A Glimpse into the Heart of a Dying Star: The First 'Stripped to the Bone' Supernova

Northwestern University astrophysicists have made a groundbreaking discovery that is set to reshape our understanding of stellar evolution. An international team, led by these researchers, has identified a new and unprecedented type of exploding star – a supernova that has been literally "stripped to the bone."

This extraordinary event, designated SN2021yfj, presents a chemical signature unlike anything previously observed. While typical supernovas of massive stars are dominated by light elements like hydrogen and helium, SN2021yfj is unusually rich in heavier elements such as silicon, sulfur, and argon. These are elements that typically remain hidden deep within a star's core, shielded from view.

Steve Schulze, who led the study, described the supernova as offering an "unprecedented glimpse into the internal structure and mass loss of massive stars before they explode." He further elaborated, "This is the first time we have seen a star that was essentially stripped to the bone. It shows us how stars are structured and proves that stars can lose a lot of material before they explode."

Unveiling the Onion-Layered Structure

This discovery provides the first direct observational evidence supporting the long-held theory of the "onion-like" structure of massive stars. This model proposes that these colossal celestial bodies are composed of progressively heavier layers, starting from an outer envelope rich in hydrogen and helium, down to a dense iron core at the very center.

Adam Miller, a senior author on the study published in the prestigious journal Nature, emphasized the immense significance of this observation.

Explaining the Extreme Material Loss

Spectral analysis of SN2021yfj indicates that an incredibly violent event must have occurred to completely strip away the star's outer layers. Researchers are exploring several potential mechanisms for this extreme material loss, including:

• Interactions with a companion star: A close gravitational dance with a binary partner could have siphoned off the star's outer envelope.
• Massive pre-supernova eruptions: Stars might undergo significant outbursts before their final collapse.
• Unusually powerful stellar winds: Intense stellar winds could have carried away vast amounts of material.

The most compelling explanation currently points towards a process known as pair-instability. In this scenario, the massive star tears itself apart through repeated violent energy bursts. These energetic pulses gradually shed the outer layers, exposing the star's deep interior just moments before its ultimate, explosive demise.

This discovery marks a pivotal moment in astrophysics, offering a direct window into the dramatic final stages of the lives of massive stars.