2 new Kepler planets with double suns discovered

A team of NASA scientists has discovered two new planets, each of which revolves around its own double suns.

They are named Kepler-34b and Kepler-35b, and together with Kepler-16b, discovered last September, there are now three such known systems in the galaxy.

While the phenomenon of binary stars has been well known for centuries, the recent discoveries prove that binary suns can also support planets.

"This work further establishes that such 'two sun' planets are not rare exceptions, but may in fact be common, with many millions existing in our galaxy," said William Welsh of San Diego State University who led the study. "This discovery broadens the hunting ground for systems that could support life."

At 4,900 and 5,400 light years from Earth, located in the constellation Cygnus, Kepler-34b and Kepler-35b are among the most distant planets discovered by NASA's Kepler satellite. The findings werepublished recently in the journal Nature.

Most suns in the universe exist in pairs, said Tsevi Mazeh of Tel Aviv University's Department of Astronomy and Astrophysics and director of the Wise Observatory.

These partnerships closely resemble human relationships so that if two suns are formed together, they stay together, unless a third star comes too close to the pair and breaks the bond.

The two new planets are both gaseous Saturn-size planets. Kepler-34b orbits its two sun-like stars every 289 days, and the stars orbit one another every 28 days. Kepler-35b orbits its smaller and cooler host stars every 131 days, and the stellar pair orbit each other every 21 days. The planets reside too close to their parent stars to be in the "habitable zone" the region where liquid water could exist on a planet's surface.

During sunsets onboth planets,one sun will descend first, followed by a twilight period. Afterwards, the second sun will set and night will fall.

Our solar system, which revolves around one sun, is more unusual, though we can't dismiss the possibility that our sun has an undiscovered distant companion, said Mazeh.

"We shouldn't limit our search by assuming that all the planets are like those in our solar system. Some of them are very different from what we have here, and every time we find a new planet, we're explorers landing on unknown territory."