This artist’s impression shows a star going supernova. About 22 million light-years away, the supernova, SN 2024ggi, exploded in the galaxy NGC 3621. Using the ESO’s Very Large Telescope, astronomers managed to capture the very early stage of the supernova when the blast was breaking through the star’s surface. Observing the breakout so early on — 26 hours after the supernova was first detected — revealed its true shape. The supernova broke out in an olive-like form. This marks the first-ever observation of the shape of a supernova explosion at this very early stage. Credit: ESO/L. Calçada
Astronomers using ESO’s Very Large Telescope pulled off something that sounds almost impossible. They caught a massive star exploding at the exact moment the blast punched through its surface, a moment so brief it usually disappears before anyone on Earth can react, as reported by SciTechDaily
The event, called SN 2024ggi, was spotted in the galaxy NGC 3621, about 22 million light years away. The distance is still enormous, but close enough in cosmic terms that scientists knew they had a rare window to study the blast as it unfolded. When the first alert went out, the team responded fast. Within hours, the VLT was pointed at the supernova, capturing the earliest light from the explosion.
What makes this breakthrough so important is the technique they used. With spectropolarimetry, astronomers can read the geometry of a supernova even when it appears as nothing more than a bright point in the sky. Hidden in the light is a fingerprint of the explosion’s shape, and this time, that fingerprint revealed something unexpected. The first burst of material shot out in an olive-like form, not a perfect sphere. That early shape lasted only a few hours before flattening as the blast pushed into surrounding gas, but the central axis stayed the same the whole time.
SN 2024ggi came from a red supergiant roughly 12 to 15 times the mass of the Sun. These stars live their whole lives in a delicate tug of war between gravity pulling inward and nuclear fusion pushing outward. When the fuel runs out, the core collapses, the outer layers crash inward, and a shock wave blasts outward, tearing the star apart. The instant that shock reaches the surface is the moment astronomers finally captured in such detail.
The VLT’s FORS2 instrument is currently the only tool in the southern hemisphere capable of doing this type of measurement. Because of that, the observations let scientists test long standing theories about how massive stars explode. Some models can now be ruled out, while others finally have evidence supporting them.
This discovery hints that many massive stars may share a common explosion mechanism that creates this kind of symmetry. It also shows how much can be learned when teams coordinate quickly and aim the right tools at the sky at the right moment.
