A lot of astronomy just isn’t as stunning visually as it is conceptually. Thank God for artists; they are able to take these concepts and make them into illustrations that are so much more pleasing than what our telescopes show us.

Case in point: New research led by Sarah Bosman and published in Monthly Notices of the Royal Astronomical Society determines that our universe finished ionizing the bulk of the hydrogen between galaxies by the time it was 1.1 billion years old. In doing this study, this team looked at the light from 67 quasars – extremely bright and distant galaxies – and looked to see if their light was absorbed by neutral hydrogen gas on its way to our telescope. Cold, neutral hydrogen gas will absorb light in specific colors, and when we see these absorptions, they tell us not only that the gas is present but also when it was present. Ionized hydrogen gas – well, light goes right through it.

After about 1.1. billion years, the universe seems to have stopped having large regions of neutral gas that absorbed light. We know the process of our universe going from a vast cloud of neutral gas to being full of stars and galaxies that ionize the gas was a long process. In follow-up research, Bosman and her team plan to map out how the gas was ionized, and look for the details of how the first stars transformed our gassy universe.

More Information

MPIA press release

“Hydrogen reionization ends by z = 5.3: Lyman-α optical depth measured by the XQR-30 sample,” Sarah E I Bosman et al., 2022 June 7, Monthly Notices of the Royal Astronomical Society