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<-   Observing the vibrations   ->

The vibration modes of the stars, stationary waves throughout the gaseous sphere, have well-known geometric structures.

The stellar vibrations result in radius and temperature variations on the surface, which lead to variations in the amount of light emitted by the star, and to periodic movements of its envelope.

Some stars have large amplitude variations, which astronomers have known about for a very long time. These are called "variable stars". However the small number of oscillation modes detected do not allow us to fully use sismology techniques.

Observing vibrations of small amplitude in distant stars, such as those observed in the Sun, is a hard task.

  • The signal received from the stars is very faint : at least 100 billion times fainter than that received from the Sun. And we only observe stars as luminous points, without any possibility of distinguishing details on their surfaces.
  • Only a few bright and close stars revealed their secrets. Thus, the Fourier spectrum of the star Alpha Centauri, observed over 10 successive nights with a telescope of 3m60, is similar to that of the Sun.