Planetary Classification

Modifying Canon for the Modern World

Projects such as TRAPPIST and the Kepler Telescope have expanded our knowledge of the wide variety of potential planets. We have discovered worlds seldom considered by science before now: "Super-Earths," "Hot Jupiters," and Hycean "Ocean Worlds," we have come to understand are quite commonplace. We have also come to know that most stars likely have some planets, and that Type M and Type K stars are the most logical candidates for "Super-Habitability"- long periods of life-friendly conditions that will stretch into tens, even hundreds of billions of years. Reality has trumped some science theory as well- we are finding planets with orbits in binary star systems for example. Where science and science fiction seem farther apart (at least for now) is finding habitable planets around hot stars: A, B and O type stars. Here, Sim central continues to take some creative license in the vein of Star Trek's model.

To try to keep up with this, the mods of the Ulysses sim decided to revamp Star Trek's traditional planetary classification system and try to expand it. There have been a few changes, and a little shuffling around. But we hope you will recognize the bones and features set forth by the franchise.

Planetary Classifications

Sim Central has sought to expand upon the definitions of planets using the traditional classification system but also includes optional sub-type descriptors and size variants.

Habitable Planets

Habitable Classes of Planetary Bodies

Habitable Planetary Classes

Science has discovered that life is fairly common in our corner of the galaxy, not the exception. However, humanoid life, based on DNA-like analogs similar to Humans, is somewhat rare. The Habitable classes of planets are those which are friendly (or at least survivable long-term) to oxygen-breathing, carbon-based life forms. These planets have, in some form, all elements necessary for survival: sunlight, water, nutrition, and a fairly temperate, reliable climate.

Class G (Glaciated)

Glass G worlds are "Snowball Earths" and include worlds like Andoria. A large portion of their surface water is found in continental glaciation- at least 50% of the planet's surface needs to be covered in glacier ice to qualify. Class G worlds tend to be exceptionally cold but still remain habitable and with breathable atmospheres. Class G worlds are sometimes worlds undergoing an Ice Age event but more often they exist in an orbital location that is colder than a temperate or hot zone.

Class H (Harsh)

Class H worlds are generally habitable, at least in part, but have reduced resources or favorable elements compared to a Class M world. Harsh planets often lack water, have thin but breathable atmospheres, extremely turbulent and destructive weather, or else have wild temperature swings. Life can and does spring from such worlds, but tends to be hardy, homogeneous (alike) and located in the most habitable pockets of the planet. Because so many Class H worlds possess life forms and ecosystems already, they are seldom considered for terraformation. Class L and Class H worlds have some similarities, the criteria being that Class H worlds have pockets or zones of habitability whereas most Class L worlds are universally less conducive to humanoid life.

Class M (Minshara/Habitable)

Class M worlds, or Minshara in the Vulcan planetary classification system, are near-Earth like and generally habitable. However, they come in a wide variety of subtypes and compositions. The criteria for a Minshara class is that it must have a breathable atmosphere for baseline humanoid life, must have tolerable temperate zones conducive to plant and animal life, and must have liquid water to sustain biological life forms. Most Minshara class worlds exist in the "Goldilocks Zone" of a parent star, a swath of potential orbits that allow for liquid water.

Class O (Oceanic)

Class O planets have all the elements conducive to life as most humanoids understand it. The main criteria for Class O status is that 85% or more of the planet is covered in water. Such worlds vary widely but otherwise meet Minshara requirements. Such worlds are different than Class W worlds- they are terrestrial worlds with rocky-metallic cores whereas Class W worlds are large bodies of differentiated liquids.

Habitable Class Subtypes

Not all Habitable worlds are the same, even within a classification. Vulcan is nothing like Earth and Earth is nothing like Qo'noS and Qo'noS is nothing like Orion. To differentiate from a baseline, Federation science uses subtypes. A world can have multiple subtypes, but probably no more than two. Vulcan, for example, is Xeri-Calidian- both Xeric and Calidian: it is hot and dry compared to the baseline Minshara.

Subtypes can also be used to differentiate a planet's deviation from the norm that may prove challenging for habitation. Class H worlds with a subtype are classified according to their largest deviations from baseline- what makes them more difficult to inhabit. A Xeric Class H world is very dry compared to a Xeric Class M, for example- but still probably has enough water somewhere to be partially habitable.

