Anyone who has seen Star Wars remembers Tatooine, the home of Luke and Anakin Skywalker. Astronomers have found a real Tatooine! Well, they have found a planet with two suns at least. It's probably nothing like how George Lucas portrayed it though.
Kepler 16-b is the first circumbinary planet ever discovered. It was first observed by the Kepler Space telescope on July 7th, 2011. The planet orbits a binary star system (Kepler-16) where one star is 70% the mass of the sun and the other is about 25%. In the system, the two stars orbit around each other, and the planet has an orbit surrounding the both of them . The planet is believed to be half rock and half gas, roughly the size of Saturn, and orbits the stars in about 228 days. An interesting point of the discovery is that the three objects all orbit in the same plane. It's as if the stars and planets are balls on a table, orbiting each other but sitting on an imaginary flat surface. This supports the theory that this planet formed from a circumbinary disk; a disk of gas and dust that surrounded the binary star system as they were forming. Until now, astronomers weren't sure that the conditions were stable enough around a binary star system for a planet to form. The discovery of Kepler 16-b will help astronomers improve their star formation models, and maybe we will find more circumbinary planets in the future!
Image Credit: NASA
