From science fiction to science fact, astronomers using the Kepler planet-hunting space telescope have announced the discovery of a "Tatooine" exoplanet that orbits around not one star but two! We have seen something similar to this before, in the science fiction world. Tatooine is the name of Luke Skywalker's home world in the movie Star Wars. This scorched desert rock orbits two yellow suns and is described by the movie’s hero as "If there's a bright center to the universe, you're on the planet that it's farthest from." A scene from the move depicts Luke Skywalker looking out towards the horizon as the two almost identical yellow stars begin to set.

Now, of course it is common place on Earth to see beautiful and spectacular sunsets that dazzle the eye as day turns into night. Now compare that with a sunset on the newly discovered planet, two stars never very far apart in the sky, one glowing yellow-orange sitting alongside its smaller deep red companion. As nighttime approaches they both gradually descend towards and then sink below the horizon producing a spectacular double sunset for anyone who may be privileged to witness it.

Reality

Unfortunately, this romantic setting seems unlikely as scientists think that the new planet named Kepler 16b is an uninhabitable cold gas giant, probably similar to Saturn. There have been suggestions in the past that planets circling double stars may exist, but until now this is the first actual confirmation. The largest of the two stars, a K dwarf, is about 69 percent the mass of our Sun, and the smallest, a red dwarf, is about 20 percent the Sun's mass.

The planet orbits its two suns every 229 days at a distance of 104 million kilometres (65 million miles), which is about the same as Venus.

Breaking the mould

Once the wow factor has settled, this spectacular discovery has thrown a few spanners into the theories of planet formation. The problem is the planet is too close to it's stars to fit in with current theories of planetary formation around double stars. Sara Seager, a planetary expert at the Massachusetts Institute of Technology commented, "People don’t really know how to form this planet. This planet broke the rule"

Location

The Kepler 16 system is located 200 light-years from Earth in the constellation Cygnus with it's component stars separated by a distance of 32 million kilometres (20 million miles).

Announcement

The discovery was announced on Thursday 15th September 2011 in a paper published online in the journal Science.