Here's why:

* Extreme Pressure and Temperature: The core is the densest and hottest part of the Sun, with immense pressure and temperatures reaching millions of degrees Celsius. These conditions are necessary for nuclear fusion to occur.

* Hydrogen Fusion: In the core, hydrogen atoms fuse together to form helium, releasing a tremendous amount of energy in the process. This energy is what powers the Sun and makes it shine.

* Energy Transport: The energy released by fusion in the core travels outwards through the Sun's layers via radiation and convection, eventually reaching the surface and escaping into space.