Amazing stuff!
"... Researchers spotted the consequential supernova, called SN 2021yfj, from California’s Zwicky Transient Facility, then determined the elements being shed by it from Hawaii’s Keck Observatory. They found that the exploded star was about 60 times the mass of our Sun, 2.2 billion light-years away, and exhibited clear layers of heavier elements like argon and sulfur usually obscured behind its lighter outsides. The work “confirms this onion skin structure of massive stars that we all expected to see,” ..."
From the abstract:
"Stars are initially powered by the fusion of hydrogen to helium. These ashes serve as fuel in a series of stages, 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.
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 exposed, 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.
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."
Extremely stripped supernova reveals a silicon and sulfur formation site (no public access)
A cosmic formation site of silicon and sulphur revealed by a new type of supernova explosion (open access, this appears to be the reprint)
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