Researchers using NASA’s James Webb Space Telescope have examined ancient galaxies to explore the secrets of the early universe. Now, astronomers have identified bright hydrogen emission from a distant galaxy, JADES-GS-z13-1.
The galaxy is located just 330 million years after the Big Bang, an unexpectedly early event in the universe.
Researchers estimated the galaxy’s distance from Earth using its brightness in different infrared filters. The initial redshift recorded by NIRCam was 12.9.
Researchers observed the galaxy using Webb’s Near-Infrared Spectrograph instrument to confirm this redshift. The resulting spectrum confirmed the redshift to be 13.0.
Astronomers discovered an unusual feature—a very bright wavelength of light called Lyman-alpha emission, produced by hydrogen atoms. Surprisingly, this light was much stronger than expected for such an early point in the universe’s history.
Roberto Maiolino, a University of Cambridge and University College London team member, said, “The early universe was bathed in a thick fog of neutral hydrogen. Most of this haze was lifted in a process called reionization, which was completed about one billion years after the Big Bang. GS-z13-1 is seen when the universe was only 330 million years old. Yet, it shows a surprisingly clear, telltale signature of Lyman-alpha emission that can only be seen once the surrounding fog has fully lifted. This result was totally unexpected by theories of early galaxy formation and has caught astronomers by surprise.”
During the early universe’s reionization era, dense neutral hydrogen surrounding galaxies blocked energetic ultraviolet light, similar to how colored glass filters light. Only after enough stars formed to ionize the hydrogen could this light, including Lyman-alpha emission, escape. Detecting Lyman-alpha radiation from this galaxy is a significant breakthrough for understanding the universe’s early stages.
NASA, ESA, CSA, JADES Collaboration, J. Witstok (University of Cambridge/University of Copenhagen), P. Jakobsen (University of Copenhagen), M. Zamani (ESA/Webb)
Kevin Hainline, a team member from the University of Arizona, said, “We really shouldn’t have found a galaxy like this, given our understanding of how the universe has evolved. We could think of the early universe as shrouded with a thick fog that would make it exceedingly difficult to find even powerful lighthouses peeking through, yet here we see the beam of light from this galaxy piercing the veil. This fascinating emission line has huge ramifications for how and when the universe reionized.”
The source of the Lyman-alpha radiation from this galaxy remains a mystery, but it could be the light from the universe’s first stars. These stars might have been unusually massive, hotter, and brighter than stars formed later, possibly ionizing the surrounding hydrogen.
Another possibility is that the radiation comes from an active galactic nucleus powered by one of the first supermassive black holes.
Joris Witstok of the University of Cambridge in the United Kingdom said, “The large bubble of ionized hydrogen surrounding this galaxy might have been created by a peculiar population of stars — much more massive, hotter, and more luminous than stars formed at later epochs, and possibly representative of the first generation of stars.”
Journal Reference
- Witstok, J., Jakobsen, P., Maiolino, R. et al. Witnessing the onset of reionization through Lyman-α emission at redshift 13. Nature 639, 897–901 (2025). DOI: 10.1038/s41586-025-08779-5
Source: Tech Explorist