The Horizon System: Olindias, at the Edge of Infinity
2nd A (1)
Olindias (Frigid Jupiter, Planet)
System - Horizon-Actinophrys
Mass - 312.5 Earths (0.983 Jupiters)
Radius - 63,945 kilometers (10.04 Earths)
Global Average Temperature - -226.5°C
Day Length - 9h 59m 2.5s
Year Length - 342.0 years
Number of Satellites - 753
ESI - 0.092
Etymology - From the Flower Hat Jelly Olindias formosus, for its chromatic beauty, fluorescence, and potentially lethal venom.
Overview
Olindias is the last of Actinophrys’s planets, drifting slowly through frigid space about 40 AU away from its sun. Highly inclined and orbiting retrograde, it spins backwards across the sky with a dense retinue of twenty-nine moons. With deep clouds of methane and nitrogen beneath a hazy blue sky, Olindias almost resembles Neptune - albeit a version over twice as wide and eighteen times as massive. On the inside, however, Olindias much more closely resembles Jupiter - great currents of churning hydrogen drive vast magnetic fields, while immense tidal forces spark its moons to life.
With its fair mass and extreme distance from Actinophrys, Olindias’s sphere of influence is even larger than Rhodactis’s. While the two planets would ordinarily be too close to be stable, their orbits face almost exactly opposite directions, conferring additional stability. Olindias’s immense gravitational basin has accumulated a fair amount of stray debris over the eons, from its thirteen regular moons to hundreds of asteroids to a weird trio of planetary-mass objects floating in the far reaches of Olindias’s irregular moon system. As Olindias sits at the edge of the region where nitrogen is a liquid, many of its large moons have extensive oceans of the substance.
Past & Future
Olindias’s orbit is a surefire sign that it is abnormal. Unlike most of the retrograde asteroids in our Solar System, which have orbits nearly perpendicular to those of the planets, Olindias’s orbit is roughly in the same plane as the other planets but backwards. While it is not impossible for a planet to form this way, it is quite unlikely and typically requires instabilities that would clear away other planets. Seeing as Rhodactis and the rest of the Actinophryidan Worlds exist, it is difficult to invoke that scenario to explain Olindias’s unusual properties.
An explanation for this anomalous world may be found a stone’s throw away from Olindias’s current location. Of all the objects in the Horizon System, its composition is most similar to the brown dwarf Physalia. It is possible that Olindias originally formed around Physalia’s suns Ceratium and Ceratophorus, was kicked out of the system by an interaction with the larger world, then was captured by Actinophrys after leaving the influence of the binary star. Though this scenario requires a truly perfect set of coincidences to pull off, it may be the only way to explain Olindias’s properties as we see them today.
Unlike Rhodactis, Olindias and its moons have changed significantly in the last few hundred million years. Prior to around 600 million years ago, they were cold enough for nitrogen atmospheres to collapse to the surface, leaving only thin envelopes like the atmosphere of Pluto. As Actinophrys brightened, they eventually thawed out, the once-expansive nitrogen glaciers melting to form the lakes and seas we know them for today.
“Some might argue that the denizens of Horizon raise questions about the nature of individuality, autonomy, and authenticity that are better left unanswered by the natural sciences. Our organization has encountered many who take offense to the idea that the rational methods might overcome the spiritual mystique they cherish, and Horizon’s callous handling of this subject offends many of them even more than we do.
But I have always considered the surrender to arbitrary speculation as a failure of ambition. Why should we hold ourselves back to preserve a nonexistent illusion of purpose when such reservations never bear fruit?“
- MINASE Chief Archivist Alexandria, “AIMS Notable Remarks & Research Goals - Q3 2276“ (2276)
Civilization
Olindias is the only planet of Actinophrys which is never visible to the naked eye from Horizon’s surface, so it could have only been discovered once the telescope was invented. While at the peak of Old Horizon’s existence they were undoubtedly aware of its existence, knowledge of the planet has largely fallen out of cultural memory after the collapse of technological civilization. Some extant Horizonian cultural groups have stories about a divinity or celestial realm that was destroyed, abandoned, or left of its own accord which may reflect the disappearance of Olindias from the cultural consciousness, but even these myths contain barely any concrete information about Olindias itself.
Unlike the relicts of Old Horizon, the space-borne inhabitants of the Horizon System are heavily intertwined with Olindias. A resource economy centered around the production of fusion and ion engine fuels has emerged between its rings which supports practically all interplanetary shipping in the Horizon System and nearby regions of the Horizon Moving Group. While not as convenient as Rhodactis, a lot of interstellar traffic passes through Olindias on its way to the inner Actinophyridan Worlds or populations centers around Praya and Physalia. Today, Olindias and Rhodactis behave as a unified trade economy not unlike Singapore or Hong Kong in our world, though infinitely greater in expansiveness. Even beyond Horizon itself, they are centers of cultural diversity - from the biomechanical wilds of Amazonia to the crystal cities of Euplectella to the hazy underworld of Pterois, people and customs from all across the Comatula Nebula find their way to this crossroads.
