Astrophysics (Index)About

radiation zone

(radiative zone, radiative region)
(region of a star transmitting energy through radiative diffusion)

The radiation zone of a star (e.g., the Sun) is that interior region where energy is transferred outward through radiative diffusion, energy being passed through material by radiative transfer, via electromagnetic radiation even though the material is opaque: photons in the radiation zone are absorbed by the material's atoms, exciting them so photons are subsequently emitted in a random direction, such a resulting random path of absorbed/emitted photons termed a random walk. This results in a slow outward transfer of energy, as some photons randomly reach the outside of the star and escape with their energy, and others randomly replace them, and so forth. The number of steps in such a trail of absorption/emission is incredibly high and calculated as requiring thousands of years for a photon entering the Sun's radiation zone to escape.

The term radiation zone (or variants) is also used for planets as well, particularly gas giants such as Jupiter and Saturn, though perhaps more often for the Sun and stellar structure.

(stars,Sun,radiative transfer,EMR,stellar structure,photons,planets)
Further reading:

Referenced by pages:
convection zone
Henyey track
Lane-Emden equation