24.3 – The Sun

*Interior*Visible Surface/

Photosphere*Atmosphere

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

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.

Granules: https://www.youtube.com/watch?v=W_Scoj4HqCQ

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

Eclipse: https://www.youtube.com/watch?v=RQiU1VlMgFI