Stars, like puppies, are born in litters. Although humans usually give birth to one offspring at a time, multiple births are the norm for stars. In fact, it’s unusual for a star to be born without siblings.
Stellar birth takes place in giant clouds of gas and dust that are slowly squeezed by gravity until they fragment into stars. Depending on its size, a single cloud can spawn dozens to millions of stars. These litters usually disperse over time as siblings drift apart, tugged this way and that by the gravitational pull of other passing stars, star clusters and gas clouds. Yet most stars manage to hang onto a sibling or two, becoming lifelong companions locked in an endless gravitational hug.
The Sun was probably born in such a litter nearly five billion years ago. But nobody knows where our star’s siblings are today. Like a litter of puppies all adopted by different homes, the Sun’s brother and sister stars have dispersed to parts unknown. Somewhere out there, the Sun’s long-lost siblings wander through space, oblivious to our yellow star and the planets huddled around it.
But now astronomers think they might have found one of the Sun’s ...