ARIST SYSTEM
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SYSTEM SUMMARY
Arist is a fairly old single-star system, consisting of a K-type main-sequence star, 7 planets, and hundreds of moons and minor planets. The system shares a surprising amount of similarity to the solar system, though more compact owing to the star's lower gravitational attraction. Despite being double the age of the solar system, the longevity of K-type stars means that Arist will still shine and remain stable for billions of years more, its habitable zone a prime location for life to thrive and develop.
ARISTArist is the lone star of the Arist system. At 0.705 times the mass of the Sun and 0.679 times its radius, Arist is a K-type main-sequence star. It houses an extensive system comparable to the solar system, though more compact. Arist has shone for 9.44 billion years, slightly more than twice the age of the Sun. Its lower mass and hence slower rate of consuming its fuel are sufficient for about another 14.5 billion years of light and warmth until it fades away at 24 billion years of age.
Although the star is around 70% of the Sun's mass, its luminosity is only 17.6% of the solar system's star. Its surface temperature is also over 1000°C cooler than the Sun, at 4291°C.
ACISENRINDAcisenrind is the innermost planet of the system. It can be considered quite a close parallel to Mercury, except for its size. Acisenrind is 0.83 times the mass of the Earth and 0.957 times Earth's radius (6094 km).
Due to the more compact nature of the Arist system, Acisenrind whips around its star in 10.2 days and has become tidally locked. As a result, the day side temperature is locked to 340°C, and the night side plunges to below zero and remains thus.
A thin band around the terminator of the planet—where day meets night—would maintain temperatures similar to Earth. However, the lack of an atmosphere and the constant bombardment of Arist's solar wind means that Acisenrind has long lost virtually all of its water, and is hence not at all habitable.
While Acisenrind is not as hot as Mercury or Venus, the closer proximity to its star means stronger solar winds, which strips away material from the planet's surface. The current rate of this mass loss is 2800 kg/s. Therefore, Acisenrind is shrinking, but at the current rate, Arist would long be a dead star before all of Acisenrind's mass is lost. Once Arist reaches the end of its life, Acisenrind will only have lost 0.03% of its mass to the solar wind. Really lets you appreciate just how big these planets are.
ACISENRINDThe second planet from Arist is slightly smaller than Acisenrind, at 0.76 times the mass of the Earth with a radius of 5945 km. However, the two planets share a similar composition and their surface features are very much alike.
With an orbit of 47.1 days, Acisenusuk is just far enough away not to be tidally locked but has developed a 2:3 resonance with the star. That is, for every 2 orbits around Arist, Acisenusuk rotates on its axis 3 times. The time required for one rotation is therefore 31.4 days.
Temperatures on the day side are about 91°C, with night also causing a plunge into sub-zero temperatures. Like Acisenrind, Acisenusuk has lost all of its water except for some ices hidden in the depths of craters.
JASUSBULAMeet the 3rd planet from Arist, a desert world on the inner edge of the habitable zone—Jasusbula. Slightly more massive than Earth, the planet is covered in shifting sands, dunes, and arid plateaus.
These clouds are deceitful—for they contain very minimal water, but a number of other substances. They should not be blue, but Universe Sandbox ² does not yet support changing atmosphere colour and atmospheric composition, and so I've had to make do with what I had.
In the ancient past, liquid water did indeed exist on the surface of Jasusbula, the evidence being a number of dry riverbeds and valleys carved by water. However, at the inner edge of the habitable zone, water was not exactly plentiful in the first place. On top of this, Arist was also much cooler and less luminous in its first billion years or so of its life. Stars gradually increase their luminosity as they age. Therefore, as time passed, Arist gradually increased luminosity, meaning a greater amount of energy and solar wind hitting Jasusbula, causing increased water loss. Over the next few billion years, surface water gradually disappeared from the planet, rendering the surface quite inhospitable. Some water has been able to avoid the fate of being stripped from the planet. These reservoirs are now trapped underground in subterranean lakes and rivers.
It is to the credit of the planet's magnetic field that no more of the water has been lost to the solar wind. Jasusbula still retains a molten core and has a fairly fast rotation rate. One day here is 3.32 Earth days. As a result, a magnetic field was able to develop and divert a portion of the star's charged particles, which are capable of blasting water away from the planet. If not for the magnetic field, the water on Jasusbula would certainly have been lost much faster, not to mention that a greater portion would have been lost.
Would life be able to survive in Jasusbula's underground water reservoirs? Whether it may or not, an advanced civilisation is unlikely to evolve here.
TROSUSLIASituated in the middle of Arist's habitable zone lies Trosuslia, a relatively small Super-Earth weighing in at 2.23 Earth masses and a radius of 8089km. In contrast to Jasusbula, Trosuslia is the only planet with liquid water oceans, as well as life evidently on its surface.
