Manual:Planet types

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A)The set of planet types is not considered finalized.
B)The below names were/are designed for internal reference only

Planet types


This is a list of planet types from milky_way.xml.


Most civilized species that achieve spaceflight move their polluting heavy industries off-planet, and humans are no exception. Trantor-class planets are worlds humans have industrialized in an attempt to leave their inhabited planets natural and pleasant. They are typically transformed from worlds that had no indiginous ecosystem to destroy, such as airless rocky worlds or worlds with reducing atmospheres. Sometimes they are terraformed with a minimalistic imported ecosystem (often consisting of genetically engineered bacteria used to remediate industrial waste), but sometimes they are left uninhabitable, with the population confined to bases and domes.

Trantor class worlds are typically heavily mechanized, with most of the industry being done by robotic factories and automated mines. Populations range from a few tens of thousands to several million, and usually consist of technicians, engineers, overseers, and industrialists on temporary shifts from more amenable planets. Trantor class worlds often have exclusive contracts for their manufactured goods, so they are poor sources of trade goods, but they provide a market for natural products. Trantor class planets usually host a substantial aerospace production industry and are good sources for starships and upgrades.






Arid planets are a subset of Bio Diverse worlds which have a complex ecosystem, but an average humidity under 50% of Earth's. As such, they are typically worlds with large areas of deserts, plains, and steppes, with small oceans and limited fresh water supplies. However, ecological variations usually result in at least small areas of the planet having forests, jungles, swamps, and other water-rich ecosystems. Arid planets are dry relative to other life-bearing planets, but they cannot be so dry they cannot sustain an ecosystem sufficient for evolving complex life (or for terraformed arid planets, to sustain a sufficiently complex constructed ecosystem.)

Arid planets are usually inhabited. The low biological productivity limits planetary agricultural production, and also results in slow industrial waste remediation, so both agriculture and industry are limited. This usually results in a slightly deflated economy and a relatively low population (10,000 - 500,000 in most cases.) However, these two characteristics can make these planets attractive to those who favor unspoiled ecosystems, wide open spaces, and cheap land. As such, they are popular with settlers, outdoorsmen, naturalists, ranchers, and retirees.

Arid planets typically subsidize enough agriculture to sustain the population, and often sell the surplus at relatively low prices. Sometimes mineral resources are also available for sale. Manufactured goods are the most common imported products.




Bio-Diverse, in the broad sense, is a classification used to refer to any planet that supports carbon-based macrobiotic life that uses water as a solvent. Macrobiotic forms are usually multicellular, however, planets where the predominant life forms consist of cooperative cellular communities (similar to slime molds), macroscopic single-celled lifeforms, and polynucleate megacells have been discovered.

Most bio-diverse worlds have complicated ecosystems with vast numbers of species filling all the traditional roles of producer, consumer, predator, and decomposer. However, a smaller number of planets have only producers and decomposers (usually because they were discovered soon after the proliferation of multicellular life) and a few planets have been discovered where the ecosystem is so wound up into a complicated symbiotic web that the classical roles do not apply.

Bio-Diverse in the more narrow sense is a classification used by humans to refer to planets with a climate and ecosystem fairly similar to Earth. Specifically, the mean temperature must be from 10-25 °C, the humidity must be from 50-200% that of Earth, and the planet's surface cannot be covered in hostile or obnoxious life-forms. After the University classification was introduced, a new requirement was added; less than 15% of the surface can be developed.

Bio-diverse planets (in this sense) are the most desirable for colonization, so nearly every known one is inhabited. The Earth-like climate makes them especially suited to classical agriculture, so many sustain thriving trades in various natural products. However, most planetary governments maintain strict regulation of heavy industry and mining to avoid damaging the environment, so typically these things are in demand.


University planets are the primary population centers of human factions. Typically Bio Diverse worlds, occasionally they develop from some of the more pleasant arid or tropical worlds as well. In order to maintain the planetary environment in the best shape possible for the colonists, polluting industry is usually restricted. The main industries tend to be those with little environmental impact; education, scientific research, engineering, medicine, art, and business, with sometimes a little bit of high-tech industry on the side. The resulting excess of universities, schools, research labs, and other intellectual facilities is what lends this class of planets their name.

University planets have populations ranging from about three hundred thousand to two billion, although occasionally the designation is also used for planets with much lower populations on which the only habitation is a single large university or research facility. University planets are the location where most of the population growth occurs in human space, because the quantity of educational and medical facilities available for children. Generally, when people living and working in space decide to settle down and have families, it is on these worlds.

University planets are not significant producers of anything, due to the highly service-based economy, but they are substantial consumers of agricultural and industrial products.




