Reionisation completes
About a billion years in, the last neutral fog clears and the universe becomes fully transparent.
- When
- Known to
- ± 100 million years
- Era
- Galaxy Assembly, Stelliferous
The ionised bubbles around galaxies finally merge and overlap everywhere, leaving intergalactic hydrogen almost entirely ionised. Absorption in the spectra of distant quasars shows the transition finishing around redshift 5.5 to 6 — later than once thought. From this point the universe is transparent to ultraviolet light, and has remained so ever since.