Free Astronomy Magazine January-February 2026

26 JANUARY-FEBRUARY 2026 ASTRO PUBLISHING because the angular scales are too tiny,” says Lifan Wang, co-author and professor at the Texas A&M University in the US, who was a student at ESO at the start of his astron- omy career. Even though the exploding star ap- pears as a single point, the polarisation of its light carries hidden clues about its geometry, which the team were able to un- ravel. The only facility in the southern hemisphere capable of capturing the shape of a supernova through such a measure- ment is the FORS2 instru- ment installed on the VLT. With the FORS2 data, the astronomers found that the initial blast of material was shaped like an olive. As the explo- sion spread outwards and collided with the matter around the star, the shape flattened but the axis of sym- metry of the ejecta remained the same. “These findings suggest a common physical mechanism that drives the explosion of many mas- sive stars, which manifests a well-de- fined axial symmetry and acts on large scales,” according to Yang. With this knowledge astronomers can already rule out some of the cur- rent supernova models and add new information to improve other ones, providing insights into the powerful deaths of massive stars. “This discov- ery not only reshapes our under- standing of stellar explosions, but also demonstrates what can be achieved when science transcends borders,” says co-author and ESO as- tronomer Ferdinando Patat. “It’s a powerful reminder that curiosity, collaboration, and swift action can unlock profound insights into the physics shaping our Universe.” A stronomers have observed a supernova just a day after it was first detected. In its early stages, the explosion hadn't yet interacted with the material surrounding the star, pre- serving its true shape, revealed for the first time. This video summarises the discovery. [ESO] star and its explosion could be, and were, observed together,” says Diet- rich Baade, an ESO astronomer in Germany, and co-author of the study published in Science Advances . “The geometry of a supernova ex- plosion provides fundamental infor- mation on stellar evolution and the physical processes leading to these cosmic fireworks,” Yang explains. The exact mechanisms behind su- pernova explosions of massive stars, those with more than eight times the mass of the Sun, are still de- bated and are one of the funda- mental questions scientists want to address. This supernova’s progeni- tor was a red supergiant star, with a mass 12 to 15 times that of the Sun and a radius 500 times larger, mak- ing SN 2024ggi a classical example of a massive-star explosion. We know that during its life a typi- cal star keeps its spherical shape as a result of a very precise equilibrium of the gravitational force that wants to squeeze it and the pressure of its nuclear engine that wants to ex- pand it. When it runs out of its last source of fuel, the nuclear engine starts sputtering. For massive stars this marks the beginning of a super- nova: the core of the dying star col- lapses, the mass shells around fall onto it and bounce off. This re- bound shock then propagates out- ward, disrupting the star. Once the shock breaks through the surface, it unleashes immense amounts of en- ergy — the supernova then bright- ens dramatically and becomes ob- servable. During a short-lived phase, the su- pernova’s initial ‘breakout’ shape can be studied before the explosion interacts with the material sur- rounding the dying star. This is what astronomers have now achieved for the very first time with ESO's VLT, using a technique called ‘spectropo- larimetry’. “Spectropolarimetry de- livers information about the geo- metry of the explosion that other types of observation cannot provide ! https://www.eso.org/public/unitedkingdom/videos/eso2520a/