This classification system is adapted from the Planetary Classification List of John M. Dollan.

Asteroidal Class

Size range 5 meters to 50 kilometers. Barring dust and rock chips, these are the smallest planetary bodies. Commonly known as asteroids and comets, these chunks of rock and ice are every bit as varied in their form as are the larger planets.







Classically called M-class asteroids, these asteroids are composed almost entirely of nickel-iron. They represent a source of great mineral wealth, and are often the sites of mining operations by colonists. Because of the relative scarcity of such heavy elements in the pre-solar nebula, these are typically the largest metal rich bodies to be found in the solar system.




Silicaceous asteroids are mainly metallic iron and magnesium-silicates in composition. Quite common, these bodies are sometimes mined, but more often used as bases or refineries for other materials. Many times these are fragments from larger bodies, even to the point of bing little more than  piles of "rubble", loose agrgates of material that have been drawn back together by gravity after the initial object was broken up.

4179 Toutatis



Rich in carbon, these bodies are the most similar in composition to the star system's primary sun, and thus represent nearly pristine relics from the formation of that solar system. They are also quite rich in water, and can be mined for this item, which is trapped within the rock of the asteroid itself.




The most rare of the Asteroidal Class, these are fragments of old, disrupted bodies that at one time had enough mass for internal heat and volcanism to be generated. What remains is a small body with basaltic rock making up much of the composition. While it is extrememly rare for these to be the remains of a completely disrupted planet, they are often the remains of a world that was formed at the beginning of the solar system's formation, and later disrupted by planetesimal impact or extreme tidal disruption.

951 Gaspra

In the depths of near interstellar space, most star systems hold Kupier Belts or Oort Clouds. Here can be found the cometary reserves, frozen left overs from the formation of the solar system. Oortean bodies all originate from these regions, but may find themselves thrown into far different orbits over time. Though many tend to be discolored by interstellar radiation, their subsurface regions are untouched samples from the primordial nebulas that form solar systems.

Halley's Comet

Planetesimal Class

Size range 51 kilometers to 1,000 kilometers. Often considered the building blocks of larger planetary bodies, these worlds can survive throughout a solar system's lifetime, mainly as larger sized asteroids. However, finding planetesimals in independant planetary orbits is just as common, and can represent "failed" planets from the formation process.







Metal dwarf...formed in the hottest part of the solar system, where all other materials have been driven off by the intense solar winds.  Uncommon in the smaller size ranges, they are quite rare in the larger sizes due to the scarcity of materials to begin with in the pre-solar nebula.




Rock dwarf

1 Ceres
4 Vesta
624 Hektor



Ice dwarf

2060 Chiron

Terrestrial Class

Size range 1,001 to 30,000 kilometers. These are the rocky planets, a deceptive name as not all of these worlds will be rocky. Their composition can be quite varied, as can their surface features and conditions. Earth is a terrestrial world, and in this Class is found all of the Gaian Type and Subtype worlds.







Volcano world...these planets are active geologically due to a variety of reasons.  Also, these planets may be of any age.  Early, still forming planets are often quite active, as are worlds that have grown close to their stars which have begun to swell into giants.  Extreme tidal flexing also is a large cause of activity.




Metal world...extremely rare, bordering on the impossible in the upper size ranges, due to the lack of material available in the pre-solar nebula.  Likely, these worlds can form only about large hot stars.




Rock world with an appreciable metal core




Rock world which is essentially dead



  Often times of smaller mass, these worlds are uninhabitable, and marked by vast expanses of open rock land or sands.  wind, for the most part, seems to be the dominant weathering mechanism.  Geological activity varies, but the older the world, the less active it is.  Atmospheres too will tend to thin the younger they are.  If a moon, these worlds may remain geologically active throughout its history, due to tidal flexing.
Geologically active, these Arean worlds can have substantial atmospheres, geochemical recycling processes, even open areas of water.  Life is indeed possible, though it is unlikely to develop very high.
Early Mars



"Fossilized" rock world...early in their history these worlds were marked by geological activity, substantial atmospheres, even the presence of liquid water and primitive life.  But, for a variety of reasons, these processes 'atrophied', leaving behind a planet with only signs of its past potential.  Life may remain in secluded and protected areas, but it is not a common occurrence.  These worlds are the best candidates for successful terraforming.

Epsilon III (Babylon 5)



Earth-like worlds...these planets share a common method of geologic, biologic, and atmospheric evolution.  Such planets have been divided up more than any other type, due to their extreme interest and importance to the colonizers of space.  In many cases, Subtypes have been created, whereas other planet Types would not be so delineated.
A young world with shallow oceans and a primitive atmosphere, and possibly the earliest life.

Early Earth



Less than 10% of the surface is covered with oceans.  Desert conditions prevail, and life may be quite limited.




Ten to 25% of the surface is ocean covered.  The climate is predominantly continental, and mainly desert conditions prevail.  The seas are typically very saline, and may be nearly uninhabitable in extreme cases.  Life is quite restricted.

