Energy
Fusion in the Sun
We've read about fusion in stars when discovering hydrostatic equilibrium in our Fluids module10. Let's take a closer look at what happens inside the layers of our own Sun.
Our Sun is currently about 4.6 billion years old and weighs approximately 1.99 × 1030 kg. Its surface temperature is 5,777 K and its composition is 92.1% hydrogen and 7.8% helium11.
A star is an ideal place for fusion. Stars are huge (we mean really, really, really big), and things with that much mass, have a ton of gravity. The sheer force of gravity in stars bring elements that would be gases on Earth so close to each other that they become liquids, which raises the temperature drastically in the interior of the sun. These high temperatures correspond to very high energy levels, enough energy to fuse two nuclei, that fusion creates a new element and releases even more energy.
Since a helium nucleus has more nucleons, it requires more binding energy to keep it together. Binding energy is negative. This means helium has less mass per nucleon than hydrogen. This extra mass is radiated as energy, which we see as light. This is done through a process known as the proton-proton chain, P-P chain for short, which we can admire here.
Now, we know why exactly our beautiful Sun shines away with life-giving energy.