Nayeren

The seventh and most distant planet from Verda, Nayeren is a frigid ice giant orbiting at the inner edge of the Faledor Belt. In old history, it served as the metaphorical gateway to the companions of the Verda System, but now has largely faded from prominence.

History

Formation

While the deep past of the Verda System has long been a subject of much confusion, most agree that Nayeren formed from an instability in the protoplanetary disk surrounding Verda and later had its atmosphere blasted away by the unfortunate close passage of a contemporary OB star. It then subsequently migrated outwards to its current position after the removal of the gaseous disk by Verda's ignition, in the process scattering much of the modern population of the Faledor Belt into its modern positions.

Upon its arrival in its current orbit, Nayeren encountered the outer world of Volarus, which it soon entered into an orbital resonance with. Over time, the planet was pulled closer and closer to Nayeren, going so far as to eject some of Nayeren's outermost captured asteroids. Around the same time, the dwarf planet Trantin and an unknown companion passed dangerously closer to Nayeren, resulting in Trantin's capture and the destruction of the majority of its original major moon system save Okari and Nerad.

Initial Explorations

Colonization and Verdan Federation Era

Modern Times

Physical Characteristics

Nowhere near the size of the larger gas giants like Jevethra, Von, and even Glau, Nayeren is only just over ten times the mass of Teralla. Due to its composition of primarily hydrogen, helium, and other volatiles, Nayeren's radius is nearly four terrestrial radii, much greater than a rocky world of equivalent mass. Nayeren is one of three ice giants in the Verda System, and the only one to orbit Verda itself.

Internal Structure

Nayeren is a prototypical ice giant, with an atmosphere extending 10-20% of the way to the core and higher concentrations of methane, ammonia of water found as one descends. Beneath this, beyond a pressure of 100,000 atmospheres, there lies a thick mantle rich in water, methane, and ammonia ices which form a hot supercritical fluid. At some pressures, water molecules break down into a soup of conductive hydrogen and oxygen ions, and sometimes even create superionic water in which the oxygen crystallizes and hydrogen freely floats within the lattice. Roughly 7,000 kilometers down, methane can decompose into diamond crystals, which rain downwards like hailstones on whoever suffers the misfortune of living there.

Beneath all of this mess of random states of matter, Nayeren's core has a mass of ~1.1 terrestrial masses and is composed of silicates, nickel and iron. This far down, the pressure reaches over six million atmospheres, and the pressurized temperature rises to hotter than the surface of Verda.

Atmosphere

At the top, Nayeren's atmosphere is composed of 80% hydrogen and 19% helium, with trace amounts of methane and iodine. These gases' absorption of reddish light is what gives the planet its distinctive lavender hue.

The atmosphere is divided into two main regions: the troposphere, where temperature decreases with altitude, and the stratosphere, where the opposite happens. The boundary lies at around 0.1 atmospheres. Beyond the stratosphere lies the thermosphere, at which point its difficult to not call it space.

Nayeren is banded by clouds of varying compositions and altitudes. The uppermost clouds are found at pressures below 1 atmosphere, where methane condensation is possible. Below this, ammonia and hydrogen sulfide clouds form, followed by ammonium sulfide, ammonia, hydrogen sulfide, and water after 5 atmospheres. Deeper clouds of water ice can be found far beneath the normal cloud decks, where the temperature reaches 0º C. Dozens of kilometers above the normal cloud decks exist transient clusters of high-altitude clouds, beneath the edge of the troposphere at 110 km above the deck. Unusually, the presence and activity of these clouds is bound to Verda's solar cycles rather than Nayeran seasons.

The haze in Nayeren's lower atmosphere is caused by the condensation of the products of ultraviolet-excited methane, like ethane and ethyne. The elevated concentration of hydrocarbons and similar groups, like carbon monoxide and hydrogen cyanide, make this region warmer than otherwise predicted through a minimal greenhouse effect.

Notably, the thermosphere is superheated to over 700 K, likely due to atmospheric interaction with ions in the magnetic field or self-dissipating gravity waves. This region contains travces of carbon dioxide and water vapor, deposited by infalling dust from Nayeren's planetary ring system.

Color

Nayeren's atmosphere is faintly lavender in the optical spectrum, more saturated than the pale brown of most of Glau. Early renderings had an annoying habit of coloring it bright purple to bring out the details of the clouds seen by Endala I and II, starting a long-running misconception of what the planet actually looked like. This pale lavender color is caused by concentrations of trace iodine in the upper atmosphere, tinting the originally blue-white color of the clouds.

