Dyson sphere

Diagram of a Dyson Sphere

Main article click Dyson Sphere

A Dyson Sphere (or "shell" as it appeared in the original paper by Freeman Dyson) is a hypothetical megastructure that was originally described

as a system of orbiting solar power satellites meant to completely encompass a star and capture its entire energy output. Dyson speculated that such structures would be the logical consequence of the long-term survival of technological civilizations, and proposed that searching for evidence of the existence of such structures might lead to the detection of advanced intelligent extraterrestrial life.

Since then, other variant designs involving building an artificial structure — or a series of structures — to encompass a star have been proposed in exploratory engineering or described in science fiction under the name Dyson sphere. Most fictional depictions of a Dyson sphere describe a solid shell of matter enclosing a star, which is considered the least plausible variant of the idea.

While it is believed that some of these design variants are impractical, if not physically impossible, some designs do not require any major breakthroughs in our basic scientific understanding for their construction.

In Halo

In the book Halo: Ghosts of Onyx, it is revealed that at the center of Onyx is a Slipspace rift that shunts those that pass through it to a Dyson Sphere, called Shield World. It is separated from normal space-time by advanced Forerunner Slipspace technology. Although Dr. Halsey calls it the Micro Dyson Sphere, the Sphere is 150 million kilometers or two astronomical units, the equivalent to the distance of the Earth orbiting its sun. The Micro Dyson Sphere has a spectra and energy output slightly smaller than the dimensions of Sol. This was going to be the shelter where the Forerunner were to seek refuge when Halo activated, but no one knows what went wrong.