There are an incredible number of variations for different kinds of worlds which can be enchanted in space, this is an index of the general planet types and their average conditions. Unless otherwise noted there can be variations which are outliers.
A / Geothermal
| Type: | Rock |
| Age: | 0-2 Billion Years |
| Atmosphere: | Sulfer Dioxide / Carbon Dioxide |
| Radius: | 500 to 5,000 km |
| Surface: | Rocky / Partially Molten |
| Composition: | Igneous Silica and Basalt |
| Location: | Any |
| Habitability: | None |
Class A planets are very small, barren worlds rife with volcanic activity. This activity traps carbon dioxide in the atmosphere and keeps temperatures on Class A planets very hot, no matter the location in a star system. When the volcanic activity ceases, the planet "dies" and is then considered a Class C planet. Examples include the planet Gothos.
B / Geomorteus
| Type: | Rock |
| Age: | 0-10 Billion Years |
| Atmosphere: | Helium / Sodium / Oxygen |
| Radius: | 500 to 5,000 km |
| Surface: | Barren / Molten in Places |
| Composition: | Iron, Potassium, Silicon |
| Location: | Hot Zone |
| Habitability: | None |
Class B planets are generally small worlds located within a star system's Hot Zone. Highly unsuited for humanoid life, Class B planets have thin atmospheres composed primarily of helium and sodium. The surface is molten and highly unstable; temperatures range from 450° in the daylight, to nearly -200° at night. No life forms have ever been observed on Class B planetoids, though they are fairly common in the universe. 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. Examples include Mercury and Nebhillium.
C / Geoinactive
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | None |
| Radius: | 500 to 7,500 km |
| Surface: | Barren and Cratered |
| Composition: | Anthracite and Basalt / Layers of Frozen Hydrocarbons & Water |
| Location: | Hot Zone / Echosphere / Cold Zone |
| Habitability: | None |
These dead worlds can appear anywhere in a star system, most Class A and B worlds eventually cool to become Class C. Other worlds such as Class E worlds that evolve too close to their parent star will eventually cool into Class C, losing their atmosphere to the stars heat or gravitational pull. The key feature of a Class C is the lack of any geological activity whatsoever and no atmosphere. 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.
Class E typically do not cool to Class C unless they are too close to the star to retain an atmosphere. Without volcanic outgassing the atmosphere will burn away leaving a geologically dead world with no atmosphere. Such evolutions are more rare than the smaller variations which evolve from Class A and B worlds. When a Class P world is too far away from the star, it can eventually evolve into a Class C world with thick layers of frozen hydrocarbons and ice clinging to the surface but no atmosphere to speak of. These worlds are too far away from the parent star for heat to melt / sublimate the frozen surface into an atmosphere. When geological activity ceases on a Class P world sufficiently far from the parent star, it can turn into a Class C if stellar heat is not sufficient to prevent the atmosphere from freezing.
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). Examples include Psi 2000.
D / Dwarf / Plutonian
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | None / Very Tenuous |
| Radius: | 50 to 2,000 km |
| Surface: | Barren / Cratered |
| Composition: | Frozen Hydrocarbons and Ice |
| Location: | Any |
| Habitability: | None |
Also known as Plutonian objects, these tiny worlds 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.
E / Geoplastic
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | Hydrogen Compounds |
| Radius: | 5,000 to 7,500 km |
| Surface: | Molten with High Surface Temperature |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Any |
| Habitability: | Carbon Cycle Life |
Class E planets represent the earliest stage in the evolution of a habitable planet. The core and crust is completely molten, making the planets susceptible to solar winds and radiation and subject to extremely high surface temperatures. The atmosphere is very thin, composed of hydrogen and helium. If the world has formed in the ecosphere of a star system, as the planet cools it will develop into a Class F world and continue its evolution to potentially become a life sustaining world. This is true of the majority of Class E worlds.
A Class E world can also form too close to its parent star and within the Hot Zone. The planet then takes a different path, it never develops into a Class F world and eventually cools to become a Class C world. As geological activity slows to a halt, its thin atmosphere begins to either dissipate (either burned away by the heat of the star or drawn away by gravitational forces). These hot Class E worlds continue to be classified as Class E until geological activity ceases, the atmospheres are gone, and they become Class C.