Magnetosphere

The Nayeran magnetosphere is created by a strong magnetic field greatly inclined from the planet's axis of rotation by 51º. Like many ice giants, its magnetic axis is offset from the planetary core by over half a radius, and these unusual orientations are likely characteristic of flows within Nayeren's interior. A convective fluid layer of electrically conductive liquid material results in a dynamo action, creating the magnetosphere.

Nayeren has dipole component at the magnetic equator of roughly 17 microteslas and a dipole magnetic moment of 2.5 × 10¹⁷ T·m³. Notably, the field possesses a complex geometry that cannot be easily modeled by a pure dipole field, including a strong quadrupole – possibly stronger than the traditional dipole. This effect may result from the field's offset from the center of the planet and the structure of the interior dynamo generation.

Interactions between the magnetosphere and the atmosphere create weak but complex aurorae near the magnetic poles, generally only dimly visible in the infrared and ultraviolet ranges and found in the mid-latitude regions because of the field's high tilt from the rotational axis. Nayeren's bow shock occurs at around 37 planetary radii from the surface, and the magentotail extends well into the Faledor Belt.

Climate

The greatest hallmark of Nayeren's climate is its dynamic and powerful storm systems, featuring winds in excess of 600 m/s in places. At the cloud tops, prevailing winds shift in speed from averages of 450 m/s at the equator to 225 m/s at the poles, with most winds moving opposite to the planet's rotation outside of the polar regions where they don't. Seasonal changes cause regular shifts in size and albedo of the polar bands over the course of Nayeren's century-long orbit, with the long period resulting in seasons lasting roughly 20 years. While it obviously possesses less prominent meteorological activity than the monstrous Glau, it is still above average for outer-system ice giants known to the Vernarcan Federation.

Compounds like methane, ethane, acetylene, and others at the Nayeran equator are orders of magnitude more concentrated at the equator than at the poles, caused by atmospheric upwelling and subsidence between the equator and polar regions.

Storms

Nayeren's weather systems are notably possessed of a number of anticyclonic storms throughout the planet's clouds, which have been present in varying combinations since long before observation began. Very rarely does a single storm begin to dominate the rest in stature, with the last such "king storm" dissipating shortly before the launch of the VES Danakil from Teralla. WIP

Internal Heating

Nayeren's highly variable weather is caused in part by its great levels of internal heating. The upper troposphere has an average temperature of 89 K, increasing to 112 K at the 1-atmosphere level and rising steadily as one descends through the layers of gas. Nayeren radiates approximately 2.7 times as much energy as it receives from Verda.

Orbit and Rotation

The average distance between Nayeren and Verda is just under 18 astronomical units or 2.66 billion kilometers, completing an orbit every 77.41 years. Its periapsis and apoapsis are at 17.563 and 18.025 AU respectively, resulting from a very low eccentricity of 0.013. The orbit is inclined from that of Teralla and the system reference frame by 4.3146º.

Nayeren's axial tilt of 13.1º is similar to that of Glau (19.7º), Admor (11.97º) and Jevethra (8.49º), causing the planet to experience seasonal changes similar to these planets, although with seasons up to 20 years in length due to the long orbital period. Its sidereal rotation period is approximately thirteen hours in length, and daylight variation is much less extreme than on the absurdly tilted Teralla and Esera.

The lack of solid structure on Nayeren makes possible differential rotation, with the equatorial regions rotating every 15.5 hours and poles every nine. Strong latitudinal wind shear thus results from the strongest rotation differential in the Verda System.

Moons

Nayeren holds 144 known natural satellites ranging in size from the almost planet-sized Trantin to the most miniscule captured asteroids, and there are likely more which remain undiscovered. Of these, 136 are below 10 kilometers in radius. The three major moons in order of distance are Okari, Trantin, and Nerad, but the minor moon of Trinrau is almost large enough to qualify.

Inner Moons

Nayeren possesses fifteen inner moons, whose orbits all lie within that of Okari. They exist in two main groups based on orbital distances: the Opix group, including the six moons of Belin, Opix, Staver, Swito, Berna, and Radovan; and the Colral group with Evora, Colral, and Jacklin. The innermost moons of Mai and Thalik are very far from the others, orbiting once every seven hours near the inner reaches of the ring system.

All of Nayeren's inner moons are closely connected to the development and maintenance of the planet's ring system, which likely resulted from the fragmentation of a larger moon. The two innermost moons, Mai and Thalik, shepherd the inner C ring, and dust kicked off of Rab results in the creation of the outermost F ring. The lonely moon of Laris is large enough to carve gaps in the ring system with its gravity and orbital resonances.

At 148 kilometers, Laris is the largest moon beneath the orbit of Okari and host to the greatest population of over 12 million people. Most of the inner moons are icy, fairly bright objects, but their albedo decreases as their orbital distance goes down.

