Hope and Fate System
The Hope and Fate system is the system which Aron belongs to. It is a binary star system between Hope and Fate. The system contains a total of 18 planets, 10 orbiting Hope and 8 orbiting Fate, along with numerous dwarf planets and moons.
Hope
Hope is a yellow dwarf star and has 10 planets and 7 confirmed dwarf planets as of 2027. Of the 10 planets 6 are rocky planets and 4 are gas giants. These 10 planets, ordered in orbit from the closest to Hope to the farthest, are Astet, Ketal, Sera, Aron, Poree, Cailus, Polion, Scurra, Giras, and Boreas. The 7 dwarf planets are Creonus, Tiecho, Cuenive, Liaka, Setria, Micherinos, and Supaolupao.
Astet and Ketal
Astet and Ketal are a binary pair of similarly sized hot planets, located the closest to Hope at only 0.4 AU. Astet, the smaller of the two, has a diameter of 3943km20.6 Sytocahr while Ketal is larger at 4395km23.0 Sytocahr. Astet and Ketal have an orbital period of only 91 days, with an extreme orbital inclination of 63 degrees and an irregular eccentricity of about 9 degrees, making it highly unusual compared to the rest of the Hope system.
Astet and Ketal orbit each other very close, with the two only being about 27674km0.3 Lumacahr apart. Despite this Astet and Ketal are slowly drifting away from this binary orbit, and will escape each other in roughly 4 billion years. Both planets have very similar environments, with a grey rocky landscape and many craters. However in contrast to Ketal, Astet does have an extremely thin atmosphere, mainly comprised of Octane. This is due to Astet's active core and subsequent volcanic activity which slowly replenishes the atmosphere as solar winds from Hope continuously strip it away, creating a cycle which sustains the thin atmosphere.
Ketal does not have any volcanic activity, and likely hasn't for hundreds of millions of years, which is why the planet is completely airless. Due to this complete lack of geological activity however, much like Nyx, Ketal still retains craters billions of years old. The greatest of these, the Korsoko Basin, is one of the largest craters in the hope system at a staggering 1593km8.3 Sytocahr in diameter. Its appearance also suggests that this crater is the result of a somewhat recent collision, happening within the last billion years.
Sera
Sera is a hot, arid planet and the second closest to Hope at a distance about 0.75 AU. It is a mid-sized planet with a diameter of 9615km50.2 Sytocahr. Despite being far from the largest planet in the Hope system, it is by far the most dense, giving it a gravitational force only slightly less than that of Aron. Sera has an orbital period of 238 days, and almost no orbital eccentricity or inclination to speak of. The environment of Sera consists mainly of endless hot wastelands and canyons. The daytime side of the planet can get as hot as 172 degrees celsius92.4 Cahree. The nighttime side is not much better, with the lowest temperatures still being around 80 degrees celsius16.2 Cahree.
The many canyons of Sera, such as the impressive Mera Ciralaro, can stretch hundreds of kilometers and are easily visible from space. The planet is still somewhat geologically active, with sparse volcanic activity and clear signs of changing terrain. This is seen nowhere better than the divide between two sections of the planet, Sero Entrus and Sero Kihnui. Sero Entrus is a darker, heavily cratered and mountainous section of the planet while Sero Kihnui, is a lighter section untouched by craters, showing that it has changed due to geologic activity over time, mainly due to volcanoes. However on a cosmic scale this geological activity is short lived, as astronomers predict that the core of Sera will fully become inactive within the next 50-100 million years
Sera also contains a somewhat thin atmosphere mainly composed of water vapor which makes up 76.5% of its mass, although the atmosphere also contains substantial amounts of compounds such as ammonia and carbon dioxide. With a pressure of about 0.01447 atm0.459275 RevoPSL Sera's atmosphere is roughly 2.5% as thick as Aron's at sea level. This is not much, however it is thick enough to give the planet its iconic yellow-orange glow, where in reality the planet is mainly deep red rock with light orange accents. This atmosphere, due to Sera's failing core, will likely be slowly stripped away by solar winds when the geological activity ends and its replenishment stops.
