Artificial planet
An artificial planet was a planet created by unnatural means. 

In 2268, based upon the apparent age of the rocks, the complexity of plant life, and lack of a magnetic field on the Kalandan outpost that James T. Kirk cited, Leonard McCoy speculated that it could be an artificial planet. When Hikaru Sulu asked where its creators were, Kirk speculated that it might be hollow. ()

See also 
 
 Gothos
 Shore Leave Planet
 The Waters

Celestial objects
Life support technology