Though it is also a blue planet, it does not share a lot of similarities compared to Earth. A day on Trosuslia is about 2.5 Earth days. Seasons are a little more than half as long as our home planet. New human arrivals would have to take some time to adjust to the higher gravity. With an atmosphere that is 143% as heavy as Earth, living in a world with higher atmospheric pressures would also take some getting used to. Only the average temperature is relatively unchanged compared to the Earth. Trosuslia's average surface temperature is 16–17°C, compared to Earth's 15°C. While this may not seem like a lot, if Earth's average temperature is 1°C warmer than it is now, sea levels would rise by 6 metres, swamping many low-lying areas. Taking this into account, Trosuslia, therefore, does not have extensive ice caps.
The large mass of Trosuslia allowed itself to sweep up most of the water present in the habitable zone during its formation. Its gravity well also attracted many small bodies containing water that was sent towards the inner Arist system by the gas and ice giants in its early days. A greater amount of its surface is covered by water compared to Earth, and it is not far from being an ocean planet with no landmasses. The high gravity of Trosuslia means that mountains cannot grow very tall before collapsing on themselves, and therefore much of the surface is covered by low-lying archipelagos.
Although there are no signs of advanced civilisations on Trosuslia, life has most definitely taken a foothold. The low-lying archipelagos are dominated by lush forests and plains, providing support to a complex and diverse biosphere. Even though Trosuslia is over twice as old as the Earth, life has had a difficult time emerging due to a multitude of severe extinction events in much of its history. It's large gravity well attracts more potentially hazardous asteroids capable of inducing such extinctions. The high mass and size of Trosuslia also mean that there is much more remnant heat in its interior than Earth, leading to periodic planet-wide eruption events, throwing up dust and blocking the star's light. It was only after about 6 billion years after its formation that impact events were not so frequent and eruptions were not so widespread.
After this time, unicellular organisms were finally able to flourish for extended periods. They did exist before this time but kept experiencing extinction events that prevented them from developing further. At around 8.5 billion years of age, the first multicellular organisms appeared in the oceans. At 8.9 billion years old, life finally made the move onto land. Now, at 9.44 billion years, both land and sea house an extensive array of biota, with their complexity and evolution showing no sign of slowing down lest another major extinction event should occur.
Like the Earth-Moon system, a relatively large moon also orbits Trosuslia. However, whereas Earth is 81 times more massive than the Moon, Trosuslia is 206 times as massive as its companion—Trosuslia I. It is believed this moon also formed via a gigantic collision early in Trosuslia's history.
On Earth, the Moon has a stabilising effect on its axial tilt, stopping the Earth from tilting erratically and keeping the climate relatively level. Although Trosuslia I is much less massive compared to its orbital parent, it also achieves the same effect, but to a lesser extent.
Compared to the monthly orbit of our Moon, Trosuslia I orbital period is only about 11 days. As a result, it appears larger in Trosuslia's sky than the Moon appears in Earth's sky, and is responsible for somewhat more prominent tides on the ocean planet.
DINURUBehold the first gas giant of the Arist system—Dinuru. Though it is certainly more massive than any terrestrial planet in the system and 12 times as massive as Trosuslia, at 27.3 Earth masses, it really isn't very impressive in the grand scale of things. By comparison, Saturn has 95.2 Earth masses. Nevertheless, it is the most massive planet in the system.
Dinuru is largely composed of hydrogen, with the gas accounting for 74% of its total mass. Water is more abundant beyond the habitable zone, and so 19% of its composition is composed of water.
All three gas giants of the Arist system have developed ring systems. The rings of Dinuru are almost entirely made of silicates.
It should be noted that Dinuru's size—or rather lack of size—is partly responsible for life having a rough start on Trosuslia. In our solar system, Jupiter acts like a cosmic vacuum, diverting potentially hazardous asteroids away from Earth. Dinuru does not have sufficient mass to act as a very effective shielder to Trosuslia.
Dinuru boasts 47 moons, the greatest number of moons of any planet in the Arist system. However, only the innermost moons and moons of radius 100 km or greater have been displayed in the simulation. This is to avoid cluttering up the system and slowing down the simulation.
At about 1 million kilometres from Diniru orbits Dinuru VII, a moon 2.52 times more massive than our Moon. The tidal forces between it and the gas giant create internal heating and a weak magnetic field to develop, shielding the moon from solar winds. Dinuru VII also lies within Dinuru's magnetic field for a portion of its orbit. Solar wind strips away atmospheric particles, but these shielding factors allow it to retain a relatively thick atmosphere compared to other moons and even some ice on its surface.