Myriad Celestia - Blackwater Diving (Moons of Olindias)
WIP
A. Core Worlds
From left to right: Turritopsis, Aglaura, Aequorea, Aglantha, Gonionemus
I. Turritopsis
Though less than 2,000 kilometers across, tiny Turritopsis bears an atmosphere, just like every other round moon of Olindias. In its case, this gaseous envelope consists of sulphur dioxide and diatomic sulphur gas, released from great volcanic eruptions across its surface and kept gaseous by geothermal heating. This envelope is very thin, both due to the moon’s low gravity and the tendency of its constituents to freeze out, so Turritopsis is still effectively airless. Though other moons of its kind frequently have their surfaces drenched in volcanic sulphur ices, the high-radiation environment of Turritopsis has scoured it to bare rock.
II. Gonionemus
With an almost pure white surface beneath a thin nitrogen atmosphere, Gonionemus seems almost dull compared to the garish wonders of the Horizon System. But even this seemingly-plain moon has its own wondrous secrets. Its surface is not the water ice typical of icy moons but in fact a kilometer-thick envelope of frozen nitrogen, riddled with geothermally-heated channels and pools of liquid. The thin, Mars-like atmosphere of this small world is too quickly eroded by Olindias’s radiation belts to let the liquid flow freely on the surface, but many of these subglacial reservoirs can rival the seas of more conventional ocean worlds.
IIIA. Aglaura
First of the oceanic moons of Olindias, this Luna-sized aquaria would be a standout jewel in most systems. But here, it practically represents a return to a gaudy, neon norm. Aglaura is large enough to maintain a significant atmosphere at the cryogenic temperatures of Olindias and warm enough to support a global liquid nitrogen ocean. Interrupted only by faint methane ice clouds in its upper atmosphere, this ultramarine world’s endless oceans represent a most perfect union between sky and sea.
IIIB. Aglantha
Though almost identical to its co-orbital partner Aglaura, this moon has the decency of relatively subtlety. Its nitrogenous seas cover only part of its surface, while hazy clouds of methane and nitrogen snow shroud out its surface from space. This moon is on the brink of the nitrogen freeze line and thus experiences a quite intriguing global cycle; about half the time its atmosphere is thin and its surface is covered by frozen nitrogen ice, which slowly reddens and darkens as it is irradiated by Actinophrys’s UV radiation until the ice collapses into the atmosphere, filling long-dry ocean basins and begetting a gloomy, snowy world altogether alien to its past.
IV. Aequorea
Though it represents the end of the Core Worlds, Aequorea differs little from the members of the Expansion Region that succeed it. Like them, it is a moon-sized aquarian world dominated by extensive oceans of liquid nitrogen beneath a neutral atmosphere, like a warmer and larger version of Pluto. Like them, its surface is tectonically active, scarred by huge rifts and escarpments. But unlike all the rest, Aequorea has a powerful geomagnetic dynamo some 10% the strength of Earth’s generated by a very large liquid metal core. Aequorea’s dipole magnetic field interacts strongly with the outer radiation belt of Olindias generating giant aurorae and some very interesting atmospheric chemistry that gives rise to the unique green hues of its high-altitude hazes.
B. Expansion Region
From left to right: Larsonia, Eutiara, Cirrhitiara, Ptychogastria, Thecocodium, Crossota, Cladonema
Halitrephes is too inclined to align with the remainder of the Expansion Region.
V. Cladonema
First of the Expansion Region, Cladonema lies some 700,000 kilometers above Olindias’s aquamarine cloud decks, far beyond the Core Worlds and their frame of asteroids. Similarly to Aglantha, Cladonema is on the colder side, but its atmosphere is much more stable against collapse. The eternal snowstorm that rages across this little world is mostly frozen carbon monoxide rather than nitrogen, which remains gaseous - though only barely.
VIA. Eutiara
One of a pair of co-orbital worlds, Eutiara is a very quite striking world. This moon was likely much warmer in the deep past, heated by a greenhouse atmosphere of methane just like Ptychogastria and Crossota are today. Unlike them, it is close enough to Olindias to be bathed in great amounts of ionizing radiation that destroyed its methane and the greenhouse effect it helped produce. Though the resulting tholins darkened Eutiara and helped it absorb more solar radiation, this was not enough to offset the global cooling. The situation eventually went critical some 800 million years ago, when what ocean remained froze suddenly in a period of at most a few thousand years and the moon’s modern nitrogen seas condensed out of the remaining atmosphere. The enormous deposits of tholins laid down at that time still stain Eutiara’s continents a stark vermilion shade, even as the oceans have cleared to a pure, azure blue.
VIB. Cirrhitiara
Unlike its co-orbital partner, Cirrhitiara always had nitrogen seas. Though there are plenty of tholin deposits across this moon, these were formed non-catastrophically over a billion years and are well-integrated with the remainder of the surface, just like those on Pluto. A greenish high-altitude haze is really the only key difference, though such materials are seen elsewhere in places like Rhodactis’s rings. Unlike on Pluto, the high pressure means that methane is essentially non-volatile, forming thick deposits of dusty snow on high mountaintops and plateaus where it condenses after being released by cryovolcanism.
