By BBC
http://www.bbc.co.uk/news/science-environment-14940885

A planet orbiting two suns - the first confirmed alien world of its kind - has been found by Nasa's Kepler telescope, the US space agency announced.

It may resemble the planet Tatooine from the film Star Wars, but scientists say Luke Skywalker, or anyone at all, is unlikely to be living there.

Named Kepler-16b, it is thought to be an uninhabitable cold gas giant, like Saturn.

The newly detected body lies some 200 light years from Earth.

Though there have been hints in the past that planets circling double stars might exist - "circumbinary planets", as they are known - scientists say this is the first confirmation.

It means when the day ends on Kepler-16b, there is a double sunset, they say.

'Stunning'

Kepler-16b's two suns are smaller than ours - at 69% and 20% of the mass of our Sun - making the surface temperature an estimated -100 to -150F (-73 to -101C).

The planet orbits its two suns every 229 days at a distance of 65m miles (104m km) - about the same distance out as Venus.

The Kepler telescope, launched in 2009, is designed to scour our section of the Milky Way for Earth-like planets.

"This is really a stunning measurement by Kepler," said Alan Boss of the Carnegie Institution for Science near Washington DC, a co-author of the study.

"The real exciting thing is there's a planet sitting out there orbiting around these two stars."

Kepler finds stars whose light is regularly dimmed when an orbiting planet passes between the star and the telescope.

In this case, the team was also able to observe dimming when one star passed in front of the other.

Nasa's scientists saw additional dips in the light in both stars at alternating but regular times, confirming the dual orbit of the planet.

Data collected by the Kepler telescope allows for very precise measurements of the mass, radius and trajectories of all three bodies - the best ever estimates of a extra-solar planet.