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  the source of the Sun's energy
  it's called fusion
  the radiation zone
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the radiation zone


Nuclear fusion in the Sun's core releases a lot of energy which is carried away by photons and neutrinos. Now, neutrinos have almost no mass and can pass straight through just about anything - several billion have passed through you already today and you didn't even notice! While neutrinos have no trouble escaping from the Sun's core, it's a bit harder for the photons.


Imagine a ball moving in a pinball machine, At first it rushes about, but it slows down as it loses energy.

You can think of an electromagnetic wave as a way of carrying energy. The amount of energy carried in each photon depends on the wavelength of the radiation.


For waves with a small wavelength, such as gamma rays and X-rays, the photons have a lot of energy.


For longer wavelengths, such as visible or infrared wavelengths, the photons have less energy.


When the photons are emitted in the centre of the Sun, they are very energetic (gamma rays), but by the time they've bounced around loads and loads of times (loosing a little bit of energy each time) they get very tired and end up as photons of visible light.


Did you know? - An average pinball is in play for between 10 seconds and 10 minutes depending how good the player is

In the radiative zone, the high energy photons interact with other particles - electrons, protons and the nuclei of other elements - and are scattered in all directions. It's like a giant pin ball machine!


Each interaction means that the photon sets off in a new (random) direction and loses some energy. This changes the photon's wavelength slightly so that by the time the energy reaches the surface, it appears as a photon of visible light rather than a gamma ray.


Photons are "packets of light".The photons produced in the fusion reactions in the Sun are very energetic, mostly X-rays and gamma rays.


What happens as the energy moves out through the layers of the Sun? At about three-quarters of the way from the centre to the surface of the Sun, a different process cuts in and the energy is carried by convection. That is the convection zone .




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