a release.

The first planet outside our solar system was definitively detected in 1995. Since then, astronomers using space and ground-based telescopes have identified 461 exoplanets. Tuesday's Kepler data release appears likely to significantly increase that number.   

"The Kepler observations will tell us whether there are many stars with planets that could harbour life, or whether we might be alone in our galaxy," said mission science principal investigator William Borucki of NASA's Ames Research Centre.

Kepler is expected to continue its search for Earth-like planets until November 2012.