Planetary Classification

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Division of Arts & Sciences Major Science Science Resources Chemicals & Particles Planetary Classification Planetary Development Scale Stellar Cartography Star Classification Science Facilities Academy Curriculum Alien Races Command Engineering Flight Control (Navigation) Medicine Miscellaneous Security & Tactical Edit this nav Natural characteristics of planets, such as age, mass and distance from their sun, place them in 20 naturally bounded classes which have been assigned an arbitrary alphabetic designation. Location refers to the planet's relative distance from its primary star (Hot zone is closest, then Ecosphere, then Cold Zone). Depending on the star's magnitude and amount of energy it radiates, the distances of each zone from the star will vary. A planet's mass determines its internal heat generation and - in combination with its zone - its ability to hold an atmosphere. Some planets pass through distinct stages as they form and age, which may put them in separate classes. Evolution refers to the geological evolutionary process of the planetary body itself. It does not refer to life-form evolution. Class A Class A planets are small, typically 1 to 1/10 the mass of Earth, and are in their sun's cold zone. They are newly formed and their surfaces are still molten. Their atmospheres still retain many hydrogen compounds, as well as reactive gases and rock vapors. These planets will cool, becoming Class C. Type: Geothermal Age: 0 - 2 billion years Diameter: 1,000 - 10,000 km Location: Ecosphere / Cold Zone Surface: Partially molten Atmosphere: Primarily hydrogen compounds Evolution: Cools to become Class C Life-Forms: None Examples: Gothos Class B Class B planets are small, typically 1/10 the mass of Earth, and are in their sun's hot zone. Due to a combination of weak gravity and strong solar radiation, their atmospheres are very tenuous, with few chemically active gases, and their surfaces are extremely hot. Type: Geomorteus Age: 0 - 10 billion years Diameter: 1,000 - 10,000 km Location: Hot Zone Surface: Partially molten, high surface temperature Atmosphere: Extremely tenuous, few chemically active gases Evolution: n.a. Life-Forms: None Examples: Mercury Class C Class C planets are small, typically 1 to 1/10 the mass of Earth and are in their sun's cold zone. Due to a combination of low solar radiation and little heat, their atmospheres are permanently frozen. Type: Geoinactive Age: 2 - 10 billion years Diameter: 1,000 - 10,000 km Location: Ecosphere / Cold Zone Surface: Low surface temperature Atmosphere: Frozen Evolution: n.a. Life-Forms: None Examples: Pluto, Psi 2000 Class D Class D planets are small, typically 1 to 1/100 the mass of Earth, or less. Due to low gravity, they have lost their atmospheres. Their surfaces, directly exposed to radiation and meteor impact, are typically lifeless and heavily cratered. Type: Asteroid / Moon Age: 2 - 10 billion years Diameter: 100 - 1,000 km Location: Hot Zone / Ecosphere / Cold Zone; found primarily in orbit of larger planets or in asteroid fields Surface: Barren and cratered Atmosphere: None or very tenuous Evolution: n.a. Life-Forms: None Examples: Moon (Sol IIIa), Lunar V (Bajor VIIe) Class E Class E planets are typically of about the mass of Earth and are in their sun's habitable zone. They are newly formed, and their surfaces are still molten. Their atmospheres still retain many hydrogen compounds, as well as reactive gases and rock vapors. These planets will cool, becoming Class F. Type: Geoplastic Age: 0 - 2 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Molten, high surface temperature Atmosphere: Hydrogen compunds and reactive gases Evolution: Cools to become Class F Life-Forms: Carbon-cyle (ie. Excalbian) Examples: Excalbia Class F Class F planets are typically about the mass of Earth and are in their sun's habitable zone. They are recently formed, and their surfaces are thin. Their atmospheres still contain some hydrogen compounds. These planets will cool further, becoming Class G. Type: Geometallic Age: 1 - 3 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Volcanic eruptions due to molten core Atmosphere: