 | This information largely comes from this web site, which in turn based it upon sources from Star Trek. |
Planets are classified according to their predominant properties. While there is, at times, overlap in some of the classifications the primary classification of a planet assists travelers through space in identifying the primary characteristics of a planet more easily.
A / Geothermal
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Sulfer Dioxide / Carbon Dioxide |
| Radius: | Unknown |
| Surface: | Rocky / Partially Molten |
| Composition: | Igneous Silica / Basalt |
| Location: | Any |
| Habitability: | Unknown |
These planets are generally young, rocky worlds that are rife with volcanic activity. This volcanic activity spews vast amounts of sulfur and carbon dioxide into the atmosphere, causing a greenhouse effect that keeps temperatures relatively hot. Such worlds have tenuous and toxic atmospheres and are unsuitable to any kind of life.
When this extreme volcanic activity eventually ceases, the planet "dies" and becomes a Class C world.
Class A planets are common in the universe; Jupiter's moon Io is a prime example.
B / Geomorteus
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Oxygen / Sodium / Hydrogen |
| Radius: | Unknown |
| Surface: | Barren / Molten in Places |
| Composition: | Iron / Potassium / Silicon |
| Location: | Hot Zone |
| Habitability: | Unknown |
Class B planets are generally very small, very rocky worlds located within a star system's hot zone. In the harsh daylight, these planets are scorched by their parent star, often to the point of rock becoming molten. Because Class B worlds have little to no atmosphere, this heat quickly radiates away at night, leaving the dark side of the planet a frigid wasteland. As a result, these planets are highly unsuitable for humanoid life.
Despite their small size, Class B planets are often extremely dense, with a large inner core, up to 55% of the planet's volume, that is made of molten iron.
Class B planets are fairly common in the universe.
C / Geoinactive
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | None |
| Radius: | Unknown |
| Surface: | Barren and Cratered |
| Composition: | Anthracite and Basalt |
| Location: | Hot Zone / Echosphere / Cold Zone |
| Habitability: | Unknown |
These worlds are rocky and barren worlds which can exist in any zone of a star system, their surface temperature largely depends on the zone which they reside, generally speaking it runs between -150 to -120 degree's Celsius since most are located far enough away from the central star to absorb enough heat to bake the surface. However, it is possible for these planets to be close enough to the central star to have surface temperatures much higher, though generally below that of a Class B world. They tend to run smaller than a Class M world, with sizes ranging from that of moons up to just a bit smaller than an M Class world. The primary classification of this class is the lack of an atmosphere, no geological activity, and the lack of any ability to support life.
These worlds are often rich in minerals and make incredibly good candidates for mining operations. Some can even have semi-molten iron cores with rich deposits of minerals produced either by steady impact of meteorites during the early phases of their existence (usually these worlds begin as Class A worlds or similar and then become more inactive as they cool over several billion years).
D / Dwarf
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | None / Very Tenuous |
| Radius: | Unknown |
| Surface: | Barren / Cratered |
| Composition: | Unknown |
| Location: | Any |
| Habitability: | Unknown |
Also known as Plutonian objects, these tiny worlds (100 - 4,000 km) are composed primarily of ice and are generally not considered true planets. Many moons and asteroids are considered Class D, as are the larger objects in a star system's Kuiper Belt. Most are not suitable for humanoid life, though many can be colonized via pressure domes. Examples include Pluto, Ceres, and Eredas-II.
H / Desert
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Oxygen, Nitrogen, Argon, and Metals |
| Radius: | Unknown |
| Surface: | Hot / Arid with < 20% Surface Water |
| Composition: | Unknown |
| Location: | Ecosphere |
| Habitability: | Unknown |
A planet is considered Class H if less than 20% of its surface is water. Though many Class H worlds are covered in sand, it is not required to be considered a desert; it must, however, receive little in the way of precipitation. These worlds are usually between 8,000 and 15,000 km in diameter. Drought-resistant plants and animals are common on Class H worlds, and many are inhabited by humanoid populations. Most Class H worlds are hot and arid, but conditions can vary greatly. Examples include Nimbus III and Ocampa.
