Key points: ESO's Very Large Telescope captured the earliest phase of a supernova from a 15‑solar‑mass red supergiant in NGC 3621, 22 million light‑years away. Observations began 26 hours after discovery and 29 hours after shock breakout, revealing an asymmetric, olive‑shaped explosion shaped by an equatorial disk of gas and dust. The star—about 25 million years old and 600 times the sun's diameter—likely left a neutron star. These images constrain and challenge existing models of massive‑star explosions.
Astronomers Capture First Moments of a Supernova — Olive‑Shaped Explosion Sheds New Light
Key points: ESO's Very Large Telescope captured the earliest phase of a supernova from a 15‑solar‑mass red supergiant in NGC 3621, 22 million light‑years away. Observations began 26 hours after discovery and 29 hours after shock breakout, revealing an asymmetric, olive‑shaped explosion shaped by an equatorial disk of gas and dust. The star—about 25 million years old and 600 times the sun's diameter—likely left a neutron star. These images constrain and challenge existing models of massive‑star explosions.
12:56 AM, 11/13/2025Science
First direct view of a supernova's earliest shape
For the first time, astronomers have captured the extremely early stage of a supernova and witnessed an unexpected, olive‑shaped explosion. Using the European Southern Observatory's Very Large Telescope (VLT) in Chile, a team observed a red supergiant star roughly 15 times the mass of the sun erupting in the galaxy NGC 3621, about 22 million light‑years away in the constellation Hydra.
The event was discovered on April 10, 2024. Thanks to a rapid follow‑up request by astrophysicist Yi Yang of Tsinghua University, the VLT began observations just 26 hours after the discovery and 29 hours after the shock from deep inside the star first broke through the stellar surface (the photosphere).
Rather than expanding spherically, the explosion was distorted into a vertical, olive‑like shape. The imagery indicates the star was encircled at its equator by a preexisting disk of gas and dust; as the core‑driven blast pushed outward, it preferentially drove material along opposite sides of the star, producing an asymmetric morphology.
"The geometry of a supernova explosion provides fundamental information on stellar evolution and the physical processes leading to these cosmic fireworks," said Yi Yang, lead author of the study published in Science Advances.
The progenitor was a red supergiant roughly 25 million years old with a diameter about 600 times that of the sun. Some stellar mass was expelled in the blast; the remaining core is believed to have collapsed into a neutron star, according to co‑author Dietrich Baade of the European Southern Observatory.
When a massive star exhausts hydrogen fuel at its center, the core collapses and launches an outgoing shock that pierces the surface and propels stellar material into space. Observing the shock breakout so soon after the event allowed researchers to study the explosion's initial geometry before interactions with surrounding circumstellar material altered the shape.
These early observations constrain theoretical models of how massive stars explode—ruling out some scenarios and helping refine others—because the asymmetric, disk‑influenced breakout points to complex preexisting stellar environments and explosion dynamics.
Why this matters: Directly imaging a supernova in its first day provides unique constraints on the explosion mechanism, the role of surrounding gas and dust, and the final fate of massive stars. Rapid telescope response and coordinated observation were critical to capturing this fleeting phase.
Reporting by Will Dunham; Editing by Daniel Wallis.