Oceanic planets are a subset of bio-diverse planets which have their surfaces entirely (or nearly entirely) covered by water. The oceans vary from hundreds of meters deep to hundreds of miles. Oceanic planets are lifebearing, although biodiversity may be reduced by the homogeneity of the environment (except for those planets with reefs or reef-analogues.) Many oceanic planets are the results of terraforming efforts and as such have a terran biota.

Most oceanic planets have extremely productive ecosystems. Primary producers can vary from planet-spanning floating stromatolites to phytoplankton-analogues to floating mangrove-like forests. Usually, some forms of macrobiotic consumers (often insect-like or fish-like) and predators exist. The primary energy input is usually solar, although on some planets (particularly those orbiting red dwarf stars or those covered entirely by ice) underwater vulcanism sustains chemolithotrophic communities.

Modern technology has made the colonization and development of oceanic planets fairly simple, and nearly all are inhabited. Populations are easier to sustain (due to the usually high biological productivity) but development is harder and more expensive. Oceanic planets are prolific producers of food and other natural products (even plants normally considered terrestrial can be engineered into floating forms), but they encounter some problems in trade due to the difficulties sometimes encountered on submerging large merchant craft. As such, large quantities of export materials are often encountered.







Planets that carry the Bio-Simple designation are planets in the early stages of evolving carbon/water based life. They have atmospheres which vary from strongly reducing (methane, ammonia, and carbon dioxide) to weakly oxidizing, with some unusual cases having hydrogen-helium atmospheres or atmospheres consisting almost entirely of noble gases. All have liquid water present in some amount. Most have substantial volcanic activity and highly unstable climates. Climates vary from planets covered entirely in ice with oceans underneath, to planets where only the poles are cool enough to be life-bearing (and in rare cases, where they are inhabitable only part of the year, with the indigenous life-forms going into endospore or endolithic life-cycles during the uninhabitable summer.)

Life forms on Bio-Simple planets vary from primitive self-replicating molecular communities, through bacteria-analogues, all the way up to complex eukaryote-analogues that contain several to dozens of different types of endosymbiote. Generally, any planet with multicellular life forms is considered Bio-Diverse, although exceptions are sometimes made in cases where only a few species of multicellular life-forms exist, and they are considered overspecialized evolutionary dead-ends.

Bio-Simple worlds are almost always uninhabited due to the typically reducing atmosphere and the danger of alien pathogens (the particular combination of planetary microbial communities and fast evolutionary environment can generate especially deadly diseases.) Most races also feel a responsibility to avoid interfering with the developing lifeforms, so they are also rarely terraformed. Most Bio-Simple worlds have unmanned scientific observation posts that can be landed at, although they provide no goods or services besides that of basic system network access.




Volcanic planets are worlds that, for a variety of reasons, have severe volcanic activity. Most volcanic worlds are between 1 and 2.5 billion years of age, and are unstable because they have recently solidified and their cores and mantles still contain most of the heat of their formation. Others are unstable because of unusually intense radioactive heating of their cores, or due to formation from easily-melted materials. Often, some or all of the satellites of gas giants will be volcanic due to heating induced by tidal deformation.

Rarer examples include volcanic worlds are experiencing temporary (on geological time scales) surges of volcanic activity. This is common on worlds that, for various reasons, do not have plate tectonics and build up internal heat until it can no longer be contained. A few extremely unusual cases are volcanic due to exposure to extreme magnetic fields (typically those of large gas giants or even pulsars) or for no known reason.

Volcanic planets are always uninhabitable. The dangerous volcanic activity is, of course, not exactly an invitation to settlement, and the atmospheres (when present) consist of corrosive and toxic gases. Most are stable enough to allow the construction of small automated bases on which it is possible to land in an emergency, but very few have any kind of population aside from a few vulcanologists.






Molten planets have surfaces composed of liquid rock. Most molten planets are molten because they have not yet cooled from their formation phase; most of these planets are from .4 to 1.7 billion years old. Some others are molten due to extremely intense tidal forces generated by close satellites (or being a close satellite to a gas giant), or due to overwhelming greenhouse effects. Some are simply too close to their host star to cool down, and a very few are molten due to extreme concentrations of radioactive elements.

A few rare molten planets are molten with no obvious cause. Usually, in these cases, the cause can be traced back to an overwhelming meteor impact that melted the surface. However, in a few cases, no obvious cause can be determined. It is of great interest to xenoarchaologists that a fraction of those worlds show evidence (generally in orbit) of ancient habitation.

Molten planets have atmospheres ranging from extremely tenuous helium shrouds to dense layers of sulfur compound and carbon dioxide.

Molten planets are completely uninhabitable for obvious reasons. A few attempts at building floating, force-shielded mining stations were made, but in the end asteroid mining was judged to be more economical.