However, with a temperature of -140°C, it is unlikely for life to develop here. Whereas moons like Europa in the solar system could have an ocean under the ice, the ice for Dinuru VII is thin compared to moons like Europa, meaning there is no ocean for organisms to seek refuge in.
ROTULISThe second gaseous planet from Arist is more closely related to Uranus and Neptune than Saturn or Jupiter. At 16.2 Earth masses, it is slightly more massive than Uranus but slightly less massive than Neptune. However, where both Uranus and Neptune are made of more than 80% water, Rotulis has hydrogen and water in more or less equal proportions, allocating it the title of being a hybrid of gas and ice giant.
Aside from these characteristics, there's nothing too different here than to Dinuru. Granted, it is certainly colder, with the temperature at Rotulis being -180°C, but the sights and experiences one would expect to see here are quite similar.
The Rotulis system contains 39 moons. Only the innermost moons and moons of radius 100 km or greater are simulated.
CHARILIAThe outermost planet of Arist and also the last of the giant planets is Charilia, and the only true ice giant of the system, with its composition made of 66% water. With a mass of 13.3 Earths, it is less massive than either Uranus or Neptune. However, its high axial tilt gives its system a somewhat analogous appearance to Uranus.
Due to the compact nature of the Arist system, Charilia would occupy about the same orbit of Jupiter should it be relocated to our solar system.
The Charilia system is heavily shrouded by icy materials. The temperatures of -200°C here allow massive amounts of ice to exist, both in the planet and within its moon systems. Some moons contain an icy crust up to hundreds of kilometres thick, most notably on Charilia VII, VIII and IX. Despite this, it is believed that Charilia offers too little tidal heating to produce liquid water oceans under the crust of ice like on Europa. The ice is likely frozen almost entirely the way through to the mantle of the moons, reducing the chance of marine organisms surviving under the ice.
The Charilia system contains 36 moons. Only the innermost moons and moons of radius 100 km or greater are simulated.
DWARF PLANETSA number of dwarf planets and minor planets orbit Arist. Of these, there are two notable members in the inner asteroid belt between Trosuslia and Dinuru. Both have a radius of about 500 km.
It is believed that the asteroid belt was unable to form an entirely new planet because of gravitational perturbations from Dinuru. This is similar to the case of Jupiter in our solar system. Although Dinuru is less massive than Jupiter, the compact orbits of Arist ensure its gravity still has a role in preventing planet formation around the outer edge of the habitable zone.
More dwarf planets exist beyond the orbit of Charilia than in the inner Arist system. This region contains another asteroid belt, analogous to the Kuiper Belt in our solar system. Due to its distance from Arist, objects here are mostly made from icy materials.
Only dwarf planets with a radius of 450 km or more are displayed in the simulation. There are hundreds more with radius 100–400km, but adding so many would be a heavy burden on the simulation.
COMETSMost comets in the Arist system originate from the asteroid belt beyond Charilia. Notable members include Comets Adtel, Eaphus, Uephus and Esmilles. All four are known to produce impressive tails on their close approaches to the star, and all four are periodic comets, capable of being seen more than three times in a human's lifetime.
The display of the comets is expected to continue as long as they contain icy volatiles on their surface. Esmilles has the closest orbit to Arist and is expected to exhaust its volatiles first, but not before it completes another few thousand orbits around the star.
The Arist system does contain more than these four comets, and even an Oort Cloud far beyond the orbits of the planets. Long period comets from there could take thousands to hundreds of thousands of years to orbit. However, these are not simulated to avoid cluttering.
TIPS- If your device is slow, download the version of the system with no particles.
- Recommend maximum timewarp rate: 2 hours/sec
CREATOR'S NOTESMy worldbuilding project after the previous Sorr system is now complete.
This system took about a day's worth of total playing time to create, split over the course of a month. While the previous binary system—Sorr—was not a bad creation, I had begun to notice some very unrealistic portions of the creation seeping through. Arist may not be as spectacular in that it does not have two stars, but my ultimate aim in worldbuilding is to build star systems so realistic, you begin to wonder if I replicated an exoplanet system we've already discovered in real life.
These systems are certainly fictional and based off of my imagination, but my methodology is to tinker with the system for the longest while, fixing little things until I am satisfied with its realism. Some of these little things you may not even notice. Orbital resonance is included in Arist. Albedo has been taken into consideration. The orbits of planets all have a certain degree of eccentricity and inclination to model the real world. Even the magnetic pole angle has been altered on objects with a magnetic field, despite it not having any effect yet in the game.
I'd appreciate any suggestions as to how I may be able to improve future systems beyond this.
