The Proton-Proton Chain

So how do we do it? How do we turn hydrogen into helium and make energy?

The process is called the Proton-Proton (PP) Chain, and it operates inside the Sun and stars of similar mass.

Step 1: Smash two protons together to make deuterium

positron: like an electron, but with positive charge
neutrino: very light, hard-to-detect particle

Step 2: A proton crashes into a deuterium nucleus, making helium-3

gamma ray: very high energy photon

Do Steps 1 and 2 again, so that we have two helium-3 nuclei. Then (69% of the time):

Step 3: Mash two helium-3 nuclei together to make helium-4

Actually this is the most common path to making helium in the Sun, but not the only one. After Step 2 is complete, other reactions can take place -- the PPII chain (31% of the time):

Or even the PPIII chain(rare, 0.3% of the time):

Here is the overall PP chain

So what did we do?

We essentially turned 4 protons into

1 helium nucleus
1 positron (this positron will bump into a electron and annihilate, creating a gamma ray - energy!).
1 gamma ray (energy!)
1 neutrino

But wait. Do we have any way of actually knowing this is true? We can't actually see into the center of the Sun. Or can we???