Finally, a Class E planet can develop just outside of a star's habitable zone in the cold zone. Such formations have a similar trajectory as their more common counterparts with the ecosphere of a star. The Class E world cools into a cold Class F world on a trajectory to becoming a Class P world. If such a world is too far outside of the ecosphere of a star, it dies as the geological heat dies and will eventually develop into a dead Class C world losing its atmosphere to condensation and eventual freezing of hydrocarbons in the atmosphere or lighter elemental gasses such as hydrogen and helium eventually bleed away into space.
F / Geometallic
| Type: | Rock |
| Age: | 1-3 Billion Years |
| Atmosphere: | Carbon Dioxide, Ammonia, Methane |
| Radius: | 5,000 to 7,500 km |
| Surface: | Volcanic and Barren |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Ecosphere or Cold Zone |
| Habitability: | Bacteria |
A Class E planet makes the transition to Class F once the crust and core have begun to harden. Volcanic activity is also commonplace on Class F worlds; the steam expelled from volcanic eruptions eventually condenses into water, giving rise to shallow seas in which simple bacteria thrive. When the planet's core is sufficiently cool, the volcanic activity ceases and the planet is considered Class G. Examples include Janus IV.
When the world forms just inside the cold zone of a star, the planet's condensing water begins to form a layer of protective ice. The interior is kept warm and simple bacteria can still develop, transforming the atmosphere far more slowly than a world found in the ecosphere. Instead of developing into a Class G world, it will develop into a frozen glaciated Class P world with minimal simple life forms.
G / Geocrystalline
| Type: | Rock |
| Age: | 3-4 Billion Years |
| Atmosphere: | Carbon Dioxide, Oxygen, Nitrogen |
| Radius: | 5,000 to 7,500 km |
| Surface: | Rocky and Mostly Barren |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Ecosphere |
| Habitability: | Vegetation / Simple Organisms |
After the core of a Class F planet is sufficiently cool, volcanic activity lessens and the planet is considered Class G. Oxygen and nitrogen are present in some abundance in the atmosphere, giving rise to increasingly complex organisms such as primitive vegetation like algae, and animals similar to sponges and jellyfish. As the surface cools, a Class G planet can evolve into a Class H, K, L, M, N, O, or P class world. Examples include Delta Vega.
H / Desert
| Type: | Rock |
| Age: | 4-10 Billion Years |
| Atmosphere: | Oxygen, Nitrogen, Argon, and Metals |
| Radius: | 5,000 to 7,500 km |
| Surface: | Hot / Arid with < 20% Surface Water |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Ecosphere |
| Habitability: | Drought-Resistant Plants & Animals |
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: | Gas Giant |
| Age: | 2-10 Billion Years |
| Atmosphere: | Hydrogen and Helium |
| Radius: | 15,000 to 50,000 km |
| Surface: | Rock, Ice, Methane, and Ammonia |
| Composition: | Hydrogen, Helium |
| Location: | Cold Zone |
| Habitability: | None |
Also known as Uranian planets, these gaseous giants have vastly different compositions from other giant worlds; the core is mostly rock and ice surrounded by a tenuous layers of methane, water, and ammonia. Additionally, the magnetic field is sharply inclined to the axis of rotation. Class I planets typically form on the fringe of a star system.
J / Jovian
| Type: | Gas Giant |
| Age: | Unknown |
| Atmosphere: | Hydrogen , Helium |
| Radius: | 25,000 to 250,000 km |
| Surface: | Liquid Metallic Hydrogen |
| Composition: | Gaseous and Liquid Hydrogen & Helium / Liquid Metallic Hydrogen |
| Location: | Cold Zone |
| Habitability: | None |
These are prototypical gas giants, class J planets are massive spheres of liquid and gaseous hydrogen, with small cores of metallic hydrogen. 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. 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: | Rock |
| Age: | 4-10 Billion Years |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | 2,500 to 5,000 km |
| Surface: | Barren and Cratered |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Echosphere |
| Habitability: | Adaptable |
Though similar in appearance to Class H worlds, Class K planets lack the robust atmosphere of their desert counterparts. Though rare, primitive single-celled organisms have been known to exist, though more complex life never evolves. Humanoid colonization is, however, possible through the use of pressure domes and in some cases, terraforming. 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 F to 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. Examples include Mars and Mudd.
