Astronomers say they have discovered the largest planet outside the solar system that orbits two suns.

The newly found world, about the size of Jupiter, is 3,700 light years from Earth. A light-year is nearly six trillion miles.

It was detected by a team led by Nasa and San Diego State University using the planet-hunting Kepler telescope. The discovery was announced during a meeting of the American Astronomical Society in San Diego.

Although the planet is in the habitable zone - where water that is crucial to life can be liquid - it is not a good candidate to support life because it is so big, scientists said.

"It's a bit curious that this biggest planet took so long to confirm since it is easier to find big planets than small ones," San Diego State astronomer Jerome Orosz said.

Planets that circle a pair of suns are nicknamed Tatooine after the fictional world in the Star Wars films that boasts a double sunset.

In 2011, scientists found the first Tatooine planet - a world about the size of Saturn 200 light years from Earth.

Nasa launched Kepler in 2009 to search for mainly Earth-like planets outside the solar system.