The James Webb Space Telescope has detected a population of unexpectedly bright and massive galaxies from the universe's first 300 million years (redshift z > 14). These objects contain millions of solar masses of stars, far exceeding predictions from standard models of hierarchical galaxy assembly.
The observations suggest that star formation in the early universe was significantly more efficient than previously thought, or that alternative mechanisms such as direct collapse of massive gas clouds may have played a larger role. Some theoretical models invoking modified dark matter properties or early supermassive black hole seeds are being reconsidered.
These findings have prompted a re-evaluation of our understanding of cosmic dawn — the epoch when the first stars and galaxies ignited and began to reionize the neutral hydrogen that filled the universe.