Kepler spies Saturn-sized worlds

Astronomers say they cannot be sure just yet but there may be a third, more Earth-sized planet present as well.

The Kepler telescope was launched last year to identify planets by looking for periodic dips in light as objects pass in front of stars.

It is equipped with the largest camera ever put in space.

The mission has so far amassed hundreds of these transit events but definitive statements about the discovery of new planets beyond our Solar System - so-called exoplanets - can only be made after many careful repeat observations.

The two Saturn-sized objects announced through the journal's online publication tool, Science Express, are the result of seven months of detailed analysis.

The planets orbit a star much like our own, more than 2,000 light-years away in the Lyra constellation.

"This is the first time we have been able to see a system in transit where there is more than one planet," Dr Holman said of the Kepler quest.

The planets lie close in to their parent with the inner planet making roughly two revolutions for every one made by the outer object - approximately 19 days for Kepler-9b and 38 days for Kepler-9c.

This resonance was one of the details that drew scientists' attention to the system, said Dr Holman, who is affiliated to the Harvard-Smithsonian Center for Astrophysics, Cambridge, US.

"They're closer to their star than Mercury is to our Sun," he explained.

"It's quite common for transit surveys to find planets very close to their stars because that's the type of planet those surveys are most sensitive to finding. So, on the scale of our Solar System, [these planets] are quite close but on the scale of what we know about a typical type of transiting system - these are relatively far out."

The third, unconfirmed object has a radius about 1.5 times that of Earth, which would put it in a category astronomers sometimes refer to as "super-Earth" because its mass would be several times that of our home planet.

It would take less than two Earth days to circle the star. Kazinform cites BBC. See www.bbc.co.uk for full version.