A Dyson sphere is an idea about a structure that surrounds a star, first thought up by physicist Freeman Dyson, and then used in some science fiction works. There are at least three types of Dyson spheres:
- A Dyson shell that is a solid structure and the inside could even become habitable if the sphere produces artificial gravity by spinning on itself. It would be extremely difficult, if not impossible to build (particularly because of the enormous quantity of material needed, the instability of the sphere and the strong gravity of the star affecting the whole structure).
- A Dyson swarm, which is not exactly a sphere, but millions of smaller bodies orbiting the star and thus forming a more or less spherical structure around it. The most physically realistic structure to built.
- A Dyson bubble that is made up of small bodies (like a Dyson swarm), but linked together with an extremely light and thin (but very large) structure such as a light sail around a star that keeps it centered because of stellar winds.