Zar'siel II

Zar'siel II is the primary world of the newly-founded Zar'siel Sept of the T'au Empire. It is a large terrestrial planet falling within the 'super-earth' classification and found in the Koronus Expanse, more specifically in the Accursed Demesne sub-sector.

History
Zar'siel II was recently colonized in the aftermath of a successful experiment by the T'au Earth Caste to develop a functioning long-range Warp Drive. It was the first habitable system discovered by the expedition after their return to Materium subsequently to the jump and was deemed to be suitable for establishing a new colony after preliminary reports were analyzed.

Further study of the surface of Zar'siel revealed no signs of intelligent life having evolved on the planet beforehand. Considering that all conditions are present and that primitive lifeforms have been encountered, it is speculated that the planet was either formed, or seeded with micro-organisms via asteroid impact relatively recently on the stellar scale.

Physical Characteristics
Zar'siel II revolves around a binary A/F star duo which emits considerable amount of luminosity, radiation, and gravitational forces. As a result, the system's habitable band is much further away from the center compared to Terra. Zar'siel II orbits at 3.82 AU from its twin stars, or about 4 times the distance between Terra and its sun. As a result, its revolution is extremely slow, taking about 4 and a half Terran years to complete one period.

The planet orbits near the colder edge of the habitable band of its system and it features a fairly thick Oxygen-Nitrogen atmosphere. The combination of distance and atmosphere protects its surface from the levels of radiation emitted by its twin stars, which would otherwise be stripped away and bombarded.

Zar'siel II is of sub-terran density despite being more massive, this signifies that a larger portion of its mass is composed of less dense silicate rock and surface water, while its dense iron core is of smaller proportions. This is a primary contributing factor to the planet's relative scarcity in precious mineral resources

Climate & Topography
Due to its pronounced axial tilt, Zar'siel II features climatic properties alien to the average human. much of its land mass is covered by tropical climates of jungles, monsoons and so on up to the 38th parallel. An also sizable frigid tundra extends from the 52nd parallel and up, leaving only a thin temperate band between the two extremes. Despite the high axis inclination, much of the planet's hot zone is covered with thick jungles with an excellent heat retention and the orbit is of very low eccentricity, thus there is not that much variation in weather, with the hot zone remaining hot and the frigid zone remaining frigid all year long. Due to the planet's extremely long revolution cycle, these minor changes are spaced out over such a long time that they are barely noticeable. The exception to this is the luminosity period, which does vary drastically between 'seasons'.

The surface of the planet is roughly evenly distributed between continental landmasses and oceans. Relatively low tectonic activity results in scarce mountainous areas and few high peaks. Inversely, the depth of the oceans is quite high, with the deepest abyssal trenches many times further away from the surface level than the highest mountains. Much of the landmasses seems to be gathered on the hot zone in a relatively condensed form, which leads to speculation that it used to be a supercontinent that began to fragment slowly over time.

Biosphere
Zar'siel II is a highly humid world featuring primarily rainforest or monsoon biomes and their subsets. Due to the large differences in temperatures between the equatorial land masses and the polar water masses, the planet sees large-scale monsoon effects - a convection effect between land and sea - over widespread areas with only the exclusion of the most in-land zones. Precipitations are frequent and abundant, with thunderstorms being especially common during the long hot season created by the planet's painstakingly slow revolutions.

The high oxygen content results in wildfires being more intense and dangerous, making each thunderstorm a worrisome event. Another effect of the high oxygen content is that it promotes gigantism in insectoid lifeforms. Incidences of megaflora are also significantly present across the planet, although they are not dominant over more average sized flora. The indigenous flora of Zar'siel II is particularly thick and tall and is especially adept at retaining heat and moisture over very long periods of time, having thus evolved to tolerate the discrepancies in temperature.

A diverse ecosystem of native lifeform is also present, dominated primarily on the surface by reptilian and avian creatures, although some species of mammals also exist, none of which have shown signs of sentience. Many of those creatures are predatorian in nature and can make traveling through the ecosystem deadly for the unprepared. The oceanic masses are also teeming with life, and deep sea probes have reported sightings of even greater incidences of abyssal gigantism. Exploration of the planet's depths has been halted after the repeated destruction of probes to unknown causes.

Satellite
The atmosphere of Zar'siel II is stabilized by a very large moon, sizable enough to qualify as a very small planet and sustaining its own atmosphere, which is of composition similar to that of the parent planet. Its climate is cooler, featuring primarily coniferous temperate biomes. The density of this satellite is extremely high and has led T'au scientists to emit the hypothesis that the two objects may have collided at a point in the past and that the satellite may have leeched large quantities of heavy matter from the planetary Core.