part of a country not connected to its main territory

Territory. ... Although the territory of a country includes its entire area, the noun can also specifically refer to an area governed by a country, but one that isn't a state or province. Puerto Rico is a territory of the United States, for example.

radiative zone

explanation    

radiative zone is the layer of the sun which energy is transferred away from the core by radiation. although, the core is the only part of the sun that produces an appreciable amount of heat through fusion. in fact, 99% of the energy produced by the sun takes place within 24% of the sun's radius.