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24.3 – The Sun
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*Interior*Visible Surface/
Photosphere*Atmosphere
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Interior• Cannot be observed directly• Produces energy by nuclear fusion• Made entirely of gases• Core
• incredibly hot (15 million degrees C), high-pressure area where fusion takes place to create light and energy
• Radiation Zone• Energy from the core moves towards the surface over the
course of 10,000 years• Convection Zone
• Circular convection currents cycle energy from hotter center to cooler surface
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Visible Surface or Photosphere
• 90% H, 10% He• Still a gas, not a solid• 500 km thick• Grainy texture called granules. Brightness
is related to hotter gases rising from below (convection currents). They cool, darken, and then sink below again every 10-20 minutes.
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Granules: https://www.youtube.com/watch?v=W_Scoj4HqCQ
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Atmosphere
• Only visible during eclipse• Chromosphere
– Thinner layer of gases above Photosphere (same stuff, just at less pressure and density)
– Emits red light, rather than yellowish/orange glow of Photosphere b/c it is cooler
• Corona– “Ionized” gases thinner than chromosphere– Some ions can escape the gravitational pull of sun
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Eclipse: https://www.youtube.com/watch?v=RQiU1VlMgFI