Night sky light
The night sky light or night sky glow (English airglow , literally translated air glow ) denotes a weak glow of higher atmospheric layers . It was discovered by Anders Ångström in 1868 .
The remaining brightness of a moonless night sky results not only from artificial light sources on the ground, the indirect scattering of sunlight and the light from the stars, but also from processes in the ionosphere : the gas atoms and molecules in this layer (especially oxygen and nitrogen ) become ionized and dissociated by the solar ultraviolet radiation . When the particles recombine , radiation is emitted in the visible range that lasts long after sunset.
The light created by this process during the day is much more intense than the night, but is outshone by the light of the sun. From outside the earth's atmosphere , the airglow appears as glowing rings at a height of around 90 to 500 kilometers above the earth's surface , with a green band predominating at 90 to 100 kilometers (caused by excited atomic oxygen, including yellowish-orange the sodium layer ) . Density changes due to gravity waves make structures appear within the airglow. Dynamic variables of the earth's atmosphere can be derived from airglow measurements. Because of its low luminosity , the glow of the night sky can only be observed with the naked eye in light protection areas from Earth .
Terrestrial telescopes are affected by airglow in the wavelength range of visible light , which is why space telescopes such as the Hubble telescope have a clear advantage here.
The SwissCube , which was launched on September 23, 2009, is intended to investigate the phenomenon of airglow .
One unit of measurement for the night sky light is the Rayleigh .
