Cosmic Starvation

The first possibility is called ram pressure stripping, a process through which all of the gas that a galaxy would use to form stars is vacuumed away by nearby intergalactic plasma. The other is that the environment inside a galactic cluster simply becomes too hot for cosmic gases to cool and condense into stars, rendering it useless as fuel.

“When you remove the fuel for star formation, you effectively kill the galaxy,” Brown writes, “turning it into a dead object in which no new stars are formed.”