Gravitational lensing reveals ionizing ultraviolet photons escaping from a distant galaxy

Ionizing photons escape a lensed galaxy Young, hot stars emit ultraviolet radiation, which can ionize a neutral gas. The first generation of stars converted most of the intergalactic gas in the Universe from neutral to ionized form during the epoch of reionization less than a billion years after the Big Bang. Rivera-Thorsen et al. took advantage of a gravitational lensing system to observe 12 images of the same star-forming region in a distant galaxy and determined the fraction of ultraviolet photons that escape into the intergalactic medium. Although this galaxy is younger than the epoch of reionization, the results provide clues about how ultraviolet photons escape their host galaxies and contribute to the reionization process. Science , this issue p. 738