近日，美国西北大学Steve Schulze团队研究了极度剥离的超新星揭示了硅和硫的形成位置。2025年8月20日，《自然》杂志发表了这一成果。

恒星最初由氢和氦的聚变提供能量。这些灰烬在一系列阶段中充当燃料，将大质量恒星转变成壳层结构。这些壳层结构由外部原生氢和内部连续较重的成分组成，预计主要由He、C/O、O/Ne/Mg和O/Si/S组成。硅和硫融合成铁，导致核心坍塌，要么发生超新星爆炸，要么形成黑洞。

剥离恒星的外层氢层被移除后，内部富氦层甚至其下方的C/O层暴露出来，为这种壳层结构及其所反映的宇宙元素产生机制提供了证据。由剥离恒星嵌入星周物质（CSM）壳中产生的超新星类型证实了这一情况。然而，目前尚无直接证据表明，大多数内壳负责产生比氧重的元素。

研究组报道了超新星（SN）2021yfj的发现，由一颗恒星剥离至其富O/Si/S层而产生。他们直接观察到一层厚厚的富Si/S壳层，在超新星爆炸前不久由前身恒星排出。从理论上讲，揭示这样的恒星内层颇具挑战性，可能需要一种很少观测到的质量损失机制。这一罕见的超新星事件揭示了恒星演化的高级阶段，形成了比任何已知大质量恒星表面检测到的更重的元素，包括硅、硫和氩。

附：英文原文

Title: Extremely stripped supernova reveals a silicon and sulfur formation site

Author: Schulze, Steve, Gal-Yam, Avishay, Dessart, Luc, Miller, Adam A., Woosley, Stan E., Yang, Yi, Bulla, Mattia, Yaron, Ofer, Sollerman, Jesper, Filippenko, Alexei V., Hinds, K-Ryan, Perley, Daniel A., Tsuna, Daichi, Lunnan, Ragnhild, Sarin, Nikhil, Brennan, Sen J., Brink, Thomas G., Bruch, Rachel J., Chen, Ping, Das, Kaustav K., Dhawan, Suhail, Fransson, Claes, Fremling, Christoffer, Gangopadhyay, Anjasha, Irani, Ido, Jerkstrand, Anders, Kneevi, Nikola, Kushnir, Doron, Maeda, Keiichi, Maguire, Kate, Ofek, Eran, Omand, Conor M. B., Qin, Yu-Jing, Sharma, Yashvi, Sit, Tawny, Srinivasaragavan, Gokul P., Strothjohann, Nora L., Takei, Yuki, Waxman, Eli, Yan, Lin, Yao, Yuhan, Zheng, WeiKang, Zimmerman, Erez A., Bellm, Eric C., Coughlin, Michael W., Masci, Frank J., Purdum, Josiah, Rigault, Mickal, Wold, Avery, Kulkarni, Shrinivas R.

Issue&Volume: 2025-08-20

Abstract: Stars are initially powered by the fusion of hydrogen to helium. These ashes serve as fuel in a series of stages1,2,3, 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 hole6,7,8,9. 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 scenario11,12,13,14,15. 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.

DOI: 10.1038/s41586-025-09375-3

Source: https://www.nature.com/articles/s41586-025-09375-3