Planetary Classifications

With a wide variety of types of planets, maybe galactic bodies found ways to classify them.

## Federation Classification

The United Federation of Planets adopted a system of classification that was a combination of the system used by humans on Earth and the system used by Vulcans.

### Class A, B, and C

These three classes were very similar and were used to define small planets -- frequently young planets at early stages of development. They were differentiated mostly by the solidity of the planet's core. These included Gothos (Class A), Mercury (Class B), and Pluto (Class C).

### Class D

Class D was used for planetoids, such as moons or asteroids. These included Regula and Rura Penthe.

### Class E, F, and G

These were planets that were considered "proto-Earths" -- larger than the previous classes but as yet unsuitable for complex life. Their exact classification was determined by their age and the solidity of their cores.

### Class H

Class H was used to define harsh, uninhabitable desert worlds. Tau Cygna V is one such planet.

### Class I

Class I designated a gas supergiant, an especially large gas giant planet.

### Class J

Class J was the smallest designation for a gas giant. Jupiter, Saturn, Uranus, and Neptune were all Class J planets.

### Class K

Class K designated a planet that was barren and had no native life but could be hospitable with terraforming or if buildings were constructed inside habitable domes. Mars was considered a Class K world.

### Class L

Class L indicated habitable planets that supported primitive life. This could be very simple fauna, or even life as advanced as a Bronze Age culture.

### Class M

Class M indicated that a planet was Earth-like both in its size, core, and age as well as in the advancement of the native creatures. Class M worlds were frequently the home of sapient species capable of traveling in space. The Vulcans used the term "Minshara Class" to denote the same kind of planet prior to the formation of the Federation.

### Class N

Class N worlds were planets with an extremely high surface temperature, and an atmosphere inhospitable to most life. Venus was a Class N world.

### Class O and P

Class O indicated a planet's surface was almost entirely comprised of water, whereas Class P indicated that a planet's surface was almost entirely ice.

### Class Q

Class Q designated a rare variety of planets, with changing environments. These were sometimes the result of peculiar orbits or stars with a variable output.

### Class R

Class R was used to describe "rogue planets" that did not orbit a star.

### Class S

Class S was used to describe gas giants. It was the second smallest designation of gas giants, one size larger than Class J.

### Class T

Class T was the largest designation for gas giants. They were considered "ultragiants".

### Class Y

Class Y was used to describe what are colloquially known as "demon worlds." These worlds were not just inhospitable, but were generally lethal to most humanoid lifeforms. If life developed on such a world, it was frequently bizarre.

### Class X and Z

Classes X and Z were also used to denote other varieties of "demon worlds."

## Source

The planetary classification system is derived from *Star Trek*. For canon information, please visit:

* Memory Alpha