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Astronomers Capture a Supernova’s Olive-Shaped Shock Breakout Within a Day

Polarized-light measurements with ESO’s Very Large Telescope reveal the explosion’s early geometry to sharpen models of how massive stars die.

Overview

  • An international team used the VLT’s FORS2 instrument to observe SN 2024ggi just 26 hours after discovery, catching the fleeting shock-breakout stage.
  • Spectropolarimetry reconstructed the first moments of the blast as elongated and axisymmetric—an olive-like shape rather than a sphere.
  • As the ejecta expanded into surrounding material, the geometry flattened but retained a stable axis of symmetry observed across subsequent measurements.
  • The event occurred in galaxy NGC 3621 about 22 million light-years away and came from a red supergiant of roughly 12–15 solar masses with a radius near 500 solar radii.
  • Published in Science Advances, the result rules out some models and supports a large-scale, neutrino-driven asymmetry, underscoring the value of rapid-response campaigns for future tests.