Which process is responsible for production of energy in stars?

The process responsible for the production of energy in stars is nuclear fusion.

Nuclear fusion is the process where two or more atomic nuclei come together to form a heavier nucleus. In stars, the fusion of hydrogen nuclei (protons) into helium nuclei is the main source of energy.

Here's how it works:

1. In the core of a star, high temperatures and pressures cause hydrogen nuclei to collide with enough force to overcome their electric repulsion and merge together.
2. This fusion of hydrogen nuclei results in the formation of helium nuclei.
3. During this fusion process, a very tiny amount of mass is converted into a large amount of energy according to Einstein's famous equation, E=mc². The mass difference is released as energy.
4. This released energy is what provides the heat and light that we observe from the stars.

This ongoing fusion process in stars is called stellar nucleosynthesis. It occurs throughout the star's lifetime until the available hydrogen in the core is depleted. At this point, depending on the star's mass, different fusion reactions may take place, leading to the production of heavier elements.

In summary, nuclear fusion, the fusion of hydrogen nuclei into helium nuclei, is the process responsible for the production of energy in stars.