Triplets become wide binaries
Astronomy & Geophysics · 2013
Triplets become wide binariesThe origins of binary star systems in wide orbits, sometimes as much as a light-year apart, have been something of a puzzle.Now simulations suggest that they could start life as triple stars.Simulations of star formation by the NASA Astrobiology team at the University of Hawaii suggest that most stars start life with a few others at the edge of their cloud cores.Gravitational pull between the stars and the gas often results in the least massive star being ejected from the system, while the more massive ones get larger and closer together.In some cases -and the team ran their simulations 180 000 times -the smallest star is not ejected, but orbits far away.If the two more massive stars then combine, the result is a wide binary."This can happen if there is enough gas in the cloud core to provide resistance," said the paper's lead author, Bo Reipurth of the Institute for Astronomy at the University of Hawaii at Manoa."Sometimes there is so much gas in the core that the two close stars spiral all the way in and collide with each other in a spectacular merging explosion."The wide binary nearest to Earth is Alpha Centauri, which has a small companion, Proxima Centauri, which orbits at a distance of about one-quarter of a light-year.All three stars were born close together several billion years ago, before a powerful dynamic kick sent Proxima out into its wide path, where it has been orbiting ever since.