Vulcan (from Star Trek)



Twenty-five to 50% of the surface is ocean covered.  The climate is predominantly continental, though oceanic climates may extend for some distance beyond the seas.  The seas, if small and restricted, can be extremely saline.  Life is less prolific than on wetter worlds, but can still be quite diverse.




Oceans cover 50 to 85% of the surface.  There is low surface relief, and the land and water are mixed in the forms of extensive swamps, lakes, forests, and semi-open woodland.  The climate is predominantly oceanic, with a higher than average global temperature due to the lack of an oceanic heat transfer system.  Life can be quite diverse.




Oceans cover 50 to 85% of the surface in the forms of large oceans.  The climate is varied, but tends to maintain an average.  Life is prolific and diverse.




Oceans cover 85 to 100% of the surface.  There may be extensive continental shelves, small continents, or only islands.  Life on these lands may be sparse, due to the fact that there never has been a long term land mass for life to develop on;  likewise, life on land might be diverse, due to recent global flooding, in which land life has had millions of years to develop on previously large continents.  An oceanic climate dominates.




Oceans cover the entire surface, and there is a marked absence of continental shelves.    The oceans themselves are kilometers deep.  Life may indeed be prolific, but it is highly unlikely that a technically advanced intelligence will develop here.




A world that is locked in the grip of coldness.  Glacial and tundral landscapes are the norm.  These worlds may be a transitory stage in the ultimate and fatal freezing of a Gaian world, or they may have reached a climatological equilibrium.  Such worlds differ from Gaian planets in the throws of an Ice Age in that this climatic level is long term, on the order of many millions of years, and that it is nearly a planetwide effect.




Characterized by a hot, sterile, and barren landscape beneath crushing atmospheric pressures.  Often times, these worlds have the highest temperatures of any planet or moon in the entire solar system.  Geological activity may remain, or the world may be entering into a period of planetary senescence.




These worlds are often small, yet retain substantial atmospheres due to their low temperatures, a result of being a fair distance from the stellar primaries.



These Europans are the ultimate in this type of world.  The planet has a thick  crust of ice, though this thickness depends both on the amount of heat received by the local star, and the amount of tidal flexing.  However, there is no open surface water, and any atmosphere is quite thin, being supported by gas release from surface fissures.  The water mantle is also likewise as deep as these two factors dictate.  At an extreme, there may only be subsurface reservoirs, centered on local hotspots, rather than a global ocean.  The core of the world is predominantly icy, with some rocky material.  Life is usually quite limited, and restricted to areas about the hotspots, though there may be hardy long ranging forms.




Ice-rock world.  Located farther out from the stellar primary, these worlds have a higher proportion of ice than rock in their mixed composition.




Ice world...some rock.  Because they are located so far from the parent sun, very little rock was incorporated into their formation.  They are very close, in fact, to being Kuiperian in nature.


Jovian Class

Mass range from 0.2 to 13 Jupiters. These are the gas giants. Varied in form and size, these are among the most beautiful planets, because of their preponderance towards multiple moons, ring systems, and widely varied color schemes.

These Epistellars exist within the tidal lock zone of the parent star.  High temperatures cause the closest worlds to glow a dull orange, while farther worlds possess, typically, a uniform blue color with a bright heat spot at the sub-astral pole, and a thick concentration of clouds at the anti-astral pole (presuming that these worlds would indeed be tidally locked).







Jovian worlds with masses up to 0.20 Jupiter's




Jovian worlds with masses of 0.21 to 8.0 Jupiters




Jovian worlds with masses of 8.1 to 13.0 (note that 13 Jupiter masses is the theoretical limit between Jovian worlds and Brown Dwarfs).




Jovians of varying masses which have, through planetary migration in the early accretion disk, have settled into orbits of 0.5 AU and closer.


Rogue Class

These planets have become interstellar wanderers through various means, most common of which is gravitational expulsion during  planetary formation. All other planet Classes are represented by this Class. It is believed, also, that this Class is nearly as numerous as standard planets; perhaps up to 10 planets, not to mention planetesimals or asteroids, are expelled by a typical forming solar system.







A terrestrial world, these planets have retained thick, dense atmospheres which are effective at retaining the heat put out by the planet itself.  So efficient is this, that these worlds have seas or oceans.  Coupled with the planet's geothermal energy, simple life may develop.  Advanced multicellular life, however, if highly unlikely, due to the lack of a high level of energy, such as a sun would provide to a normal world.

Artificial Metallic A terrestrial world artifically engineered to sustain life on a grand scale. These worlds are engineered with materials of a high density to sstain the constant effects of the cosmos. Generally these metallic worlds have an artifical sun with an infinite life expectancy generally depending on fueling its massive generators. Ringworld
Dyson's Sphere

Stellar Class

These are not planets but of a stellar nature. Used primarily as companion stars in a binary star system.





Companion Star


A Binary or more star companion.

Brown Dwarf A Semi-dead star or jovan that started out to becoming a star but didnt have the energy to do so.