Light of the night sky

The light of the night sky is the very weak emission of visible Lumière by the atmosphere of the Ground, thus preventing a night from being never completely black. It is caused by various physical phenomena occurring in the upper atmosphere. She was noticed for the first time in 1868 by the Swedish astronomer Anders Jonas Ångström.

Observation

The phenomenon is difficult to observe, because the emission of light is more or less uniform on all the atmosphere. For an observer located on the ground, it is with its maximum of luminosity towards 10° to the top of the horizon: this angle makes it possible at the same time taking into consideration to cross a layer of important atmosphere and is not too low not to be constrained by the atmospheric effect of extinction.

However, this emission of light remains perceptible and is one of the factors limiting the sensitivity of the terrestrial Télescope S to the visible wavelengths, even if they are located at the best observatories.

Origin

The origin of the night light is complex and derives from several distinct phenomena:
  • the Chimiluminescence is the process which contributes more to the total luminosity. It results from the chemical reactions between various molecules in the Thermosphère. The Sun breaks some of these molecules during the day and their recombination nocture is accompanied by a light output.
  • the excitation of the atmosphere by cosmic rays.
  • the recombination of Atome S ionized by the Sun during the day also results in producing visible light (in a way similar to the polar lights).

See too

Internal bonds

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