The Aurora System
Excerpt from the UNSC Galactic Codex: 3238 Edition
Original article by Antoine D'Coolette
In all of the time that I have been in transit between dozens and dozens of alien star systems throughout Human space and beyond, I have neglected to explain the world in which I was born and grew up in; the world I left behind and have rarely seen since after embarking on the endeavor that is this Codex. It is fair to assume that by the time this volume reaches the publishing stage that many Humans may arrive in our world and may seek knowledge, though justifiably, many have opted to remain on Mobius.
However, this section will hope to contain the knowledge necessary to describe the system in full, as I have managed to observe it in a unique way that many of my kin could not even imagine. This shall be broken down into several sections much like the previous chapters, sections, and subsections of the Codex, but I shall expand upon them to the best of my ability using both ancestral scientific fact from centuries of observation from Mobius, my own personal experiences, and UNSC Frontier Corps analysis.
-General Description-
The Aurora System contains ten major planets and approximately twelve minor worlds that orbits a single star. The central star is known as Aurora, but mainly in the context of outside reference (i.e. when a Mobian is travelling in another system), though for ceremonial or educational purposes, it retains its proper moniker. In astronomical context, it is necessary to refer to Aurora as such as it is technically the same star as Sol, the primary around which the planet Earth revolves around.
Aurora is a G2V-class main sequence dwarf that burns with a yellow-white true color, but when viewed in an oxygen-rich environment, takes on any color from bright yellow to deep red. For all intents and purposes, it is the exact same star as Sol, retaining an identical stellar mass, as well as stellar radius, and even an identical surface temperature of 5778 Kelvin. Because of such little fluctuation, it has been determined not only by modern standards, but by the colonization fleet of the Lost Million, that the frame of time between Sol and Aurora is rather small, indicating that the time gap between the two worlds is limited to less than twenty thousand standard years. As such, Aurora seems to maintain the same habitable zone as its Home Universe counterpart, though in the context of this document, Mobius' homeworld, known as EUS-0, will be henceforth referred to as Zone-1.
Aurora also seems to possess the same velocity as it orbits around the Zone-1 version of the Milky Way galaxy, which has been tagged EGC-0-1 under the Extrauniversal Galactic Catalogue, EUS-0, Object 1. This orbital time is estimated to be 250 million years, identical with HU.
It must be stated though that Aurora goes through solar cycles at a slightly slower rate, on average taking 13.5 years to complete, and accurately repeat. Every cycle change, flares become more prevalent, and seem to have the same strength as Sol. Sunspot formation appears to be consistent with the HU counterpart.
This concludes the general notes on the star at the center of the Aurora system. The next section will explain the ten major planets of the system. Each planet seems to bear the name of a Greek god rather than Roman gods as the planets of the Sol system seem to bear. Whether or not the initial inhabitants of the system named them as such or if they were named by the Lost Million is no longer known as records from both these time periods have been lost.
-Planets - Inner System-
The inner system of Aurora consists of four terran bodies, meaning that they are rocky and contain metallic cores at various states of activity. Though all of the bodies are rocky, not all are capable of supporting life, nor do all of them harbor liquid water on their surface. To many this will not be a surprise, since on the whole, this differs little from HU.
Aurora I – Hermes
.38 AU Semi-major Axis
88 Day Rotation, 88 Day Orbit
4,878 km diameter
The Innermost planet of the Aurora system is named Hermes, the messenger of the gods. Named such on account of its quick revolution speed of eighty-eight days around Aurora. It is a small dense ball of iron and silica measuring 4,879 kilometers in diameter, making it roughly a third the size of Mobius. It is silvery grey in color due to the deposits of silicon in its regolith. In the heat of the sun, it has an incredibly high surface temperature of around 700 Kelvin on the daytime-facing side, and in the darkness, the temperature dips to 100 Kelvin.
As a point of reference, the freezing point of water is 273.2 Kelvin, and its boiling point is 373.2 Kelvin.
Hermes is tidally locked, much like Mercury is around Sol. Due to its proximity to Aurora, the tidal forces between the star and the planet force it to rotate at the exact same time as it revolves, meaning its 'day' is 88 days long. The same side always faces the star no matter what.
An interesting point to know is that for its size, Hermes has an exceptionally large core; far larger when compared to other planets of the same size, taking up 85% of the planet's radius. There is a theory within the laboratories and campuses of the Kingdom of Acorn that Hermes is what is known as a Cthonian planet, meaning that the planet itself is the remains of a far larger world, possibly a gas giant that has had its outer atmospheric layers stripped by solar wind. This would account for the larger core in comparison to the planet surrounding it, though there is no evidence to support this theory.
Some cultures on Mobius refer to this world as Muckury, as an obvious call to its solar name. This practice is believed to stem from Lost Million colonial lore that has embedded itself into the lives of said cultures and is possibly a linguistic corruption of its original name. Other cultures, most notably in the north of Rus, refer to the planet as Pangla, the Runner. This name is embedded into cultural mores to describe those who are quick in either body or mind.
