Transcript:Narrator: The scene is recognized instantly by any Star Wars fan--. Karl Stapelfeldt, Spitzer Scientist, Jet Propulsion Laboratory: The movie Star Wars has this very famous scene of Luke Skywalker, walking out to contemplate his future around a double sunset in his planetary system, and that's a science fiction visualization of what was thought to be possible. Narrator: Double sunsets are not only possible— NASA scientists now believe the universe could be full of them. More than half of all stars are twins, outnumbering single stars like our sun. Stapelfeldt; The suns we knew would be there. The question was--was there a planet to be the place where you could stand and see these sunsets, and the inference is getting stronger now that there must be such planets, based on what Spitzer has found. Narrator: NASA’s Spitzer Space Telescope with its infrared eye can detect clues to locations of planets. It spots dusty disks– material around stars, that’s left over when planets are formed. Geoff Bryden, Spitzer Scientist, NASA's Jet Propulsion Laboratory What we did here differently. We didn’t look for stars directly. Instead, we looked for dust. This dust gives off heat that can be detected with the Spitzer Space Telescope. Stapelfeldt: Those are an indirect indicator. The dust particles, they're an indirect indicator of an asteroid belt and asteroids are the leftovers from the formation of rocky planets like Earth. So by chain of reasoning--say, I see dust particles, therefore, there’s an asteroid belt there, therefore, there’s a high chance of rocky planets like the Earth being in that system. Narrator: The astronomers also discovered that not all double star, or binary, systems are friendly places for planets to form. The systems most likely to have them are twins situated far apart from each other, or those found close together. Bryden: The tight binaries we find are most likely to have orbiting materials, asteroids, comets and we're guessing they're the most likely systems to have planets. Bryden : This planet Tatooine may be very normal. It seemed very unusual and exotic system. Something different from our own system, but that doesn’t necessarily mean it’s unusual. Narrator: So planets like ours with a single sun dipping below the horizon each night, might be even less common in the cosmos than the dual sunset scene in Star Wars.