Recent findings from the James Webb Space Telescope (JWST) have shed light on a group of small yet powerful galaxies that played a crucial role in clearing the cosmic fog following the Big Bang. These galaxies, despite their diminutive size, were significant sources of ultraviolet radiation, making them strong candidates for aiding in the reionization of the early universe.

Astronomers have long debated the impact of dwarf galaxies on the early universe, and data from the JWST now suggests that these small galaxies may have been instrumental in illuminating the cosmos after the cosmic dark ages.

Isak Wold, an assistant research scientist at the Catholic University of America, highlighted the importance of these tiny galaxies during the 246th meeting of the American Astronomical Society. According to Wold, these numerous small galaxies could have produced sufficient light for reionization without the need for more exotic features.

Following the Big Bang, the universe entered a phase known as the cosmic dark ages, characterized by a dense fog of neutral hydrogen atoms that absorbed light. It wasn't until the emergence of the first stars and galaxies several hundred million years later that intense ultraviolet radiation began to reionize the hydrogen, allowing light to permeate the universe.

While various theories have been proposed regarding the trigger for this transformation, new JWST data points to the role of small, low-mass galaxies in this process. These galaxies acted as cosmic flashlights, illuminating the early universe and clearing the dense fog.

To identify these galaxies, researchers focused on the Abell 2744 galaxy cluster, also known as Pandora's Cluster, located about 4 billion light-years away. By leveraging the gravitational lensing effect of this massive cluster and the JWST's advanced instruments, scientists were able to peer back nearly 13 billion years in time.

The team used the JWST's Near-Infrared Camera and Near-Infrared Spectrograph to search for a specific green emission line from doubly ionized oxygen, a signature of intense star formation. This light, emitted in the visible range, was stretched into the infrared as it traveled through the expanding universe.

The search revealed 83 tiny, starburst galaxies that were actively forming stars when the universe was just 800 million years old, a mere 6% of its current age. These galaxies, with their significant ultraviolet power, were found to have played a critical role in reionizing the early universe.

Primitive galaxies like these, including 'green pea' galaxies, are rare today but are known to release a substantial amount of their ionizing UV radiation into space. If early galaxies functioned similarly, they would have generated enough light to make the universe transparent by reionizing the hydrogen fog.

Isak Wold emphasized the remarkable ability of these small galaxies to produce ultraviolet light, stating that they exceeded expectations in their contribution to the reionization process.