Abstract

The first billion years after the Big Bang represents the final observational frontier in assembling a coherent picture of cosmic history. During this period early stars and galaxies formed and hydrogen in the intergalactic medium transitioned from a neutral gas to one that was fully ionized. Recent measures of electron scattering of microwave background photons by the Planck satellite suggest that reionization was a rapid process occurring over the redshift range 6-12. This raises the exciting prospect that we may be able to directly observe the first generation of galaxies. Deep exposures with the Hubble Space Telescope provide the primary evidence that star-forming galaxies were present during the relevant period. Detailed spectroscopy is now required to relate their early formation to cosmic reionization. I will review the rapid progress being made in this area with current facilities, and the prospects with upcoming ones, including the James Webb Space Telescope.