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| | Sun - MSN Encarta |
 | | The radiative zone spans from the outer edge of the core, which is 174,000 km (108,000 mi) from the Sun’s center, to 496,000 km (308,000 mi) from the Sun’s center. |
 | | Because of this continued ricocheting in the radiative zone, about 170,000 years, on average, are required for a photon of energy to work its way outward from the Sun’s core to the bottom of the convective zone. |
 | | At the boundary of the cooler convective zone, the radiative energy has lost too much intensity and the material is too cool and dense to allow the energy to pass through. |
| encarta.msn.com /encyclopedia_761562112_4/Sun.html (1502 words) |
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