Alexandru System (LVL's Marstopper)

The **Alexandru System** is a solar system located in the Andromeda Galaxy (known locally as the Gatlantis Galaxy). The system contains a Sun-like G3V star known as Alexandru and 8 orbiting planets: 4 gas giants and 4 ice giants. In addition to Alexandru's 8 planets, the system contains an unknown number of dwarf planets and an even higher number of smaller minor bodies such as asteroids, comets, etc. The system is also notably the home system of the Lordions and the Great Morbidian Empire, which controls the entirety of Andromeda as well as the neighboring Triangulum Galaxy.

Alexandru forms a binary star system with Gherghescu, a K-type star. However, the two have an exceptionally large average distance between them of 9,080 AU. Because of those, both stars are able to host their own planetary systems; Gherghescu boasts a large system of 18 planets.

## Structure and Composition

Much like the Solar System, the Alexandru System's parent star, Alexandru, forms the dominant gravitational member of the system. All objects in the system are gravitationally bound to Alexandru.

### Orbits

Like the Earth's Solar System, the Alexandru System's 8 major planets all orbit in the same plane, or eliptic, while smaller minor bodies such as dwarf planets, asteroids, and comets tend to have more erratic and inclined orbits compared to those of the planets. All 8 planets bear host to large systems of moons, with many of them being tidally locked to their parent planets. Being giant planets, the Alexandru System's 8 planets also bear host to ring systems containing bands of inumerable tiny particles orbiting their parent object together. The only exception to both of these cases is the first planet Thysis, whose extremely close orbit to Alexandru renders the orbits of any ring system or moon unstable.

Also like the Solar System, most objects in the Alexandru System orbit in the same direction as Alexandru's rotation (which is counterclockwise) while moons do the same, but with their parent planet. Exceptions to both cases exist and are much more common in small, minor objects like comets, though a few large moons have retrograde orbits.

A majority of planetary orbits in the Alexandru System are roughly circular, with more elliptical orbits usually being limited to asteroids, comets, and other objects of a similar scale. A notable exception, however, exists with the second planet Adenistia, whose orbit is highly elliptical despite the planet being comparable in mass to Jupiter. The cause of this anomaly is unknown; theories include interference from Cytosistoras (whose close orbit with Adenistia, in fact, is predicted to result in its destabilization within a few thousand years) to a close passage with the neighboring Gherghescu System, but evidence is still inconclusive.

Because of Alexandru and Gherghescu's significant distance from each other, their influence on each other's systems' orbits is insignificant to none, being limited to disruptions in the paths of some particularly far-out comets. Any significant interactions between the two systems orbit-wise likely occurred in their distant past. Both the two stars themselves and their respective systems rotate and orbit in the same direction, suggesting that the two stars formed at the same time together rather than capturing each other.

### Composition

The overall structure of the Alexandru System differs significantly from the Solar System's. The Alexandru inner system consists of four large gas giant planets all comparable in size and mass to Jupiter or Saturn. The outer system consists of four smaller ice giant planets similar to Uranus or Neptune. Beyond the four ice giants exists an extensive region of comets and ice asteroids similar to the Kuiper Belt or the known as the Khionian Field. Because of Alexandru's binary companion Gherghescu, the Khionian Field is significantly smaller in size, extending out to only around 200 AU, and contains a bulge in the direction of Gherghescu caused by the companion star's gravity. Gherghescu's outer comet cloud carries a similar shape, but is even more deformed due to Alexandru's higher gravity. Alexandru contains no asteroid belts, as the high masses of its planets render any asteroid belt within the orbit of the eighth planet unstable.

Alexandru forms the primary component of the Alexandru System, with its mass accounting for over 90% of the total mass of the system. However, because all of its planets are giant planets, Alexandru accounts for less of the total mass of the Alexandru System than the Sun accounts for the total mass of our Solar System. The non-stellar mass of the Alexandru System is mostly made up of the masses of Thysis, Adenistia, Cytosistoras, and Guanus. In general, however, planetary mass in the Alexandru System is spread more evenly amongst the 8 planets due to the greater similarities between their masses compared to the Solar System, where significant mass margins exist between the terrestrials and the giant planets.

Alexandru, like the Sun, is primarily composed of hydrogen and helium. However, it contains a much greater concentration of elements heavier than the two and has a higher metallicity, which explains the system's high number of gas giant planets (stars with higher metallicities tend to have more giant planets). Alexandru's planets, being giants, are also composed mostly of hydrogen and helium, though Adenistia notably has unusually low levels of hydrogen.

