Astronomers have discovered the largest planet yet known that orbits two suns.

In addition, they say the planet appears to be in a Goldilocks zone - not too hot and not too cold, but just right - that could potentially have water, which is crucial for life as we know it.

A planet circling two suns is known as a circumbinary planet, and this one is farther from its stars than the handful of other known circumbinary planets. These planets are also nicknamed "Tatooine" after the fictional body in the "Star Wars" films that boasts a double sunset.

The first so-called Tatooine planet was discovered in 2011 when astronomers discovered a world about the size of Saturn 200 light-years from Earth.

The newly discovered planet, dubbed Kepler-1647, is about the size of Jupiter, but its large size makes it a poor candidate to support life. Worse, it's a gaseous orb, thus rendering it uninhabitable. But professional star-gazers say one of its moons could be potentially habitable.

The Kepler space telescope was launched in 2009 to search for potentially habitable planets outside our solar system.

The hidden planet

Given its large size, scientists expressed surprise it wasn't found sooner.

"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 in a statement.

The discovery was announced Monday, at a meeting of the American Astronomical Society in San Diego.

But aspiring space travelers should be prepared for a very, very, long trip. Situated near the Cygnus constellation, the planet lies some 3,700 light-years away from the Earth. A light-year is about 6 trillion miles, or 9.5 trillion kilometers.

Astronomers at NASA and San Diego State University discovered the large planet. They say its wide orbit around the two suns takes 1,107 days - a little more than three years - to complete.

Scientists say that at 4.4 billion years old, the planet is about the same age as the Earth. Likewise, they say its two stars are similar to the Earth's sun, with one slightly larger and the other slightly smaller.

Astronomers can detect planets outside the solar system - known as exoplanets - when they pass in front of their stars, causing "slight dips in brightness," according to the researchers.

"But finding circumbinary planets is much harder than finding planets around single stars," co-author William Welsh, an SDSU astronomer, said. "The transits are not regularly spaced in time and they can vary in duration and even depth."

bik/kl (AP, AFP)