End of Cosmic Dark Ages: Universe Becomes Transparent
c. 12.7 Billion years ago · Prehistoric
Approximately 1.1 billion years after the Big Bang, the universe completed the process of reionization. The first massive stars and proto-galaxies emitted intense ultraviolet radiation that gradually ionized the neutral hydrogen gas pervading intergalactic space. The XQR-30 survey of 67 high-redshift quasars established that the last significant patches of neutral hydrogen were ionized by redshift z=5.3, marking the moment the universe became fully transparent to light. This transition ended the Cosmic Dark Ages and enabled the large-scale cosmic structures observable today. The completion of reionization represents the boundary between the opaque early universe and the transparent cosmos.
Locations
Early Universe
Topics
astronomycosmologycosmic dark agesreionization
Connected Events — 4 Connections
The first stars initiated reionization by emitting ultraviolet radiation into the surrounding neutral hydrogen First Star formed
The first galaxies produced the ultraviolet radiation that drove reionization, gradually ionizing the neutral hydrogen that had kept the universe opaque Formation of First Galaxies: Birth of Stellar Structures
Population III stellar nucleosynthesis and subsequent supernovae provided the first sources of ionizing radiation that began reionizing the universe, ending the cosmic dark ages by creating the first light sources since recombination First Heavy Elements: Birth of Stellar Nucleosynthesis
The intense ultraviolet radiation from dense star clusters like the Cosmic Gems contributed to the reionization process that ended the Cosmic Dark Ages Cosmic Gems Arc: Proto-Globular Star Clusters Form at Extreme Density
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