Nuclear Fusion

We know that the Sun is extremely hot. Its surface temperature is 5,500 K. Temperature is a measurement of energy. So, we know that the Sun possesses huge amounts of energy. Where does that energy come from? How does the Sun create that much energy?

Credit: Gravity Warp Drive website. This image shows how the Sun generates energy.

Through a process called nuclear fusion, the Sun manages to create enough energy to keep itself from collapsing onto itself. Specifically, the Sun follows the cycle known as the proton-proton chain.

We have two branches above. Since they are exactly the same, we shall look at one of the branches. We start off with two protons with high kinetic energy. Due to their high kinetic energy, they were able to overcome the repulsive force (like charges repel) and smash into each other. In the process, a positron, a neutrino and a proton-neutron combo are created. The positron is anti-electron: it acts just like an electron, but with a positive charge instead. The positron finds an electron, and they annihilate each other, creating energy through the form of two gamma rays (electromagnetic radiation). The neutrino is created to preserve momentum. They are created from the decay of a proton into a neutron, which is how we have a proton-neutron combo. Next, the proton-neutron combo and a proton smash into each other releasing energy in the form of a gamma ray, and producing a helium isotope, containing two protons and one neutron. In total, three gamma rays of energy were produced. The same thing occurs in the other branch. It produces a positron, neutrino, a gamma ray, and a helium isotope, containing two protons and one neutron. The positron finds an electron, they annihilate each other, and produce two gamma rays of energy. So, in total three gamma rays of energy were produced from the other branch. The two helium isotopes smash into each other creating two individual protons, and another helium isotope, containing two protons and two neutrons. Overall, including both branches, six gamma rays of energy were produced. It may not seem like a lot. However, with the huge hydrogen supply, the Sun can smash a lot of hydrogen together creating enough outward radiation pressure to balance the inward gravitational force. The Sun consumes 620 million metric tons of hydrogen every second and produces 616 million metric tons of helium. So it creates an energy equivalent to 4 million metric tons, using E = mc^2.

The insane amount of energy the Sun creates helps keep itself alive, keep us alive, and every being on planet Earth. Without nuclear fusion, we just can’t survive.