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Kepler-47b is a circumbinary extrasolar planet orbiting the Kepler-47 binary star system, located about 4,900 light years away in the constellation Cygnus. It was discovered on August 3, 2012, along with a companion planet, Kepler-47c. The Kepler-47 binary system is the first to be discovered with multiple planets.

Discovery
The Kepler Space Telescope was used by scientists at NASA's Ames Research Center and at Israel's Tel-Aviv University to indicate the existence of orbiting planets in the Kepler-47 system by noticing dips in the binary system's luminosity. Additionally, astronomers from the University of Texas at Austin aided in the analysis of the characteristics of the stars and planets of the Kepler-47 system.

system
The Kepler-47 system consists of two stars, Kepler-47A and Kepler-47B. They are orbited by two planets, Kepler-47b and Kepler-47c. The planets lie on the same orbital plane, which is different from the sporadic orbits of many multi-planet systems but similar to the Earth's solar system. Kepler-47b orbits the parent stars with a period of 49.5 days. It is about three times the size of earth.

Significance
The Kepler-47 system, the fifth binary system discovered with orbiting planets,, is the first to be discovered with more than one orbiting planet. Before this discovery, it was not thought that binary systems could harbor more than one planet, as gravitational disturbances could theoretically cause the destruction of one or more planets. William Borucki, a scientist working for the Kepler mission, said regarding the discovery of these two planets, "many stars are part of multiple-star systems where two or more stars orbit one another. The question always has been - do they have planets and planetary systems? This Kepler discovery proves that they do". Kepler-47b, being only three times the size of Earth, is the smallest known transiting circumbinary planet.