The world's first 3D simulation, which simultaneously considers the movement of dust and growth, in a disk around a young star, has shown that dust from the central region can be entrained and then ejected by gas outflows, and eventually fall back into the outer regions of the disk where it can aggregate into planets. This process can be compared to the volcanic "ash fall" in which the ash carried by the gas during an eruption falls on the area around the volcano. These results help explain the dust structures observed around young protostars. Observations by the Atacama Large Millimeter / submillimeter Array (ALMA) have revealed gaps in the protoplanetary disks of gas and dust around young stars. The gravitational effects of the planets are thought to be one of the reasons for the
formation of these rings. However, some rings have been seen even farther than Neptune's position in the Solar System. At these distances, dust, a vital component of planet formation, should be scarce. Furthermore, the dust is expected to move to the central region of the disc as it grows. So how planets can form in the outer regions has been a mystery so far.
A research group led by Yusuke Tsukamoto of Kagoshima University used ATERUI II, the world's
most powerful supercomputer
dedicated to astronomical calculations at the National Astronomical Observatory of Japan, to perform the first 3D simulation at world of movement and growth of dust in a protoplanetary disk. The team found that large dust particles grown in the central region can be carried perpendicular to the disc by streams of gas, called bipolar outflow, which erupt from the disc. This dust then comes out of the outflow and gravity pulls it back towards the outside of the disk. The simulation shows that this "stellar ash fall" can enrich the large dust in the outer region of the protoplanetary disk and facilitate planetary formation, which can eventually cause the formation of planets.
