2.2 Planetary Classification

Created by on 21 Feb 2016 @ 12:51pm

Planetary Classification

A planet is a celestial body in orbit around a star or stellar remnants that has sufficient mass for self-gravity and is nearly spherical in shape. A planet must not share its orbital region with other bodies of significant size (except for its own satellites), and must be below the threshold for thermonuclear fusion of deuterium.

If a celestial body meets those requirements, it is considered a planet; at that point, the planet is further classified by its atmosphere and surface conditions into one of twenty-two categories.




Class A – Geothermal


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.


Age: 0-2 billion years old
Diameter: 1.000-10.000 km
Location: Hot Zone/Ecosphere/Cold Zone
Surface: Partially molten, very hot
Atmosphere: Carbon dioxide, hydrogen
Evolution: Cools to become Class C
Lifeforms: None
Examples: Gothos

Class B - Geomorteus


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.


Age: 0-10 years old
Diameter: 1.000-10.000 km
Location: Hot Zone
Surface: Partially molten
Atmosphere: Extremely tenuous
Evolution: N/A
Lifeforms: None
Examples: Mercury, Nebhilum

Class C – Geoinactive


When all volcanic activity on a Class A planet ceases, it is considered Class C. Essentially dead, these small worlds have cold, barren surfaces and possess no geological activity.


Age: 2-10 billion years old
Diameter: 1.000-10.000 km
Location: Hot zone/Ecosphere/Cold Zone
Surface: Barren
Atmosphere: None
Evolution: N/A
Lifeforms: None
Examples: Psi 2000

Class D – Dwarf


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.


Age: 2-10 billion years old
Diameter: 100-4.000 km
Location: Hot Zone/Ecosphere/Cold Zone
Surface: Barren and cratered
Atmosphere: None or very tenuous
Evolution: N/A
Lifeforms: None
Examples: Pluto, Ceres, Eredes-II

Class E – Geoplastic


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. As the surface cools, the core and crust begin to harden, and the planet evolves into a Class F world.


Age: 0-2 billion years old
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: Molten, high surface temp.
Atmosphere: Hydrogen compounds
Evolution: Cools to become Class F
Lifeforms: Carbon cycle
Examples: Excalbia

Class F – Geometallic


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.


Age: 1-3 billion years old
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: Volcanic, barren
Atmosphere: Carbon dioxide, ammonia, methane
Evolution: Cools to become Class G
Lifeforms: Bacteria
Examples: Janus IV

Class G – Geocrystalline


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.


Age: 3-4 billion years old
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: Rocky, mostly barren
Atmosphere: Carbon dioxide, oxygen, nitrogen
Evolution: Cools to Class H, K, L, M, N, O, P
Lifeforms: Vegetation, simple organisms
Examples: Delta Vega

Class H – Desert


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. 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.


Age: 4-10 billion years old
Diameter: 8.000-15.000 km
Location: Ecosphere
Surface: Hot, arid; >20% surface water
Atmosphere: Oxygen, nitrogen, argon, metals
Evolution: N/A
Lifeforms: Drought-resistant plants/animals
Examples: Dimovius, Nimbus III, Corneria, Ocampa

Class I - Ice Giant (Uranian)


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.


Age: 2-10 billion years old
Diameter: 30.000-100.000 km
Location: Cold Zone
Surface: Rock, ice, methane, ammonia
Atmosphere: Hydrogen, helium
Evolution: N/A
Lifeforms: None
Examples: Uranus, Neptune, Q’tahL

Class J - Gas Giant (Jovian)


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.


Age: 2-10 billion years
Diameter: 50.000-500.000 km
Location: Cold Zone
Surface: Liquid metallic hydrogen
Atmosphere: Hydrogen, helium
Evolution: N/A
Lifeforms: None
Examples: Jupiter, Saturn

Class K – 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.


Age: 4-10 billion years old
Diameter: 5.000-10.000 km
Location: Ecosphere
Surface: Barren, little surface water
Atmosphere: Thin, mostly carbon dioxide
Evolution: N/A
Lifeforms: Primitive single-cell organisms
Examples: Mars, Mudd

Class L – Marginal


Class L planets are 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.


