Atacama Large Millimeter/submillimeter Array | 2014 Dec 04
With new Atacama Large Millimeter/submillimeter Array (ALMA) observations, astronomers led by Shigehisa Takakuwa, Associate Research Fellow at the Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), Taiwan, have found spiral arms of molecular gas and dust around "baby twin" stars. Gas motions supplying materials to the twin were also identified. These results unveil for the first time, the mechanism of the birth and growth of binary stars, which are ubiquitous throughout the Universe. The study was published on November 20 in The Astrophysical Journal.
Stars form in interstellar clouds of molecular gas and dust. Previous studies of star formation focused primarily on single stars like the Sun, and a standard picture of single star formation has been established. According to this picture, a dense gas condensation in an interstellar cloud collapses gravitationally to form a single protostar at the center. Previous observations have found such collapsing gas motions feeding material toward the central protostars.
Compared to single star formation, our understanding of binary star formation has been limited, even though more than half of stars with a mass similar to that of the Sun are known to be binaries. It is thus crucial to observe the physical mechanism of binary formation to obtain a more comprehensive understanding of star formation. Theory suggests that a disk surrounding a young binary will feed material to the central "baby twin" in order for them to grow. While recent observations have found such disks (known as "circumbinary disks"), it was not possible to image the structure and gas motions because of the insufficient imaging resolution and sensitivity.
The research team, led by Shigehisa Takakuwa, used the ALMA telescope to observe the baby-twin star L1551 NE , located in the constellation of Taurus at a distance of 460 light years, with a 1.6 times better imaging resolution and a 6 times better sensitivity than those of their previous observations with the SubMillimeter Array (SMA). They used the emission from dust at a wavelength of 0.9mm to trace the distribution of interstellar material, and emission from carbon monoxide to study gas motions using the Doppler Effect. ...
Angular Momentum Exchange by Gravitational Torques and Infall
in the Circumbinary Disk of the Protostellar System L1551 NE - Shigehisa Takakuwa et al