G. Rodighiero

The cosmic microwave background is faint light left over from the Big Bang. It fills the sky uniformly, but it encounters obstacles along the way. One such obstacle is galaxy clusters, which contain very hot gas. When CMB photons pass through this gas, some of them get an extra kick and change energy.

A street where houses have just been built. Some shine with clean windows, others are covered in construction dust. That's roughly what galaxies looked like when the universe was only a few hundred million years old. The new James Webb telescope peered into that era and saw dozens of bright star islands.