2023-08-09 17:14:00
There is only one sun in the solar system. But in fact, most stars are born with multiplicity. The problem is that the process of its formation is still a subject of debate. Therefore, finding out the mechanism of formation of multiplicity is very important for a comprehensive understanding of star formation theory. So far, several scenarios have been proposed for the mechanism of multiplicity formation. However, the truth is still hidden. In order to understand the multiplicity formation process, ALMA[1]It is important to directly observe the moment when multiple stars are born with high-resolution and high-sensitivity observation facilities such as Additionally, by recent fetal[2] Observations often report “streamers”, gas structures that flow towards the embryonic star, so studying the streamer is important because it shows how the embryonic star draws in gas to grow. In a multi-star system, the gas flow around the embryonic star must have a complex structure. ALMA’s high-resolution footage can be a powerful tool in studying streamer origins. Recently, an international research team led by Professor Jeongeun Lee of Seoul National University observed the multiple protostellar system IRAS 04239+2436, where three embryonic stars are being born together, with the Atacama Large Millimeter/Submillimeter Interferometer (ALMA) and detected three large spirals around the embryonic stars. discovered that the arm exists. These spiral arms took shape in the light emitted by sulfur monoxide (SO) molecules. The gas distribution and velocity distribution obtained from ALMA observations were compared with numerical simulations performed by Professor Tomoaki Matsumoto of Hosei University using a supercomputer. It was confirmed that these three spiral arms act as streamers that supply material to the triplets, in other words, they act like an umbilical cord that supplies nutrients to the fetus. The origin of the recently discovered streamers has been questioned, but the combination of ALMA observations and fluid dynamics simulations has revealed for the first time that streamers can be created in the dynamic process of multiplicity formation. Triplets forming in turbulent interstellar clouds, IRAS 04239+2436. Credit: ALMA (ESO/NAOJ/NRAO) The research team used ALMA to observe radio waves emitted by several molecules, including molecules of sulfur monoxide (SO) around the young multi-protostar system IRAS 04239+2436. IRAS 04239+2436 is a ‘triple protostellar system’, or triplets fetal star, located regarding 460 light-years from Earth. The research team expected that if they detected SO molecules in the region where the shock wave exists, they would be able to see the violent gas motion around the embryonic star. As a result of the observation, the research team detected SO molecules around the triplets fetal star, and found that the distribution of SO molecules formed a large spiral arm extending up to 400 astronomical units. Also, by using the Doppler effect, we succeeded in obtaining the velocity distribution of a gas containing SO molecules. Analysis of the gas’s motion revealed that the spiral arms traced by the SO molecules were actually streamers flowing towards the triplet star. “The most shocking feature of this ALMA image is the large multi-arm structure distributed along the SO emission,” said Prof. Jungeun Lee, emphasizing the significance of the discovery. I got the impression that they were dancing. Later, I was able to find out that these spiral arms are channels that supply material to the fetal star.” explained. Gas distribution around the triple protostar IRAS 04239+2436 (left) observed in molecular SO emission by ALMA and (right) reproduced by numerical simulations on the supercomputer ATERUI. In the left panel, A and B, shown in blue, represent radio waves from the dust around the embryonic star. A contains two undissolved fetal stars. In the right panel, the positions of the three embryos are marked with blue crosses. Credit: ALMA (ESO/NAOJ/NRAO), J.-E., Lee et al. To further investigate the motion of the gas, the research team compared the velocity of the gas obtained from ALMA observations with that obtained from numerical hydrodynamic simulations reproducing multistar formation in clouds of interstellar gas. ‘ATERUI’ and ‘ATERUI II’, supercomputers dedicated to astronomy at the Center for Computational Astrophysics of the National Astronomical Observatory of Japan (NAOJ)[3]The simulation, performed using , showed that gas perturbed around the three embryonic stars creates spiral arm-shaped shock waves. Professor Matsumoto, who led the numerical simulation, said, “We found that gas flows in the shape of spiral arms towards the three embryo stars, which shows that the spiral arms act as streamers