Researchers used ALMA and advanced simulation techniques to elucidate the formation process of multi-star systems, identifying and explaining the role of "gas flows" in providing energy to developing protostars. The latest observations and simulations have found that in a three-dimensional protostar system, there are three spiral arms that provide gas material to three forming protostars, thus clarifying the formation process of multi-star systems.

Artistic impression of the triple protostar IRAS04239+2436. New research using observations and simulations sheds light on how multi-star systems form. Source: ALMA (ESO/NAOJ/NRAO)

Most stars with masses similar to our sun formed with other stars in multi-star systems. Therefore, understanding the formation of multi-star systems is important to the overall theory of star formation. However, astronomers are uncertain about its formation due to its complexity and lack of high-resolution, high-sensitivity data. In particular, recent observations of protostars often report "streamline" structures of gas flowing toward the protostar, but it has been unclear how these streamlines are formed.

Gas distribution around the ternary protostar IRAS04239+2436, (left) SO emission observed by ALMA, (right) numerical simulation reproduction by supercomputer ATERUI. Protostars A and B, shown in blue on the left, represent radio waves from the dust surrounding the protostar. In Protostar A, two unresolved protostars are thought to exist. In the image on the right, the positions of the three protostars are indicated by blue crosses. Source: ALMA (ESO/NAOJ/NRAO), J.-E. Leeetal. Leeetal.

An international research team led by Seoul National University professor Jeong-Eun Lee used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the three-dimensional protostar system IRAS04239+2436 located 460 light-years away in the constellation Taurus. The team found that emissions from sulfur monoxide (SO) molecules traced three spiral arms around the three protostars that formed in the system.

Comparison with simulations conducted by Professor Tomoaki Matsumoto of Hosei University using the supercomputers "ATERUI" and "ATERUIII" at the National Astronomical Observatory of Japan's Center for Computational Astrophysics showed that these three spiral arms are streamlines that transport material to the three protostars.

The combination of observations and simulations reveals for the first time how streamlines are created and contribute to the growth of the central protostar.

Simulation of multiple star formation by the supercomputer "ATERUI". The video shows that multiple protostars are born in filamentous turbulent gas clouds, which excite spiral arms and disturb the surrounding gas as they move. Source: Tomaki Matsumoto, Takaaki Takeda, 4D2U Project, NAOJ