Kepler-47 detected by NASA’s Kepler space telescope, is the first transiting circumbinary system – multiple planets orbiting two suns – 4,900 light-years from Earth, in the constellation Cygnus. An artist’s concept illustration, credit: NASA/JPL-Caltech/T. Pyle.
Kepler space telescope measures minisucule changes in the brightness of more than 150,000 stars to search for planets that pass in front of or ‘transit’ their host star.
As seen from our vantage point on Earth, the two orbiting stars regularly eclipse each other every 7.5 days. One star is similar to the sun in size, but only 84 percent as bright. The second star is diminutive, measuring only one-third the size of the sun and less than one percent as bright.
Two planets also eclipse, or transit, the host stars. The inner planet, Kepler-47b, orbits the pair of stars in less than 50 days. At three times the radius of Earth, it is the smallest known transiting circumbinary planet.
Kepler-47 system diagram. Credit: NASA/JPL-Caltech/T. Pyle. Click the image to enlarge