The radiation zone is the middle zone in the Sun

Sun

The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

's interior. Energy travels out of the core into the radiation zone. Energy that travels through the radiation zone is in the form of electromagnetic radiation

Electromagnetic radiation

Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

. The radiation zone is so dense that the waves bounce around. The energy may not leave the radiation zone for millions of years.
The radiation zone is directly below the convection zone and directly above the core. It takes an average of 171,000 years for energy from the core to leave the radiation zone.

External links

• SOHO ... Solar and Heliospheric Observatory — official site of this NASA
  NASA
  The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
  
   and ESA
  European Space Agency
  The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
  
  joint project.
• Animated explanation of the Radiation zone (University of Glamorgan).
• Animated explanation of the temperature and density of the Radiation zone (University of Glamorgan).