Solitary suns like ours are not as rare as we once thought, boosting the likelihood that there are other life-friendly solar systems in the universe.

It is not always easy to tell if a star has a companion, since they are often too close together to distinguish as separate objects with a telescope. But astronomers can look for other clues, such as periodic changes in the star system's light spectrum caused by the motion of the stars as they orbit one another.

Previous surveys had suggested that most systems containing a star the same mass as our sun have two or more stars orbiting each other, in contrast to our solar system. Now that has been thrown into doubt.

When Deepak Raghavan of Georgia State University in Atlanta and colleagues looked at 454 sun-like stars, they found that 56 per cent were single like our sun and just 44 per cent had a stellar companion. Their study will be published in The Astrophysical Journal.

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