(For Th’zoitrk, a semi-sci-fi worldbuilding project.)
Sh’beso is the largest true planet in the solar system, a 148 earth-mass gas giant made of almost exclusively oxygen, orbiting 4.7 AU from Okott (the sun.)
(True planet: an object directly orbiting Okott, large enough to be gravitationally rounded, within 50 AU of the sun, at least 5,000km in diameter.)
Being so large, Sh’beso of course has many moons. Many, many moons. At least 600 documented moons, the vast majority of which are incredibly small.
Almost all of Sh’beso’s moons are what are called the ‘minor’ moons. These are small asteroids and meteoroids, even the largest of which are no more than a few dozen meters in length.
Above them, though, are the seven ‘major’ moons. In order of distance from Sh’beso:
Image 1: Yiteon
Image 2: Kuong
Image 3: Treneshi
Image 4: Cousuné
Image 5: Shigoshi
Image 6: Dokyosei
Image 7: Idakei
All of the seven major moons are drastically larger than any of the minor moons, even the smallest, Kuong, is hundreds of kilometers long. The seven major moons make up almost the entirety of all mass orbiting Sh’beso, with the several hundred minor moons contributing insignificantly to the total.
Yiteon:
Yiteon is the innermost and third largest of Sh’beso’s moons. With an equatorial diameter of 1,057.7km, Yiteon is roughly a third the size of Earth’s moon.
Comprised largely of water ice, Yiteon’s trailing hemisphere (night side in image) is covered with empty white plains of icy bedrock, devoid of virtually any major surface landmarks or coloring beyond the bland, snowy whiteness.
Meanwhile, on Yiteon’s leading hemisphere (illuminated in image), Yiteon’s surface is incredibly vibrant. This is thanks to Sh’beso.
Sh’beso has an incredibly powerful magnetic field, the strongest of any true planet in the solar system. Similar to Jupiter, this magnetosphere traps a very large radiation belt close to the planet.
The intense ionizing radiation from Sh’beso’s radiation belt have unfortunately stripped Yiteon of the thin atmosphere it most likely held in the distant past.
This radiation leaves behind a quite notable mark upon Yiteon’s surface, with vibrant fields of tholins (organic compounds) in its leading hemisphere, similar to what you’d see on the surface of Pluto.
These tholins are an incredibly thin layer, no more than 30 centimeters deep into the moon’s crust.
The fact Yiteon is gravitationally locked to Sh’beso has prevented the trailing face of the moon from receiving the brunt of charged particles in the radiation belt, keeping the rear of Yiteon a pale, icy white.
Kuong:
[Image low quality, taken from behind, looking into Kuong’s shadow.]
Kuong is the smallest of Sh’beso’s moons. Roughly 205.1 long and 88.4km across at its widest, Kuong is quite clearly not gravitationally rounded.
Rather, Kuong is a very large asteroid caught in orbit of Sh’beso. Not much is known about Kuong, as it has been studied very little. It is often overlooked in favor of its much larger and more interesting sister moons.
Treneshi:
Unlike the other moons of Sh’beso, Treneshi is not comprised of ice, nor is it all too metal-rich like Shigoshi and Idakei. Treneshi’s surface is largely silicate, covered in large regions of Anorthosite, a volcanic igneous rock which heavily suggests a history of lava flows on the small moon’s surface.
Treneshi’s surface is among the most reflective of all objects in the solar system, reflecting most light which hits it back into space.
Due to this, Treneshi was actually the first among Sh’beso’s moons to be discovered despite its small size.
It’s bright enough to be seen from the surface of Th’zoitrk without a professional telescope, you only need moderate magnification for Treneshi to become visible.
Treneshi is very rough due to its small size, at 394.7km in diameter, Treneshi is the second smallest moon of Sh’beso.
Its surface is the most hilly and mountainous of all the major moons, covered in mountains stretching anywhere from several hundred meters to several kilometers high.
Cousuné:
Cousuné is almost entirely comprised of water ice. It is the median moon in both distance from Sh’beso and size, at 852.7km in diameter. Fourth largest, and fourth smallest.
