Interpreting the Hertzsprung-Russell Diagram
The purple area shows the main sequence, where stars spend most of their lives. Stars located here undergo nuclear fusion, where they fuse Hydrogen into their cores while also remaining stable. During nuclear fusion, Hydrogen is converted into Helium.
This reaction can very easily be described by the Proton-Proton Chain Reaction where two protons fuse together to produce Deuterium. Deuterium is a stable isotope of Hydrogen and is given by the following chemical equation,
\[p\ +\ p\ \to\ _1^2D\ +\ e^++v_e+1.442\ MeV\]
Upon completion, the Deuterium can fuse with another proton to produce the light isotope of Hydrogen. This reaction is given by,
\[_1^2D\ +\ _1^1H\ \to_2^3He+\gamma+5.49\ MeV\]
To the right of the diagram, we see the Red Giants whose cores' Hydrogen have been exhausted. The Red Giants have lower temperatures than the stars located in the main sequence but have higher stellar luminosity values.
The final stage presented by a Hertzsprung-Russell Diagram is the formation of White Dwarfs, but since our data did not include White Dwarfs we cannot explain them.
The Proton-Proton Cycle
We already discussed the basic chemical equation by which two protons produce Deuterium. Now we will study this process in greater detail.
Our two protons can be seen as two \(_1^1H\) atoms, and we can rewrite the chemical equation as,
\[_1^1H+\ _1^1H\to\ _1^2D\ +e^++v_e\]
Where \(e^+\) is the Positron and \(v_e\) the Neutrino.
Due to the collision between electrons and positrons, annihilation occurs whereby two other particles are produced.