The core is the only region in the Sun that produces an appreciable amount of thermal energy through fusion; 99% of the power is generated within 24% of the Sun's radius, and by 30% of the radius, fusion has stopped nearly entirely.
The core is the only region in the Sun. This only region in the Sun produces an appreciable amount of thermal energy through fusion.99% of the power is generated within 24% of the Sun's radius. Fusion has stopped nearly entirely. This was by 30% of the radius.