Dyson Sphere
Cannon Info

Freeman Dyson was an excitingly imaginative scientist who proposed that a highly advanced technological civilization would ultimately completely surround its host star with a huge shell to capture 100%
of the useful radiant energy.
This "Dyson shell" or "Dyson sphere" as subsequent writers have called it, would have a gigantic cluster of artificial planetoids
(called a "Dyson cloud") with billions of billions of inhabitants who would make use of the energy captured by the Dyson shell.
Freeman Dyson also made the most intriguing speculation that a Dyson sphere viewed from afar--from other star systems or other galaxies--would have a highly distinctive and unnatural light.
He advised that astronomers search the heavens for such tell-tale colored stars, which could only signify highly advanced, intelligent life.
Startrek Cannon Information:
Dyson Sphere:
A large sphere that was built around a G star. This sphere is around 200 million KM in diameter and is large enough to fit 250 earth sized planets inside. Named after a scientist who made the theroy. Freeman Dyson of the 20th century. The makers of this sphere are unknown and all records seem to have been lost. USS Jenolen was crashed on the surface outside of the sphere and inside was Chief Engineer of the Enterprise A Scott Montgomery and he was in the transporter buffers. The enterprise D came along and got trapped inside the sphere and used the Jenolen to escape.