## Formation and evolution

The Alexandru System formed 7.1 billion years ago in a similar fashion to other Sun-like systems, beginning as a molecular cloud floating in deep space. This molecular cloud likely contained a higher concentration of elements heavier than hydrogen and helium than most, which would explain Alexandru and Gherghescu's high metallicities.

The molecular cloud then condensed due to gravity until several protoplanetary disks formed with protostars in their centers. Among them were the protostars that would become Alexandru and Gherghescu; it is likely that the two stars formed at the same time and became gravitationally bound to each other at an early age, though it is yet unknown why the two stars did not become a closer binary. This molecular cloud likely gave birth to several other stars in addition to Alexandru.

Alexandru's protoplanetary disk then condensed to form its planets; due to its high metallicity, most of the planets formed were large gas giants or ice giants. It is possible that the giant planets all formed further from Alexandru, where volatile icy compounds could remain solid, before migrating inwards and settling into their current orbits. It is also possible that many other planets, perhaps hundreds, initially populated the system before colliding with the current planets or getting ejected; the fourth planet Guanus, for instance, likely suffered from a collision with a Neptune- or Uranus- sized object, giving it its signature axial tilt.

Within around 50 million years after forming, Alexandru began nuclear fusion and became a true star, marking the beginning of its main sequence phase. Around that time, the planets began forming moons. Alexandru is currently still within the main-sequence, which is expected to last roughly 10-12 billion years.

### Future

In 3-5 billion years, Alexandru will exhaust its supply of hydrogen and expand into a red giant. Assuming that its planetary system has experienced no changes by then, the expanding Alexandru will likely engulf the orbits of Thysis and Adenistia. There is also a chance that Alexandru will engulf Cytosistoras' orbit as well. Afterwards, the star will contract and begin fusing helium as a subgiant.

Because Alexandru is a low-mass star, it will not fuse elements heavier than hydrogen and helium. Instead, it will expand into a red giant once more as it sheds off its outer layers. The end result will be a white dwarf around the size of Sarsistoras surrounded by a large planetary nebula, which will then condense to form new stars.

## Major Objects

### Alexandru

**Alexandru** is the central star of its eponymous system. It is a G3V-type star very similar to the Sun, being only 0.98 times as massive and 1.05 times as large. Alexandru is 7.1 billion years old and is expected to exhaust its hydrogen and transition into a red giant within 3-5 billion years.

### Thysis

**Thysis** is the first planet of the Alexandru System. It is a hot Jupiter-type world which has the properties and composition of a gas giant similar to Jupiter or Saturn, but orbits at a much smaller distance from its host star. As a result, high temperatures sear this planet and drive extremely turbulent weather patterns, with a massive storm occupying roughly a fourth of Thysis' surface area churning on the gas giant's sunward-facing side. For the same reason, Thysis is tidally locked to its host star. Thysis is also notable for its unusual pink and blue hues.

### Adenistia

**Adenistia** is Alexandru's second planet as well as its largest planet, with the gas giant boasting a radius roughly 1.38 times Jupiter's. Adenistia is notable for having a rather eccentric orbit - its periapsis takes it into an orbit closer to Alexandru than Mercury is to the Sun while its apoapsis takes it to a distance similar to that between Earth and the Sun. As such, Adenistia suffers from extreme temperature changes, which in turn fuels dozens of massive storms in its atmosphere.

Adenistia usually carries a greenish-yellowish hue caused by gaseous sulfur in its atmosphere, which is able to exist due to the planet's unusually low hydrogen content. However, as it approaches the periapsis of its orbit, the planet transitions into a Sudarsky Class II gas giant - its atmosphere darkens in color as the abundance of alkali metals substantially increases due to the heat. Adenistia then gradually rverts back to its usual light green hue once it loops back towards its apoapsis.

Adenistia contains a large moon known as Lastalia with a comparable size to Earth. Lastalia is subjected to the same extreme temperature swings its parent planet experiences; most of the time, Lastalia carries an inhospitable environment somewhat similar to that of Venus, with its surface reaching extremely high temperatures thanks to a thick atmosphere of water vapor and other greenhouse gasses. However, when Adenistia reaches its farthest distance from Alexandru, Lastalia's temperatures rapidly cool, allowing the aforementioned water vapor to condense and fall to the surface as rain. This ultimately results in Lastalia temporarily adopting a habitable tropical environment consisting of small sandy islands dotting a large planetwide ocean. Once Adenistia begins moving back towards its parent star, Lastalia's oceans evaporate and its thick atmosphere returns, eliminating its habitability until the next time its parent planet reaches apoapsis.

