Artificial planet

Its defining characteristic is that it has sufficient mass to generate its own gravity field that is strong enough to prevent atmosphere from escaping,[3][4] although the term has been sometimes used to describe other types of megastructures that have self-sufficient ecosystems.

Mark Hempsell suggested that an artificial replica planet could be created in the Solar System as preparation for future space colonization, probably in the habitable zone between the orbits of Venus and Mars.

[1][4] They would have similar purpose to other large scale megastructures intended as living spaces (such as O'Neill cylinder) or the concept of colonizing (or terraforming) existing planets.

It has also been suggested that such an endeavour would be more challenging than terraforming existing planets, although both ideas are mostly speculative at this point of human history.

Such a structure would resemble the concept of a Dyson sphere, as the habitable surface would exist on the inner side, but it would be built around a massive stellar body, such as a giant planet or a black hole.