Astronomers using the Einstein Probe space telescope have captured the initial shock breakout flash of exploding supernova SN 2026gzf in March. Ground-based telescopes around the world observed the rapidly brightening stellar explosion in a galaxy 500 million light-years away within hours of the detection.
Two research teams presented observations confirming that the faint initial X-ray flash represented a shock breakout. This moment occurs when the powerful shockwave of a supernova explosion pushes through the outer layers of a star. Shock breakouts can last only a few seconds, making SN 2026gzf only the second confirmed detection of its kind in the last two decades.
Catching the supernova at such an early stage provides a unique opportunity to study the final moments of massive stars. Dr Jillian Rastinejad of the University of Maryland told the Daily Mail: "You can think of the shock like radar - as the shock ploughs through the star's outer layers and any material in the vicinity, it leaves an imprint on the signal that we detect in X-rays." She added: "We can use these X-rays to give us an unprecedented, close-up view of the star at the brink of collapse."
Theory predicts that stars in this stage are volatile and surrounded by dense material, but previous observations remain rare. Dr Rastinejad said: "With this event, we're finally able to match theoretical predictions with what we observe." Telescopes across the globe confirmed the blast as an Ic-BL supernova, a category known for powerful relativistic jets of matter shot out close to the speed of light that typically trigger gamma-ray bursts.
Unexpected missing gamma rays
Despite matching characteristics of energetic supernovae linked to gamma-ray bursts, SN 2026gzf produced no initial flash of gamma rays. Dr Brendan O'Connor, an astronomer at Carnegie Mellon University, said: "SN 2026gzf looks remarkably similar to other energetic supernovae that have been previously linked to gamma-ray bursts." He noted: "Yet multi-wavelength follow-up observations using the most sensitive facilities found no evidence for a relativistic jet or an afterglow, which are typically seen in those events."
Dr O'Connor suggested that the jet might have been choked by the surface of the star itself or by debris floating in its orbit. The initial X-ray shock breakout was also the faintest ever associated with a supernova of this kind, despite the explosion itself not being dim.
Archival records revealed that the star was 20 times the mass of the Sun and had a violent lifestyle. The system was a rare Wolf-Rayet star that burned through all its hydrogen very early on. In the build-up to the explosion, the star underwent several irregular periods of mass loss, shooting out all its hydrogen and oxygen, leaving behind a strange volatile star mainly made of carbon and oxygen.
These findings suggest that the final days of a very large star can be a lot more varied than scientists previously thought.
Stellar lifecycle and binary interactions
Going forward, researchers hope to catch more shock breakouts so that they can start to solve remaining mysteries. Dr Rastinejad stated she wants to see how the presence of a second massive object, known as a binary, affects a star's lifecycle.
Dr Rastinejad said: "Supernovae and massive stars are laboratories for astrophysicists to study how the laws of physics behave in extreme environments - think high densities, high temperatures, material that is several times the mass of our Sun - that we can't recreate here on Earth." She added: "By studying them, we learn more about the laws of our Universe."
Around 90 per cent of stars in the sun are what scientists call main sequence stars, which fuse hydrogen into helium in their cores and range from about a tenth of the mass of the sun to about 200 times as massive. Main sequence stars start as clouds of gas and dust, which collapse under gravity into protostars until pressure and heat start nuclear fusion. Stars keep burning helium until it runs out in around 10 to 20 billion years, entering post-main sequence phases as red dwarfs, white dwarfs, red giants, or neutron stars.
Mechanisms of supernova explosions
A supernova occurs when a giant star explodes, shooting debris and particles into space. A supernova burns for only a short period of time, but it tells scientists a lot about how the universe began and shows that the universe is expanding at an ever increasing rate while playing a key role in distributing elements.
In 1987, astronomers spotted a titanic supernova in a nearby galaxy blazing with the power of over 100 million suns. Scientists recognize two known types of supernova.
The first type occurs in binary star systems when a carbon-oxygen white dwarf steals matter from its companion star until it accumulates too much matter and explodes. The second type occurs at the end of a single star's lifetime when nuclear fuel runs out and mass flows into its core until the core collapses under gravitational force, scattering elements that form new stars, planets, and everything else in the universe.
