What is the primary substance being transformed in the sun's core?

In the sun's core, the primary substance undergoing transformation is hydrogen. This process primarily occurs through nuclear fusion, where hydrogen nuclei (protons) collide with sufficient energy to overcome their electrostatic repulsion and fuse to form helium nuclei. This fusion releases a tremendous amount of energy, which is what powers the sun and produces heat and light.

The core of the sun has extreme pressure and temperature conditions, allowing for this fusion to take place efficiently. As hydrogen is converted into helium, it also facilitates the release of energy in the form of gamma rays, which then gradually makes its way to the sun's surface and eventually radiates into space as sunlight.

While oxygen, carbon, and helium are all present in the sun in varying amounts, they do not primarily undergo fusion in the core under the current conditions of the sun. Instead, helium is actually the product of the hydrogen fusion process, and heavier elements like carbon and oxygen are formed in later stages of stellar evolution, not during the sun's current life cycle. Thus, the correct focus is on hydrogen as the primary substance being transformed in the sun's core.