“Oxygen is produced by stars, which are inside of galaxies. We know that the oxygen had to be inside of the galaxies at some point in the past, so the oxygen must have been ejected.”

NASA · Nov 1 · Hubble finds dwarf galaxies missing most oxygen produced by their stars

“And to do that, you need energy from massive stars and supernova explosions to drive material out of the host galaxies and into the space between galaxies.”

NASA · Nov 1 · Hubble finds dwarf galaxies missing most oxygen produced by their stars