Sunset on a planet of a binary system. Credit:NASA.
Over the last years 40 planetary systems have been discovered surounding binary star systems. In all cases the configuration appears to be circumstellar, where the planets orbit around one of the stars, the secondary acting as a disturber. This could have happened in our own solar system if Jupiter was much bigger than it actually is.
The formation of planets in the binary star systems is more difficult than around single stars due to the gravitational action of the companion on the dynamics of the protoplanetary disk. Wiley Kley has presented relevant observational evidence that planets can really exist in in binary systems. (read more)