An axisymmetric shock breakout indicated by prompt polarized emission from the type II supernova 2024ggi
- Yi Yang
- Xudong Wen
- Lifan Wang
- Dietrich Baade
- J. Craig Wheeler
- Alexei V. Filippenko
- Avishay Gal-Yam
- Justyn Maund
- Steve Schulze
- Xiaofeng Wang
- Chris Ashall
- Mattia Bulla
- Aleksandar Cikota
- He Gao
- Peter Hoeflich
- Gaici Li
- Divya Mishra
- Ferdinando Patat
- Kishore C. Patra
- Sergiy S. Vasylyev
- Shengyu Yan
2025-11-12
The death of massive stars is triggered by an infall-induced bounce shock that disrupts the star. How such a shock is launched and propagates through the star is a decade-long puzzle. Some models assume that the shock can be reenergized by absorbing neutrinos, leading to highly aspherical explosions. Other models involve jet-powered shocks that lead to bipolar explosions reflected in the geometry of the shock-breakout emission. We report measurement of the geometry of the shock breakout through unprecedentedly early spectropolarimetry of the nearby type II supernova 2024ggi starting ~1.2 days after the explosion. The measurement indicates a well-defined symmetry axis of the shock breakout, which is also shared by the hydrogen-rich envelope that emerged after the circumstellar matter was engulfed by the ejecta, revealing a persisting and prominent symmetry axis throughout the explosion. These findings suggest that the physical mechanism driving the explosion of massive stars manifests a well-defined axial symmetry and acts on large scales.