Finally, Sera also has two moons orbiting it, the asteroid Beluria and the larger but still small moon Eki, with a diameter of 12.79km34.21 Gettacahr and 526.46km2.75 Sytocahr respectively. Despite their small size, these two moons are clearly visible from the surface of Sera, as the orbits of both get very close to the planet. Due to this they can sometimes cause Seran solar eclipses. Unlike on Aron these eclipses do not fully cover Hope, however they do somewhat dim it for short periods of time as the asteroids pass in front of Hope, in Eki's case its eclispe is almost comparable to Aron's Nyx. Beluria is a grey, dead asteroid. Eki is more interesting, having a diverse red and yellow surface, exposing its large sulfur deposits. Due to the chemical similarity of Sera and Eki, it is believed that Eki is the result of a large collision is Sera's past, somewhere between 3.8-4.2 billion years ago. Overall Sera is a highly interesting world, and with its diverse environments is one of the most similar planets to Aron in the Hope system, therefore making it an ideal place to search for past life.
Aron
Aron is a wet, highly hospitable planet and the home of everything Aronians have ever known. It orbits about 0.99 AU away from Hope and is the second largest rocky planet in the Hope system, with a diameter of 12,251km0.1 Lumacahr. It takes roughly 358 days for Aron to orbit Hope and said orbit has very slight inclination and eccentricity. Aron is full of diverse environments, from forests to mountains and deserts, anything can be found. Aron's average temperature is 27 degrees celsius-27.6 Cahree, making it the most livable planet in not just the Hope system, but the entire Hope and Fate system as a whole. The planet has an atmosphere composed of 77.9% nitrogen, 20.9% oxygen, and small percentages of other gases.
Aron is not just unique in its habitability but also its moons. Aron has two moons, Nyx and Parvus, with a diameter of 3470km18.1 Sytocahr and 2676km14.0 Sytocahr respectively, making them among the largest moons of any non-gas giant planet in the Hope and Fate system.
Nyx
Nyx is a white-grey essentially airless moon with a large amount of cratering and due to this, freezing temperatures as low as -52 degrees Celsius-93.1 Cahree. It orbits an average of 304,412 kilometers3.1 Lumacahr away from Aron with limited eccentricity. Nyx likely formed during Aron's earlier formation when it slammed into another protoplanet.
Parvus
Parvus, in contrast, is a temperate ocean moon. It has a thick atmosphere for its size, triple the pressure of Sera and in some areas up to 10% the thickness of Aron's. This atmosphere consists mainly of carbon dioxide and chlorine, with some amounts of nitrogen and argon, giving the moon a distinctive green color and an average temperature of -42 degree celsius-84.8 Cahree. Although the chlorine dominates the atmosphere's color overall, when seen through the light, and during sunsets, the purple of the argon becomes much more apparent. Unlike Nyx, Parvus is not heavily cratered, showing that the moon does have some forces re-shaping its surface. Parvus also has vast oceans of ammonia and water mixed with small amounts of Copper (II) Chloride, making it an extremely unique moon.
These oceans, along with Parvus' wildly different chemical composition, orbital eccentricity, and inclination compared to Nyx, suggests that Parvus is not from the Aron system. The leading theory is that during the formation of the Hope system Parvus was a protoplanet orbiting quickly somewhere around Sera's orbit, and may have grazed Sera. This far extended its early and volatile geological activity, exerted massive gravitational forces on it, and most importantly rapidly spun the moon and its core to allow Parvus to still have a weak magnetic field. This therefore lead to the creation of the basins for Parvus' oceans and flung it outward towards Aron where it was eventually pulled into a stable orbit around Aron along with Nyx. However it formed, Parvus is a unique part of the Aron system, and on nights where Nyx is not visible, Parvus casts a pale green glow on Aron.
Poree
Poree is a frigid ice planet and the 4th farthest from Hope with an average distance of 1.81 AU from the star. It is a mid-sized planet, having a diameter of 8648.45km45.18 Sytocahr, making it the second smallest planet in the Hope system. Poree has very little orbital eccentricity or inclination, however it has a very long orbital period of roughly 889 days. Poree's mass is about 20% of Aron's, this in combination with its size makes Poree much less dense than Aron. Poree's distance from Hope, along with its reflectivity, makes the planet very cold, with an average temperature of roughly -109 degrees celsius-140.2 Cahree.
Poree has a relatively thick atmosphere around 47% as thick as Aron's, having an atm of roughly 0.4745 and mainly composed of Nitrogen. This composition gives the atmosphere a bright white glow from space, however on the ground the sky is a more yellow tint. At the higher latitudes of the planet liquid nitrogen has been observed to rain down in the upper atmosphere, where temperatures can get as low as -225 degrees celsius-236.3 Cahree.
