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The sun

by eaae last modified 2006-04-16 13:46

Some facts about the sun

  • Its distance from the earth is 149 598 000 km.
  • Its angular diameter is 32'.
  • Its radius is 700,000 km (109 tines greater than the radius of the Earth).
  • Its mass is 1,99 1030kg (328 000 times that of the Earth).
  • Its surface temperature is 6400 K
  • The sun is principally made up of hydrogen (70%) and helium (25%), and of a small proportion of other chemical elements.

The crown

The crown is the external atmosphere of the sun. It extens as far as several solar rays. Apart from during eclipses, the crown is only visible with the aid of a coronograph. (an invention by Bernard Lyot).
Images of the crown can also be obtained from the ground with the help of telescopes which observe the X-radiation emitted by the crown.
The crown is essentially composed of plazma, in which the temperature is above 100 000 K. The flux of particules coming from the expansiveness of the crown constitutes solar wind.

The chromosphere

The chromosphere is a very inhomogeneous layer with an average thickness of between 2,000 and 3,000 km. Its temperature is 10.000 K.
The chromosphere is visible in monochromatic light, in the hydrogen ray (h-alpha).

The photosphere or solar surface

It is visible in white light or in the ionised calcium ray (klv). Its approximate width is 300 km. The photosphere is a partially transparent layer of gas, in which the temperature increases with depth. On the "Surface", the temperature is around 5800 K.

The connective zone

The connective zone is the seat of intense movements, of all sizes, from the granulation which shows on the surface (dimension = 1000 km) all the way to the gigantic cells which affect all of the connective zone, and of which we any have indirect information.

The radiative zone

The transport of thermonuclear energy is done by radiation. Owing to their diffusion on the electrons, the photons which reach us from the radiative zone, take between 106 and 108 years to leave this zone.

The core

The centre of the sun (core) is the seat of thermonuclear reactions. These are  at the origin of the energy which is radiated by the sun.
The temperature of the core varies from 16 million degrees at the centre to 8 million degrees at about 175 000 km from the centre.

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