Here's why:

* Nuclear Fusion: Stars produce light and heat through a process called nuclear fusion. This is where hydrogen atoms are forced together under immense pressure and temperature, forming helium. This process releases a tremendous amount of energy, some of which is emitted as light.

* Self-Luminous: Stars are self-luminous, meaning they generate their own light. Unlike planets, which reflect light from stars, stars create light from within.

* Dominant Light Source: Stars are the dominant source of light in most of the universe. While other objects, like galaxies and nebulae, also emit light, they often do so by reflecting light from nearby stars or due to processes like gas ionization.

So, in summary, stars are the primary sources of light because they generate their own light through nuclear fusion and are the dominant source of light in the universe.