Poree has a wide array of diverse environments, and a noticeable lack of cratering. This is likely due to the shifting nature of the ice sheets and constant cryo-volcano activity, which is also the reason Poree has held onto its atmosphere. Past geological activity, likely from around a billion years ago before the planet's core cooled, has led to the existence of vast mountain ranges and glacier formations across the planet with endless ice sheets between them. Across these ice sheets frigid winds reach an average of 100 kilometers0.5 Sytocahr an hour, smoothing the landscape. Due to the planet's low density and abundance of ice it is believed that below the surface is a subsurface ocean hundreds of kilometers deep, which some believe could harbor life fueled by geothermal vents at the bottom.
Poree's defining feature is its rings, a thin belt of rock and ice surrounding the planet, due to the high distance of the rings from Poree, far outside the planet's roche limit, it is believed that these rings are the result of collisions from past asteroid moons of Poree, likely created by the capturing of asteroids flung into the inner Hope system from Cailus. Up to 5 of these moons are thought to have existed before colliding with each other to create the ring system. Currently Poree only has 1 moon, named Paite, a leftover remnant of these past collisions. This moon is a freezing white asteroid, and only has a diameter of slightly over a kilometer. Paite orbits just 6935 km36.2 Sytocahr above Poree's surface at its closest, however the moon's orbit has a very high eccentricity and inclination.
Creonus
Creonus is the first dwarf planet in the Aron system, uniquely situated between the rocky planet Poree and the gas giant Cailus. It is relatively small with a diameter of about 1017 km5.3 Sytocahr. It orbits at a distance of roughly 2.64 AU from Hope, and takes 4.38 years to orbit the star.
Creonus has an above average orbital inclination and eccentricity, with the inclination being about 8.34 degrees and the eccentricity being about 0.0267. Creonus is an extremely cold planet due to its high orbital distance and complete lack of atmosphere, having temperatures below -200 degrees celsius-215.6 Cahree on the night side, although the day side can reach up to -40 degrees celsius-83.1 Cahree. It is a blueish-grey rocky world, and heavily cratered by billions of years of impacts as Creonus has likely not been geologically active since its formation.
Cailus
Cailus is the first of four gas giants in the Hope system and it is also the largest of them with a diameter of 139,972 km1.4 Lumacahr. The massive planet orbits at a distance of 4.06 AU, with tiny eccentricity and almost no inclination. This distance gives the gas giant an orbital period of about 10.75 years, although despite this it is by far the closest to Hope of the gas giants in the system. The planet is overall a light blue color, with distinctive shades of blues forming the weather systems of its deep atmosphere. Cailus is also the most massive object in the Hope system, having a mass over 340 times that of Aron, although being a gas giant Cailus is not very dense.
Cailus has no physical surface to stand on, and is instead made up of layers upon layers of clouds and atmosphere, mostly composed of hydrogen. These regularly form into huge superstorms, some of which can reach sizes larger than that of other planets and last 100s of years, such as Caili-Surtora, a massive superstorm over 18000km0.2 Lumacahr in diameter which forms a deep blue oval on Cailus' surface. Wind speeds inside the planet average around a huge 500 kilometers2.6 Sytocahr per hour while areas like Caili-Surtora can reach up to 1000 kilometers5.2 Sytocahr an hour. Due to its distance from Hope, Cailus has an average temperature of -220 degrees Celsius-232.1 Cahree. The frozen windy atmosphere of Cailus continues tens of thousands of kilometers down, until around 25,000 kilometers0.3 Lumacahr from the core the pressure becomes so intense that the hydrogen atmosphere compresses into a liquid hydrogen ocean, and 10,000-15,000 kilometers0.2 Lumacahr deeper lies a roughly Aron sized superheated rocky-metallic core where temperatures reach as high as 30,000 degrees celsius24,787.6 Cahree. Due to this internal structure Cailus hosts the largest magnetic field in the Hope system, and an expansive radiation belt which makes living within 1,500,000 kilometers15.3 Lumacahr of the planet essentially impossible. The planet's name comes from the Palmarian god of nature Cailus.
However, the most interesting part of Cailus is its 6 major moons, though this does mean that material for the moons is more spread out which means its moons have a lower size than most gas giants in the Hope and Fate system. These moons are split into 2 major catagories. The 3 largest are known as the Megeleian Moons, after Megeleia Galoni, the first recorded astronomer to observe the Cailus moon system. The smaller 3, due to the distance in size between them and the Megeleian Moons, are known as the Siternein Moons, after ancient Phydrian Astronomer Siternei, who wrote the first record of Cailus' existance. The 6 moons, in order of largest to smallest, are as follows: Ise, Alneim, Serendai, Charayl, Monacle, and Kiethe.
