Reionisation Epoch

Harleah Fonteyn

Junior Researcher

2026-03-30

Harleah is a Junior Researcher at Unset. She investigates subjects across culture, history, education and everyday life, helping to research and develop the material that becomes part of unset.world.

The reionisation epoch was the period when the first stars and galaxies emitted enough high-energy light to reionise the hydrogen gas filling the universe. After the long “dark age,” this radiation cleared the fog-like neutral gas, making the universe transparent to light and allowing modern cosmic structures to form fully.

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cosmic stella epochs