Class B - Gas Giant Class
Class B Planets are usually found in a star's outer or "cold zone". They are typically 50 thousand to 140 thousand kilometers in diameter and have high core temperatures but do not radiate much heat. Low stellar radiation and high planet gravity enables them to keep a tenuous surface comprised of gaseous hydrogen and hydrogen compounds.

Class C - Reducing Class
Planets of this class are usually found in a star's "habitable zone". They are typically 10 to 15 thousand kilometers in diameter. They have high surface temperatures due to the "greenhouse effect" caused by their dense atmospheres. The only water found is in vapor form.

Class D - Geo Plastic Class
lanets of this class are usually found in a star's "habitable zone". They are typically 10,000 to 15,000 kilometers in diameter. They have a molten surface because they have been recently formed. The atmosphere contains many hydrogen compounds and reactive gases. Class D planets eventually cool, becoming Class E.

Class E - Geo-Metalic Class
Planets of this class have a molten core and are usually found in a star's "habitable zone". They are typically 10,000 to 15,000 kilometers in diameter. Their atmospheres still contain hydrogen compounds. They will cool further eventually becoming Class F.

Class F - Geo Crystaline Class
Class F planets are usually found in a star's "habitable zone". They are typically 10 to 15 thousand kilometers in diameter and have surfaces that are still crystalizing. Their atmospheres still contain some toxic gases. They will cool eventually becoming Class C, M or N.

Class G - Desert Class
Planets of this class can be found in any of a star's zones. They are typically 8 to 15 thousand kilometers in diameter. Their surfaces are usually hot. Their atmospheres contain heavy gases and metal vapors.

Class H - Geo-Thermal Class
Planets of this class are usually found in a star's "habitable zone" or "cold zone". They are typically 1,000 to 10,000 kilometers in diameter. They have partially molten surfaces and atmospheres that contain many hydrogen compounds. They cool becoming Class L.

Class I - Asteroid/Moon Class
Planetary bodies of this class can be found in any of a star's zones. They are usually found in orbit of larger planets or in asteriod fields. They are typically 100 to 1,000 kilometers in diameter. They have no atmospheres. Their surfaces are barren and cratered.

Class J - Geo-Morteus Class
Planets of this class are found in a star's "hot zone". They are typically 1,000 to 10,000 kilometers in diameter. They have high surface temperatures due to the proximty to the star. Their atmospheres are extremely tenuous with few chemically active gases.

Class K - Adaptable Class
Planets of this class are usually found in a star's "habitable zone". They are adaptable for humanoid colonization through the use of pressure domes and other life support devices. They are typically 5,000 to 10,000 kilometers in diameter. They have thin atmospheres. Small amounts of water are present.

Class L - Geo-Inactive Class
Planets of this class are usually found in a star's "habitable zone" or "cold zone". They are typically 1,000 to 10,000 kilometers in diameter. Low solar radiation and minimal internal heat usually result in a frozen atmosphere.

Class M - Terrestrial Class
Planets of this class are found in a star's "habitable zone". They are typically 10,000 to 15 thousand kilometers in diameter. They have atmospheres that contain oxygen and nitrogen . Water and life-forms are typically abundant. If water covers more than 97% of the surface, then they are considered Class N.

Class N - Pelagic Class
Class N planets are usually found in a star's "habitable zone". They are typically 10,000 to 15 thousand kilometers in diameter. They have atmospheres that contain oxygen and nitrogen . Water and life-forms are typically abundant. If water covers less than 97% of the surface, then they are considered Class M.

Class S - Near Star Class
Planets of this class are usually found in a star's "cold zone". They are typically 50 million to 120 million kilometers in diameter and have high core temperatures causing them to radiate heat and light. These are the largest possible planets, because most planetary bodies that reach this size do become stars.

Class T - Gas Ultragiant Class
Planets of this class are usually found in a star's "cold zone". They are typically 10 to 50 million kilometers in diameter. They have high core temperatures causing them to radiate enough heat to keep water in a liquid state.

Class Y - Demon Class
Class Y - Demon Planets and planetoids of this class can be found in any of a star's zones. They are typically 10,000 to 15 thousand kilometers in diameter. Atmospheric conditions are often turbulent and saturated with poisonous chemicals and thermionic radiation. Surface temperatures can reach in excess of 500 K. Starfleet Note: Communication is frequently impossible, and transport may be difficult. Simply entering orbit is a dangerous prospect. No known environment is less hospitable to humanoid life than a Class Y planetary body.