How Multiple Star Systems Come Together

Multiple star systems are a staple of science fiction. The heroes stumble across a parched desert searching for some escape from the three suns burning in the sky. As they struggle for their lives, perhaps our protagonists might take a moment to consider the chain of astronomical events that brought them to this moment.

Astronomers can offer some clues. Researchers working with the National Science Foundation’s Very Large Array (VLA) radio telescope have imaged several of these multiple star systems still in the early stages of formation. There are a few competing theories at work right now:

• protostars and their surrounding disks fragment from a larger parent disk, or
• the protostars form separately, and then the capture each other into a mutual orbit

The researchers looked at an object called L1551 IRS5, which consists of several protostellar objects enshrouded in gas and dust, and located about 450 light-years from earth. Their research indicates that the protostellar disks are aligned with each other, and aligned with the larger disk of material they’re forming out of. This means the first choice is more likely; they all formed together.

But things aren’t so simple. The researchers also turned up a third young star with a dust disk that isn’t aligned with the other two. So maybe this third star was captured. In other words, these multiple star systems could form together, or be caused by stars that capture one another, or some combination in between.

This research, done by Jeremy Lim, of the Institute of Astronomy & Astrophysics, Academia Sinica, in Taipei, Taiwan, and Shigehisa Takakuwa of the National Astronomical Observatory of Japan is published in the December 10 issue of the Astrophysical Journal.