Age: 4-10 billion years
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: Rocky; little surface water
Atmosphere: Argon, oxygen, trace elements
Evolution: N/A
Lifeforms: Limited to vegetation
Examples: Alarin III, Ciden II, Indri VII

Class M – Terrestrial


Class M planets are robust and varied worlds composed primarily of silicate rocks, and are highly suited for humanoid life. To be considered Class M, between 20% and 80% of the surface must be covered in water; it must have a breathable oxygen- nitrogen atmosphere and temperate climate.


Age: 4-10 billion years
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: Temperate climate; Abundant surface water
Atmosphere: Nitrogen, oxygen, argon
Evolution: N/A
Lifeforms: Vegetation, animal & humanoid
Examples:Earth, Cardassia, Kalidar, Vulcan

Class N – Reducing


Though frequently found in the Ecosphere, Class N planets are nonconductive 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.


Age: 3-10 billion years
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: Barren; high temperatures
Atmosphere: Carbon dioxide and sulphides
Evolution: N/A
Lifeforms: None
Examples: Venus

Class O – Pelagic


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.


Age: 3-10 billion years
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: 80% water, archipelagos
Atmosphere: Nitrogen, oxygen, argon
Evolution: N/A
Lifeforms: Cetacean, humanoid, animal
Examples: Azati Prime, Ka’Tula Prime, Zirat

Class P – Glaciated


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.


Age: 3-10 billion years
Diameter: 10.000-15.000 km
Location: Ecosphere
Surface: 80% frozen water, cold
Atmosphere: Nitrogen, oxygen
Evolution: N/A
Lifeforms: Vegetation, animal & humanoid
Examples: Andoria, Exo III, Rebena Te Ra, Rura Penthe

Class Q – Variable


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 kilometres of each other, while glaciers can simultaneously lie very near the equator. Given the constant instability, it is virtually impossible for life to exist on Class-Q worlds.


Age: 2-10 billion years
Diameter: 4.000-15.000 km
Location: Hot Zone/Ecosphere/Cold Zone
Surface: Molten, frozen, jungle, etc
Atmosphere: Very tenuous to very dense
Evolution: N/A
Lifeforms: None
Examples: Genesis Planet

Class R – Rogue


A Class R planet usually forms within a star system, but at some point in its evolution, the planet is expelled, likely the result of a catastrophic asteroid impact. 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.


Age: 2-10 billion years
Diameter: 4.000-15.000 km
Location: Interstellar space
Surface: Temperate
Atmosphere: Primarily volcanic outgassing
Evolution: N/A
Lifeforms: Non-photosynthetic plants, animals
Examples: Dakala, Veneihm, Founders’ Homeworld (prior to 2371)

Class S - Gas Supergiant


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.


Age: 2-10 billion years
Diameter: 0, 5 million-100 million km
Location: Cold Zone
Surface: Liquid metallic hydrogen
Atmosphere: Hydrogen and helium
Evolution: N/A
Lifeforms: None
Examples: Tethe-Alla IV

Class U - Gas Ultragiant


Class T 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. However, Class T planets occasionally form within a star system's Hot Zone. 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.


Age: 2-10 billion years
Diameter: 50 million-120 million km
Location: Hot Zone/Cold Zone
Surface: Liquid hydrogen, deuterium
Atmosphere: Hydrogen and helium
Evolution: Can evolve into red dwarf stars
Lifeforms: None
Examples: Diadem, Tethe-Alla V

Class X – Chthonian


Class X planets are the result of a failed Class T planet in a star system's Hot Zone. 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.


Age:2-10 billion years
Diameter: 1.000-10.000 km
Location: Hot Zone
Surface:Barren, extremely hot
Atmosphere: None
Evolution: N/A
Lifeforms: None
Examples: Osirus

Class Y – Demon


Perhaps the most environmentally unfriendly planets in the galaxy, Class Y planets are toxic to life in every way imaginable. The atmosphere is saturated with toxic radiation, temperatures are extreme, and atmospheric storms are amongst the most severe in the galaxy, with winds in excess of 500 kph.


Age: 2-10 billion years
Diameter: 10.000-15.000 km
Location: Hot Zone
Surface: Barren; extremely hot
Atmosphere: Turbulent, with toxic radiation
Evolution: N/A
Lifeforms: Mimetic
Examples: Planet Hell (Delta Quadrant)




This information comes from the website of Star Trek the Final Frontier.


Categories: Information Databank