Overview

• A Nature study identifies SN2021yfj as the first observed supernova dominated by deep-layer elements, providing a direct view of a massive star’s onion-like structure.
• The Zwicky Transient Facility detected the September 2021 event about 2.2 billion light-years away, with Keck Observatory data confirming the heavy-element signatures.
• A crucial spectrum from a UC Berkeley colleague arrived after other telescopes were unavailable, enabling the swift analysis that uncovered the unusual composition.
• Analysis indicates a progenitor roughly 60 times the Sun’s mass that had been nearly stripped of its outer layers before collapse, exposing silicon-, sulfur- and argon-rich regions.
• The physical cause of the extreme stripping remains uncertain, and researchers urge rapid follow-up observations as the Vera C. Rubin Observatory is expected to find more such events.