First Planet Orbiting Two Stars Discovered by the NASA Kepler Spacecraft

By Dr. Laurance Doyle, an astrophysicist at the SETI Institute, and lead author of a paper that will appear in the journal Science on September 15, 2011.
For the first time, astronomers with the NASA Kepler spacecraft mission have discovered a planet orbiting two stars. This is a fundamentally different kind of planetary system than has ever been discovered before. The new system is known as “Kepler-16″ and consists of two stars — one about 69% the mass of the Sun, and the other only 20% the mass of the Sun, which circle each other every 41 days. Around both of these circles the Saturn-mass planet, half rock and half gas, known as Kepler-16b, with a period of 229 days. Even though the planet has an orbital period of less than a year, it is still outside the habitable zone of the stars because the stars are much dimmer than our Sun.
Where the Sun Sets Twice – NASA’s Kepler mission has discovered a world where two suns set over the horizon instead of just one. The planet, called Kepler-16b, is the most “Tatooine-like” planet yet found in our galaxy. Tatooine is the name of Luke Skywalker’s home world ...