Scientists announced 9/15/2011 the discovery of the first planet known to orbit a binary star system, now named Kepler B at NASA Ames Research Center. The world is thought to be composed of half gas and half rock.
How to find Exoplanets: When there are two stars orbiting each other They orbit around a common center of gravity (much like the intertwined hands of two figure skaters as they circle each other) If this dance is seen edge on (line of sight) from earth, telescopes can detect subtle shifts in the light coming from the binary system as one star passes in front of the other based on our vantage. In Kepler B's case, another set of shifts in the light received was detected and it was slightly out of sync with the first set(A third skater circling the other two). This means that while the stars orbit each other, a third object is orbiting around both of them. The variation of light received is used to calculate the Mass (volume not weight) of the object. Because the difference was extremely small it is confirmed to be a planet.
It is easier to find larger bodies using this method because of the greater change they make in the observations.
Links:
NASA's Official News Release:
Press Conference:
My Thoughts:
I used the discovery of Gliese 581 C as a presentation for public speaking class because of the excitement around its orbit in the Goldilocks zone of Gliese 581, however discoveries about its atmosphere have lead scientists to believe Gliese 581 G is a better candidate for habitability. The context of my speech was that it wasn't too long ago that extra solar planets were only theoretical, and now we seemed to be discovering them all the time. With each discover advances are made, methods and tools refined, which in turn leads to better and more discoveries.
* Note the Goldilocks or Habitable Zone is the range of orbits around a star or stars that is temperate enough for liquid water to exist on a planets surface; being that each time liquid water is found on Earth, life is also found.
