Astronomers have captured the first radio waves ever detected from a rare class of exploding star, a discovery that has given them an unprecedented look into the final years of a massive star before its death in a powerful stellar explosion called a supernova.
Their findings, published in The Astrophysical Journal Letters , focus on a stellar explosion called a Type Ibn supernova. These explosions occur when a massive star blasts apart into clouds of helium-rich gas it shed shortly before death.
Using the National Science Foundation's Very Large Array radio telescope in New Mexico, the researchers tracked faint radio signals from the explosion over roughly 18 months. The radio waves revealed tell-tale signs of gas the star ejected just years before it blew apart — information that cannot be captured with optical telescopes alone.
Raphael Baer-Way, a third-year Ph.D. student in astronomy at the University of Virginia and lead author of the study said, "We were able to use radio observations to 'view' the final decade of the star's life before the explosion. It's like a time machine into those last important years, especially the final five when the star was losing mass intensely."
He explained that stars giving rise to Supernovae in other galaxies are usually too dim and far away to observe directly until they explode, but if a star sheds a lot of mass before its demise, that gas can act as a "mirror" that reveals the star's final stages when the explosion's shockwave crashes into it. This interaction creates strong radio waves.
Baer-Way said his team found evidence that the star was likely in a binary system — two stars orbiting each other — and that interaction with a companion may have driven the dramatic mass loss immediately before the explosion.
"To lose the kind of mass we saw in just the last few years… it almost certainly requires two stars gravitationally bound to each other," he explained.
The new radio data not only confirm that this kind of pre-explosion mass shedding happens but also open a new way to study stellar death across the universe. Until now, researchers depended mostly on optical light to infer such behavior. Radio observations add a powerful new tool to the resources available to the scientists who study these phenomena.
According to Baer-Way, the next steps are to extend this work by studying a larger sample of supernovae to see how often these intense mass-loss episodes occur and what they reveal about how stars evolve.
"Raphael's paper has opened a new window to the Universe for studying these rare, but crucial Supernovae, by revealing that we must point our radio telescopes much earlier than previously assumed to capture their fleeting radio signals," said Maryam Modjaz, professor of astronomy at UVA and an expert on massive star death and supernovae.
