How binary-stars are formed

Scientists, using the upgraded Karl G. Jansky Very Large Array (VLA), have discovered previously-unseen binary companions to a pair of very young protostars, which has now provided strong support for one of the competing explanations for how double-star systems form.

John Tobin, of the National Radio Astronomy Observatory (NRAO), said that the only way to resolve the debate is to observe very young stellar systems and catch them in the act of formation, asserting that's what they've done with the stars they observed, and they got valuable new clues from them.

Their new clues support the idea that double-star systems form when a disk of gas and dust whirling around one young star fragments, forming another new star in orbit with the first.

Young stars that still are gathering matter from their surroundings form such disks, along with jet-like outflows rapidly propelling material in narrow beams perpendicular to the disk.

When Tobin and an international team of astronomers studied gas-enshrouded young stars roughly 1,000 light-years from Earth, they found that two had previously-unseen companions in the plane where their disks would be expected, perpendicular to the direction of the outflows from the systems. One of the systems also clearly had a disk surrounding both young stars.

Tobin said that this fits the theoretical model of companions forming from fragmentation in the disk.

The research has bee published in the Astrophysical Journal.