New Delhi: Astronomers have confirmed that environmental factors were already shaping galaxy growth when the Universe was only 1.2 billion years old. Astronomers turned
the sensitive infrared gaze of the James Webb Space Telescope to the Loktak Protocluster, a massive structural precursor to a galaxy cluster, existing 12.6 billion years ago. The research shows that galaxies in highly dense cosmic environments grow more extended than counterpart galaxies situated in isolated or average environments. The protocluster was initially discovered by the Hyper Suprime-Cam on the Subaru Telescope, by mapping Lyman-alpha emissions from star-farming stellar nurseries, or clouds of mostly neutral hydrogen gas.
The massive system consists of four distinct concentrations of galaxies linked together into a singular, vast structural construction site. Subsequent high-resolution infrared imaging from the JWST allowed researchers to compare the physical dimensions of the protocluster galaxies against typical control populations from the same cosmic epoch. When evaluated in ultraviolet light, which highlights active star-formation cores, both groups exhibited nearly identical sizes. However, when measured in optical wavelengths to trace the broader distribution of older, pre-existing stars. The galaxies within the dense protocluster environment were on average 1.4 times larger than those in ‘normal’ surroundings.
Follow-up observations planned
This structural discrepancy indicates that while central star-formation rates remained uniform across different environments, galaxies inside crowded clusters accumulated their outer stellar distributions much earlier and more rapidly. The findings demonstrate that galaxy evolution is not dictated solely by internal characteristics or mass. Instead, environmental mechanisms were actively modifying structures of galaxies during the earliest chapters of cosmic history, long before mature galaxy clusters fully developed. The scientists plan to conduct follow-up spectroscopic surveys using the Subaru Telescope, with continued JWST investigations expected to establish whether these accelerated growth patterns wire widespread throughout the early Universe, or specifically unique to the Loktak Supercluster. A paper describing the research has been published in The Astrophysical Journal Letters.
