Researchers using the James Webb Space Telescope have uncovered a distant galaxy that sheds light on a crucial period in the early universe, suggesting that a significant evolutionary phase occurred earlier than previously believed. The galaxy, known as JADES-GS-z13-1, was observed by Webb approximately 330 million years after the Big Bang, which marked the beginning of the universe roughly 13.8 billion years ago – a timeline considerably earlier than the age of Earth at 4.5 billion years.
After the initial rapid expansion following the Big Bang, the universe entered a phase known as the cosmic dark ages, where a thick veil of electrically neutral hydrogen gas shrouded the infant cosmos. This era gave way to the epoch of reionization, when the universe began to emit light. Webb’s findings indicate that JADES-GS-z13-1, among the earliest galaxies discovered, had already transitioned into this illuminating period.
Lead author of the study, astrophysicist Joris Witstok from the Cosmic Dawn Center at the University of Copenhagen, highlighted the galaxy’s distinct characteristics, suggesting a potent source of ultraviolet radiation and an early initiation of reionization. This period, known as cosmic dawn, marked the emergence of the universe’s first stars, black holes, and galaxies, catalyzing the chemical transformation of hydrogen gas through reionization and allowing light to permeate the cosmos.
The researchers explained that radiation from young stars and burgeoning supermassive black holes altered the hydrogen gas by stripping off electrons, gradually rendering the universe transparent to ultraviolet light. The glow detected by Webb in JADES-GS-z13-1 might be attributed to intense star formation at the galaxy’s core, the presence of an active supermassive black hole consuming surrounding material, or a combination of both factors.
Measuring approximately 230 light-years across, JADES-GS-z13-1 is significantly smaller than the Milky Way. Webb, launched by NASA in 2022 and operational since 2023, continues to unravel the mysteries of the cosmos with its unparalleled observational capabilities.
To gain a deeper insight into the early universe, researchers have identified only four galaxies existing slightly before the current one. The record holder, observed 294 million years after the Big Bang, along with the other galaxies, did not exhibit signs of reionization. The discovery of JADES-GS-z13-1, surrounded by a notable bubble of ionized hydrogen, has surprised the researchers. Reionization was previously believed to have commenced much later, making this galaxy a potential starting point of the reionization era. The exact beginning of this era remains a major unanswered question in cosmology. Will Dunham reported on this finding, edited by Rosalba O’Brien.
