Planetary Classifications

Every planet in the galaxy has a set of characteristics that make it the unique world that it is. These characteristics help scientists to classify them under a set of categories as displayed below.


D class planets are most commonly found in the Ecosphere of a system but are not strictly limited to – they are found as well in the Hot and Cold Zones – they range between 5 to 10 thousand kilometres in diameter. They are barren and rocky, often possessing no atmosphere. Animal life is unable to form on D class planets. Depending on their proximity to a star, a D class may be hot and arid or cold and frozen. These planets can be made habitable by terraforming as was the case with Weytahn by the Andorians during the 2050s.

Example: Mercury


H class worlds are found in the Ecosphere of a system and range between 5 to 15 thousand kilometres in diameter. Their atmospheres may be rich in oxygen, carbon dioxide, or another common gas. The planet holds little to no surface water; the entire world a sea of dunes and sand and is sustained to be very dry, hot, and barren. Little life is known to inhabit these worlds. They are inhabitable by either pressure domes or colonies, depending on the atmospheric content, through supply replenishment; use of aquifiers is necessary.

Example: Tau Cygna V


Typically located in a system’s Cold Zone, J classes are uninhabitable. Also known as Gas Giants due to their general lack of a solid surface, their dense atmospheres are most commonly made of gases such as ammonia, ethane, fluorine, helium, hydrogen, and methane. Windspeeds average 2000 kilometres per hour, however the USS Defiant in 2372 recorded windspeeds of 10 thousand kilometres per hour on an unnamed J class when rescuing a Karemma vessel. The diameter of a J class ranges between 50 and 140 thousand kilometres, therefore they possess a very strong gravitational pull which results in dozens to hundreds of planetoid moons in their orbits. Rings made up of spacial debris caused by lunar collisions and the collection of space dust and ice are common. As observed by the USS Enterprise-D in 2369, the collision of two J class planets can ignite the birth of a star. A single J class does not have sufficient resources or energy to cause fission resulting the creation of a star, however when two collide their combined resources is enough to do so.

Examples: Jupiter, Saturn, Betelgeuse III


Similar to a J class, the Class 6 is distinctly different in that is has a global ocean composed of liquid gases beneath its layered atmosphere. These oceans are known to be made of water-ammonia and hydrogen-methane.

Examples: Uranus, Neptune


K class planets are located within the Ecosphere of a system and range 5 to 15 thousand kilometres in diameter. They have very thin atmospheres usually composed of carbon dioxide, nitrogen, and/or argon. Their weak magnetic fields allow large quantities of solar radiation to reach the surface and heat to escape back into space. K class surfaces are barren, often cold, and cannot support animal life as there is commonly no liquid water or too little to sustain vegetation. Colonisation is possible by the use of pressure domes.

Examples: Mars, Mudd


L class planets are located within the Ecosphere of a system and range between 10 to 15 thousand kilometres in diameter. The atmosphere is mostly made up of oxygen and argon but also has a very high concentration of carbon dioxide. Unlike the M class, the L class has little water and vegetation, but it could thrive if conditions were set properly. Life tends to be predominantly plant life with few animals. Most L classes are suitable for humanoid colonisation.

Example: Indri III


M class planets are located within the Habitable Zone of a system and range between 10 to 15 thousand kilometres in diameter; they are the rarest class of planet. Their atmospheres are rich in nitrogen and oxygen. Water and animal lifeforms are very common due to an overabundance of marine and surface vegetation which thrive on the planet’s temperate climate. M class planets are home to the vast majority of sentient and technologically advanced species, especially humanoids. At least 75% of the planet is covered in liquid water.

Examples: Earth, Vulcan, Romulus, Cardassia Prime, Bajor, Qo’Nos


N class planets are located within the Ecosphere of a system and range 5 to 15 thousand kilometres in diameter. They have very thick, dense, atmospheres carbon dioxide as well as sulfides that stage an irreversible and constantly worsening greenhouse effect. This causes an extremely high surface temperature that enables water to exist only in the form of vapour. Abundant volcanism is very common. Animal life is unable to exist and colonization is not possible.

Examples: Venus


P class planets are found in the Ecosphere of a system and range between 10 to 15 thousand kilometres in diameter. A planet falls under this classification when its surface is 80%+ water ice and its atmosphere mainly consists of nitrogen and oxygen. Animal and humanoid life forms are usually common and so is rugged tundra-like vegetation.

Examples: Andor, Exo III


The T class Super or Ultra Giant is a Gas Giant on the verge of becoming a star. It may also be the immediate result of two colliding J class planets if star birth does not immediately occur thereafter. These planets are hot enough to appear to be molten or burning and produce their own dim light. Moons orbiting this planet may become globules of liquid if once frozen or may singe their atmospheres. These extreme heats, however, only occur in the final stages of a Super Giant’s. Before becoming a star it is also known as a Brown Dwarf. The Super Giant is the largest of all known planetary classes, homing in with a diameter anywhere between 350 to 700 thousand kilometres. In 2375, the USS Voyager encountered a Super Giant in the Delta Quadrant that had radiogenic rings.


Y class planets can be found anywhere within a system and they range between 10 to 15 thousand kilometres in diameter. A planet is classified as a Demon when their atmospheres are toxic, temperatures are above 500 Kelvin, and they give off bursts of thermionic radiation. Entering orbit of a Y class planet can be harmful to crew and ship alike.

In 2374, the USS Voyager was forced to land on a Y class planet on its return voyage from the Delta Quadrant to retrieve desperately needed deuterium. It was discovered that the deuterium was inside a bio mimetic lifeform called ‘Silver Blood’ which created a duplicate of Voyager and its crew. The duplicate was ultimately destroyed a year later in 2375.


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