Twin stars found with multiple planets

U.S. astronomers say the Kepler planet-hunting mission found the first multi-planet solar system orbiting a binary star, bringing images of "Star Wars" to mind. "It's Tatooine, right?" University of Texas at Austin astronomer Michael Endl said, referring to the fictional planet with twin suns in the popular movie series. The discovery, which proves entire planetary systems can form in a disk around a binary star, was made in observations of the binary system Kepler-47, consisting of a primary star is about the same mass as the sun and its companion, a dwarf star one-third its size, a university release reported. Astronomers have detected an inner planet three times the size of Earth and orbits the binary star every 49.5 days and an outer planet 4.6 times the size of Earth with an orbit of 303.2 days. "Unlike our sun, many stars are part of multiple-star systems where two or more stars orbit one another," William Borucki, Kepler mission principal investigator at NASA's Ames Research Center in Moffett Field, Calif., said. "The question always has been -- do they have planets and planetary systems? This Kepler discovery proves that they do," he said. "In our search for habitable planets, we have found more opportunities for life to exist."