Planetary classification

The following is a chart of the standard planetary classification system used by the United Federation of Planets.

Planetary Classification Chart

Class	Description	Diameter	Zone	Surface	Atmosphere	Examples	Notes
Class A	geothermal	1,000 - 10,000 km	Ecosphere / Cold Zone	partially molten, volcanic	hydrogen compounds	Gothos, Io	cools to become Class C (FASA: Class H)
Class B	geomorteus	1,000 - 10,000 km	Hot Zone	partially molten, high temperature	extremely tenuous, chemically inactive	Mercury	(FASA: Class I)
Class C	geoinactive	1,000 - 10,000 km	Ecosphere / Cold Zone	low temperature	partially frozen	Pluto
Class D	dwarf / asteroid / moon	100 - 1,000 km	Hot Zone / Ecosphere / Cold Zone	barren and cratered metallic, iron-nickel-silicate	none or very tenuous	Luna, Regula, Weytahn	generally found in orbit of larger planets or in asteroid fields (FASA: Class D or Class J)
Class E	geoplastic	10,000 - 15,000 km	Ecosphere	molten, high temperature	hydrogen compounds and reactive gasses	Excalbia	surface cools to become Class F (FASA: Class I)
Class F	geometallic	10,000 - 15,000 km	Ecosphere	volcanic	hydrogen compounds	Janus VI	molten core cools to become Class G
Class G	geocrystalline	10,000 - 15,000 km	Ecosphere	crystalizing	carbon dioxide, some toxic gasses, possible oxygen and nitrogen	Delta Vega	evolves into Class H, K, L, M, O or P (FASA: Class F)
Class H	desert	8,000 - 15,000 km	Hot Zone / Echosphere / Cold Zone	hot and arid, little or no water	may contain heavy gasses and metal vapors	Rigel XII, Tau Cygna V	(FASA: Class G)
Class I	ice giant	25,000 - 100,000 km	Cold Zone	tenuous, heavier gasses surrounding an ice or iron core	variable pressure and composition, may contain ammonia, methane, water vapor, carbon, or other heavy gasses, with little hydrogen or helium	Neptune, Uranus	"Uranian" giants (FASA: Class B)
Class J1	gas giant	50,000 - 140,000 km	Cold Zone	tenuous, comprised of gaseous hydrogen and hydrogen compounds, radiates heat	variable pressure and composition	Jupiter, Saturn, Ba'Syladon	"Jovians" are often remnants of a failed star (FASA: Class A)
Class J2	gas giant	50,000 - 140,000 km	Hot Zone	tenuous, lower density than Class J	variable pressure and composition		"Hot Jovians", extremely close to primary, tidally locked; possibly failed brown dwarfs
Class K	adaptable	5,000 - 10,000 km	Ecosphere	barren, little or no water	thin, mostly carbon dioxide	Mars, Mudd
Class L	marginal	10,000 - 15,000 kkm	Ecosphere	rocky and barren, little water	oxygen/argon, high concentration of carbon dioxide	Gateway, Indri VIII, Kaijur XII, Mestiko
Class M	terrestrial	10,000 - 15,000 km	Ecosphere	abundant water	nitrogen, oxygen and trace elements	Andoria, Earth, Vulcan, Qo'noS,Cardassia Prime
Class N1	hot reducing	10,000 - 15,000 km	Ecosphere, Hot Zone	extreme high temperature	extremely dense, carbon dioxide and sulfides	Medusa,Venus, Tholia (possibly)	(FASA: Class C)
Class N2	cold reducing	3,000 - 10,000 km	Cold Zone	extreme low temperature, liquid methane lakes, ice	extremely dense, nitrogen, methane	Titan (pre-terraforming)
Class O	pelagic	10,000 - 15,000 km	Ecosphere	liquid water covers 80% or more; few, small landmasses	nitrogen, oxygen and trace elements	Argo, Chal, Droplet, Tazi Prime	(FASA: Class N)
Class P	glaciated	10,000 - 15,000 km	Ecosphere, Cold Zone	water ice covers 80% or more; possible equatorial habitable zone	nitrogen, oxygen and trace elements	Exo III, Psi 2000, Rigel X	Sometimes former Class M or N2 or P worlds
Class Q	variable	4,000 - 15,000 km	Hot Zone / Ecosphere / Cold Zone	various	tenuous to very dense	Crateris, Delta Canaris IV, Genesis Planet, Remus, Vor II	Extremely variable conditions, sometimes partially habitable, sometimes home to extremophiles, sometimes unstable
Class R	rogue	4,000 - 500,000 km	Interstellar space or cometary halos	various - terrestrial or gaseous	tenuous to very dense	Dakala	"Rogue" planets, extremely variable in composition
Class S	gas supergiant	140,000 - 10mil km	Cold Zone	tenuous, comprised of gaseous hydrogen and helium compounds, may radiate considerable heat	variable pressure and composition, may contain water vapor	Q'tahL	Includes "Class 9 gas giants"; failed protostars; depending on mass, could migrate and become a Hot Jovian, reduce into Class X, or ignite into a red dwarf (SC: "Class I")
Class T	gas ultragiant	10mil - 50mil km	Cold Zone	tenuous, comprised of gaseous hydrogen and helium compounds, may radiate considerable heat	variable pressure and composition, may contain water vapor	Kern III	failed protostars; depending on mass, could migrate and become a Hot Jovian, reduce into Class X, or ignite into a red dwarf (SC: "Class S")
Class U	gas ultragiant	50mil - 120mil km	Cold Zone or Hot Zone	tenuous, hydrogen and helium compounds, may radiate considerable heat	variable pressure and composition, may contain water vapor	Beta Orionis VI, Deneb Kaitos VI	failed protostars; depending on mass, could migrate and become a Hot Jovian, reduce into Class X, or ignite into a red dwarf (SC: "Class T")
Class X	chthonian	1,000 - 10,000 km	Hot Zone	barren, rich in resources	none		leftover core of a former gas super- or ultragiant after migration into hot zone, usually destroyed by parent star
Class Y	demon	10,000 - 50,000 km	Hot Zone / Ecosphere / Cold Zone	barren, rocky or molten iron, deuterium and/or silicate; temperature can exceed 500 K	turbulent, saturated with toxic chemicals and therionic radiation	Nukara Prime, Tholia (possibly)	could support crystalline/silicon or biomimetic life

Notes

• This chart is mostly derived from classification system presented in Star Trek: Star Charts, and subsequently (mostly) adopted by canon, though some alterations have been made to incorporate additional data, including several sub-classes postulated by The Final Frontier fan fiction series. Notations have been made allowing conversion from the earlier classification system used by FASA and other earlier licensed sources.

External links

• Planetary classification article at Memory Alpha, the canon Star Trek wiki.
• Planetary classification article at Memory Beta, the non-canon Star Trek wiki.
• Planetary classification article at Star Trek Expanded Universe, the fanon and fanworks Star Trek wiki.