Aestian

Aestian worlds have strong, often varied tidal forces. This can come from the unusually active movement of magma near the crust of the oceans which causes heat swells, or it could be the effect of a Trojan planet, a large moon, multiple moons, or the habitable body itself being a moon and being affected by its parent's gravity. It could also be that the planet is affected by the passing orbit of another, much larger planet's gravity. When the two worlds are closer, gravity affects the tides. Aestian worlds have periods that ocean or large lake water may intrude deeply into lowlands only to retreat and expose kilometers of seabed for hours at a time. Aestian worlds with multiple moon may have strange, varying tides multiple times a day as different moons affect the planet.

Altumian

An Altumian world has unusually deep oceans or other bodies of water. These water bodies can plunge even dozens of kilometers under the surface and lead to some radically different hydrochemical compositions, pressures, and oxygenation levels. Life may or may not be able to develop in such depths. These vast depths can affect the planet's climate in a pronounced way.

Calidian

Kolar, a Calidian Subtype

Calidian world are hotter than the baseline model. On average the planet is warmer globally. This could be for various reasons- the planet is closer to its star, it more effectively transfers equatorial heat to the equator, it may have a lower surface, cloud or water albedo (how much light is absorbed vs. reflected back into space). Calidian worlds are not necessarily drier or more humid, they are only warmer. Most Calidian worlds lack glaciers (unless it has some truly massive mountains) and thus, stores of freshwater may have to originate from other sources.

Cyclical Calidian

Cyclical Calidian worlds are thought to be at or near a baseline of temperature, but their global temperatures are rising. This could be because of an aging star, variations in the star's output (a solar maximum), an alteration or variation in the planet's orbit, a change of the planet's albedo (such as by mass urbanization or drying out period), or increasing greenhouse effects. But the effect is either temporary (on a geological time scale- which could be thousands of years), or it could be a transition from a baseline model into a permanent Calidian subtype.

Planar

Ariannus, a Planar Subtype

Borderline Planets

"Borderline" Classes of Planetary Bodies

Borderline Planetary Classes

The Borderline classes of planets are survivable with technological gear or for short-term durations. Federation science recognizes some of these worlds as potentially habitable with technology or with planet-scale geo-engineering and atmospheric changes. But as they are now, they are too hostile for a typical humanoid to survive on for very long.

Uninhabitable Planets

Uninhabitable Classes of Planetary Bodies

Uninhabitable Planetary Classes

Uninhabitable planets are those that have very little to offer a typical oxygen-breathing, carbon-based life form. They lack almost all the ingredients necessary for such life to survive. The Federation does occasionally colonize such worlds, but these are enclosed facilities with biospheres sealed and independent of the surrounding planet. Examples of uninhabitable worlds would be Luna and Memory Alpha.

Class C (Carbonaceous)

The versatile qualities of carbon make carbon-dominated planets unlike those found with silica, iron-silicate, or water in their composition. Carbon is present in most worlds but when it dominates due to a lack of iron or silicate building materials, the result is uninhabitable- and extremely alien.

Carbon sublimates- it moves from solid straight to a gas- therefore only under extreme pressure and temperature would carbon gas behave like a liquid. Tectonic activity cannot happen within a carbon-based world- carbon does not form its own version of magma. Carbon is an active element that bonds with many other elements with ease, quickly fixing to the building block materials we recognize as necessary for life. At this level of atomic dominance, carbon forms compounds completely alien or inconducive to Human life. An irony, as most lifeforms in the known galaxy are carbon-based.

Carbon-dominated worlds almost never have expansive oceans or polar caps. Free carbon will bond with oxygen and hydrogen long before the latter can form water, resulting in methane, ammonia or carbon dioxide atmospheres. Very few carbon worlds have any appreciable level of free oxygen.

Class D (Dead, Dormant)

A Class D world is a "dead" or "dormant" planet that has never had all of the necessary ingredients to support life as Humanoid beings know it. They may possess some of the necessary elements- water ice, traces of oxygen, organic compounds- but not in abundance enough to support life in the long term. However, life may have existed or exists in transience as space-borne life that inhabits these bodies as a habitat. A "classic" Class D world is an asteroid, dead moon, or a "round rock in space."

