Free Astronomy Magazine November-December 2025

43 NOVEMBER-DECEMBER 2025 ASTRO PUBLISHING the Keck I telescope the night SN 2021yfj was discovered — we were able to obtain a spectrum that di- rectly led to the realization that this was an incredibly special new type of supernova. Opportunities of this kind are rare!” Instead of typical carbon and oxygen — found in other stripped super- novae — the spectrum was domi- nated by strong signals of silicon, sulfur and argon. Nuclear fusion pro- duces these heavier elements within a massive star’s deep interior during its final stages of life. “This star lost most of the material that it produced throughout its life- time, ” Schulze said. “So, we could only see the material formed during the months right before its explo- sion. Something very violent must have happened to cause that.” While the precise cause of this phe- nomenon remains an open ques- tion, Schulze, Miller, Yang, Filip- penko, and their colleagues propose a rare and powerful process was at play. They are exploring multiple scenarios, including interactions with a potential companion star, a massive pre-supernova eruption, or even unusually strong stellar winds. But, most likely, the team posits this mysterious supernova is the result of a massive star literally tearing itself apart. As the star’s core squeezes in- ward under its own gravity, it be- comes even hotter and denser. The extreme heat and density then reignite nuclear fusion with such in- credible intensity that it causes a powerful burst of energy that pushes away the star’s outer layers. Each time the star undergoes this powerful pulse, it sheds more mate- rial. “We still don’t fully understand how nature created this particular explo- sion,” Miller said. “This star under- scores the need to uncover more of these rare supernovae, so we can continue to study them.” versity of California, Berkeley, had been very interested in infant su- pernovae himself and was intrigued by the object. Fortuitously, he hap- pened to be observing at Keck Ob- servatory and was able to quickly pivot to capture the spectrum of this newly discovered celestial tran- sient using Keck Observatory’s Low- Resolution Imaging Spectrograph (LRIS). “It’s so exciting to discover a new class of exploding star, espe- cially one that provides a confirma- tion of some of our theories of how massive stars evolve with time yet also reveals interesting new puz- zles,” said Filippenko. “It was very fortunate that my team was using !