GRB Cosmology: Probing the Early Universe

Current observations are about to open up a direct observational window into the final frontier of cosmology: the crucial first billion years in cosmic history when the first stars and galaxies formed. Even before the launch of the James Webb Space Telescope, it would be possible to utilize Gamma‐Ray Bursts (GRBs) as unique probes of cosmic star formation and the state of the intergalactic medium up to redshifts of the first stars. The ongoing Swift mission might be the first observatory to detect individual Population III stars, provided that massive metal‐free stars were able to trigger GRBs. Swift will empirically constrain the redshift at which Population III star formation was terminated, thus providing crucial input to models of cosmic reionization and metal enrichment.