Ise
Ise is the largest moon of Cailus, about 400 kilometers2.1 Sytocahr larger than Alneim and the farthest major moon from Cailus by far, orbiting at a distance of 2,559,139 kilometers26.1 Lumacahr. Ise has a diameter of 6254 kilometers32.7 Sytocahr. It is a Blue-red moon with large iron-oxide deserts. It has a much less cratered surface than Alneim, showing continued activity on beneath the surface. Ise is the most unique moon of Cailus in the fact that it is the only one with a substantial atmosphere, mainly comprised of volcanic Sulfur Dioxide, Nitrogen, and Ethylene. This atmosphere is about 3/5 the pressure of Aron's at 0.6588 atm0.32672 PSL however it has an intense greenhouse effect due to considerable amounts of Sulfur Hexafluoride in its composition. The atmosphere is replenished by gases escaping the planet's interior, and has a long lifetime due to the fact that unlike most moons, Ise's core spins fast and hot enough to create a magnetic field.
The most interesting part of Ise however are its oceans. Ise is the only other body in the Hope system to have surface water, as Ise's oceans are mainly comprised of liquid water, however they do also contain sizable amounts of Sulfur Dioxide and Ammonia. The moon is likely kept warm enough for these oceans to exist due to the intense greenhouse effect of the atmosphere as well as the heat of the core and tidal heating by Cailus. These factors make it the most promising Hope system body to find current or past life on, and it is believed that certain Aronian lifeforms could survive the conditions on Ise, given they are supplied with oyxgen and food. Like Alneim, Ise was first discovered in 1529 DME by Megeleia Galoni. Ise is named after the Palmarian goddess of aquaria and oceans.
Alneim
Alneim is the second largest moon of Cailus and in contrast to Ise, it is also the closest to the planet, it has a diameter of 5842 kilometers30.5 Sytocahr and orbits 771,714 kilometers7.9 Lumacahr away from Cailus.
The moon has a grey, cratered rocky surface, though the most iconic part of Alneim are the deep blue patches of the moon. These patches are formed due to the moons high amount of azurite, a blue stone found often in copper deposits. This azurite is believed to be consistently resurfaced over millions of years as the gravity of Cailus pulling on Alneim resurfaces the moons geological activity every couple hundred million years and causes the azurite deposits to be visible. Alneim, along with a majority of Cailus' major moon system, was first observed by Megeleia Galoni in 1529 DME. Alneim is named after the Palmarian god Alneim, son of the god Cailus.
Serendai
Following Alneim and Ise the size of Cailus' moons drop dramatically. Serendai is a mid sized moon at 3794 kilometers19.8 Sytocahr in diameter, and like Ise orbits far out, having an average orbital distance of 2,419,193 kilometers24.7 Lumacahr from Cailus. It, like Alneim, is a airless, heavily cratered rock. However unlike Alneim, Serendai does contain volcanic deposits on the surface, showing that the moon does have an unstable past of volcanic activity, potentially from a collision at some point within the last 300 million years, which would explain the large dark-grey basin near its northern hemisphere. Otherwise, however, Serendai is a very standard rocky moon. First observed by Megelai Galoni like the other Megeleian moons, Serendai is named after the goddess Serendai, younger sister of the god Alneim.
Charayl
Charyal is the 4th largest moon of Cailus, and thus falls into the catagory of the Siternein moons. It has a diameter of 1302 kilometers6.8 Sytocahr and orbits at a distance of 1,126,471 kilometers11.5 Lumacahr from Cailus, with minimum eccentricity or inclination. Charyl uniquely sits at the very inner edge of Cailus' Eicho Belt, a roughly 800,000 kilometer8.2 Lumacahr wide belt of asteroid moons where a majority of Cailus' moons of that type are located, and what separates the inner belt of Major moons from the outer belt. Charayl is therefore likely to be the remaining culmination of the material left on this inner section of the Eicho belt after the formation of Alneim, an explanation that likely also replies to Charayl's sibling moon Monacle and its much larger neighbor moon Ise.
Charayl, and moons like it, are often referred to as "mini-Porees" due to their icy environment and possible subsurface oceans. Charayl is no different in this, hosting a fridgid icy shell dozens of kilometers thick, hiding a subsurface ocean of water that likely extends close to the core of the moon. Charayl is also unique with its cryo-volcanos, a phenomenon that other than on Charayl is only seen on Poree and possibly Giras' moon Matha. Charayl has also been observed to have large cracks across its white-blue surface, likely pointing to reshaping of the surface due to constant cryo-volcanic activity. Charayl follows the naming scheme of most Hope system objects, and is therefore named after the Palmarian goddess Charayl.