Narrator: This is Science Today. The sun, as far as scientists know, is a single star. That is, there isn't another star that orbits it or that it orbits. But lots of stars are binaries - two stars orbiting one another. In studying massive stars using a computer model run on one of the nation's supercomputers, astrophysicist Mark Krumholz of the University of California, Santa Cruz found that these stars, which are twenty times the size of the sun, are essentially all members of binary or multiple systems.
Krumholz: That's not something that we set out to study in this project, but what we found was that our simulation spontaneously made a binary star.
Narrator: The simulation showed that as interstellar gas collapses, it spins up and causes a disc to form, so rather than collapsing directly onto a star, things collapse onto a disc of material around the star. Parts of the disc became more attracted by gravity to other parts of the disc, causing it to lump up and eventually grow to become a second star.
Krumholz: We think that this is a generic phenomenon that will happen anytime one of these very massive clouds of gas collapses.
Narrator: For Science Today, I'm Larissa Branin.