Sun's Layers Overview

Overview

This lecture covers the layers of the Sun, their order and properties, and how energy moves from the Sun's core to space.

The Sun has ordered layers: core, radiative zone, convective zone, and photosphere.
The core is the innermost layer where nuclear fusion occurs, producing energy.
Moving away from the core, both temperature and density decrease.

The radiative zone is directly above the core; it is very hot and dense but not enough for fusion.
Atoms here are ions (missing electrons), so they cannot absorb light.
Light moves in a random, zigzag path, losing energy with each interaction, transforming gamma rays into lower-energy light.

Above the radiative zone is the convective zone, which is less dense and cooler.
Some atoms here have electrons and can absorb light, heating the gas, which then rises.
Hot gas rises, cools at the top, sinks back down, creating convection currents.

The photosphere is the thin visible surface layer where light escapes into space.
The photosphere is made of gas (not solid) and is what we see as the Sun’s "surface."
It takes light about 150,000 years to travel from the core to the photosphere due to the radiative zone, then 8 minutes to reach Earth.

Core — Central region where nuclear fusion produces the Sun's energy.
Radiative Zone — Layer above the core where energy moves as light by bouncing between ions.
Convective Zone — Layer above the radiative zone where hot gas rises and cool gas sinks.
Photosphere — The visible "surface" of the Sun where light escapes into space.
Convection — Process where hot material rises and cool material sinks, transferring energy.
Ion — Atom with missing electrons.