超新星爆発の新しい観測から星の内部構造を解明（First-of-its-kind supernova reveals inner workings of a dying star）

2025-08-20 ノースウェスタン大学

＜関連情報＞

• https://news.northwestern.edu/stories/2025/08/first-of-its-kind-supernova-reveals-innerworkings-of-a-dying-star/
• https://www.nature.com/articles/s41586-025-09375-3

極端に剥離された超新星がシリコンと硫黄の形成場所を明らかにする Extremely stripped supernova reveals a silicon and sulfur formation site

Steve Schulze,Avishay Gal-Yam,Luc Dessart,Adam A. Miller,Stan E. Woosley,Yi Yang  (杨轶),Mattia Bulla,Ofer Yaron,Jesper Sollerman,Alexei V. Filippenko,K-Ryan Hinds,Daniel A. Perley,Daichi Tsuna,Ragnhild Lunnan,Nikhil Sarin,Seán J. Brennan,Thomas G. Brink,Rachel J. Bruch,Ping Chen,Kaustav K. Das,Suhail Dhawan,Claes Fransson,Christoffer Fremling,Anjasha Gangopadhyay,… Shrinivas R. Kulkarni
Nature  Published:20 August 2025
DOI:https://doi.org/10.1038/s41586-025-09375-3

Abstract

Stars are initially powered by the fusion of hydrogen to helium. These ashes serve as fuel in a series of stages^1,2,3, transforming massive stars into a structure of shells. These are composed of natal hydrogen on the outside and consecutively heavier compositions inside, predicted to be dominated by He, C/O, O/Ne/Mg and O/Si/S (refs. ^4,5). Silicon and sulfur are fused into iron, leading to the collapse of the core and either a supernova explosion or the formation of a black hole^6,7,8,9. Stripped stars, in which the outer hydrogen layer has been removed and the internal He-rich or even the C/O layer below it is exposed¹⁰, provide evidence for this shell structure and the cosmic element production mechanism it reflects. The supernova types that arise from stripped stars embedded in shells of circumstellar material (CSM) confirm this scenario^{11,12,13,14,15}. However, direct evidence for the most interior shells, which are responsible for producing elements heavier than oxygen, is lacking. Here we report the discovery of the supernova (SN) 2021yfj resulting from a star stripped to its O/Si/S-rich layer. We directly observe a thick, massive Si/S-rich shell, expelled by the progenitor shortly before the supernova explosion. Exposing such an inner stellar layer is theoretically challenging and probably requires a rarely observed mass-loss mechanism. This rare supernova event reveals advanced stages of stellar evolution, forming heavier elements, including silicon, sulfur and argon, than those detected on the surface of any known class of massive stars.