supplying gas to the embryo stars. In the simulation and observation, Since the velocity distributions of the obtained gases are consistent, it can be considered that the results of the numerical simulations well explain the origin of the streamer.” said. The research team compared observational data and numerical simulations to study the birth mechanism of these triplets. So far, two scenarios have been proposed for multiplicity formation. The first is the ‘turbulent eruption scenario’, in which an interstellar cloud containing turbulence differentiates into several dense gas clumps, each of which evolves into a protostar. The second is a ‘disk eruption scenario’ in which a gas disk surrounding a protostar differentiates to form multiple stars through the process of creating a new protostar. Similar to the “turbulent eruption scenario”, the star formation process begins in the triplet fetus observed through this study, and then, like the “disk eruption scenario”, new star seeds are created in the disk, and the surrounding It can be described as a hybrid scenario in which turbulent flow in the gas and associated spiral arms form to suck in matter. Observation results and fluid dynamics simulation results are very similar, and this is the first time that multiplicity is formed by a hybrid scenario through the observed triplets. “This is the first time that the origins of a embryonic star and a streamer have been comprehensively revealed at the same time,” said Professor Matsumoto. “The combination of ALMA observations and simulations is a powerful tool to uncover the secrets of star formation.” Professor Jeongeun Lee said that this study was able to estimate how difficult it is to form a planet in a multi-star system. Professor Jeongeun Lee said, “Planets are formed from a disk of gas and dust that forms around a protostar. In this triplet system, the disk around the protostar is small, which means that the protostars are concentrated in a narrow central region, and the protostars are Because they orbit close to each other and gravitationally removes material from each other’s disks, planets can only form following a long period of calm, so the surroundings of IRAS 04239 + 2436 are not conducive to planet formation. “he explained. Professor Matsumoto said, “The actual observation of the formation process of multiple star systems in the manner of a hybrid scenario will greatly contribute to resolving the controversy over multiple star formation scenarios. In addition, this study confirms the existence of the recently discovered streamer. Not only that, but we’ve made important strides by explaining how they form.” This study, through a study comparing high-resolution and high-sensitivity ALMA observations with hydrodynamic numerical simulations using supercomputers, showed that the formation of multiple star systems is not the previously proposed binary mechanism, but rather a hybrid method in which the two mechanisms are combined. This is the first case. It is also suggested for the first time that spiral arm-shaped streamers that supply material to embryonic stars can be formed in the process of multistar formation, although it is significant. The findings were published in the Astrophysical Journal on August 4, 2023. Paper title: Triple spiral arms of a triple protostar system imaged in molecular lines #Explanation of terms
[1] ALMA (Atacama Large Millimeter/Submillimeter Wave Interferometry): A radio interferometer refers to a method of arranging multiple radio telescopes and interfering with each other to make them operate as one giant radio telescope. ALMA is the world’s largest radio interferometer built and operated in the Atacama Desert, Chile. MOST), Taiwan Central Research Institute (ASIAA), and Korea Astronomical Research Institute (KASI).
[2] Fetal star: Fetal star and protostar are the same term, and mean a state in which nuclear fusion has not yet occurred in the center. A multiple star system is a group of stars in which several stars are gravitationally bound to each other. A steamer is a stream of gas whose velocity structure is falling toward the center.
[3] “ATERUI” and “ATERUI II”: NAOJ’s supercomputers for astronomical numerical simulations at the National Astronomical Observatory of Japan (NAOJ) Mizusawa Campus (Oshi City, Iwate Prefecture). “ATERUI” (Cray XC30) ran from 2013 to 2018, and had a theoretical peak performance of 1.058 petaflops (1 petaflop is the performance of 1 trillion calculations per second). “ATERUI II” (Cray XC50) has been in operation since 2018 and is the world’s fastest supercomputer for astronomy with a theoretical peak performance of 3.087 petaflops. © My Neighbor Scientist Unauthorized reproduction and redistribution prohibited
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