Overview

• Astronomers observed spectra dominated by silicon, sulfur and argon, providing the first direct glimpse of a massive star’s deepest layers just before explosion.
• Measured ejecta speeds reached about 3,000 kilometers per second, indicating the material originated close to the star’s core.
• The event occurred roughly 2.2 billion light-years away after the progenitor had shed hydrogen, helium and even lighter-element shells, leaving oxygen–silicon layers exposed.
• The team proposes extreme pre-supernova mass loss with colliding shells, potentially from pair-instability pulses, though this mechanism remains a working hypothesis pending more examples.
• The discovery hinged on a fortuitous Keck spectrum obtained within a day of ZTF’s alert, and researchers suggest the phenomenon may represent a provisional new class dubbed Type Ien.