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. By definition it is regarded as a Class B stellar engine.
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.
Following the publication of Dyson's proposal, it was pointed out that a solid circumstellar sphere would be subject to intolerably high stresses. Dyson replied that what he actually envisaged was a loose collection of over 100,000 objects traveling on independent orbits in a shell about 1 million kilometers thick. This Dyson Swarm arrangement is a Type I Dyson sphere and a solid shell is Type II.
A Dyson shell can support vast amounts of processing power, especially if arranged in concentric shells as a Matrioshka Brain.
Configurations and variations:
|Dyson Swarm||As a solid shell will be initially impossible for its builders, a swarm will have enough solar collector satellites around the star to absorb the starlight. Each member of the swarm can serve as both a habitat and collector.|
|Jenkins Swarm||This swarm consists of thousands of elements in inclined orbits, each with a slightly different ascending node and pericenter. This arrangement ensures the elements never come close to each other. The various orbits form a toroid shape, surrounding the star.|
|Snailshell Swarm||By surrounding the star with bands of power collectors or habitats at different radii and inclination the entire star can be encapsulated quickly.|
|Dyson Bubble||This uses lightweight sails to float on radiation pressure from the star. These floating solar collection satellites are called statites which are closer to the star and therefore efficient.|
|Closed Sphere||This is only possible with higher level Type II civilizations or beyond. This is an inverted living space on the underneath of a solid shell with the sun at the centre. Its surface area can support trillions of inhabitants.
|Dyson Tree||These consist of trunk structures growing out from a comet nucleus. Branches grow from the top of each trunk and intertwine and merge with each other to form a single structure. The trunks and primary branches are hollow and contain a breathable atmosphere and symbiotic ecology as well as a space adapted ecology on their exteriors. Growth of a new tree begins when a suitable comet is diverted into a close solar orbit and a seed is planted on it. Average tree lifetimes run to a millennium and a mature tree may support a population in the millions. In systems where the trees have been long established, entire 'orbital forests' may be found.|