Hydrogen compounds Evolution: Cools to become Class G Life-Forms: Silicon-based (ie. Horta) Examples: Janus IV Class G Class G planets are typically about the mass of Earth and are in their sun's habitable zone. They are younger than the Earth, and their surfaces are still crystallizing. Their atmospheres retain small amounts of toxic gases. As these planets continue cooling they may become other classes. Type: Geocrystalline Age: 3 - 4 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Still crystallizing Atmosphere: Carbon Dioxide, some toxic gases Evolution: Cools to become Class K, L, M, N, O, or P Life-Forms: Primitive single-celled organisms Examples: Delta Vega Class H Class H planets are typically about the mass of Earth and are in their sun's hot zone. Their gravity allows them to retain an atmosphere of heavy gases and metal vapors, but due to strong solar radiation, their surfaces are very hot. Type: Desert Age: 4 - 10 billion years Diameter: 8,000 - 15,000 km Location: Hot Zone / Ecosphere / Cold Zone Surface: Hot and arid, little or no surface water Atmosphere: May contain heavy gases and metal vapors Evolution: n.a. Life-Forms: Drought- and radiation-resistant plants, animal life Examples: Rigel XII, Tau Cygna V Class I Class I planets (Gas Supergiants) are very large, typically 300 to 1,000 times the mass of Earth, and are their sun's cold zone. Low solar radiation and high gravity have allowed them to keep thick atmospheres of hydrogen compounds. High core temperatures cause them to radiate heat. Type: Gas Supergiant Age: 2 - 10 billion years Diameter: 140,000 - 10 million km Location: Cold Zone Surface: Tenuous, comprised of gaseous hydrogen and hydrogen compounds; radiates heat Atmosphere: Zones vary in temperature, pressure and composition; water vapor may be present Evolution: n.a. Life-Forms: Unknown Examples: Q'tahL, Jupiter Class J Class J planets (Gas Giants) are large, typically 10 to 100 times the mass of Earth, and are in their sun's cold zone. Low solar radiation and high gravity have allowed them to keep thick atmospheres of hydrogen and hydrogen compounds. Type: Gas Giant Age: 2 - 10 billion years Diameter: 50,000 - 140,000 km Location: Cold Zone Surface: Tenuous, comprised of gaseous hydrogen and hydrogen compounds; radiates some heat Atmosphere: Zones vary in temperature, pressure and composition Evolution: n.a. Life-Forms: Hydrocarbon-based (Jovian) Examples: Saturn Class K Class K planets are small, typically 1 to 1/10 the mass of Earth, and are in their sun's habitable zone. Due to weak gravity, their atmospheres are tenuous, but water is usually present. Type: Adaptable Age: 4 - 10 billion years Diameter: 5,000 - 10,000 km Location: Ecosphere Surface: Barren, little to no surface water Atmosphere: Thin, mostly carbon dioxide Evolution: n.a. Life-Forms: Primitive single-celled organisms; adaptable for humanoid colonization through the use of pressure domes Examples: Mars, Mudd Class L Class L planets are small, typically 1 to 1/10 the mass of Earth, and are in their sun's habitable zone. Their atmospheres are closer to breathable, and water is usually present if hard to find. Type: Marginal Age: 4 - 10 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Rocky and barren, little surface water Atmosphere: Oxygen / argon, high concentration of carbon dioxide Evolution: n.a. Life-Forms: Limited to plant life; suitable for humanoid colonization Examples: Indri VIII Class M Class M planets are typically about the mass of Earth and are in their sun's habitable zone. Their atmospheres contain significant oxygen, liquid water is a significant surface feature, and lifeforms are generally abundant. With more water they would be class N. Type: Terrestrial (Minshara Class) Age: 3 - 10 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Surface water abundant; if water or ice covers more than 80% of surface, planet is considered Class O or Class P Atmosphere: Nitrogen, oxygen, trace elements Evolution: n.a. Life-Forms: Extensive vegetation, animal life, humanoids Examples: Earth, Vulcan, Cardassia Prime Notes: Class M planets can vary widely in color, cloud cover, and overall appearance. Most Class M planets are characterized