Airglow

"Night glow" redirects here. For the hot air balloon event, see Balloon glow. For luminance of the night sky caused by artificial light sources, see skyglow.

Airglow over Auvergne, France
Yellow, green and red bands of airglow along Earth's limb as seen from space.

Airglow (also called nightglow) is a faint emission of light by a planetary atmosphere. In the case of Earth's atmosphere, this optical phenomenon causes the night sky never to be completely dark, even after the effects of starlight and diffused sunlight from the far side are removed. This phenomenon originates with self-illuminated gases and has no relationship with Earth's magnetism or sunspot activity.