We may have found out what first lit up the universe. Recent data from the Hubble and James Webb Space Telescopes suggests that small dwarf galaxies played a crucial role by clearing the dense fog of hydrogen that filled intergalactic space. A study highlighting this was published in February 2024.
Astrophysicist Iryna Chemerynska from the Institut d’Astrophysique de Paris stated, “This discovery shows how ultra-faint galaxies influenced the early stages of the universe.” These galaxies produced ionizing photons that converted neutral hydrogen into ionized plasma during the cosmic reionization phase.
In the universe’s early moments, after the Big Bang, a hot fog made it dark and unclear. This fog didn’t allow light to pass through until about 300,000 years later. At that point, protons and electrons formed neutral hydrogen gas, but light sources were scarce. As the first stars emerged, they sent out powerful radiation that reionized the gas, allowing light to shine through.
Fast forward to about one billion years post-Big Bang, the universe had fully reionized, marking the end of what we call the cosmic dawn. But astronomers faced challenges in studying this distant time due to the cosmic fog.
Initially, scientists believed that massive black holes or large galaxies dying in turmoil were behind the clearing. However, the James Webb Space Telescope has revealed that dwarf galaxies might be the real stars of this story.
An international team led by Hakim Atek from the Institut d’Astrophysique de Paris studied a galaxy cluster known as Abell 2744. This cluster is so dense that it bends space-time, allowing light from distant galaxies to be magnified. They discovered that these dwarf galaxies were not only abundant in the early universe but also surprisingly bright. In fact, they outnumbered larger galaxies by 100 to 1 and emitted four times the ionizing radiation typically associated with bigger galaxies.
Atek noted, “These tiny galaxies are surprisingly powerful. Their combined energy output was enough to reshape the universe.”
While this research presents compelling evidence for dwarf galaxies’ role in reionization, it’s just a piece of the puzzle. The team focused on a small section of the sky and aims to identify more areas to ensure their findings are representative. Upcoming studies will include other cosmic lens regions to broaden their understanding of early galaxies.
This ongoing research brings us closer to unveiling the mysteries of the universe’s origins. Astrophysicist Themiya Nanayakkara from Swinburne University remarked, “With the James Webb Space Telescope, we are venturing into new territory. This opens the door to even more questions about the universe’s evolution.”
To explore more on this topic, check out the full study published in Nature.
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