Bold takeaway: This discovery rewrites what we know about how some massive stars die, revealing a dramatic pre-explosion eruption that was hiding in plain sight. And this is the part most people miss: the first-ever radio glimpse of a Type Ibn supernova shows the star shed a thick helium-rich shell in the final years, a clue to binary-driven explosions that challenges previous assumptions. Here's the revised, expanded version with the same core facts and context.
Astronomers using the national facility for radio astronomy, the NSF’s Very Large Array (VLA), have achieved a groundbreaking observation: the first radio detections from a rare class of stellar explosion known as a Type Ibn supernova. This milestone offers new insight into how some of the universe’s most massive stars end their lives and provides a rare window into the last years of a star’s evolution, previously hidden from view.
The event, labeled SN 2023fyq, presents a unique chance to witness a massive star’s final act. Type Ibn supernovae occur when a star explodes into material that is rich in helium and was expelled from the star’s surface prior to the blast. By leveraging the VLA’s sensitive radio capabilities, researchers tracked radio emissions from this explosion over about 18 months, uncovering compelling evidence about the environment surrounding the dying star.
“One of the most striking findings is the first-ever radio signal from a star exploding into helium-rich gas shed just before the explosion,” explained Raphael Baer-Way, a UVA graduate student working with Maryam Modjaz (UVA) and Poonam Chandra (NRAO) and the study’s primary investigator. “Radio observations let us effectively ‘watch’ the star’s final decade before it ended, revealing a dramatic shedding of helium layers. Notably, there was a significant five-year surge in mass loss immediately before the supernova, which supports a scenario in which a gravitationally bound companion star drives these exotic explosions.” This means the progenitor star underwent a pronounced period of mass loss, likely triggered by the influence of a close stellar partner.
The team used radio and X-ray data to map the density and reach of the helium-rich material expelled before the explosion. They found the star was losing mass at an extraordinary rate—up to about 0.4% of the Sun’s mass per year—during a brief yet intense phase leading up to the supernova. This rapid mass-loss episode aligns with theoretical expectations for stars in close binary systems and provides direct, empirical evidence of the processes that can produce such rare supernovae.
Until this detection, the presence of dense surroundings around most Type Ibn supernovae had been inferred primarily from optical observations. Dr. A.J. Nayana of UC Berkeley, a co-lead investigator, notes, “Our study probes material ejected years before the explosion, showing that the star experienced a powerful mass-loss phase in the final 0.7–3 years of its life.” By determining when and how strongly the star shed mass, astronomers fill a key gap in understanding how the most massive stars end their lives and contribute to the enrichment of the universe.
This landmark observation paves the way for future radio studies of supernovae, with the potential to deepen our grasp of stellar life cycles and the forces shaping our galaxy. Dr. Wynn Jacobson-Galan of Caltech, another lead investigator and VLA program principal investigator, remarks, “This work opens a new path for constraining the endpoints of certain massive stars and underscores the importance of systematic radio follow-up of similar events with powerful instruments like the VLA and GMRT.”
About NRAO
The National Radio Astronomy Observatory is a facility of the U.S. National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.
