WASHINGTON — In a solar system thousands of light years away, a star about half the size of our sun is being orbited by two planets that seem like smaller versions of Jupiter and Saturn, astronomers report.

The simultaneous discovery of two planets is rare and this was the first time researchers had the opportunity to do so using a technique called gravitational microlensing. “You could call it luck, but I think it might just mean that these systems are common throughout our galaxy,” lead author of the report, Scott Gaudi of Ohio State University, said in today’s issue of the journal Science. The star and its planets were observed when they passed in front of a more distant star in 2006. A lensing effect magnified the light of the distant star 500 times, the researchers explained.

Mr. Gaudi analyzed the data and discovered a distortion that he thought was caused by a Saturn-mass planet. Then, less than a day later, came an additional distortion he wasn’t expecting: a “blip” in the signal that appeared to be caused by a second, larger planet orbiting the same star.

It took two months to confirm the two-planet find. A research associate professor of astrophysics and cosmology at the University of Notre Dame, David Bennett, refined the preliminary model revealing additional details about the system.

The researchers said the newly discovered planets appear to be gaseous, like Jupiter and Saturn, but only about 80% as big. Four single planets have been found previously using microlensing.