The JWST used gravitational lensing to search for the sources of light that triggered the Epoch of Reionization and brought darkness to an end. The white hazy blobs are galaxies in Pandora's Cluster, which acts as the gravitational lens. The red objects are the distant and ancient objects magnified by the lens, some of them warped into arcs. Many of them are early dwarf galaxies, some of them responsible for the Epoch of Reionization.
To reach back in time and answer fundamental questions about our Universe is the James Webb Space Telescope’s greatest gift. The powerful infrared space telescope has peered back into the earliest stages of the Universe’s life and shown astronomers the forces that shaped it. One of our biggest questions about the Universe concerns the that occurred several hundred million years after the Big Bang, ending the Universe’s Dark Ages.
Quasars were another candidate because they emit so much light above the threshold needed to ionize hydrogen. But there weren’t enough of them to trigger the EOR. Massive galaxies were also a candidate, but astronomers think that they would’ve absorbed much of their own light. , the space telescope was able to see some of the earliest galaxies. Among them were LyC dwarf galaxies, some of the faintest objects in the early Universe.
The Ultra Compact Dwarf Galaxy M60-UCD1 is not ancient and is only about 50 million light years away. But it’s similar to the ancient dwarf galaxies found by the JWST. It’s only about 1/500th the diameter of the Milky Way, yet is densely packed with stars and extremely luminous. As each galaxy emitted ionizing radiation, it created a bubble of transparent hydrogen around them. These bubbles grew until they overlapped. Eventually, the hydrogen in the IGM was ionized, and light could travel freely. While other sources, like quasars and massive galaxies, could’ve created their own smaller bubbles of ionized hydrogen, it was the smaller bubbles that allowed the Universe to ionize more homogeneously.