Astronomers Catch a Newborn Supernova Just Hours After Its Explosion

Astronomers Catch a Newborn Supernova Just Hours After Its Explosion

Only hours after it first flared, teams of astronomers captured the immediate aftermath of a nearby supernova, offering an unprecedented look at the earliest moments of a massive star’s death. A study published in Science Advances reports that rapid action and precise geometric analysis revealed new clues about how some of the universe’s most powerful explosions unfold.

Rapid response and a lucky window

On April 10, 2024, astronomers mobilized to document supernova SN 2024ggi. Co-author Yi Yang of Tsinghua University learned of the detection shortly after arriving in San Francisco. About 12 hours later he submitted an observing request to the European Southern Observatory (ESO). The ESO approved the request quickly, and staff at the ESO’s Very Large Telescope (VLT) in Chile pointed the array toward the Hydra constellation, where the exploding star lies roughly 22 million light-years from Earth. In all, it took about 26 hours from first detection to collecting VLT observations — fast enough to witness a never-before-seen phase in the death of a red supergiant.

“The first VLT observations captured the phase during which matter accelerated by the explosion near the centre of the star shot through the star’s surface. For a few hours, the geometry of the star and its explosion could be, and were, observed together,”

— Dietrich Baade, ESO astronomer and study co-author.

What happens when a massive star dies

Most stars remain roughly spherical while nuclear fusion in their cores balances gravity. When fusion fuel runs out in a very massive star, the core collapses. For scale, SN 2024ggi began with a mass of about 12–15 times that of the Sun and a radius roughly 500 times solar. The imploding core causes outer shells to plunge inward and then rebound outward as shock waves. Those waves weaken the outer layers until they burst through the surface — the moment the star becomes a true supernova, releasing intense light and energy.

Seeing the breakout geometry

Unlike most studies that begin after shock interaction with surrounding material, the VLT observations captured the very first breakout geometry — the shape produced when the explosion first pierces the star’s surface and before substantial interaction with circumstellar matter. To decode this tiny angular structure the team used spectropolarimetry, a technique that measures the polarization of light across different wavelengths to reveal three-dimensional geometry at small scales.

“Spectropolarimetry delivers information about the geometry of the explosion that other types of observation cannot provide because the angular scales are too tiny,”

— Lifan Wang, astronomer and study co-author.

Using spectropolarimetry and complementary instruments, the researchers found that SN 2024ggi’s first blast created an olive-shaped region around the progenitor. As the explosion expanded and interacted with nearby material, that shape flattened while the ejecta retained a stable symmetry axis.

“These findings suggest a common physical mechanism that drives the explosion of many massive stars, which manifests a well-defined axial symmetry and acts on large scales,”

— Yi Yang, co-author.

Implications and next steps

The new data already lead researchers to discard some existing theoretical models and refine others. The observations set stricter constraints on how asymmetry and axial symmetry develop during core-collapse explosions, improving our understanding of stellar evolution and supernova physics. The detailed results have also helped illustrators produce some of the most accurate visual reconstructions yet of a supernova’s birth.

“This discovery not only reshapes our understanding of stellar explosions, but also demonstrates what can be achieved when science transcends borders,” said Ferdinando Patat, ESO astronomer and study co-author.

Bottom line: Fast coordination and spectropolarimetric observations of SN 2024ggi captured the earliest breakout phase of a red supergiant’s explosion, revealing an initially olive-shaped blast that flattens as it expands — a result that refines models of how massive stars explode.