Dyson sphere

A Dyson sphere is a megastructure that completely encompasses a star and captures a large percentage of its power output. It's used by a spacefaring civilization to meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Only a tiny fraction of a star's energy emissions reach the surface of any orbiting planet. Building structures encircling a star would enable a civilization to harvest far more energy.

The collected energy can be beamed to remote locations for use in life support, industry, computational processing, or transport; these beams can also be used for defense or communication. Energy can also be stored using antimatter.

The concept was popularized by Freeman Dyson who speculated that such structures would be the logical consequence of the escalating energy needs of a technological civilization and would be a necessity for its long-term survival. He proposed that searching for such structures could lead to the detection of advanced, intelligent extraterrestrial life. Different types of Dyson spheres and their energy-harvesting ability would correspond to levels of technological advancement on the Kardashev scale.

A Dyson shell can support vast amounts of processing power, especially if arranged in concentric shells as a Matrioshka Brain.

This megastructure is a vast artificial structure. Some examples of it are in Halo, Stellaris and Doctor Who. A cinematic example is Nidavellir.