Reionization of the universe happened about 500 million to 900 million years after the Big Bang. This represents the transformation of neutral hydrogen into an ionized gas and marks the end of the “Dark Ages” in the history of the universe. Currently, astronomers using the NASA/ESA/CSA James Webb Space Telescope have obtained spectra of eight ultrafaint dwarf galaxies that existed less than a billion years after the Big Bang. Their observations could help settle long-standing scientific debates about the driving force of reionization and could also be essential to understanding the formation of the first galaxies.
Astronomers estimate that 50,000 near-infrared sources are represented in the Webb image of galaxy cluster Abel 2744. Image credits: NASA / ESA / CSA / I. Labbe, Swinburne Institute of Technology / R. Bezanson, University of Pittsburgh / A. Pagan, STScI.
There is still much we don’t understand about the period in the early history of the universe known as the Era of Reionization.
It was a time of darkness, without stars or galaxies, and filled with a thick fog of hydrogen gas, until the first stars ionized the surrounding gas and light began to pass through.
Astronomers have spent decades trying to identify sources that emit radiation powerful enough to gradually remove this hydrogen fog that blanketed the early universe.
“Our discovery reveals the important role played by ultrafaint galaxies in the evolution of the early universe,” said astronomer Dr. Irina Chemelinska from the Paris Institute of Astrophysics.
“They produce ionizing photons that convert neutral hydrogen into ionized plasma during the reionization of the universe.”
“This highlights the importance of understanding low-mass galaxies in shaping the history of the universe.”
“These cosmic power plants collectively emit more than enough energy to accomplish their work,” said Dr. Hakim Atek, also of the Paris Institute of Astrophysics.
“Despite their small size, these low-mass galaxies produce large amounts of energetic radiation, and their abundance during this period is so great that their collective impact alters the state of the entire universe can do.”
In the study, astronomers captured and analyzed the spectra of eight very faint galaxies magnified by the lensing star cluster Abel 2744.
They found that these galaxies emit large amounts of ultraviolet light, at levels four times higher than previously thought.
This means that most of the photons that reionized the Universe likely came from these dwarf galaxies.
“With the web, we have stepped into uncharted territory,” said Dr. Themiya Nanayakkara, an astronomer at Swinburne University of Technology.
“Our study reveals more provocative questions that must be answered in efforts to chart the evolutionary history of our beginnings.”
of result It was published in the magazine Nature.
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H. Atek other. 2024. Most of the photons that reionized the universe came from dwarf galaxies. Nature 626, 975-978; doi: 10.1038/s41586-024-07043-6
Source: www.sci.news
