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First direct imaging of a young binary system
Posted: December 17, 2009

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A team of astronomers have captured the first direct image of a young binary star system using the Coronographic Imager with Adaptive Optics on the Subaru Telescope.

Observed and simulated images of the young binary star SR24 (distance: 520 light years). Image: The graduate University for Advanced Studies & the National Astronomical Observatory of Japan/Chiba University.

The binary star system, SR24, resides 520 light years away in the constellation Ophiuchus. The study, conducted in July 2006, provides important information about how binary stars are born and evolve. In binary systems, two stars orbit around a common centre of mass; the brighter star or massive star is referred to as the primary star and the fainter or less massive star the secondary star. Both star host a disc of material and a third disc may envelope both stars and supply the stars' discs with mass via a connecting spiral arm.

Despite most stars forming in binary or multiple systems, their discs and spiral arms have rarely been directly imaged, that is, until now. The team, lead by astronomers at the National Astronomical Observatory of Japan, captured a high resolution near-infrared image of the discs around each star – the first such image of twin protoplanetary discs around a young stellar object. The images also revealed a long spiral arm extending out from the disc, and a bridge of gas connecting the two discs.

Three-dimensional numerical simulation image of young binary star system. Image: Hosei University.

By inputing various aspects of the observations into supercomputer simulations of accretion and disc formation, the team were able to generate structures similar to those seen in the image. The results suggest that fresh material streams along the spiral arm, replenishing the primary star's disc with a reservoir of gas contained in the disc surrounding both stars. The simulations also suggest that the bridge connecting the stars' discs corresponds to gas flow and a shock wave caused by the collision of gas rotating around the primary and secondary stars.

The findings provide a better understanding of the process of star and planet formation in a binary system by clarifying the role of supporting structures in maintaining the binary system.