Planet

A planet is a celestial body typically found in orbit around a star. Planets are typically spheroid and may have other bodies in orbit of themselves such as moons, rings or artificial satellites which can include communications or defense technology or orbital facilities such as starbases and shipyards. There are two basic types of planets, small solid rocky planets which may have a thin atmosphere and gas giants which are almost entirely atmosphere. Small planet-like bodies are planetoids or dwarf planets and smaller bodies still are asteroids.

Planetary Classification
The Federation classified planets it cataloged based on criteria such as atmospheric composition, surface temperature, and conditions, the size of the body, and the presence of animal and plant life. This system is used to determine the suitability of the planet for exploration, colonization, and scientific research.

Each class of planet is assigned a letter in the alphabet based on its suitability. For example, Class M (sharing meaning with the Vulcan designation Minshara class) is applied to planets that can support life without any special circumstances, such as Earth, Vulcan, or Cardassia. 

The Klingons had a separate classification system, one of which is a Q'tahL class. 


 * Two partially conflicting listings of planetary classification have been given by the 1989 book The Worlds of the Federation and the 2002 book Star Charts. The two sources have classes D, K and M in common, but otherwise assign classifications to conflicting letters.