White diamonds show the locations of 20 of the 83 young, low-mass, starburst galaxies found in infrared images of the giant galaxy cluster Abell 2744. This composite incorporates images taken through three NIRCam filters (F200W as blue, F410M as green, and F444W as red). The F410M filter is highly sensitive to light emitted by doubly ionized oxygen — oxygen atoms that have been stripped of two electrons — at a time when reionization was well underway. Emitted as green light, the glow was stretched into the infrared as it traversed the expanding universe over billions of years. The cluster’s mass acts as a natural magnifying glass, allowing astronomers to see these tiny galaxies as they were when the universe was about 800 million years old. Credit: NASA/ESA/CSA/Bezanson et al. 2024 and Wold et al. 2025

Scientists using NASA's James Webb Space Telescope (JWST) have made an exciting discovery about the early universe. They found dozens of small galaxies that played a huge role in transforming our cosmos from a dark, foggy place into the bright, clear universe we see today.

Imagine the as a room filled with thick fog. For its first billion years, space was clouded by that blocked most light from traveling far. Today, this same gas is "ionized," meaning it has been stripped of electrons and can let light pass through freely. This transformation, called reionization, essentially cleared the cosmic fog and allowed galaxies to shine brightly across vast distances.

The newly discovered galaxies are surprisingly tiny compared to our Milky Way. You would need between 2,000 to 200,000 of these to equal the mass of our own galaxy. Despite their size, these miniature powerhouses were incredibly effective at producing ultraviolet light.

These tiny galaxies had two key advantages that made them perfect fog-clearers. First, their small size meant they couldn't gather as much hydrogen gas around them, making it easier for their powerful ultraviolet light to escape into space. Second, they experienced intense periods of star formation called "starbursts" that not only created lots of ultraviolet light but also carved pathways through their own material, helping that light break free.

The research team used JWST's incredible infrared vision to peer back in time to when the universe was only 800 million years old, just 6% of its current age of 13.8 billion years. They focused on a called Abell 2744, nicknamed "Pandora's cluster," which acts like a natural magnifying glass, making distant objects appear larger and brighter.

The scientists looked for a specific green light signature from that had lost electrons, a telltale sign of the high-energy processes happening in these ancient galaxies. This , originally visible to the naked eye billions of years ago, had been stretched into infrared light by the time it reached Webb's sensors.

The team discovered 83 of these small starburst galaxies and studied 20 in detail. Their analysis suggests that if these ancient galaxies released about 25% of their into surrounding space, similar to comparable galaxies today, they could account for all the energy needed to clear the fog that pervades the universe.

This discovery helps solve a long-standing mystery about which types of objects were responsible for reionization. While astronomers previously debated whether large galaxies, small galaxies, or drove this cosmic renovation, JWST's observations strongly support the small galaxy theory.

These findings remind us that sometimes the smallest players can have the biggest impact, fundamentally changing our understanding of how the universe evolved from darkness into light.

Provided by Universe Today