Su suggerimento di @GiMa

Sul blog Io9 Anders Sandberg  prova a immaginare come sarebbe un pianeta toroidale, ovvero dalla caratteristica forma di una ciambella.

It is not obvious that a toroid planet is stable. For all practical purposes planets are liquid blobs with no surface tension: the strength of rock is nothing compared to the weight of a planet. Their surfaces will be equipotential surfaces of gravity plus centrifugal potential. If they were not, there would be some spots that could reduce their energy by flowing to a lower potential. Another obvious fact is that there exists an upper rotation rate beyond which the planet falls apart: the centrifugal force at the equator becomes larger than gravity and material starts to flow into space.

 

Immagine da Flickr