The alien solar system Kepler-47 joins four previously discovered double-star systems that have only one planet each. Most of the stars in our galaxy that are like our sun are in binary star systems.
The inner planet of the Kepler-47 system, a world named Kepler-47b, has 3 times the diameter of Earth and orbits its twin suns in 49.5 Earth days. The outer planet, Kepler-47c, has 4.6 times Earth’s diameter and a year of 303.2 Earth days.
With binary stars at their center, the Kepler-47 planets have two suns like Tatooine, the fictional home world of Luke Skywalker in the "Star Wars" universe.
Kepler 47-c orbits within the habitable zone of its parent binary star. Its orbit is the largest yet found for a planet outside our solar system.
Astronomers have confirmed about 700 planets beyond our solar system as of early 2012, but the latest statistical analysis suggests that our galaxy likely harbors more than 100 billion alien worlds. One in six of the Milky Way's 100 billion stars may have a Jupiter-size planet, while nearly two-thirds may host a world slightly larger than Earth.
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