Astronomers have captured the earliest moments of a supernova explosion, revealing an unexpected olive-shaped blast. The event, SN 2024ggi, was observed using the European Southern Observatory's Very Large Telescope just hours after its discovery. This breakthrough provides new insights into how massive stars end their lives.
On April 10, 2024, Yi Yang, an assistant professor at Tsinghua University in Beijing, China, discovered the supernova SN 2024ggi shortly after arriving in San Francisco. Recognizing its proximity and potential for study, Yang submitted an observation request to the European Southern Observatory (ESO) 12 hours later. ESO approved it swiftly, and by April 11—26 hours after discovery—the Very Large Telescope (VLT) in Chile began observations.
SN 2024ggi occurred in the galaxy NGC 3621, in the constellation Hydra, about 22 million light-years from Earth. This relatively close distance allowed detailed analysis. The star was a red supergiant with a mass 12 to 15 times that of the Sun and a radius 500 times larger, a classic example of a massive star nearing its end.
Using the VLT's FORS2 instrument for spectropolarimetry, the team captured the explosion's initial geometry. "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," said Dietrich Baade, an ESO astronomer and co-author.
The breakout revealed an olive-shaped blast, which flattened as it expanded but maintained axial symmetry. "The geometry of a supernova explosion provides fundamental information on stellar evolution and the physical processes leading to these cosmic fireworks," explained lead author Yi Yang. These findings suggest a common mechanism driving many massive star explosions on large scales.
When a massive star exhausts its fuel, its core collapses, triggering a shock wave that rips through the surface, making the supernova visible. This rare early observation, enabled by global collaboration, refines models of stellar deaths and highlights the power of rapid international teamwork. The results were published on November 12, 2025, in Science Advances.