The phrase "background glow" refers to a soft and gentle light that illuminates the surroundings, usually appearing in the background. It creates a subtle brightness that adds a pleasing atmosphere to the environment. Full definition
What was left was a dim background glow never seen before. (discovermagazine.com)
The numerous galaxy collisions literally tear some galaxies apart and scatter their stars onto wide orbits around the newly created large galaxies, which should give them a faint background glow of stellar light. (sciencedaily.com)
The CIBER rocket experiment detected this diffuse infrared background glow in the sky — and, to the astronomers» surprise, found that the glow between galaxies equals the total amount of infrared light coming from known galaxies. (sciencedaily.com)