Reionization
Reionization refers to a phase in the early universe during which neutral hydrogen became ionized due to radiation from the first luminous sources. It marks a transition in the thermal and ionization state of cosmic matter.
Reionization is discussed in cosmology, astrophysics, and studies of early structure formation.
Status
Reionization is investigated through observations of the cosmic microwave background, high-redshift galaxies, and absorption features in quasar spectra. Its timing, duration, and dominant sources remain active areas of research.