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Hubble Finds UV Light Escaping Early Galaxy’s Star Clusters

6/25/2026

Summary

Story summary

Hubble Space Telescope detected ionizing ultraviolet photons from galaxy MXDFz4.4, existing 1.4 billion years after the big bang (redshift 4.4).
The galaxy 100 times smaller than the Milky Way forms stars ten times faster, while a cluster of massive stars emitted ionizing bursts that let 50-100 percent escape the gas.
Supernovae from these short-lived stars created bubbles that opened pathways for ultraviolet light, providing the first example that massive-star clusters helped end the cosmic fog.

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Story summary

Hubble Space Telescope detected ionizing ultraviolet photons from galaxy MXDFz4.4, existing 1.4 billion years after the big bang (redshift 4.4).
The galaxy 100 times smaller than the Milky Way forms stars ten times faster, while a cluster of massive stars emitted ionizing bursts that let 50-100 percent escape the gas.
Supernovae from these short-lived stars created bubbles that opened pathways for ultraviolet light, providing the first example that massive-star clusters helped end the cosmic fog.