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. Read more