Great perturbations occur between the inner moons, particularly within the tightly packed Opix and Colral groups. These perturbations may eventually push the moons onto crossing orbits, resulting in a future collision in the absence of preventative measures. The presence of populations on these objects makes avoiding this eventuality a priority.

While not really an inner moon, the asteroid Gryspik is difficult to categorize elsewhere due to its orbit in an 11:13 resonance with Okari.

Original Major Moons

Prior to the capture of Trantin, Nayeren's orbit held somewhere between four and seven major moons in a regular configuration, from roughly Okari's current position out to ~600,000 km distance. The innermost moon, likely ~450 km in radius, was pushed inwards by interactions with Trantin and broke up, forming Nayeren's famous ring system. The others were likely either destroyed or ejected in much the same way, leaving behind only Okari unscathed. Nerad may be one such original, catapulted outwards onto its highly eccentric orbit.

Okari

Okari is the last intact survivor of Nayeren's original moon system. Originally orbiting at roughly 1.4 times its current distance, the capture of Trantin shoved it inwards to its current position. This interaction also partially resurfaced the moon through internal heating, giving its distinctive patchwork appearance.

Okari was home to both the mysterious disappearace of Fica Colony, and the first signatory of the Verdan Federation charter alongside Trantin. Today, it is home to over 4 billion people across its surface and small gravitational influence.

Trantin

Uniquely for a major moon, Trantin follows a retrograde and highly inclined orbit. Thus, it is clearly a captured satellite, likely originating in the Faledor Belt before its capture. It is also one of the coldest known objects with a substantial atmosphere, primarily composed of nitrogen with small quantities of methane and carbon dioxide. With a surface temperature of 41 K, it is one of the coldest objects in the Verda System due to its high albedo, causing it to be covered by nitrogen, methane and carbon dioxide ices.

Notable surface features include large-scale "cells" and ripples along the surface, the large southern polar cap, and substantial cryovolcanism across the northern hemisphere. Trantin's geyser plumes can erupt to over nine kilometers in height. The moon hosts a population of almost 29 billion people across its surface, including a substantial minority of computerized individuals taking advantage of its extremely low temperature.

Nerad

The third largest moon of Nayeren, Nerad orbits on a prograde but highly eccentric orbit. It was likely scattered into this position by the capture of Trantin from its original spot in the regular moon system. Nerad has a highly irregular appearance, with a large range of albedos over its surface, and a chaotic rotational axis. In size, Nerad dominates the non-Trantin irregular satellites, making up over 95% of their total mass. Not counting captured planets like Trantin and Sulpha, Nerad is almost a third the mass of all total irregular moons within Verda's system. The moon's population is fairly low, at only 940 million people across its surface.

Other Irregular Moons

Other than Trantin and Nerad, the irregular moons of Nayeren go from ~170 km (Trinrau) all the way down to the point where everyone arbitrarily stops calling them moons. The Alibilan Group, consisting of 29 retrograde moons between 6 and 7 million kilometers distant and 138º-150º inclination. The moons of Merell and Bilana within this group are notably completely gone and replaced with habitation structures built out of their material.

Inclinations between 60 and 140 degrees are largely devoid of moons due to the Kozai instability, where perturbations from Verda or Volarus at their apoapses causes them to develop unsustainable eccentricities and impact on inner moons or eject from the system. The small moon of Malgirak is within this zone, and this process has given it the most eccentric lunar orbit in the Verda System.

Rings

The Nayeran rings are composed of bright, icy particles varying in size from micrometer-scale dust to the average house. Nineteen distinct rings exist around the planet, with the brightest being known simply as Ring I. These rings are very young, as they would have dissipated over the age of the Verda System, and likely formed from the breakup of a moon or captured comet roughly 15 million years ago.

The rings contain numerous gaps in which particle density sharply drops, three of which are opened by known moons embedded within them. Most of the rest are caused by a variety of resonances with the larger inner moons, Okari, and Trantin. Other gaps remain unexplained. A stabilizing resonance ensures the longevity of the outermost clearly visible ring, Ring VIII. Nayeren's axial tilt of 11.6 degrees ensures that the rings are tilted from the Verda System's reference plane in the same way.

Population

Like most gaseous worlds, Nayeren's planetside population of 140 million individuals is limited to the inhabitants of floating cities or orbital ring chandelier cities. The primary industry on the "surface" was the extraction of Helium-3, a commonly used fusion isotope, but with the proliferation of kugelblitz and antimatter-based energy generation this industry has suffered a bust.

Nayeren's sphere of influence, as large as it is, is filled with numerous habitation structures, adding up to a population of over 780 billion people of all manner of species. Many of them are concentrated within the gravitational influence of Okari and Trantin, the planet's two largest moons.