An international team of researchers has discovered how three child stars are powered by spiral arms of gas in a triple protostar system. The team led by Professor Jeong-Eun Lee of Seoul National University used the powerful Atacama/submillimeter Array (ALMA) telescope to observe a system called IRAS 04239+2436, located at a distance from Earth. earth about 460 light years. They found that the gas around the three protostars contained sulfur monoxide (SO) molecules, indicating the presence of shock waves caused by the complex interactions of the protostars. The distribution of SO molecules forms three large spiral arms extending up to 400 astronomical units (AU), or about 60 billion km. The team also measured the gas velocity and compared it with numerical simulations led by Professor Tomoaki Matsumoto of Hosei University. They found that the spiral arms act as streamers, or streams of gas, supplying the protostars and helping them to grow.

This discovery is important for understanding the process of star formation, which remains a mystery in astronomy. More than half of all stars are born in multiple star systems, but how they form is still poorly understood. There are several proposed scenarios for multi-star formation, but none of them can explain all observations. Presence of streamers One of the main features observed in many protostar systems is the presence of streamers, showing how protostars accumulate gas from their environment. . However, it is not known how these lines form and what role they play in the formation of many stars. By observing the three protostar system with ALMA, the team was able to reveal the origin and structure of the streamers in unprecedented detail.

“The most striking feature in our ALMA images are the well-defined, large multi-branched structures,” said Lee, lead author of the study published in The Astrophysical Journal Letters. detected in SO emissions”. “My first impression was that they were dancing together, around the central protostar system, although we later discovered that the spiral arms are the channels of material that feed the baby stars. “

The team also suggests that spiral arms may have formed due to the gravitational instability of a disk of gas and dust orbiting the protostar. This instability can cause parts of the disk to collapse and form streamers connected to the protostars. To further investigate the gas’s motion, the team compared the gas velocities obtained from this observation with numerical simulation velocities that reproduce the formation of multiple stars in a natural gas cloud. These simulations were carried out using the supercomputers “ATERUI” and “ATERUI II”, dedicated to astronomy at the National Astrophysical Observatory’s Center of Japan (NAOJ) Center for Computational Astrophysics. NAOJ’s ATERUI (Cray XC30, left) and ATERUI II (Cray XC50, right) supercomputers were used in this study. “We found that the spiral arms exhibit gas flows up to the three protostars; they are the gas generators for protostars,” explains Matsumoto, who led the numerical simulations on this study. “The gas velocities obtained from the simulations and observations are very consistent, suggesting that numerical simulations can indeed explain the origin of the streamers.” Correlation of observations and simulations By comparing observations with numerical simulations, the team studied the birth of this trio of protostars. To date, two scenarios have been proposed for multiple star formation. The first is the “chaotic fragmentation scenario,” in which the turbulent gas cloud fragmentes into gaseous condensates, each of which develops into a protostar. The second is the “Disk Fragmentation Scenario”, in which the disk of gas surrounding the protostar fragments forms a new protostar, resulting in many stars.

source: https://iopscience.iop.org/article/10.3847/1538-4357/acdd5b