JWST unveils the mysteries of distant quiescent galaxies: Why do they stop growing?

Galaxies are astronomical objects composed of billions or even trillions of stars. Our Earth and solar system are just a tiny part of the Milky Way; it is one of countless galaxies in the universe. These immense systems are the fundamental building blocks of cosmic structure. During the universe's 13.7 billion-year history, the first few billion years marked a golden age for galaxy formation, when galaxies actively turned their gas reservoirs into new stars.