Dense galaxies are carving out a bubble in the early universe
When JWST's first science results started rolling in, it was a triumph for scientific vision and persistence. For years, the fate of the powerful space telescope was uncertain. It went way over budget, and for 25 years, troubling conversations accompanied its ongoing development. Several times, it seemed like it would be canceled, and in 2011, Congress came close to ending the program.
In December 2021, when the James Webb Space Telescope (JWST) launched successfully after years of budget overruns and near cancellation, astronomers around the world were thrilled with the prospect of groundbreaking findings from the early universe. Among JWST's first major surveys, JADES (JWST Advanced Deep Extragalactic Survey), led by researchers from the Center for Astrophysics, Harvard & Smithsonian, has provided some surprising observations.
One of these findings, detailed in a study published in The Astrophysical Journal, is the discovery of a galaxy overdensity candidate dating back to just 500 million years after the Big Bang. This overdensity contains 18 galaxies in a tightly packed cluster, with a galaxy number density four times higher than the average in similar regions.
The researchers detected increased Lyman-alpha radiation in the region, which can indicate the presence of an ionizing bubble caused by the intense radiation from young, star-forming galaxies. If confirmed, this could be the earliest evidence of cosmic reionization, the period when the first stars and galaxies illuminated the universe, transforming it from a dark, opaque state to its current transparent condition.
Further observations with JWST and ALMA are planned to map the 3D structure of this overdensity and test its role in the early reionization process.
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