Giant star stripped to its core reveals origins of silicon and sulfur

Giant star stripped to its core reveals origins of silicon and sulfur
by Clarence Oxford
Los Angeles CA (SPX) Aug 26, 2025
Researchers led by Northwestern University and the Weizmann Institute of Science have identified a rare type of supernova that exposes the hidden inner layers of a massive star, revealing where heavy elements such as silicon and sulfur are produced.

The discovery centers on SN2021yfj, a stellar explosion detected in September 2021 by the Zwicky Transient Facility. Unlike most observed supernovae, which mainly display hydrogen and helium, this event was dominated by signatures of silicon, sulfur, and argon. The findings provide direct observational proof of the onion-like structure long theorized in massive stars.

"This is the first time we have seen a star that was essentially stripped to the bone," said lead author Dr. Steve Schulze of Northwestern University. "It shows us how stars are structured and proves that they can be completely stripped all the way down and still produce a brilliant explosion that we can observe from very, very far distances."

The research, published in Nature, suggests the progenitor star lost nearly all of its outer layers before collapse, allowing scientists to peer into deeper regions than ever before. The stripped material collided violently, creating an exceptionally bright explosion visible from 2.2 billion light years away.

Obtaining the spectrum proved challenging as weather and scheduling delayed global telescope observations. A breakthrough came when colleagues at the University of California Berkeley captured the crucial data. Analysis confirmed that instead of helium, carbon, or oxygen, the light carried the signatures of much heavier elements forged deep inside the star's core.

"This star lost most of the material that it produced throughout its lifetime," Schulze explained. "So we could only see the material formed during the months right before its explosion. Something very violent must have happened to cause that."

The team believes possibilities include a pre-supernova eruption, interaction with a companion star, or extraordinarily powerful stellar winds. Most likely, the star tore itself apart as extreme core conditions reignited nuclear fusion, ejecting layers that later collided.

Prof. Avishay Gal-Yam of the Weizmann Institute emphasized the significance: "Once we identified the spectral signatures of silicon, sulfur and argon, it was clear this was a major step forward. Peering into the depths of a giant star helps us understand where the heavy elements come from."

More than 25,000 supernovae have been cataloged, but SN2021yfj is the first to reveal such heavy-element spectra, underscoring its rarity. The study involved collaborators from the United States, Europe, Israel, China, and Japan, making it one of the most comprehensive investigations into stellar explosions to date.

Research Report:Extremely stripped supernova reveals a silicon and sulfur formation site