When stars are born, more times than not, they arrive into the universe as twins. In the first step of stellar creation, a large cloud of gas and dust collapses due to gravity, often fragmenting into pieces. If each piece collapses again, multiple stars will be birthed from the same gas cloud. These infant suns are then surrounded by a halo of matter, the precursor to planets, known as a planet-forming disk. And, if these stars are close enough, the planet-forming disks around them can even swirl together, creating fantastic spiral tails.
Their goal is to understand how neighboring stars influence the planet-forming disks. “A large fraction of stars probably go through such a phase,” Perez says, referring to their sibling-filled childhood, “but we know little about it.” Nearby sibling stars can orbit each other, or one star can drop by for a visit to another, known as a fly-by. These new images are a first step toward determining which scenario happened for each of the three systems.
“We expect that most stars form in dense regions of the galaxy and are surrounded by other stars forming at almost the same time,” says Philipp Weber, astronomer at Universidad de Santiago de Chile and lead author of the study. Despite this fact, astronomers “mainly treat protoplanetary discs as isolated systems.”
Their new observations suggest that, for many star systems, this is a bad assumption to make. Fly-bys “could have lasting effects” on the structure of these planet-forming disks, says Weber, who still has a number of outstanding questions. How common are fly-bys? How do sibling stars change the evolution of disks and their planets? These new data will no doubt keep astronomers busy refining their theories as they seek to understand how planets form.