Though rare, simple single cell organisms can still thrive on these barren worlds 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: | Rock |
| Age: | 4-10 Billion Years |
| Atmosphere: | Argon & Oxygen with Trace Elements |
| Radius: | 5,000 to 7,500 km |
| Surface: | Rocky with Little Surface Water |
| Composition: | Silicone, Iron, Magnesium, Aluminum |
| Location: | Ecosphere |
| Habitability: | Vegetation Only |
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: | Rock |
| Age: | 4-10 Billion Years |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | 5,000 to 7,500 km |
| Surface: | Abundant Surface Water, Temperate Climate |
| Composition: | Silicone, Iron, Magnesium, Aluminium |
| Location: | Ecosphere |
| Habitability: | Prime conditions for large populations of animal, planet, and humanoid life. |
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 or cold snowy planets can be Class M.
N / Reducing
| Type: | Rock |
| Age: | 3-10 Billion Years |
| Atmosphere: | Carbon Dioxide and Sulfides |
| Radius: | 5,000 to 7,500 km |
| Surface: | Barren with High Surface Temperatures |
| Composition: | Silicone, Iron, Magnesium, Aluminium |
| Location: | Ecosphere |
| Habitability: | None |
Though frequently found in the Ecosphere, Class N planets are not conducive to life. The terrain is barren, with surface temperatures in excess of 500° and an atmospheric pressure more than 90 times that of a Class-M world. Additionally, the atmosphere is very dense and composed of carbon dioxide; water exists only in the form of thick, vaporous clouds that shroud most of the planet. Examples include Venus.
O / Oceanic / Pelagic
| Type: | Rock |
| Age: | 3-10 Billion Years |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | 5,000 to 7,500 km |
| Surface: | 80% Water & Archipelagos |
| Composition: | Silicone, Iron, Magnesium, Aluminium |
| Location: | Ecosphere |
| Habitability: | Vegetation, Cetacean, Animal, Humanoid |
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: | Rock |
| Age: | 3-10 Billion Years |
| Atmosphere: | Oxygen, Nitrogen, Argon |
| Radius: | 5,000 to 7,500 km |
| Surface: | Cold, Glaciated |
| Composition: | Silicon, Iron, Magnesium, Ice |
| Location: | Ecosphere and Cold Zone |
| Habitability: | Varied; Cold-Resistant Vegetation, Animal, and Humanoid / Bioluminescent Single-Celled Organisms / Possibly None |
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. Any planet whose surface is more than 80% frozen is considered Class P. These glaciated worlds are typically very cold, with temperatures rarely exceeding the freezing point. Though not prime conditions for life, hearty plants and animals are not uncommon, and some species, such as the Aenar and the Andorians, have evolved on Class P worlds. Examples include Andorra and Rita Penthe.
When a Class P world forms in the ecosphere of a star, they tend to develop some kind of cold-resistant life forms which can develop when the planet is still kept warm by geological activity rather than the sun. In such cases bioluminescent bacteria and other single-celled organisms can stay alive deep within the planet where geological heat maintains a layer of liquid water. Eventually when the planet cools sufficiently the layer of liquid water freezes and the world effectively dies. Worlds of this type typically hold onto their atmosphere with heavier diatomic elements like Oxygen and Nitrogen and will build up thick layers of permafrost. Such worlds have the potential to be terraformed, if the ice was to thaw many single-celled bacteria and similar life forms may revive and propagate.
Q / Variable
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | Varies - Nitrogen, Oxygen, Argon Ranging from Thin to Very Dense |
| Radius: | 2,000 to 7,500 km |
| Surface: | Varies - Molten, Frozen, Jungle, etc. |
| Composition: | Silicon, Iron, Magnesium |
| Location: | Any |
| Habitability: | None |
These rare planetoids typically develop with a highly eccentric orbit, or near stars with a variable output. As such, conditions on the planet's surface are widely varied. Deserts and rain forests exist within a few kilometers of each other, while glaciers can simultaneously lie very near the equator. Given the constant instability, is virtually impossible for life to exist on Class-Q worlds. Examples include the Genesis Planet.
R / Rogue
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | Volcanic Outgassing |
| Radius: | 2,000 to 7,500 km |
| Surface: | Hot, Temperate, or Cold |
| Composition: | Silicate Compounds and Iron |
| Location: | Interstellar Space |
| Habitability: | Non-Photosynthetic Plants and Animals if Any |
A Class R planet usually forms within a star system, but at some point in its evolution the planet is expelled. This is likely the result of a catastrophic asteroid impact or destruction of another planet within the system. The shift radically changes the planet's evolution; many planets merely die, but geologically active planets can sustain a habitable surface via volcanic outgassing and geothermal venting. The ejection of such a planet from a system can also occur due to high-gravity objects such as a black hole passing close enough to pull the planet out of orbit but not so close that the planet gets captured by the 2nd object.
