Astronomers using the European Southern Observatory’s Very Large Telescope (VLT) captured a rare early view of a supernova’s explosion, including the shape of its expanding shock wave. The star, SN 2024ggi, erupted in April 2024 in the galaxy NGC 3621 about 22 million light-years away. Observations just a day after discovery revealed that the blast was elongated – an olive-like shape rather than spherical. This first-of-its-kind snapshot provides new clues about how massive stars die.
Capturing the Explosion
According to media reports, the supernova was first detected on April 10, 2024, and the VLT began follow-up observations the next day. Using the FORS2 instrument for spectropolarimetry, astronomers measured the polarisation of the star’s light. Although the supernova appeared as a point of light, its polarization pattern revealed details of the explosion’s shape. This rapid spectropolarimetric snapshot captured the shock-breakout phase – the moment the explosion’s blast wave punched through the star’s surface – a phase normally too brief to study.
Olive-Shaped Blast Surprises
According to the recent study published in Science Advances, analysis of the FORS2 data revealed that the early blast was indeed olive-shaped, flattening as it expanded while retaining the same axis of symmetry. This points to a global mechanism driving the explosion along that axis.
Interestingly, when the blast interacted later with older gas shed by the star, the explosion’s axis seemed to shift-maybe because a companion star had affected the geometry. Already, these results rule out some models of supernovae and fill in details of others, sharpening the picture of how stars die.
