How Does Kepler Find Planets?

While there are a number of different ways that astronomers infer the existence of exoplanets, NASA's Kepler mission uses what's known as the transit method. This method assumes that some percentage of planets will pass between our line of sight and the stars they orbit around, causing those stars to dim just a fraction from our perspective. If that dimming occurs regularly, astronomers can assume it's due to an orbiting planet rather than, say, a passing asteroid.

A planet with two suns may seem straight from science fiction, like Luke Skywalker's home planet of Tatooine in the Star Wars saga. But in 2011, scientists found proof of Kepler-16b, the first definitive example of a circumbinary planet, or one that orbits two stars.

Since the Kepler-16 system is binary (it has two stars), scientists can pick up on regular dips in light emitted from the system every time the two stars eclipsed each other. But when they noticed other dips in brightness not caused by the eclipses, they knew that a third body was circling the stars. Lo and behold, it was Kepler-16b, an exoplanet about the size of Saturn.

But before you get your hopes set on a two-starred sci-fi paradise to colonize, beware. Kepler-16-b is gaseous, cold and orbits outside its system's habitable zone. It might take quite a bit of technology and equipment to make the exoplanet appealing to us warm-blooded humans.