There is some variability with these worlds, a Class A or B planet can be ejected from its orbit and remain very hot never developing life while a Class A, B, E, F, G, H, K, L, M, or N with high enough levels of volcanic activity could either develop or maintain an environment minimally suited toward the evolution of non-photosynthetic planets and animals which live in perpetual darkness.
Class R planets are very rare and such a planet maintaining the ability to support life or evolving life after ejection from its star system is even more rare. Most common a planet ejected from its orbit becomes a Class C3 / D3 or Class C or D Rogue Planet (see subclassifications). To be classified as a Class R the planet must have an atmosphere that is heated to by geothermal energy and not be orbiting a star.
S / Gas Supergiant
| Type: | Gas Giant |
| Age: | 2-10 Billion Years |
| Atmosphere: | Hydrogen and Helium |
| Radius: | 250,000 to 50,000,000 km |
| Surface: | Liquid Metallic Hydrogen |
| Composition: | Gaseous and Liquid Hydrogen & Helium / Liquid Metallic Hydrogen |
| Location: | Cold Zone |
| Habitability: | None |
Aside from their immense size, Class S planets are very similar to their Class J counterparts, with liquid metallic hydrogen cores surrounded by a hydrogen and helium atmosphere. Aside from their colossal size, there is little that differentiates a Class S: Super Giant world from its Class J: Jovian counterpart. Located in a star system’s cold zone, they often boast impressive ring systems and harbor dozens of moons.
Giant worlds like Class S and the other gaseous planetoids tend to act as “shields” for the terrestrial planets in the ecosphere, as their powerful gravitational fields tend to divert comets and asteroids away from the interior of a star system. Examples include Tethe-Alla IV.
T / Transitional
| Type: | Gas Giant / Rock Hybrid |
| Age: | 2-10 Billion Years |
| Atmosphere: | Frozen Hydrocarbons, Ice, Hydrogen, Helium |
| Radius: | 250,000 to 25,000,000 km |
| Surface: | Liquid Metallic Hydrogen |
| Composition: | Osmium, Iridium, Platinum, Tungsten |
| Location: | Cold Zone |
| Habitability: | None |
Existing in size between the Class I ice giants and the Class V super-terrestrials, Class T planets are large enough and with strong enough gravity to retain a thick atmosphere of hydrogen, helium and hydrocarbons. The atmosphere transitions to oceans of semiliquid compressed hydrogen mixed with semisolid ice / hydrocarbon over a metallic ore core. Sometimes known as gas dwarfs - something of a misnomer for such large planets.
U / Gas Ultragiant
| Type: | Gas Giant |
| Age: | 2-10 Billion Years |
| Atmosphere: | Hydrogen and Helium |
| Radius: | 25,000,000 to 60,000,000 km |
| Surface: | Liquid Metallic Hydrogen |
| Composition: | Gaseous and Liquid Hydrogen & Helium / Liquid Metallic Hydrogen |
| Location: | Cold Zone |
| Habitability: | None |
Class U planets represent the upper limits of planetary masses. Most exist within a star system's Cold Zone and are very similar to Class S and J planets. If they are sufficiently massive (13 times more massive than Jupiter), deuterium ignites nuclear fusion within the core, and the planet becomes a red dwarf star, creating a binary star system.
These titanic gaseous worlds represent the upper limits of planetary masses. Structurally similar to their Class J and S counterparts, only on a far more grandiose scale, these planets have astounding diameter between 50,000,000 and 120,000,000 kilometers. Most Class U planets are content to loom in the cold zone of a star system, but if the planet is sufficiently massive (13 times the size of Jupiter), nuclear fusion ignites the deuterium within the core, and the planet becomes a red dwarf star, creating a binary star system.
The great mass of ultra giants that do not transition into stars occasionally force them to assume eccentric orbits. This causes them to spiral inward toward the heart of the star system and become a “Hot Jupiter,” a gas giant orbiting extremely close to its parent star. This destructive process disrupts the entire star system, ejecting smaller planets into interstellar space, and ultimately ends with the Class U planet’s demise as a desolate Class X world.
