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The first billion years after the Big Bang represent the final frontier in assembling a complete picture of cosmic history. During this early period the first galaxies formed and the universe became bathed in light. Hydrogen clouds in the space inbetween galaxies were then transformed from an atomic gas to an ionised medium of detached protons and electrons. A key goal for JWST is to explore the emergence of the earliest galaxies in the redshift range z > 12, beyond reach of current facilities. Recent studies of cosmic microwave background data provide some evidence for such early star formation. Since time is compressed at high redshift, we can gain further insight via measures of dust, metals and mature stellar populations seen in galaxies at redshifts z~8-10. I will review the evidence for early star formation from observations undertaken with HST/Spitzer and ALMA, and conclude with the prospects for direct detection of the implied progenitors with JWST. |
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