Binary stars prime candidates for alien life

Binary star systems could be prime candidates for alien life, according to a new study from the University of Sheffield.

Researchers have developed a model which predicts the range of the so-called habitable zone, the distance a planet can be from a star and still retain the liquid water which is essential for life.

Everywhere humanity has found liquid water, it has also found life - although that is solely in regards to our own planet, which occupies the Sun's habitable zone.

Planets which are too close to the Sun, if they held water, saw it boiled away into the atmosphere and off into outer space by the heat. On those which are too distant from the Sun, the water has frozen into ice.

Image:There is a limited distance from stars in which planets could sustain life. Pic: NASA

Undergraduate student Bethany Wootton and Dr Richard Parker of the University of Sheffield examined what the habitable zone would be like in binary systems.

Roughly a third of all stellar systems in our galaxy are thought to be composed of two or more stars, and binaries - a system of two stars orbiting a common centre of mass - are especially common among young stars too.

When these stars are quite far apart then they won't impact each other's habitable zones. But if they are closer, their zones could benefit from heat from both of the stars, and would thus be more likely to retain liquid water.

Researchers developed computer simulations to model how young stars interact with each other, and found that it was relatively common for a binary system to be composed of two stars quite close together.

According to the researchers, in some situations the stars may be so close that their habitable zones even overlap - creating a giant zone around two tightly orbiting stars.

Image:An artist's impression of life on a planet orbiting binary stars. Pic: Mark Garlick

Ms Wootton said: "The search for life elsewhere in the universe is one of the most fundamental questions in modern science, and we need every bit of evidence we can find to help answer it.

"Our model suggests that there are more binary systems where planets sit in Goldilocks zones than we thought, increasing the prospects for life.

"So those worlds beloved of science fiction writers - where two Suns shine in their skies above alien life - look a lot more likely now."

Their work is published in the Letters of the Royal Astronomical Society's monthly notices.