Planet with 2 suns discovered

A planet that orbits two suns at the same time — just like Tatooine in Star Wars — has been found for the first time.

A planet that orbits two suns at the same time — just like Tatooine in Star Wars — has been found for the first time.

"The discovery is stunning," said Alan Boss, co-author of the paper describing the findings, in a statement. "Once again, what used to be science fiction has turned into reality."

Boss is a researcher at the Carnegie Institution for Science in Washington, D.C. The study was published online Thursday in Science, and NASA was to hold a news conference at 2 p.m. ET.

The planet is similar to Saturn, but denser, and orbits the two small stars every 229 days. The smaller of the two stars is just a fifth the mass of the sun. ((JPL-Caltech/NASA))
The research was led by Laurance Doyle, a researcher at the SETI Institute, a non-profit research group in Mountain View, Calif., that describes itself as dedicated to exploring the origin, nature and prevalence of life in the universe. His group specializes in looking for eclipsing binaries — systems of two stars that orbit each other and eclipse each other every time one passes in front of the other.

The researchers combed through data collected by the Kepler telescope, which is focused on the part of the sky containing the constellations Cygnus and Lyra and is designed to look for planets outside our solar system. It does so by precisely measuring the brightness of stars and any dimming caused by an orbiting planet passing in front of the star.

Doyle's team identified 2,000 eclipsing binaries, then carefully looked at them one at a time.

"My eye was drawn to some extra eclipses that occurred out of sequence," Doyle said in a podcast interview with Science. Some were caused by a third star — that is, the two-star system turned out to be a three star system.

But in one case, the two stars were very small — just 20 per cent and 69 per cent as massive as the sun respectively — and the extra "eclipses" dimmed the stars only very slightly, indicating that the object that caused the dips was planet-sized.

Based on careful measurements, the team figured out that the two stars orbit each other every 41 days, and the Saturn-sized planet orbits the two stars every 229 days. The planet is denser than Saturn, suggesting that it contains rock as well as gas, and its distance from the centre of its orbit is about 70 per cent of the distance between the Earth and the sun.

The planet is thought to be cold and not habitable.

Kepler was launched into space in March 2009. As of February, the telescope had found more than 1,200 "planet candidates" or data suggesting possible planets.