VII. Larsonia
This dark, clouded world is one of the strangest of the moons of Olindias. Larsonia is one of the warmer moons of Olindias, with surface temperatures approaching the boiling point of nitrogen. Clouds of liquid nitrogen intermixed with small amounts of tholins cloak the surface in near-total darkness and endless torrential rain, grinding its landmasses down to their water-ice bedrock. Though the moon itself rotates once every eleven days, the atmosphere circulates much faster, rushing to equalize temperature imbalances and building up massive charges that unleash truly enormous lightning storms. Though the Horizon System has no shortage of scorching hells, frozen ones are much harder to come by.
VIII. Ptychogastria
As one of two moons of Olindias with predominantly hydrocarbon-based seas, Ptychogastria is quite distinct from the hordes of cryogenic nitrogen worlds that surround it. The seas of this world consist mainly of methane with solvated long-chain hydrocarbons and aromatic substances, but it lacks the extended haze layers of most worlds of this type. A fair amount of greenhouse heating comes from hydrogen released by the interior; though Ptychogastria is too small to retain hydrogen, the gas escapes slowly enough that it remains a significant part of the atmosphere. The temperatures are just high enough to allow methane to melt and so it rarely makes its way up into the upper atmosphere where it can photolyze. Like a few other moons in the Horizon System, Ptychogastria has rings formed from a large comet that passed through its Roche limit.
IX. Thecocodium
Though it is the last of the nitrogen worlds of Olindias, Thecocodium differs little from the rest. It rotates just once every 34 days, so it experiences significant variations in surface temperature over the course of its day. Though the oceans remain clear throughout the day, even relatively large lakes can freeze completely solid in the night. During spring and autumn, a more or less continuous eastward wind occurs as the atmosphere rotates faster than the surface does, causing great torrential rains and snows at dusk, but the high obliquity of Olindias allows more complex circulation to occur during the summer and winter months. The drastic changes in circulation can completely restructure atmospheric and oceanic circulation across the moon, obliterating old seas and creating new ones.
X. Crossota
Crossota closely resembles what Eutiara would have looked like many millions of years ago - a warm, reddened methane world covered in tholinaceous stains. Like Ptychogastria, Crossota’s oceans are composed of methane with various solvated organics ranging from polycyclic hydrocarbons to acrylic polymers to amino acids, which are synthesized in the lower atmosphere by UV radiation. At some 4.4 million kilometers from Olindias, Crossota sits at the boundary between its magnetosphere and the solar wind. Its freezing upper atmosphere forms a cold trap that prevents methane from forming high-altitude hazes, causing all the complex chemistry of the magnetospheric boundary to occur practically at ground level, explaining its very red yet haze-less appearance.
XI. Halitrephes
Halitrephes is the last of the ‘native’ moons of Olindias. It orbits its host planet at a distant 7 million kilometers, taking some 120 days to circle it just once. It is the only normal moon of Olindias far enough to avoid tidal locking as well as the only one fully outside its magnetosphere. Halitrephes was once rich in hydrogen and significantly warmer, but the solar wind has stripped this light gas and left behind a weakly greenhouse atmosphere of mostly carbon monoxide, which also constitutes its oceans. The deep violet color is caused by a suspension of tholin particles in the upper atmosphere charged by electrostatic interactions, as well as grains of dust from its rings. Halitrephes is bordered outside its orbit by a sparse disk of asteroidal debris, much of which is locked in resonance with the moon.
C. Oscillating Exterior
From left to right: Velella, Polypodium, Porpita, Halitrephes (Expansion Region)
XII. Porpita-Velella
These two terrestrial moons are some of the strangest bodies of the Horizon System. Though captured in orbit around Olindias, they are much more like planets than moons, with masses around a quarter Earth’s and highly active geology. Much like Galaxea, they are still wreathed in their primordial hydrogen atmospheres, crushing their surfaces under tens of bars of greenhouse gas. Unlike Galaxea, not even this aggressive global warming can render them habitable. The oceans on their surfaces are not like those of Earth, but rather eutectic water-ammonia solutions sitting at a frosty 200 Kelvin. With temperatures even more bitterly cold than vaguely analogous Cryogenia, these azure worlds are but a shallow vision of habitability.
XII-I. Polypodium
Circling the common center of mass of Porpita and Velella is a small aquarian world. Polypodium is not altogether foreign from Pluto, though with its uniformly grey surface it draws closer comparisons to Eris and Haumea. Like the former, Polypodium is massive enough to retain a whisper of nitrogen atmosphere, which condenses across its icy crags as snowbanks and dunes as tall as mountains. Yet even this little world is with its secrets, for a warm, geothermal subsurface ocean lies just kilometers below its rock-hard crust.
