Glossary term: Radiative Zone

Also known as radiative envelope

Description: Energy is released by nuclear fusion reactions in the core of a star, and eventually radiated away into space from the star's photosphere. There are several ways that energy is transported from the star's core to the photosphere. The radiative zone, radiative region, or radiation zone is the region within a star where the energy is transported outwards by means of radiation, with photons repeatedly scattering off nuclei and electrons, losing some energy in the process but also leading to the emission of new thermal-radiation photons. Due to frequent scattering, progress is slow; in our Sun, photons need thousands of years to cross the radiative zone.

In the Sun the radiative zone lies between the core and the convective zone. In more massive stars the core itself is convective with the radiative zone extending from the convective core to the star's photosphere. Below 0.3 solar masses, stars have no radiative zone at all and are entirely convective.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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