Galaxies Were Already Dying Just 700 Million Years After the Big Bang

When galaxies run out of primordial hydrogen and helium, they cease star formation, shifting to primarily long-lived red stars. These galaxies are considered "red and dead." It usually takes billions of years for galaxies to run out of hydrogen, but now astronomers using JWST have found examples of galaxies that have already stopped forming stars just 700 million years after the Big Bang, much earlier than predicted by cosmological models.