Uninhabitable Class Subtypes

Post-Archaean

A Post-Archaean world is one that has left the Class E protoplanetary types. The planet is no longer collecting material through accretion or heavy bombardment from accretion disk materials. Post-Archaean bodies are still extremely young. They may or may not be achieving hydrostatic equilibrium (a spherical shape) and have probably differentiated (if they have sufficient mass and material). Their cores are probably still molten or semi-molten, they may still have their primordial atmospheres and they may still have some volcanism. However, a Post-Archaean body does not have the ingredients to push it into the Borderline or Habitable categories.

Hostile Planets

Hostile Classes of Planetary Bodies

Hostile Planetary Classes

Hostile worlds are not merely uninhabitable- they are a challenge (or even impossible) for advanced technology to keep a humanoid alive and safe. Such worlds are so alien to the humanoid condition that their environments may not be accessible with current technology. However, a number of Hostile planet types are known to exhibit life- but not life with any relation or similarity to most humanoids. Perhaps the most infamous Hostile wold is the Class-Y Tholian homeworld.

Class E (Elastic/Exothermic)

Class E worlds can theoretically be found throughout a solar system, though the vast majority will be located in the terrestrial, rocky zones of the inner system. A broad category, Class E covers very young worlds which will reclassify into any number of planetary types, but Class E also includes some perpetually resurfacing, heavily bombarded worlds- and worlds simply so close to their stars that their surfaces remain partially or completely molten. Some Class E worlds are beginning differentiation through pressure, while others may have active, roiling molten cores that have not yet calmed enough to allow a continuous rocky surface. The defining characteristic of Class E planet is persistent, widespread lava and magma activity on the surface.

Class T (Toxic)

Toxic worlds are rocky, terrestrial bodies which are not conducive to life as Humans and most humanoids understand it. They have geological or atmospheric chemistries that are damaging, harmful, or lethal to most known life forms and their technology. Life has been found on such worlds (such as atmospheric archaeobacteria on Venus) but it is seldom recognized as compatible with a life matrix Humans are a part of. Toxic worlds vary widely, classified by their compositional elements more than the features of their terrain. Class T worlds can be found in every orbital zone around a star, but begin life as terrestrial (rocky) bodies. They may have thick or thin atmospheres and may or may not have metallic cores enough to generate a magnetic field.

Class J and N Subtypes

Hot Zone Class

There are two types of Hot Zone Jovians: Class J Migrants who partially or fully formed in the outer system and moved into the inner system. The second is a Class J Native, a world that somehow formed in the inner system and remained there.

Carbonized

A native Class J type.

Coronal/Icarian

A migrated Class J type.

Metallicized/Hephaestan

A native Class J type.

Silicated

A native Class J type.

Thermal/Daedalan

A migrated Class J type.

Planet Size and Mass Classes

Terrestrial Classes

Class 2

A Class Two terrestrial has achieved Hydrostatic Equilibrium (it is round or spheroid, though its spin may make it oblate) and has sufficient mass to have gravitationally differentiated its materials- a core composed of heavier materials than those forming a crust. Most Class 2 bodies are the size of Ceres- beginning at around 500 km in diameter- up until roughly the size of Earth's Moon. Young Class 3 planets may have molten interiors. Mature or aging Class 2 bodies are probably geologically dead. They do not have enough of an internal heat mechanism to keep a molten core. Some Class 2 bodies made up of lighter materials could be subject to tidal heating forces when around a large planet or are near a star. Its interior is kept slushy or partially liquid by external gravitational forces acting upon it.

Class 3

A Class Three terrestrial has achieved Hydrostatic Equilibrium (it is round or spheroid, though its spin may make it oblate) and has sufficient mass to have gravitationally differentiated its materials- a heavy metallic core and lighter materials and minerals forming a crust. Most Class 3 bodies are less than the size of Earth's Moon- beginning at around 2,500 km in diameter. Young Class 3 planets may still generate magnetic fields and have molten interiors. Mature or aging Class 3 bodies do not have sufficient self-generated internal heat convection to maintain geological processes- they are usually not seismic or volcanic. Their inert (or mostly inert) cores produce little to no magnetic field. A Class 3 may be subject to tidal heating forces from a very large planet (in the case of a moon) or close proximity to a star that flexes the insides like a raw egg. Luna and Mercury are Class 3.

Class 4

Mars is a Class 4 terrestrial.

Class 5

Earth is a Class 5 terrestrial.