The first images of a supernova upend a belief that's stood for half a century
Astronomers have achieved something remarkable: the inaugural map of a supernova’s actual shape. By leveraging data from the European Southern Observatory’s Very Large Telescope (VLT) in Chile, researchers found that the earliest moments of a star’s explosion aren’t perfectly spherical after all—they’re stretched and uneven.
On April 10, 2024, the ATLAS project (Asteroid Terrestrial-impact Last Alert System) detected the initial flash from a colossal dying star, estimated to be 12–15 times more massive than the Sun. In just 26 hours, scientists directed the VLT to the event to capture a rare, front-row view of a star’s explosive finale (https://www.futura-sciences.com/en/a-star-stripped-to-its-core-astronomers-discover-an-extraordinary-supernova_19898/).
The striking image—an artist’s impression informed by real VLT data—demonstrates that, with rapid observation, researchers could glimpse the explosion’s shape in its earliest moments. Had they waited even one day, this initial geometry would have disappeared.
The event, designated SN 2024ggi, occurred in the spiral galaxy NGC 3621, about 22 million light-years away in the Hydra constellation. A VLT image captured on April 11 accurately pinpointed the explosion’s location within that distant galaxy.
What happens when a star dies
A massive star remains nearly perfectly spherical because gravity’s inward pull is balanced by the outward force produced by nuclear fusion in the core. When that balance tips, gravity takes over. The core collapses, pulling the outer layers inward until they rebound, generating a powerful shock wave that races outward.
When that shock pierces the star’s surface, a tremendous amount of energy is released, lighting up space in a dramatic event we call a supernova. Yet the precise way that shock forms and propagates has long puzzled scientists.
For a brief window after the blast—before the debris interacts with surrounding material—astronomers can glimpse the supernova’s original shape. Using a sophisticated method known as spectropolarimetry, which separates light by wavelength and analyzes the direction of wave vibration, VLT researchers captured that shape for the first time.
An olive-shaped explosion
Data from the VLT’s FORS2 instrument—the sole Southern Hemisphere tool capable of such measurements—revealed that the earliest light from the explosion was not emitted uniformly in all directions. Instead, it stretched along a single axis, resembling an olive rather than a perfect sphere.
As the supernova expanded, its light revealed how the blast interacted with surrounding gas. By day ten, the hydrogen-rich outer layers became visible—and they aligned with the same axis as the initial shock. That consistency implies the explosion’s core was directional from the outset, pointing to an underlying physical mechanism behind the symmetry.
This groundbreaking perspective challenges some long-standing supernova models while supporting others, bringing astronomers closer to deciphering how massive stars end their lives in such spectacular catastrophes.
Futura Team
