What process at the core of the protosun caused it to shine during the formation of our solar system?

The process that allowed the protosun to shine during the formation of our solar system is fusion. In the context of stellar formation, fusion refers to the nuclear reactions occurring in the core of a star, where lighter atomic nuclei, such as hydrogen, combine to form a heavier nucleus, such as helium. This process releases a tremendous amount of energy in the form of light and heat, which is what causes the protosun to shine.

In the early stages of the solar system, as the protosun accumulated mass from surrounding gas and dust, the pressure and temperature at its core increased significantly. Once these conditions were sufficient, hydrogen nuclei began to undergo fusion, igniting the nuclear reactions that would eventually lead to the sun we see today. This energy output is essential not only for the star's illumination but also for maintaining its temperature and balance against gravitational collapse.

The other processes mentioned, such as radiation, fission, and conduction, do not describe the primary mechanism of energy generation for stars. Radiation refers more generally to the emission of energy in the form of waves or particles, fission is the splitting of heavy atomic nuclei (the opposite of fusion), and conduction involves heat transfer through direct contact but is not related to the processes within a star