The night sky has an overall background luminosity. We are aware of the localized sources of light in a moonless night sky (the stars and planets, the zodiacal light, and gegenschein), but in addition to the astronomical sources there is an overall uniform luminosity originating from the Earth's own atmosphere. We are not normally aware of this airglow because it is so uniform. It is the combination of astronomical and airglow sources that allows us to see the silhouette of an object held against the "dark" sky on a clear moonless night.

1868Anders Angstrom discovers green line is present in the night sky even when no aurorae are present
1920'sRobert John Strutt (4th Baron Rayleigh) begins investigations [Note: he is referred to as the "airglow Rayleigh"; his father John William Strutt, 3rd Baron Rayleigh, is the "scattering Rayleigh"]
1923John McLennon & G.M. Shrum identify green line to be due to atomic oxygen
1929Vesto Melvin Slipher discovers sodium layer (a contribution to airglow)
1931Sydney Chapman suggests airglow is result of chemical recombination
1939Chapman suggests reaction cycle to sustain sodium nightglow
1950term "airglow" coined after other atmospheric emissions are identified
1956SAR arc discovered by Barbier over France