The reionization of the Universe occurred some 500 to 900 million years after the Big Bang. It represents the transformation of neutral hydrogen into ionized gas and marks the end of the ‘Dark Ages’ in cosmic history. Now, astronomers using the NASA/ESA/CSA James Webb Space Telescope have obtained the spectra of eight ultra-faint dwarf galaxies that existed less than a billion years after the Big Bang. Their observations could help settle a long-running...
