• the core at the Sun's center, densest part of the Sun, where the nuclear fusion occurs;
• the extensive radiation zone, through which the heat and light from the core slowly, over tens of thousands of years are radiated out to the convection zone, and
• the convection zone, about the upper third of the Sun in which the energy is transported by overturning motions, like the bubbling of a pot of boiling water, up to the surface and back.

This illustration of the internal structure has been superimposed on an EIT 304Å image from January 8, 2002.

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