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The Sun's radiative zone lies between the incredibly hot core and the outer convective zone.
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The Sun's Radiative Zone

The Sun's radiative zone is the section of the solar interior between the innermost core and the outer convective zone. In the radiative zone, energy generated by nuclear fusion in the core moves outward as electromagnetic radiation. In other words, the energy is conveyed by photons. When the energy reaches the top of the radiative zone, it begins to move in a different fashion in the convective zone. In the convective zone, heat and energy are carried outward along with matter in swirling flows called convection cells. This motion is similar to the roiling flows seen in a pot of boiling water.

The inner parts of the Sun (core and radiative zone) spin differently than the outer layers (convective zone). The boundary between these two types of rotation, which lies between the radiative and convective zones, is called the tachocline.

Many other stars also have radiative zones. The Sun's radiative zone extends from the core outward to about 70% of the Sun's radius. In a smaller (than the Sun) star that is cooler than our Sun, the convective zone tends to be larger, extending deeper into the star's interior. Thus the radiative zone tends to be smaller. In very small, cool stars the convective zone may reach all the way to the star's core, and there may be no radiative zone at all. In a larger (than the Sun) star with a higher temperature, the radiative zone tends to be larger and the convective zone smaller. Especially large, hot stars may not have a convective zone at all - their radiative zone may extend all the way from the core to the star's surface.

Last modified August 23, 2005 by Randy Russell.

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