Dwarf galaxies made the universe transparent 5.5 Dwarf galaxies are difficult to study because of their low mass and weak emission. Recently, a team of astrophysicists used the James Webb and Hubble Space Telescopes and the gravitational patterns of the Pandora star cluster to investigate the role of dwarf galaxies after the Big Bang.

The early Universe was dark because hydrogen atoms had already formed (later, for example, hydrogen atoms formed interstellar gas), but neither stars nor galaxies had yet formed from them. Most of the relic’s radiation was absorbed by gases that had not yet combined. But soon his two key periods (recombination and reionization), each lasting hundreds of millions of years, caused the universe to look much like what we are used to seeing. During the recombination period (378 million years after the Big Bang), free electrons and protons combined to form the first atoms (neutral hydrogen atoms), and the universe became transparent and rapidly cooled. Then, during the process of reionization (previously thought to have occurred 600 million to 800 million years after the Big Bang), ions are formed from hydrogen atoms, and as a result of gravitational attraction, stars, galaxies, quasars, etc. Other large planets were formed. Space objects were formed from interstellar gas. In cosmology, there is debate among researchers about the causes of reionization. To find the answer to this question, more than 30 authors recently came together and published their findings in the journal Nature. Astrophysicists have discovered that the main source of reionization is dwarf galaxies. Previously, quasars were considered sources of reionization in some models of cosmic evolution due to their powerful ionizing radiation. Dwarf galaxies have far fewer stars than the Milky Way and differ in brightness by about a factor of 100. Low-mass galaxies are dark, making spectroscopic studies difficult. In a recent paper, the astrophysicist used the James Webb Space Telescope and the Hubble Telescope to investigate his eight dwarf galaxies in the Pandora star cluster. Galaxy clusters act as gravitational lenses, making it possible to amplify the radiation flux from objects. Scientists have discovered that in the billions of years after the Big Bang, faint dwarf galaxies produced ionizing radiation four times more intense than previously thought. In other words, the ionizing radiation from dwarf galaxies is enough to reionize the universe. According to scientists, a small portion (5 percent) of the photons do not interact with neutral atoms and do not disrupt the reionization process. The researchers note that the redshift value for this epoch is 6 (z = 6, equivalent to 0,929,639,000 years after the Big Bang). The redshift value is needed to learn more about the reionization period. In a study published in the Astronomical Journal in 2001, the authors argued that the universe is nearing the end of reionization at z = 6. “It is now well established that the main source of ultraviolet radiation during the reionization phase is faint galaxies,” the study authors stress. The question of what exactly made the universe transparent to radiation again (that is, did the hydrogen it contained become ionized) is an important question. Because the answer depends on an understanding of the evolution of the universe as a whole. If a quasar (actively radiating near a large black hole) did this, the completion date of reionization would be one day, but if a dwarf galaxy did this, it would be completely different.

source: https://www.nature.com/articles/s41586-024-07043-6