V / Super-Terrestrial
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | Carbon Dioxide, Oxygen, Hydrogen, Helium |
| Radius: | 10,000 to 15,000 km |
| Surface: | High Pressure / Temperature |
| Composition: | Iron, Iridium, Tungsten, Nickel |
| Location: | Ecosphere / Cold Zone |
| Habitability: | Pressure Resistant Planet / Animal Life |
The so-called "super-Earths," large rocky/metallic planets intermediate in size between terrestrial and ice giants. Their higher gravity allows them to retain dense, hydrogen-rich atmospheres. Surface temperature and pressure are high and unsuitable for humanoid habitation, but complex life resistant to the extreme environment can evolve, and they are potentially viable for colonization using pressure domes.
W / Divided / Locked
| Type: | Rock |
| Age: | 0-10 Billion Years |
| Atmosphere: | Oxygen / Sodium / Hydrogen |
| Radius: | 500 to 7,500 km |
| Surface: | Half Barren / Molten and Half Cold, Glaciated |
| Composition: | Iron, Potassium, Silicon |
| Location: | Hot Zone / Ecosphere |
| Habitability: | None |
Rocky planets kept tidally locked to the parent star or sister planet by the intense gravitational interaction of other bodies in their system. One side is overlit and heated, displaying molten areas and a burnt, desert-like surface. The far side is kept in perpetual darkness and cold, sometimes with a more temperate dividing line if the atmosphere is dense enough to mediate the heat. Such planets may be colonised, and some display native life that has adapted to the extreme environment, often in unusual ways.
X / Chthonian
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | None |
| Radius: | 500 to 5,000 km |
| Surface: | Barren & Extremely Hot |
| Composition: | Molten Iron |
| Location: | Hot Zone |
| Habitability: | None |
Class X planets are the result of a failed Class S or U planet in a star system's Hot Zone, the atmosphere has been stripped away leaving only the dense, metal-rich core. Instead of becoming a gas giant or red dwarf star, a Class X planet was stripped of its hydrogen/helium atmosphere. The result is a small, barren world similar to a Class B planet, but with no atmosphere and an extremely dense, metal-rich core. These planetoids are rare and valuable. Uninhabitable and ultimately doomed to absorption by their parent star.
Y / Demon
| Type: | Rock |
| Age: | 2-10 Billion Years |
| Atmosphere: | Turbulent with Toxic Radiation |
| Radius: | 5,000 to 7,500 km |
| Surface: | Barren & Extremely Hot |
| Composition: | Molten Iron & Sulphur, Deuterium, Silicates |
| Location: | Hot Zone |
| Habitability: | None |
Perhaps the most environmentally unfriendly planets in the galaxy, Class Y planets are toxic to life in every way imaginable. Most often found in the hot zone of a star system, these worlds possess extremely thick, highly toxic atmospheres which are plagued with violent storms that discharge thermionic radiation; surface temperatures exceed 200°C, and winds may reach 500kph. Incredibly, a type of biomimetic life form was discovered on a Class Y planet in the Delta Quadrant in 2374. This is the only time life has ever been found on a Class Y planet. Although Class Y planets are extremely rare in the universe, they are generally unremarkable, average-sized planets when their harsh atmosphere is taken out of the equation. The surface is predictably barren, and composed primarily of iron, deuterium, and silicate rocks.
Specialized Sub-Classes
These classes are sub-classes applying to certain types of planets in special conditions.
1 / Retinal
Applicable to Class H, L, M, O, and P.
On most planets, the indigenous vegetation uses chlorophyll–based photosynthesis for energy, and the end result is a familiar-looking world with blue oceans and wide swaths of green forest. However, terrestrial planets in orbit of a red dwarf star do not receive enough light for chlorophyll-based photosynthesis to take place; instead, the vegetation must use retinal-based photosynthesis. The end result is a world covered in purple vegetation.
For example, a Class M planet in orbit of a red dwarf star is operationally identical to a Class M planet in orbit of any other star. As such, any terrestrial planet in a red dwarf star system would retain its primary classification—a Class M planet is still Class M—but with retinal subclass applied as a secondary classification. A Class M planet would therefore be identified as Class M1 or sometimes Class M (Retinal).
2 / Satellite
Applicable to nearly any rock type world, class A, B, C, D, E, F, G, H, K, L, M, N, O, P, Q, and Y.
When a celestial body is in orbit of another planet, it is automatically labeled a satellite, or more commonly, a moon. Moons can assume a variety of different shapes and sizes. Many are small, barren chunks of nondescript rock, but it is entirely possible for a moon to be a perfectly habitable Class M world, one that would be considered a planet outright had it settled into orbit around a star. Class Q2 satellites are more common than full Class Q worlds, due to the orbital path around a gaseous planet giving the surface more erratic exposure to the central star of a system.
