Scientists have recently discovered the first planet orbiting a binary star after analyzing data collected from the Kepler Mission. It was previously thought only single stars would have planets due to the gravitational changes imposed by binary stars (extreme gravitational change would likely cause unstable orbits for any planets able to form). The discovery is significant since most Sun-like stars are members of binary systems and it suggests we will be finding more Earth-like planets than previously thought.

However, there are some problems. In this new system, the combined mass of both stars is less than our Sun and the planet is a gas giant about 1/3 the size of Jupiter. It doesn’t help establish whether or not Earth sized or solid planets can form in a binary system. Additionally, this find does not determine if planets can form around larger binary stars. Low mass binary stars don’t output as much heat which means planets need to orbit closer in order to sustain water. But as planets get closer to their sun(s), exposure to harmful x-ray and ultraviolet radiation increases – not a good situation for life to develop. Finally, other factors such as tidal locking (which would eliminate or greatly reduce the planets magnetic field), planet land mass and the highly variable luminosity of the binary star system mean orbiting planets likely do not have life.

Launched on March 7, 2009 by NASA, the Kepler spacecraft is equipped with a space observatory designed to support it’s primary mission – to determine how many of the billions of stars in our galaxy have Earth-like planets in the habitable zone. It has been very successful at finding planets; to date it has found 1,235 planet candidates, 5 of which are located in the habitable zone and earth sized.

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