Astrophysicists use a variety of observational techniques to study reionization. These include examining the Lyman-alpha forest in quasar spectra, which reveals the state of hydrogen in the intergalactic medium (IGM). Observations from telescopes like the Hubble Space Telescope and the James Webb Space Telescope (JWST) also provide insights into the early universe. Additionally, studying the 21-cm signal from neutral hydrogen offers a direct probe of the reionization era.
