Hubble uncovers a distant galaxy that pierced the early universe's hydrogen fog

The Hubble Space Telescope detected ultraviolet light from MXDFz4.4, a compact, star-forming galaxy at redshift 4.4, showing bursts of ionizing UV radiation from a dense cluster of hot, massive stars. This radiation helped ionize surrounding neutral hydrogen, offering a closer look at the Epoch of Reionization when the universe became transparent to ultraviolet light. The finding, supported by JWST observations that reveal the galaxy’s star-formation history, suggests that bursts from young star clusters in early galaxies played a major role in clearing the fog of neutral hydrogen in the early universe; the results appear in The Astrophysical Journal.