Astronomers achieved a groundbreaking milestone by mapping the shape of a supernova for the first time, revealing unexpected details about its explosion. The supernova, known as SN 2024ggi, erupted approximately 22 million light-years from Earth in the galaxy NGC 3621, located in the constellation Hydra. This significant event was detected on April 10, 2024, when the Asteroid Terrestrial-impact Last Alert System (ATLAS) captured its first light.
Just 26 hours after the explosion, astronomers directed the Very Large Telescope (VLT) in Chile towards the supernova. This prompt observation provided a rare opportunity to study the initial phase of the star’s death, which typically eludes detection if observed later. The resulting image, an artist’s interpretation based on data from the VLT, showcases the supernova explosion, highlighting its distinct features during its earliest moments.
Researchers learned that a massive star maintains a near-perfect spherical shape due to a balance between gravitational forces and the outward pressure created by nuclear fusion at its core. When this balance is disrupted, the star collapses under its own weight, pulling its outer layers inward. This collapse generates a shock wave that eventually tears the star apart, leading to a dramatic increase in brightness as the shock wave breaks through the star’s surface.
One of the long-standing debates in astrophysics centers on how the shock wave forms and propagates outward. The VLT’s observations utilized a method known as spectropolarimetry, which analyzes light based on its wavelengths and the direction of light wave vibrations. This technique allowed scientists to capture the supernova’s initial “breakout” shape for the first time.
Data from the VLT’s FORS2 instrument, the only one in the Southern Hemisphere capable of such measurements, revealed that the light from the exploding star was not emitted uniformly. Instead, the initial shock wave exhibited an elongated shape, resembling an olive rather than being perfectly spherical.
As the explosion expanded, the light began to interact with the surrounding gas. By around day ten, the hydrogen-rich outer layers of the star became visible, aligning with the same axis as the initial shock wave. This observation indicates that the core explosion maintained a stable, directional shape from the outset, suggesting a consistent underlying mechanism at play.
The findings challenge some existing supernova models while supporting others, providing new insights into the catastrophic deaths of massive stars. The study was published on November 12, 2025, in the journal Science Advances. This work not only enhances our understanding of supernovae but also opens new avenues for research into the life cycles of stars.
As scientists continue to explore the cosmos, discoveries like SN 2024ggi remind us of the dynamic processes at play in the universe, revealing layers of complexity in stellar phenomena.