Hawaii’s Observatory Uncovers Unique Supernova Discovery

Astronomers at Hawaii’s Keck Observatory have made a groundbreaking discovery by identifying a new type of supernova located approximately 2 billion light-years from Earth. This supernova, designated SN 2021yfj, sheds light on the processes that may have created elements essential for life, such as carbon and oxygen, which are forged in the hearts of stars before they explode.

The discovery was led by Steve Schulze, an astrophysicist at Northwestern University, whose team published their findings on March 15, 2025, in the journal Nature. Schulze noted, “We know over 10,000 supernovas, but we detected a supernova that is very, very different from anything we’ve observed before.” This unique event challenges previous understandings of stellar evolution and supernovae.

Unraveling the Layers of a Star

Typically, when stars reach the end of their life cycle, they release a mix of elements into the cosmos. However, SN 2021yfj exhibited a different phenomenon, where the star appeared to have lost its outer layers over thousands of years before the explosion. The research team discovered that the star had an estimated mass of around 60 times that of our Sun.

The observations were facilitated by data from the Zwicky Transient Facility at the Palomar Observatory in California, along with detailed analysis using the Keck Observatory’s powerful instruments. The light from the supernova revealed a layered structure, consistent with the theoretical model of stars resembling onions. The outer layers contain lighter elements, while the core is composed of heavier materials, including iron.

Upon the detonation of the star’s iron core, the explosion illuminated a previously expelled layer rich in silicon, sulfur, and argon, confirming the anticipated layered structure of massive stars. According to Matt Nicholl, an astrophysicist at Queen’s University Belfast, who was not involved in the study, this discovery provides strong evidence for the expected onion-like configuration of massive stars.

Unanswered Questions and Future Prospects

While the findings are significant, the exact mechanism that led to the extreme stripping of the star’s layers remains uncertain. Schulze suggests that violent internal pulses may have contributed to this process, sequentially removing material over time. An intriguing aspect of this discovery is the presence of helium in the outer layer, which raises questions. “It’s a fly in the soup that shouldn’t be there,” Schulze remarked, highlighting that helium typically should have been expelled long before the explosion.

Possible explanations for the unusual presence of helium include interactions with a companion star that may have influenced the shedding of layers or powerful jets that could have dredged up material from deeper within the star.

Supernovas are generally classified into two main categories: Type I, which lack hydrogen, and Type II, which contain hydrogen. However, SN 2021yfj represents a new class, termed Type 1en. Schulze emphasized the uniqueness of this supernova, stating, “There is no object that is even remotely similar.”

The team estimates that only about one in 1,000 supernovas experiences such extreme stripping. These events are often difficult to detect due to their resemblance to more common supernova types. Schulze acknowledged the role of chance in this discovery, stating, “There was a lot of luck involved in making this discovery.”

As technology advances, astronomers anticipate identifying more Type 1en supernovas. The upcoming Vera C. Rubin Observatory in Chile is set to conduct a decade-long survey of the cosmos, beginning later this year. “Rubin is going to detect thousands of supernovae every day,” noted Anya Nugent, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and a co-author of a related article. This surge in observations may lead to the discovery of even more types of supernovae, further enriching our understanding of the universe.