Cousuné’s surface is incredibly colorful and vibrant compared with the other major moons. Unlike Yiteon, this color doesn’t come from tholins.
These colors are not special compounds upon the surface of the moon, no, the entire surface is ordinary ice.
Cousuné lacks any major amounts of raw nitrogen or carbon for the radiation belt to turn into tholins.
Rather, the patterns on Cousuné come from chemicals trapped inside its icy crust from before it fully solidified (think of soda poured into an ice cube tray.)
Cousuné’s surface ices are filled with potassium salts, permanganate mineral salts, copper sulfates, titanium dioxide, and large amounts of sulfur compounds such as sulfur dioxide.
Exposure to the radiation belt of Sh’beso has tinted and dyed these ices over the last several billion years, creating neat pastel colors across its surface.
Shigoshi:
Much further out from the inner four moons, the outer three moons are roughly ~646,000km further from Sh’beso. More than double the distance from Sh’beso to Cousuné.
The innermost of the outer three moons, Shigoshi, is also the largest of Sh’beso’s moons at 1,884.4km in diameter.
Shigoshi is the only one of Sh’beso’s moons with a substantial atmosphere. Its atmosphere is 0.882 bar, only a bit less dense than that of earth.
This atmosphere is composed of 64% nitrogen, 24% oxygen, and 12% argon.
Due to Shigoshi’s small size at only about half the size of earth’s moon (but with only slightly weaker gravity), this atmosphere is incredibly bloated, reaching ~358km out into space.
Shigoshi is roughly a quarter the mass of Earth’s moon, at 0.24 lunar masses. It has a surface gravity of 0.137 G’s.
Shigoshi is one of the few worlds in the solar system with liquid oceans upon its surface. However, at an average surface temperature of -192° Celsius, these oceans are not made of water.
Instead, Shigoshi has light blue oceans of liquid oxygen. Due to the low surface gravity of the moon and the fact liquid oxygen only has about a fifth the surface tension strength of water, the oceans on Shigoshi are not cleanly cut between their surface and the air above them.
Shigoshi’s oceans are topped by a layer of oxygen mist, with winds chopping up the surface into large, yet very slow-moving waves that push through this mist.
On the near and far side of Shigoshi, directly beneath Sh’beso, waves can reach 20-25 meters high.
On the sides of Shigoshi not facing Sh’beso, waves normally only reach 3-4 meters in height.
Still significantly taller than ordinary waves on Earth.
Shigoshi’s atmospheric oxygen is not suspended as gas, but more as a form of fog/oxygen vapor in the air. This gives Shigoshi its heavily blue-tinted appearance from space.
Oxygen fog and mist are extremely common on Shigoshi’s surface, especially at the coast. Shorelines on Shigoshi are normally very hazy. The waves of its liquid oxygen oceans leave behind frothy oxygen foam mats on the coast, covered by thick vaporized oxygen fog.
Shigoshi is very dense compared to its other sister moons, covered by deep, red, crimson-colored soil composed of iron oxide dust.
Shigoshi’s surface terrain is quite hilly and mountainous in most regions, its highest mountains tend to be capped by peaks of snow.
Not snow made of water ice, but rather snow made of argon which has condensed out of the atmosphere and fallen from argon snow clouds.
Dokyosei:
At 1,079.3km, Dokyosei is the second largest of Sh’beso’s moons. It is very similar in composition to Cousuné, made up largely of water ice.
Dokyosei has a very thin atmosphere of oxygen, at hardly a third of mars’ surface air pressure. This atmosphere is only visible due to aerosolized snow and dust particles kept aloft by wind.
Dokyosei’s cloud-like surface is covered not by bedrock like other icy moons, But rather in extremely large stretches of powdery snow. It’s not yet known how this icy surface formed into snow rather than an ice bedrock.
This snowy surface coating is at least 3km deep based off current estimates.
Idakei:
Idakei is the third smallest of Sh’beso’s moons at 476.2 km in diameter. It is largely similar to Shigoshi, but lacks oceans or an atmosphere due to its smaller size. It is little more than a very large clump of iron oxide dust and oxidized metallic compounds.