In a scenario out of "Star Wars,' astronomers have detected a planet outside our solar system with not one, but three suns, a finding that challenges astronomers' theories of planetary formation. The planet, a gas giant slightly larger than Jupiter, orbits the main star of a triple-star system known as HD 188753 in the constellation Cygnus ("The Swan'). The stellar trio and its planet are about 149 light-years from Earth and about as close to each other as our sun is to Saturn, US scientists reported in the current edition of the journal Nature.