by a relatively thin, techtonically active crust floating on a molten rock mantle, which in turn surrounds a liquid metal outer core and a solid inner core composed of metal crystals. Class N Class N planets are typically of about the mass of Earth and are in their sun's habitable zone. Due to the greenhouse effect of dense atmospheres heavy in carbon dioxide, their surfaces are very hot and water is found in vapor form, if present at all. Type: Reducing Age: 3 - 10 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: High surface temperature due to greenhouse effect; water exists only as vapor Atmosphere: Extremely dense, carbon dioxide and sulfides Evolution: n.a. Life-Forms: Unknown Examples: Venus Class O Class O planets are typically about the mass of the Earth and are in their sun's habitable zone. Their atmospheres contain significant oxygen, liquid water covers over 80 percent of the surface. Lifeforms are generally abundant. With less water they would be Class M. Type: Pelagic Age: 3 - 10 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Liquid water covers 80% or more of surface area Atmosphere: Nitrogen, oxygen, trace elements Evolution: n.a. Life-Forms: Aquatic vegetation, animal life, humanoids Examples: Argo, Alpha Centauri IV Class P Class P planets are typically about the mass of the Earth and are in their sun's habitable zone. Their atmospheres contain significant oxygen, water ice covers over 80 percent of the surface. Lifeforms are generally rare, but resilient. With a higher temperature they could be Class M or O. Type: Glaciated Age: 3 - 10 billion years Diameter: 10,000 - 15,000 km Location: Ecosphere Surface: Water ice covers 80% or more of surface area Atmosphere: Nitrogen, oxygen, trace elements Evolution: n.a. Life-Forms: Hardy vegetation, animal life, humanoids Examples: Exo III Class Q Type: Variable Age: 2 - 10 billion years Diameter: 4,000 - 15,000 km Location: Hot Zone / Ecosphere / Cold Zone Surface: Ranges from molten to water and/or carbon dioxide ice, due to eccentric orbit or variable output of star Atmosphere: Ranges from tenuous to very dense Evolution: n.a. Life-Forms: Unknown Examples: Genesis Planet Class R Type: Rogue Age: 2 - 10 billion years Diameter: 4,000 - 15,000 km Location: Interstellar space, cometary halos Surface: May be temperate due to geothermal venting Atmosphere: Primarily volcanic outgassing Evolution: n.a. Life-Forms: Non-photosynthetic plants, animal life Examples: Dakala Class S-T Class S and T planets (Gas Ultragiants) are very large, typically 10,000 times the mass of Earth, and are in their sun's cold zone. Low solar radiation and high gravity have allowed them to keep thick atmospheres of hydrogen and hydrogen compounds. High core temperatures cause them to radiate visible light. These are the largest possible planets, as more massive bodies generate enough core heat to initiate fusion reactions and become stars. Type: Ultragiant Age: 2 - 10 billion years Diameter: 10 - 50 million km (Class S); 50 - 120 million km (Class T) Location: Cold Zone Surface: Tenuous, composed of gaseous hydrogen and hydrogen compounds; radiates considerable heat Atmosphere: Zones vary in temperature, pressure and composition; water vapor may be present Evolution: n.a. Life-Forms: Unknown Examples: Unknown Class Y Class Y planets (Demon Class) are typically about the mass of earth and are in their sun's habitable zone. Their gravities are about Earth's. Their atmospheres are full of toxic gases, radiation, etc. Their atmospheres release spikes of thermeonic (ther-me-on-ick) radiation. The temperature on the planet is over 500 degrees Kelvin. Type: Demon Age: 2 - 10 billion years Diameter: 10,000 - 50,000 km Location: Hot Zone / Ecosphere / Cold Zone Surface: Temperature can exceed 500ºK Atmosphere: Turbulent, saturated with toxic chemicals and thermionic radiation Evolution: n.a. Life-Forms: Mimetic (Delta Quadrant) Examples: "Class-Y Planet" in Delta Quadrant Notes: Classes X, Y, and Z are reserved for planets with environments particularly hostile to humanoid life. NOTE: All information above is taken from Geoffrey Mandel's "Star Trek Star Charts: The Complete Atlas of Star Trek" available from Pocket Books.