The Origins of Binary Stars: New Model Reveals Why Multi-Star Systems Form

Scientists are learning a bit more about the origins of stars and how they form. They've created new models that examine what happens when unstable clusters of newly formed protostars break up and explain why there are so many binary stars are present in the universe.

About two-thirds of all stars within 81 light-years of Earth are either binary stars or part of multi-star systems. Younger star and protostar populations have a higher frequency of multi-star systems than older ones. In order to find out why this is, the researchers turned to models.

Protostar clusters are formed when the core of a molecular cloud collapses due to its own gravity and breaks up into pieces. One force that impacts this collapse is the magnetic field that threads the clouds, potentially stifling the fragmentation process. The new model showed that when a cloud collapses, the fragmentation process depends on the initial strength of the magnetic field, which acts against the gravity that causes the collapse. Above a certain magnetic field strength, single protostars are formed. Below it, the cloud fragments into multiple protostars. This second scenario seems to be commonplace, given the number of binary and multi-star systems.

"When we look up at the night sky, the human eye is unable to see that binary stars are the rule, rather than the exception," said Alan Boss, one of the researchers, in a news release. "These new calculations help to explain why binaries are so abundant."

The findings reveal a bit more about binary stars in our universe and show a bit more about how stars first begin to form. In addition, the new model can be applied to future research.

The findings are published in The Astrophysical Journal.