Richard Doyle

See also: Scintillation

In Astronomy, the scintillation is the fast fluctuation of the luminous glare of the star S when one observes them with the naked eye. It is due to the weak glare of stars and turbulences in the atmosphere.

Scintillation is explained by the temperature variations and of pressure caused by turbulences of the atmosphere and the differences in density between the various atmospheric layers. The Index of refraction of the air is thus not uniform and when the light crosses the various mediums which it meets, it each time undergoes a negligible deviation responsible for the flutter.

Various parameters influence the intensity of scintillation:

  • the apparent Diameter of the source of light. In the case of a star, the source of light is close to the Infini, its diameter apparent is quasi null so that stars are like luminous points with the fragile glare. It is not the case of the planets which one can observe the disc with a simple telescope.

  • the turbulence of the Air. It varies according to the sites of observation and the weather. Scintillation is lower in altitude because turbulences as well as the atmospheric pressure are lower there. For the same reason, scintillation is more important close to the horizon than to the zenith because the light of the stars crosses the air there at a more important distance.
  • the opening of the optical System. In the case of an observation with the naked eye, the diameter of the Pupille in the darkness is of approximately 6 Misters the recourse to an objective makes it possible to collect a broader beam of light. In this case, one does not observe scintillation but the images become fuzzy.
  • the Wavelength of the light. Scintillation is more important when the wavelength of the light is short because it undergoes a more important refraction. The stars with the red glare, like Antarès, of the constellation of the Scorpion, scintillate less than stars of blue color like Sirius, of the constellation of the Large Dog.

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