Astronomers have discovered a population of tiny galaxies that may have played a crucial role in clearing the cosmic fog that shrouded the universe after the Big Bang. These small but numerous galaxies could produce all the light needed for reionization, a process that gradually cleared the dense fog, allowing starlight to travel freely through space.
About 380,000 years after the Big Bang, charged particles combined into neutral hydrogen atoms, creating a thick, light-absorbing fog. It wasn’t until several hundred million years later that intense ultraviolet radiation from the first stars and galaxies began reionizing this primordial hydrogen.
The James Webb Space Telescope (JWST) has provided new data that points to tiny galaxies as the key players in this dramatic transformation. The telescope’s Near-Infrared Camera and Spectrograph instruments searched for a specific green emission line from doubly ionized oxygen, a hallmark of intense star formation.
A team led by assistant research scientist Isak Wold analyzed data from Abell 2744, a massive galaxy cluster located about 4 billion light-years away. They found 83 tiny galaxies that were vigorously forming stars when the universe was just 800 million years old, around 6% of its current age.
According to Wold, these small galaxies “punch well above their weight” in terms of producing ultraviolet power. If they functioned similarly, they would have generated enough light to reionize the hydrogen fog and make the universe transparent.
Source: https://www.space.com/astronomy/james-webb-space-telescope/tiny-galaxies-may-have-helped-our-universe-out-of-its-dark-ages-jwst-finds