The process by which neutral hydrogen was ionized by early stars.
The first black holes emerged from the chaotic aftermath of the Big Bang, but their origins remain one of cosmology’s deepest puzzles. This guide explores the leading theories—light seeds from the first stars and heavy seeds from direct gas collapse—and places them in the full context of cosmic evolution, from the Planck epoch to the present day.
Cosmic reionization was the transformative period when ultraviolet light from the first stars and galaxies ionized the neutral hydrogen that filled the early universe, ending the cosmic dark ages and making space transparent to light. This article explores the full timeline from the Planck epoch to structure formation, the role of the cosmic microwave background, and the key missions that revealed this history.
The first stars emerged roughly 100–200 million years after the Big Bang, ending the cosmic dark ages. This article traces the full evolution of the universe—from the Planck epoch through inflation, recombination, and reionization—and explains how the first atoms, stars, and galaxies formed, with key evidence from COBE, WMAP, Planck, and JWST.
Population III stars are the hypothetical first generation of stars, formed from primordial hydrogen and helium. They were likely massive, hot, and short-lived, and their radiation reionized the early universe. This article explores their formation, properties, and cosmic significance.
