Map of material circulation in the disk around protostar G358-MM1. Movement away from the viewer is revealed in red/orange and motion towards the audience is revealed in blue/green, showing that the disk is turning. A global research group led by Ross A. Burns at NAOJ utilized VLBI methods combining radio telescope selections around the world to map the maser emissions in the disk around a high-mass protostar known as G358-MM1. When a clump of material falls from the disk on to the protostar, it launches a burst of energy that warms the inner part of the disk, amazing methanol maser emission.
Map of material distribution in the disk around protostar G358-MM1. The white “+” marks the location of the protostar. The contour lines show signal strength. The colors represent the line-of-sight speeds. Motion far from the viewer is displayed in red/orange and movement towards the viewer is revealed in blue/green, showing that the disk is turning. Overlaid gray lines indicate the spiral arms determined through data analysis. Credit: R. A. Burns
Recent observations have actually discovered a spiral pattern in the material disk surrounding a young, high-mass protostar, recommending the existence of gravitational instability within the disk. This finding carries substantial ramifications for how high-mass stars form.
During the process of star formation, a protostellar disk serves as a way of providing material to the nascent “protostar” at its core. When it comes to high-mass protostars that have currently exceeded 8 times the mass of the Sun and continue to grow, it is hypothesized that rather of a steady stream, clusters of material periodically came down from the disk onto the protostar, activating intense but short growth spurts.
An international research team led by Ross A. Burns at NAOJ utilized VLBI methods combining radio telescope arrays around the globe to map the maser emissions in the disk around a high-mass protostar referred to as G358-MM1. This high-mass protostar is the third-ever case of an observationally verified development burst, and was intensely studied by the maser tracking company (M2O). The team was able to investigate the phenomenon in detail for the very first time.
The observational results reveal clear rotation around the central protostar and a spiral pattern with four arms. Spiral arms in rotating protostellar disks signify instability, a characteristic which was long theorized to be associated with huge star formation, however had yet to be proven observationally. This discovery not only revealed the first spiral-driven accretion disk in a high-mass protostar but likewise connected spiral arm instabilities with the episodic development bursts that are central to high-mass star formation theory.
When a clump of material falls from the disk on to the protostar, it releases a burst of energy that heats up the inner part of the disk, interesting methanol maser emission. By observing the regions that fired up maser emission triggered by this heating it was possible to map the surface of the disk in G358-MM1.
The team, comprising a partnership of more than 90 astronomers from around the world, now wishes to apply this strategy to observe the disks of other high-mass protostars which go through growth bursts in the future.
Reference: “A Keplerian disk with a four-arm spiral birthing an episodically accreting high-mass protostar” by R. A. Burns, Y. Uno, N. Sakai, J. Blanchard, Z. Fazil, G. Orosz, Y. Yonekura, Y. Tanabe, K. Sugiyama, T. Hirota, Kee-Tae Kim, A. Aberfelds, A. E. Volvach, A. Bartkiewicz, A. Caratti o Garatti, A. M. Sobolev, B. Stecklum, C. Brogan, C. Phillips, D. A. Ladeyschikov, D. Johnstone, G. Surcis, G. C. MacLeod, H. Linz, J. O. Chibueze, J. Brand, J. Eislöffel, L. Hyland, L. Uscanga, M. Olech, M. Durjasz, O. Bayandina, S. Breen, S. P. Ellingsen, S. P. van den Heever, T. R. Hunter and X. Chen, 27 February 2023, Nature Astronomy.DOI: 10.1038/ s41550-023-01899-w.
The study was funded by the Japan Society for the Promotion of Science, the University of Guanajuato, the Ministry of Education and Science of the Republic of Poland, the National Science Centre, Poland, the Italian Ministry of University and Research, and the Ministry of Science and Higher Education of the Russian Federation.