The early universe was quite dark because it was full of hydrogen, which blocked out light. It wasn't until the first stars appeared and began to illuminate their surroundings with UV light that light appeared. This happened during the era of reionization, a process that caused matter in the universe to become reionized after the end of the "Dark Ages." But even before this era, a specific and mysterious type of light - Lyman-alpha radiation - was piercing the darkness.

Scientists have long tried to figure out where these emissions come from? Lyman-alpha radiation appears in the UV range and comes from hydrogen atoms. Astronomers have named the spectrum of these emissions Lyman-alpha noise. "One of the great mysteries was the light from hydrogen atoms in the very early universe, which should have been completely blocked by the pristine neutral gas that formed after the Big Bang," said cosmologist Callum Witten from the University of Cambridge in the United Kingdom, the Telegraph reports.

"Where Hubble saw just one large galaxy, Webb sees a group of smaller galaxies"

The James Webb Space Telescope (JWST) helped scientists find a solution to this phenomenon. It is a revolutionary, nine billion dollar infrared space telescope that is a hundred times more sensitive than the Hubble telescope.

JWST primarily observes the vastness of space in the infrared spectrum, which allows it to penetrate clouds of gas and dust and can detect photons emitted by stars in the first galaxies. Hubble operated primarily in optical and ultraviolet wavelengths.

"Where Hubble saw just one large galaxy, Webb sees a group of smaller galaxies interacting with each other. This has influenced our understanding of the unusual hydrogen emissions from some of the earliest galaxies," said Sergio Martin-Alvarez of Stanford University.

Simulation of galactic mergers and their interactions

Early galaxies were huge star-forming industries and a rich source of Lyman-alpha emission. Most of the emission was blocked by the primordial neutral hydrogen that filled the space between galaxies in the early universe. Most of the objects emitting Lyman-alpha radiation are galaxies with close neighbors, indicating that galactic mergers and their abundant star formation are behind the Lyman-alpha emissions.

Scientists tested this idea by simulating galactic mergers and their interactions. The simulation showed that stars emitting Lyman-alpha radiation created regions of ionized hydrogen within neutral hydrogen that blocks the light that allows Lyman-alpha emissions.

The research showed that there were more galactic mergers in the early universe than we could see before JWST appeared. These mergers, interactions and abundant creation are responsible for the creation of Lyman-alpha emissions and their penetration through the darkness of the early universe.

The study, called AstroSat's detection of Lyman continuum emission from a z = 1.42 galaxy, was published in the journal Nature Astronomy. /Telegraph/

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