Opening flash of a giant star explosion captured for the first time

Today’s Image of the Day from the European Space Agency features a rare and fast-moving scene: the explosive death of a massive star caught at the exact moment the blast pushed through the star’s surface. 

Astronomers used the European Southern Observatory’s Very Large Telescope in Chile to capture this brief window in time. The moment passed within hours. By the next night, it would have vanished.

These early stages are hard to catch. Most supernovae are discovered after they brighten, long after key details fade away. 

This time, a fresh explosion called SN 2024ggi gave researchers an opening to study its first shape before the blast plowed into the material around the star.

A supernova in its opening moments

Supernova SN 2024ggi was first spotted on April 10, 2024. It sits about 22 million light-years away in the galaxy NGC 3621. Early detections helped set the stage for rapid action.

An international team of experts led by Professor Yi Yang of Tsinghua University moved quickly once the alert went out. 

The next night, on April 11, ESO approved the team’s observing request and turned the Very Large Telescope toward the blast. The first measurements came in just 26 hours after the discovery. 

“The first VLT observations captured the phase during which matter accelerated by the explosion near the center of the star shot through the star’s surface,” noted Dietrich Baade, an ESO astronomer in Germany.

“For a few hours, the geometry of the star and its explosion could be, and were, observed together.”

How massive stars reach the breaking point

Massive stars live with a fragile balance. Gravity pulls them inward while the pressure from nuclear reactions pushes outward. This balance holds for millions of years until the star runs out of fuel. 

When that happens, the core collapses. Layers of gas fall inward and rebound in a violent shock. The shock cuts through the star and sends energy racing outward.

As soon as the shock breaks through the surface, the supernova brightens. For a brief time, its first shape can be seen before the expanding blast smashes into surrounding gas. 

That early shape has always been hard to measure because the view usually arrives too late.

SN 2024ggi’s parent star was a red supergiant with about 12 to 15 times the mass of the Sun. Its radius stretched to nearly 500 times larger than the Sun’s, making it a textbook example of a massive star heading toward collapse.

A fresh look at the explosion’s shape

The team used an observing technique called spectropolarimetry to reveal the shape of the blast. This approach measures the polarization of light. 

Even though the star looks like a single point, the polarization pattern encodes the geometry of the explosion.

“Spectropolarimetry delivers information about the geometry of the explosion that other types of observation cannot provide because the angular scales are too tiny,” said study co-author Lifan Wang, a professor at the Texas A&M University.

The southern hemisphere has only one instrument capable of this kind of work: the FORS2 instrument on the Very Large Telescope.

With those observations, the researchers discovered that the initial burst of material was shaped like an olive. As the explosion expanded and collided with nearby gas, its shape flattened, but the axis of symmetry stayed the same. 

“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,” said Professor Yang.

The physics of our universe

Astronomers have long debated the exact chain of events that sets off the collapse of a massive star. 

Different models describe different shapes and behaviors. With the new measurements, some of those ideas can now be ruled out. Others can be improved.

This supernova also highlights the value of fast coordination between telescopes and research teams. 

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

“It’s a powerful reminder that curiosity, collaboration, and swift action can unlock profound insights into the physics shaping our Universe.”

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–