Charlotte Mason's research focuses on how the first stars and galaxies appeared in the early Universe, and how they transformed the space in between the galaxies. The first clumps of structure that conglomerated a few 100 million years after the Big Bang were surrounded by neutral and relatively opaque gas. However, as the first stars formed in these clumps, their energetic radiation was emitted started "carving out" — or ionizing — bubbles that eventually overlapped, leaving the whole Universe transparent to all light.

Exactly how, when, and for how long this process — known as the Epoch of Reionization — took place is currently the center of attention for a large fraction of the astronomical community. Not the least because recent observations with the James Webb Space Telescope have challenged our understanding of the process, in particular how early the galaxies appeared, and how quickly they grew.

"One of the big surprises that James Webb has given us is a much larger number of very bright galaxies in the early Universe than we thought possible," Mason says. "But we can only see the brightest galaxies directly. To get a census of the small, faint ones, which are much more numerous, we must infer their properties via the impact they had on their surroundings by ionizing the gas around them."