Planet

Planets were, simply speaking, large spherical masses in space. planets are lare spherical objects in every sloar system in every galaxy, they orbit around a sun which often takes years eg.earth takes a year to orbit our sun, and moons orbit planets.



Overview
Planets generally orbit stars, but rogue planets (DC: The Rogue Planet) and wandering planetoids were not uncommon. (DW: Revenge of the Cybermen)

There are a number of highly unusual planets in the universe, including Magla, in reality an immense amoeba with a crust-like shell (DW: Destiny of the Daleks), and the artificial planet Arcadia. (NA: Deceit)

Some planets were artificially accelerated through the interference (intentional or not) of other life forms. Normally in these cases large starships provided the initial large mass which began the process of planetary formation. Such a fate befell the Minyan ship the P7E by accident (and nearly also happened to another Minyan vessel, the R1C) (DW: Underworld), and the vessel carrying the last of the Racnoss by design. (DW: The Runaway Bride) the Cheetah planet had some sort of affect on other lifeforms which eventually transformed them into cheetah people, I am unsure if it has that affect on all lifeforms or just humanoids, just like the master and ace (time lords and humans are the same in appearance which might be the reason that humans and timelords can be infected). And in torchwood:children of earth, the 456 needed to stay in an environmental chamber which housed different gases due to fact that earth has different gases, e.g oxygen, carbon dioxide, nitrogen, hydrogen.