I / Ice Giant / Uranian
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Hydrogen , Helium |
| Radius: | Unknown |
| Surface: | Rock, Ice, Methane, Ammonia |
| Composition: | Hydrogen, Helium |
| Location: | Cold Zone |
| Habitability: | Unknown |
These planets are gas giants with a core of mostly rock surrounded by tenuous layers of methane, water, and ammonia. They have a sharply inclined magnetic field compared to the axis of rotation. They typically form on the fringe of a solar system. They can be excellent sources of Hydrogen and Helium, smaller than a Class J and with a weaker magnetic and gravitational field making extracting Hydrogen easier than a Class J. These are similar to Neptune and Uranus in the Sol System.
J / Gas Giant / Jovian
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Hydrogen , Helium |
| Radius: | Unknown |
| Surface: | Liquid Metallic Hydrogen |
| Composition: | Hydrogen, Helium |
| Location: | Cold Zone |
| Habitability: | Unknown |
These planets are massive spheres of liquid and gaseous hydrogen, with small cores of metallic hydrogen similar to Jupiter in the Sol system. Their atmospheres are extremely turbulent, with wind speeds in the most severe storms reaching 600 kph. Many Class J planets also possess impressive ring systems, composed primarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I planets. The strong magnetic and gravitational fields can pose a navigational hazard to nearby vessels and also can make extraction of Hydrogen more difficult than Class I worlds.
K / Adaptable
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | Unknown |
| Surface: | Barren and Cratered |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Echosphere |
| Habitability: | Unknown |
Adaptable planets represent an unfortunate part of planetary development: a failed world. Over the course of a terrestrial planet's long and arduous evolution (from Class E to Class F to Class G), something, somewhere goes wrong, and the blossoming young planet fails to reach its full potential. Volcanic activity slows to a halt, the tenuous atmosphere begins to disperse, any liquid on the surface evaporates, and the rocky young world essentially dies. These worlds have atmospheres of dwindling size after volcanic activity slows and the molten core begins to solidify.
Though rare, simple single cell organisms can still thrive on these barren worlds, but more complex forms of life never evolve. As a result, Class K planets are easily colonized via the use of pressure domes, and are often prime candidates for terraforming. Average temperatures are quite cold by humanoid standards, but a warm summer day on a terraformed Class K planet might creep as high as 20°C.
L / Marginal
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Argon & Oxygen with Trace Elements |
| Radius: | Unknown |
| Surface: | Rocky with Little Surface Water |
| Composition: | Unknown |
| Location: | Ecosphere |
| Habitability: | Unknown |
These planets are usually between 10,000 and 15,000 km in diameter, typically rocky, forested worlds devoid of animal life. They are, however, well-suited for humanoid colonization and are prime candidates for terraforming. Water is typically scarce, and if less than 20% of the surface is covered in water, the planet is considered Class H. Examples include Alarin III, Ciden II, and Indri VII.
M / Minshara / Terrestrial
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | Unknown |
| Surface: | Abundant Surface Water, Temperate Climate |
| Composition: | Silicone, Iron, Magnesium, Aluminium |
| Location: | Ecosphere |
| Habitability: | Unknown |
These planets are robust and varied worlds composed primarily of silicate rocks. Located in a star system's habitable zone, most are temperate worlds with vast blue oceans and wide swaths of verdant forest. However, conditions can vary greatly between worlds and still be considered Class M; as long as the surface is between 20 and 80 percent water, the climate is generally temperate, and the atmosphere made of oxygen and nitrogen, even dry rocky worlds and cold snowy planets can be Class M.
O / Oceanic / Pelagic
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | Unknown |
| Surface: | 80% Water & Archipelagos |
| Composition: | Silicone, Iron, Magnesium, Aluminium |
| Location: | Ecosphere |
| Habitability: | Unknown |
Any planet with more than 80% of the surface covered in water is considered Class O. These worlds are usually very warm and possess vast cetacean populations in addition to tropical vegetation and animal life. Though rare, humanoid populations have also formed on Class O planets.
P / Glaciated
| Type: | Unknown |
| Age: | Unknown |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | Unknown |
| Surface: | Cold, Glaciated |
| Composition: | Silicon, Iron, Magnesium, Ice |
| Location: | Ecosphere, Cold Zone |
| Habitability: | Unknown |
On the distant edge of a star system's ecosphere, habitable planets are still numerous, but they are a far cry from the lush garden worlds closer in. Cold, barren, and glaciated planet is covered in solid ice, and while many possess narrow stripes of green along the equator, where hearty plant and animal life may flourish, many glaciated worlds are entirely frozen.
Despite the harsh conditions, humanoid life can thrive on a glaciated world.