How does nuclear fusion power stars?

Nuclear fusion powers stars by converting hydrogen into helium, releasing a tremendous amount of energy in the process.

In the core of a star, the conditions are extremely hot and dense. This environment is perfect for nuclear fusion, a process where atomic nuclei combine to form a heavier nucleus. In stars, the most common form of nuclear fusion is the proton-proton chain reaction, which involves hydrogen nuclei (protons) combining to form helium.

The process begins when two protons collide and fuse, creating a deuterium nucleus (one proton and one neutron), a positron (a positively charged electron), and a neutrino. The deuterium nucleus then collides with another proton, forming a helium-3 nucleus and releasing a gamma-ray photon. Finally, two helium-3 nuclei collide and fuse to create a helium-4 nucleus and two protons. This entire process releases a significant amount of energy, which we perceive as light and heat from the star.

The energy produced by nuclear fusion is what keeps a star 'alive'. It creates an outward pressure that balances the inward pull of gravity, preventing the star from collapsing in on itself. This delicate balance between gravity and pressure is known as hydrostatic equilibrium.

The fusion process also leads to the creation of heavier elements in stars. Once a star has exhausted its hydrogen supply, it can begin fusing helium into carbon and oxygen, and so on, creating heavier and heavier elements. This process, known as stellar nucleosynthesis, is responsible for the creation of all elements heavier than hydrogen and helium in the universe.

In summary, nuclear fusion is the powerhouse of stars. It not only provides the energy that makes stars shine, but also creates the diverse array of elements found in the universe.