PLANET
CLASS T: TERRA/SILICATE
TYPE
Terrestrial
CORE
Iron and nickel
MANTLE
Molten silicate rock
SURFACE
Oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium
ATMOSPHERE
Nitrogen, oxygen, argon
LIFE
Numerous biomes ideally suited for the development of complex forms of flora and fauna
Class T: Terra/Silicate worlds are formed in a planetary disc rich in oxygen and silicate materials. Typically found in the inner-region of a star system—where surface water is able to exist in liquid form, Class T planets are among the most common in the universe and are rich in both geologic and biologic diversity. Due in part to a temperate climate and abundant surface water, it is common for life to thrive on Class T planets, and many of these robust worlds are able to support advanced humanoid civilizations.
The core of a Class T world is typically a solid inner-core of iron that is suspended in a molten outer-core composed of iron and nickel. The inner-core spins at a speed different from the rest of the world and are responsible for generating a magnetic field that shields the planet from the charged particles that emanate from the parent star. Surrounding the outer-core is a semi-molten layer of molten silicate rocks. Intense heat from the core causes these rocks to rise. They cool as they approach the surface and sink back down into the core. This convection is responsible for plate tectonics—the movement of crustal plates across the planet’s surface. When the mantle pushes through the crust, volcanoes erupt.
Atmospheric conditions are generally tranquil; severe storms are small and generally last no more than a couple of weeks. Though some Class T worlds experience temperature extremes, most are temperate.
CLASS T1: PROTOPLANET
A protoplanet is a large planetary embryo developing within the protoplanetary disc of a young star system. Such bodies will have undergone some internal melting to produce a differentiated core. Over the span of many millions of years, protoplanets, will gain more matter through collisions with nearby bodies, and eventually attain a spherical shape.
In the case of a Class T protoplanet, this embryo would be rich in oxygen and silicates.
CLASS T2: MOLTEN
A molten planet is typically a newly formed world with a crust that has yet to harden. These planets will usually cool and evolve into something more hospitable, though planets very close to a star may remain molten indefinitely due to tidal forces.
CLASS T3: PRIMORDIAL
A primordial world is a young planet that has cooled sufficiently for the crust to harden. The youngest primordial planets are barren and still rife with geologic activity; steam from volcanic eruptions condenses in the atmosphere and falls to the surface as rain, giving birth to the first shallow seas. It is within these seas that the first primitive organisms may take shape.
CLASS T4: BARREN
Not all silicate worlds are paradise. In fact, many are dead and lifeless worlds that have either a tenuous atmosphere or none at all. Many barren worlds come to be due to their unfortunate proximity to a star. Others are simply failed worlds, and though inhospitable, these worlds can be made habitable via pressurized domes and are prime candidates for terraforming.
CLASS T5: ARID
Silicate worlds with very little surface water are considered arid. Many of these planets are hot and covered in sand; the proverbial desert world. Though inhospitable, hearty plants and animals can still thrive here.
CLASS T6: GLACIATED
These frozen planets typically lurk in the outermost reaches of a star system's habitable zone and are a far cry from the lush garden worlds closer in. While life may still flourish upon narrow stripes of green along the equator, many of these planets are completely frozen.
CLASS T7: HOTHOUSE
The outliers of the silicate worlds, these hellish planets form with a very dense atmosphere rife with carbon dioxide, which promotes a greenhouse effect that gives rise to temperatures above 460° C. The surface pressure is often crushing, making hothouse worlds thoroughly uninhabitable.
CLASS T8: GARDEN
Garden worlds are temperate planets with vast blue oceans and wide swaths of verdant forest... among countless other diverse habitats. They are ideally suited for the development of complex life and are the cradle of civilizations across the universe.
CLASS T9: MARGINAL
Marginal worlds are rocky and barren and tend to have very little surface water. Life may struggle to take hold on these worlds, and is typically restricted to limited to plants, though they may be well suited to humanoid colonization.
CLASS T10: PELAGIC
These warm, tropical worlds are mostly water, dotted with chains of islands. Though plants and animals--and even humanoids--may flourish on the limited land, the oceans on pelagic worlds are rich with diversity. Due to the warm atmosphere and vast oceans, violent tropical cyclones are frequent on these worlds.
CLASS T11: OCEANIC
Oceanic worlds are completely covered with water and are therefore not favorable for humanoid life without the construction of a suitable habitat. Cetacean life, however, may thrive and in rare cases, become sentient. Much like their pelagic counterparts, oceanic worlds breed powerful tropical cyclones in their warm waters.
SUBCLASS TA: AMMONIA
These rare planets supplant water in the ecosystem with ammonia. Rich in alkaline earth metals, they would function similarly to a traditional silicate world, but the unusual composition would give rise to brown oceans and black vegetation.
SUBCLASS TB: BIOLUMINESCENT
Though extremely uncommon, plantlife on worlds that receive very little sunlight may generate light of their own.
SUBCLASS TC: CHTHONIAN
A Chthonian planet is the metallic core of a gas giant that has spiraled inward from the cold zone of a star system and has been stripped of its gaseous components. A Class T Chthonian world would simply be the oxygen-rich core of a gas giant.
SUBCLASS TD: DWARF
Any Class T world that does not meet the minimum size requirements of a planet is considered a dwarf.
SUBCLASS TG: GIANT
A very common subset of the terrestrial worlds, giants are otherwise known as "super-Earths," and are merely silicate worlds that are much larger than average.
SUBCLASS TH: HALOARCHEAN
Before the ecosystem of a young planet is well established, simple organisms known as haloarchea absorb sunlight using retinal (instead of chlorophyll as is common on more mature worlds). The result is a planet covered in purple plants.
SUBCLASS TM: MOON
Any object that would otherwise be considered a planet, but is a satellite orbiting another body is considered a moon.
SUBCLASS TR: ROGUE
A planet that has been ejected from its star system and is adrift in interstellar space.
SUBCLASS TX: IRRADIATED
A planet that is heavily irradiated by its parent star.