Discovery Helps Explain Binary Systems
December 31, 2013

New Discovery Adds Weight To Binary Star Formation Theory

Lee Rannals for - Your Universe Online

Astronomers using the Very Large Array (VLA) have made a discovery that helps explain how double-star systems form. Half of all sun-like stars are part of double or multiple-star systems, and scientists have long debated over how these systems form. The latest discovery of previously-unseen binary companions to a pair of young protostars lends strong support for one of these explanations.

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

The team wrote in the Astrophysical Journal that they studied young stars roughly 1,000 light-years away from Earth, during which they found two previously-unseen companions in the plane where their disks would be expected.

"This fits the theoretical model of companions forming from fragmentation in the disk," Tobin explained. "This configuration would not be required by alternative explanations.”

The findings support the disk-fragmentation idea, which asserts that double-star systems form when a disk of gas and dust whirling around one young star fragments. The disk fragments under its own gravity, which in turn forms a second star within the disk surrounding its own disk. Stars that are still gathering matter from their surroundings form these disks, along with jet-like outflows that rapidly propel material in narrow beams perpendicular to the disk.

"Our new findings, combined with the earlier data, make disk fragmentation the strongest explanation for how close multiple star systems are formed," Leslie Looney of NRAO and the University of Illinois said in a statement.

Claire Chandler of NRAO said the upgrades done to VLA helped to make the new discovery possible. "The increased sensitivity of the VLA, produced by a decade-long upgrade project completed in 2012, made the new discovery possible," Chandler said.

The team of astronomers, from the US, Mexico and Netherlands, used VLA’s highest frequency band, from 40 to 50 GHz, to make the discovery. Scientists are able to use this frequency to find dust in the disk surrounding young stars that emit radio waves.