Overgrown planets are a subset of bio-diverse planets in which the planet is judged to be uninhabitable or undesirable based on the indigenous life forms. The most common examples are planets that are completely overgrown, usually by primary producers. Common forms include spike-trees similar to the lycophytes of Earth's carboniferous period, forms similar to algae and kelp on oceanic worlds, kudzu-like macrophytes, planet-wide jungles, and microbial mats half a meter to hundreds of meters high.

The overgrown designation applies to other types of biological problems as well. Other examples include worlds with especially dangerous and unpredictable predators, worlds with extremely resilient biota that resist all attempts at agriculture, worlds with extremely delicate ecological webs that would completely collapse at the slightest change, and worlds with lifeforms that are destructive to colony structures or technological devices. Examples include worlds on which lifeforms have evolved biological electromagnetic pulse mechanisms for hunting or defense, and worlds on which the producers or decomposers cannot be stopped from breaking through colony floors.

A few rarer examples include one recently discovered world (the exact designation is classified) where extremely destructive microbes cause any non-resistant life-form to dissolve into waste products and indigestible material within several minutes of exposure. Another is a planet on which huge, underground mycorrhizal networks remove huge amounts of material, occasionally result in the formation of great chasms and earthquakes.

Overgrown worlds are by definition not colonizable (or at least not desirable for colonization), although they can be terraformed by containing or destroying the problematic life-forms. A world so terraformed is considered to have been converted to another type (usually Bio-Diverse or Tropical.)

An interesting note is that the Aera and Bzbr homeworlds would both be considered overgrown by any modern standard.




The Gas Giant class of planets, often referred to as the Major Gas Giants or the Jovian planets (by humans), consists of large planets primarily composed of Hydrogen and Helium between 2.5x10^28 kg and 1.15x10^27 kg. Above masses approximately 2.5x10^28 kg or larger, compression of the interior will eventually reach temperatures high enough to fuse deuterium, and the object will be classified as a Brown Dwarf. Under masses less than 1.15x10^27 kg, internal structural changes occur that result in a much lower density and a greatly reduced magnetic field, and the body is defined as a Medium Gas Giant (a Minor Gas Giant or Saturnian plant.)

Gas Giants commonly attract a small accretion disk of their own during the planetary formation process, and usually have 1-9 major satellites. These satellites usually vary in size from 10^25 - 10^21 kg. The environments on these moons vary greatly, with moons strongly affected by tidal and magnetic heating usually being molten or volcanic and moons less strongly affected being either rocky, icy, or less commonly oceanic or otherwise lifebearing. Most Gas Giants form outside of their primary's habitable zone, but moons may be heated by solar radiation, infrared radiation given off by the slow contraction heating of the Gas Giant, the Gas Giant's magnetic field, tidal heating, or internal radioactivity.

Gas Giants cannot be landed on. Indeed, it is difficult to understand what landing would mean in relation to a gas giant; under the atmosphere lies a great sea of liquid hydrogen, under that another sea of liquid metallic hydrogen, and under that a core of surely molten silicates and metals. However, it is common for spacecraft to 'park' in the upper atmosphere, using their thrusters to hover while feeding their idling engine with deuterium filtered from the clouds.



The Medium Gas Giant class of planets, often referred to as the Minor Gas Giants or the Saturnian planets (by humans), consists of large planets primarily composed of Hydrogen and Helium under 1.15x10^27 kg but still large enough to compress hydrogen to liquid metallic forms. Over 1.15x10^27, structural changes take over that result in a much greater density and a much stronger magnetic field, and the planet is considered a Gas Giant. A Hydrogen-Helium giant that cannot compress liquid metallic hydrogen in the core has a much lower temperature and nearly no magnetic field, and is considered a Dwarf Gas Giant of the Hydrogen-helium dwarf subtype. The mass estimated to be required to compress hydrogen into liquid metallic forms is estimated to be approximately 2.3x10^26 kg, but it varies depending on planet temperature, age, and composition.

Medium Gas Giants sometimes attract a small accretion disk during planetary formation, and form 1-5 major satellites. Satellites strongly affected by tidal heating are usually volcanic, while others are often rocky or rocky/icy. Since Medium Gas Giants usually form outside the habitable zone and do not usually give off as much heat by contraction or tidal heating as Gas Giants, they have fewer habitable satellites. Habitable moons are usually of the ammonia-solvent biological type, or orbit planets that have 'wandered in' after formation to more habitable zones.

Spacecraft can be 'parked' in the atmospheres of Medium Gas Giants in the same sense as with Gas Giants, but the reduced magnetic field strength and usually calmer atmosphere makes them a better environment for it.