Here's why:

* Nuclear Fusion: The core is where nuclear fusion takes place. This is the process where hydrogen atoms fuse to form helium, releasing tremendous amounts of energy.

* High Energy Reactions: The fusion reactions in the core are incredibly energetic, releasing not only light and heat, but also high-energy gamma rays.

* Absorption and Re-emission: The gamma rays, along with other forms of radiation, are constantly absorbed and re-emitted by the dense plasma in the core, eventually making their way outwards.

It's important to note that by the time these photons reach the surface of the Sun and escape into space, they have been downgraded to lower energy photons, primarily in the visible light spectrum. The journey from the core to the surface can take millions of years!