James Webb space telescope confirms the earliest known supernova to date

The James Webb space telescope has documented a supernova whose light originates from a time when the universe was only around 730 million years old. The chronological classification is based on the distance measurement immediately after a gamma-ray burst registered on March 14, 2025. This gamma-ray burst was classified as GRB 250314A and provided the necessary warning time to precisely target observational resources. Four hours after the discovery, the distance was determined using the European Southern Observatory’s Very Large Telescope. Due to the extreme cosmological expansion, the signal was significantly elongated, allowing sufficient time to plan the follow-up observations of the James Webb Telescope.

The analysis of the collected data shows that the supernova has a comparable structure and luminosity development to explosions of massive stars from later cosmic epochs. This is remarkable insofar as stars in the early universe had a lower metallicity, which would lead us to expect structural differences. Despite these different initial chemical conditions, the observed properties are similar to supernovae of modern galaxies. The research team emphasizes that the host galaxy exhibits typical features of that epoch and does not show any unusual deviations. At the same time, the scientists point out that further observations are needed to clearly identify potential differences in early stellar evolution.

The duration of the gamma-ray burst itself was only a few seconds, but the subsequent optical afterglow was visible over a much longer period. Three and a half months after the initial detection, the supernova reached its maximum brightness in the spectrum used by Webb. The researchers assume that this was the collapse of a massive star. Two scientific papers in the journal Astronomy & Astrophysics present the complete data analysis. The earliest previously confirmed supernova was dated to around 1.8 billion years after the Big Bang, so the new discovery pushes the known time limit far forward.

Conclusion

The observation of this supernova expands our understanding of stellar evolutionary processes in the early universe. It indicates that central mechanisms of massive stellar explosions were already pronounced at a relatively early stage. The combination of early gamma-ray burst, precise distance measurement and later follow-up observation by the James Webb telescope enables a rare study of stellar evolution less than a billion years after the Big Bang.