Regardless of shape and size, any and all moons are assigned the satellite subclass. For example, Class D: Dwarf in orbit of another planet would be designated Class D2, Class D Satellite, or Class D Moon. Normally while a moon is designated a specific class, if the moon is a normal non-life bearing moon with unremarkable features (such as Earth's Moon in the Sol system) it's official class is not needed. Same for asteroidal moons that are typical (such as the 2 moons of Mars in the Sol system).
3 / Ejected / Rogue
Applicable to worlds which cannot maintain their surface temperature to become a Class R or are gas giants, class C, D, I, J, S, T, U, and V.
When a planet gets ejected from its orbit around a star through some means, such as with a Class R, but cannot maintain its surface temperature, it is a subtype 3. These planets quickly cool when no longer exposed to the heat of a star, rock worlds mostly are Class C or D while gas giants stay the same class but are designated as Rogue anyway noting they exist in interstellar space. In rare cases a Class U planet slowly gathers enough mass to ignite fusion, becoming a dwarf star in its own right. Rock planets which are not heated by geothermal and do not have an atmosphere are classified as Ejected / Rogue in this way. See Class R for more details.
Class T or V worlds ejected from their natural orbits can maintain surface temperatures not through geothermal emissions but rather though the intense pressure provided by their size and incredibly strong gravitational fields. Such worlds are exceedingly rare, more rare than even a Class R with intelligent life as a Class T or V world is very rare to begin with.
Such planets are classified as Class I3, Ejected Class I, or Rogue Class I.
4 / Large / Heavy
Applicable to nearly any rock type world, class A, B, C, D, E, F, G, H, K, L, M, N, O, P, Q, and Y.
Some planets do not exactly fit into an existing classification. This subclass specifically identifies a planet as being otherwise fitting with an existing classification but otherwise too large or too heavy to be classified as such. For these class worlds the planet fits all categories except size / mass. Such worlds are not rare, this subclass is mostly for precise cataloguing purposes. Although can be referred too explicitly to differentiate with other classifications, especially when other planets in the system share the same class but fit within size / mass guidelines. These worlds often have thicker atmospheres and higher gravity than their more common contemporaries. This classification is not terribly uncommon, though tends to not be into the more ideal Class M or O but instead tend toward Class N. Class H, K, L, or P are also somewhat common.
Examples include; Class E4, Heavy Class E, or Large Class E.
5 / Small / Light
Applicable to nearly any rock type world, class A, B, C, D, E, F, G, H, K, L, M, N, O, P, Q, and Y.
Some planets do not exactly fit into an existing classification. This subclass specifically identifies a planet as being otherwise fitting with an existing classification but otherwise too small or too light to be classified as such. For these class worlds the planet fits all categories except size / mass. Such worlds are not rare, this subclass is mostly for precise cataloguing purposes. Although can be referred too explicitly to differentiate with other classifications, especially when other planets in the system share the same class but fit within size / mass guidelines. These worlds often have thinner atmospheres and lower gravity than their more common contemporaries. In contrast to a subclass 4 world, many of these planets do not reach Class M or O status tending more toward Class H, K, L, N, or P. This is primarily due to the gravitational pull of the world being too small for the thicker atmosphere required for a Class M / O. These planets are more rare than their larger cousins unless they have an unusually dense core which can hold onto more atmosphere and water.
Examples include; Class L5, Light Class L, or Small Class L. While occasionally the term Dwarf is used in colloquial terms, it is not considered an official designation to avoid confusion with Class D.
6 / Artificial Ocean
Applicable to only Class O worlds.
This is a specific type of classification. Class O worlds require greater than 80% of the surface be made of water, even with worlds that have 100% water coverage there is still a dense molten rock core which creates the gravitational field to maintain an atmosphere and pressure for liquid water. With a subtype of 4 this is not the case. Also called a Class O6 or Artificial Class O these are worlds that are not naturally occurring. Such "Ocean Worlds" are held together not by gravity but by a containment field generated at their core and is otherwise entirely made of water. As such the age, size, and evolutionary history of the world do not conform to most known standards. The size will be entirely dependent on the size of the containment field, though even if life is seeded in this artificial ocean world it will have a unique evolutionary path, just like any planet.
Only one such world has ever been located, called The Waters by the Monean in the Delta Quadrant.