Adenistia's orbit brings it rather close to that of its neighbor Cytosistoras. In the past, the two planets' orbits have remained stable, but studies have shown that their orbits are slowly moving closer together. It is expected that Adenistia and Cytosistoras will destabilize each others' orbits within 9 millennia if no further action is taken.

### Cytosistoras

**Cytosistoras** is the third planet and another gas giant planet, smaller in size than Adenistia but more massive. Cytosistoras orbits at a similar distance from Alexandru to Mars from the Sun, granting it a light blue color caused by water clouds in its atmosphere. Cytosistoras also boasts a set of prominent rings similar to Saturn's.

Though Cytosistoras orbits just outside of Alexandru's habitable zone, tidal heating allows its moons to reach Earth-like temperatures. All of its moons, however, are too small to retain a breathable atmosphere except for Sarsistoras, a super-Earth whose gravity is more than sufficient to maintain a thick breathable atmosphere in the long-term. Sarsistoras is the homeworld of a sentient species known as the Lordions, whose appearance resembles that of a rabbit on Earth except anthropomorphic and red in color. Based on its relatively normal orbit, Sarsistoras likely formed alongside Cytosistoras and its other moons rather than being captured later on.

Cytosistoras' orbit brings it rather close to that of its neighbor Adenistia. In the past, the two planets' orbits have remained stable, but studies have shown that their orbits are slowly moving closer together. It is expected that Adenistia and Cytosistoras will destabilize each others' orbits within 9 millennia if no further action is taken. Once the destabilization event takes place, Cytosistoras will likely exit the habitable zone, in turn leading to the loss of Sarsistoras' habitability. This theory notably forms one of the chief justifications for the Great Morbidian Empire's imperialist and colonialist policies.

### Guanus

**Guanus** is the fourth planet of the Alexandru System and a gas giant planet with a mass and size similar to Jupiter. Clouds of hydrogen, helium, and ammonia give this planet's atmosphere warm colors. Two storms similar to Jupiter's Great Red Spot also exist on this planet. In addition, Guanus bears host to a large ring system with a significant gap in its middle; some astronomers refer to Guanus' ring system as two separate ring systems: one inner and one outer.

Uniquely, Guanus has a near-90 degree axial tilt similar to that of Uranus, giving it unique weather patterns and seasons. It is thought that a collision with a Neptune-sized ice giant object gave the gas giant planet its unique axial tilt, but the cause of this property is still under investigation.

### Panthiave

**Panthiave**, the fifth planet, is the first of four outer ice giants. Panthiave in particular is similar to Neptune, with a vivid blue hue caused by large quantities of methane in its atmosphere. However, Panthiave has a somewhat larger mass and size than both Uranus and Neptune, with a mass roughly 32 times Earth's. Panthiave hosts a visible but rather narrow ring system.

### Eltheove

**Eltheove** is the sixth planet and another ice giant planet. Eltheove has an appearance more akin to that of Uranus than Neptune, with a relatively featureless atmosphere light blue in color. Eltheove also boasts the largest ring system in the entire Alexandru System. Aside from physical appearance, Eltheove is very similar to its neighbor Panthiave, with a similar mass of around 35 times Earth's and a similar composition.

### Cornelia

The seventh planet **Cornelia** is an ice giant with a mass and size closely matching those of Neptune. Its atmosphere is rather stormy and turbulent, with winds regularly exceeding the speed of sound. A tenuous ring system with a large gap similar to the one found in Guanus' rings also surrounds Cornelia.

Cornelia's most defining feature is its vivid pink and magenta hue. The cause of this is still unclear, but a popular theory amongst Lordions is that the characteristic blue methane of ice giants mixes with red tholins (the compound that gives gas giants like Guanus as well as dwarf planets their red color) to form purple.

### Euphemia

**Euphemia** is the eighth and final planet of the Alexandru System and another ice giant. In terms of its weather, Euphemia can be compared to Uranus; lower wind speeds mean that its atmosphere is not nearly as turbulent as Cornelia, making the planet appear rather featureless from afar. A thin set of rings orbits close to the planet. Like Cornelia, Euphemia possesses an unusual pink hue, but it is much lighter and paler in comparison possibly as another side effect of its relatively calm atmosphere.

## Khionian Field

Beyond the orbit of Euphemia lies the **Khionian Field**, an extensive region of dwarf planets, asteroids, comets, and other minor objects. It can be compared to the Kuiper Belt or Oort Cloud around the Sun. The Khionian Field is relatively small compared to the aforementioned regions due to influence from Alexandru's neighbor Gherghescu, extending out to only around 200 AU on average. The Khionian Field is also thicker in the direction of Gherghescu due to the companion star exerting its gravitational force on the field's object.