Scientists discover Tatooine-style world 200 lightyears off

Two suns, yes. Captive princesses in gold bikinis, unlikely

Scientists have discovered a planet that orbits two suns, like Luke Skywalker's home planet Tatooine in Star Wars. Two hundred light-years away from Earth, gaseous Kepler-16b is similar to Saturn in both size and mass and – like the desert planet that nurtured the young Skywalker – enjoys a double sunset.

We refer you to the famous scene in Star Wars IV: A New Hope

But unlike Tatooine – a once-lush but now dry and hot desert planet settled by humans and giant Hutts – Kepler-16b is a cold gas giant with an estimated surface temperature of -100°F to -150° F (-73°C to -101°C). It is not believed to harbour any life. Both of Kepler-16B's stars are smaller and cooler than our Sun, resulting in the low temperatures.

There have a been a number of suspected Tatooine planets in recent years, including the discovery in 2005 of one planet that supposedly orbited three suns. However, the astronomers behind the Kepler discovery claim that theirs is the first confirmed example:

“Kepler-16b is the first confirmed, unambiguous example of a circumbinary planet – a planet orbiting not one, but two stars,” said Josh Carter of the Harvard-Smithsonian Center for Astrophysics (CfA)."

The study from the Harvard Smithsonian CfA is published in the 15 September issue of the journal Science.

Shifting light patterns alerted astronomers to the existence of the planet.

NASA's Kepler mission detected the planet through what is known as a planetary transit – an event where a star dims when a planet crosses in front of it. The planet’s discovery was complicated by the fact that the two stars in the system eclipse each other, causing the total brightness to dim periodically.

And a further complication of the light patterns indicated a planet.

Astronomers noticed that the system’s brightness sometimes dipped even when the stars were not eclipsing one another, hinting at a third body. The additional dimming events reappeared at irregular time intervals, indicating that the stars were in different positions in their orbit each time the third body passed. This showed that this third body was circling, not just one, but both stars.

The final piece of evidence came from the Whipple observatory in Arizona, allowing scientists to conclude that the two stars orbit each other every 41 days at an average distance of 21 million miles.

“Much of what we know about the sizes of stars comes from such eclipsing binary systems, and most of what we know about the size of planets comes from transits,” said lead author and Kepler scientist Laurance Doyle of the SETI Institute. “Kepler-16 combines the best of both worlds, with stellar eclipses and planetary transits in one system.”

The new exoplanet boffinry is published today in the journal Science. ®