Chapter 10 Recap
Why does the Sun shine?
• The Sun shines because gravitational equilibrium (pressure balancing gravity) keeps
its core hot and dense enough to release energy through nuclear fusion.
How does nuclear fusion occur in the Sun?
• Fusion of hydrogen into helium, which occurs via the proton–proton chain.
• Gravitational equilibrium acts as a thermostat that keeps the fusion rate steady.
How do we know what is happening inside the Sun?
• theoretical models
• use known laws of physics and then check the models against observations and
How does the energy from fusion get out of the Sun?
• Energy moves through the deepest layers of the Sun— the core and the radiation
zone—in the form of randomly bouncing photons. After energy emerges from the
radiation zone, convection carries it the rest of the way to the photosphere, where it is
radiated into space as sunli