Astronomers Unveil New Supernova Type from Hawaii’s Keck Observatory

Astronomers have made a groundbreaking discovery regarding the life cycle of stars, identifying a new type of supernova approximately 2 billion light-years from Earth. This finding, detailed in a paper published on March 15, 2025, in *Nature*, sheds light on the intricate processes that occur within stars before they explode. The research was led by Steve Schulze, an astrophysicist at Northwestern University, and reveals that the star, designated SN 2021yfj, underwent an unprecedented stripping of its outer layers prior to its explosion.

The supernova was first detected through data collected by the Zwicky Transient Facility survey at the Palomar Observatory in California. Subsequent observations at the W.M. Keck Observatory on Maunakea provided crucial insights into the explosion’s light spectrum and the elements released during the event. Schulze noted, “We know over 10,000 supernovas, but we detected a supernova that is very, very different to anything we’ve observed before.”

This unique supernova, estimated to have originated from a star with a mass approximately 60 times that of the Sun, exhibited a distinct layered structure. Typically, supernovas disperse a mixture of elements into space, but SN 2021yfj revealed an orderly shedding of layers over thousands of years. The outer layers, comprised of lighter elements, were stripped away, exposing richer layers of heavier materials like silicon and sulfur before the core’s explosion.

Unraveling the Layered Structure of Stars

The discovery supports the long-held theory that stars possess an onion-like structure, with lighter elements on the outside and heavier ones, including iron, at the core. The research team observed the moment the star’s iron core detonated, illuminating previously expelled materials rich in silicon, sulfur, and argon. Matt Nicholl, an astrophysicist from Queen’s University Belfast, commented on the significance of the findings, stating that it “confirms this onionskin structure of massive stars that we all expected to see.”

While the reasons behind the star’s extreme layer shedding remain unclear, Schulze’s team proposes that intense internal pulses could have caused the sequential removal of material. An intriguing aspect of this discovery is the presence of helium in the star’s final layer. Schulze described it as “a fly in the soup that shouldn’t be there,” as helium is typically one of the first elements to be ejected during a star’s life cycle. Anya Nugent, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and co-author of a related article, suggested that a companion star might have influenced the process or that jets from the original star could have stirred up material.

A New Class of Supernova

SN 2021yfj represents a new category of supernova, which Schulze and his team are naming Type 1en. This classification arises from the unique properties observed in this event, with Schulze noting, “There is no object that is even remotely similar.” The team estimates that such extreme stripping occurs in only about one in 1,000 supernovas, making them exceptionally rare and difficult to identify without detailed spectral analysis.

Schulze acknowledged the element of luck involved in this discovery, emphasizing that advancements in observational technology could lead to the identification of more Type 1en supernovas. The upcoming launch of the Vera C. Rubin Observatory in Chile, which is set to conduct a decade-long survey of the universe, is expected to detect thousands of supernovae daily, potentially uncovering many more types previously unknown.

This discovery not only enhances our understanding of stellar evolution but also contributes to the broader narrative of cosmic origins, echoing the sentiments of Carl Sagan, who famously stated that we are all made of star-stuff. As astronomers continue to explore the depths of space, findings like SN 2021yfj remind us of the intricate connections that bind the universe together.