Aurora II – Aphrodite
.723 AU Semi-major Axis
243 Day Rotation, 223 Day Orbit
12,104km diameter
Aphrodite is the second planet in the Aurora system and takes the general place of the HU version of the planet Venus. Much like its counterpart in the Sol system, Aphrodite is named after a god of love, and much like its Solar counterpart, it is a hot world. However, this planet seems to have differences that separate it. Upon initial observation, Aphrodite has significantly less cloud cover over its surface, with landmasses being more visible from an orbit. The reasoning for this is that there is significantly less volcanic activity on the surface of the planet. This does not mean however that Aphrodite is a safe world. On the contrary; no less than 400 volcanoes are active at any given time over the globe, spewing immeasurable tons of carbon monoxide, sulfuric compounds, and carbon into the atmosphere, where thick wind currents wrap it over the land. However, it seems that the greenhouse effect that covers Venus is not as apparent over Aphrodite.
Aphrodite has a sidereal year that is longer than its sidereal day. It is hypothesized that an impact event in the distant past may have caused the planet to rotate at a slower speed. This impact event is still present in the modern era as Aphrodite has a single moon, measuring approximately 1500 kilometers in radius.
Though expeditions to Aphrodite are few and far between, judging by records that survived the Dark Ages, the composition of the moon is fairly similar to that of its host world, meaning that the formation of the moon, known from antiquity as Cupid, may have been formed in the Aurora system's ancient past, far before the appearance of the Lost Million. Cupid is able to retain an atmosphere of sulfur dioxide as well as carbon dioxide, though the air pressure is far lesser than that of its host world. It also orbits at half the distance the Broken Moon does to Mobius, and does so once every fifteen days, causing geological instability as it goes.
Orbital scans indicate that structures of some sort are present on the surface of Aphrodite, but only in the highest of mountain ranges, where surface pressure approaches that similar to Mobius at sea level, though atmospheric composition is still lesser than that of a Mobian's requirement. The oxygen content in the planet's atmosphere is trace.
Aurora III – Mobius
1 AU Semi-Major Axis
24 Hour Rotation, 365 Day Orbit
12,765km diameter
Mobius is the homeworld of our collective species of creatures; the only life-bearing planet in the system and is situated in the middle of Aurora's habitable zone where water remains in liquid form on the surface. It should be noted that Mobius is only one of the accepted names of the planet, generally used on the Northamer continent. A far more prevalent name in other parts of the world, especially though speaking other Latin-derived languages, tend to use the name Gaia. The former name, Mobius, is direct tribute to the leader of the Tau Ceti expedition, Doctor Matthew Mobius. Mobius himself designed and oversaw the creation of the jumpgate that would supposedly connect Sol and the other (now heavily populated) system of Tau Ceti, but through unforeseen circumstances, the fleet was transported to what we now consider to be our home. Gaia on the other hand is an interpretation of the Greek personification of the earth. Gaia is also a quasi-religious invocation of the spirit of nature and the planet, though this last interpretation is generally seen among the inhabitants of Albion in the north of Yurop.
Mobius is a warm terran world that has the exact same size and mass dimensions of the planet Earth. As such, its air pressure still remains at 101.5 kilopascals at sea level, and its surface gravity is exactly one G, or 32 feet per second, so visiting Humans do not need to acclimate to a different environment with the exception of a far cleaner air quality in areas otherwise covered with mega cities, especially those in the Asian analogue, where the greatest differences are seen. A large ocean covers Mobius' surface which takes up over 72% of available surface area. This ocean is mainly composed of liquid water with sodium silicates mixed in. However, additional free-standing bodies of water in-land also exist, and are free of salt content, meaning that it is suitable for drinking. Numerous pre-industrial nations primarily use these for potable sources. More advanced nations are able to treat sea water.
Though Mobians are currently the dominant form of life on the planet, with the exception of modern-day Humans that live alongside as citizens of the various sovereign nations as well as proposed colonial spaces in other areas of the planet, two additional and older form of Humanity were present before 3234 - the Terra Novans, and an unknown pre-historic Human civilization. Starting with the former, Terra Novans were Humans that were descended from the Tau Ceti expedition stock. They were intelligent, physically fit, and were medically resistant to diseases, meaning that they were all hand-selected to be the first wave of Humans to arrive at their new home. These Humans were physically stronger than their kin due to spliced DNA that integrated itself into their genetic structure following another accident upon arriving in Zone-1. As of the 33rd Century, Terra Novans have gone extinct after surviving for centuries in this world. The older race is more mysterious. It is known for a fact that this race is Humanity, but it cannot be ascertained at what technological level this race was at, as traces of their achievements have been seen around the Aurora system, though recovered samples of their devices indicate a living level of late 21st Century to early 22nd Century. It is unknown if technology was distributed based on need or was stratified based on quality of life. It is known that they were capable of advanced artificial intelligence, and at the very least interplanetary space travel in large numbers. However, no Human from this time period has survived even to the arrival of Terra Novans.
On the other hand, living creatures of non-sapient levels have large numbers on Mobius, with the kingdom animalia being represented just as diversely, if not moreso than Earth. Amazingly, when compared to Earth, several animals present on one, were not present on another. Mobius contains still living and thriving animals that went extinct in the Pleistocene era on Earth. Megafauna roam frozen wastes and dry savannahs, with documented sightings of Mammuthus primigenius, Panthera leo atrox, and as of the current date, exactly one confirmed sighting of Carcharocles megalodon off the coast of Afrik with remaining sightings unconfirmed. Biologists find the more varied ecosystem fascinating for research groups as nearly all examples of megafauna are reproduced in labs or were the result of cloning technology, leading researchers to come to Mobius to see how these creatures lived in situ. Virtually all of these creatures are non-sapient and are more or less equal to their Terran relatives in HU.
Mobius rotates in approximately 24 hours on its axis and revolves around Aurora in 365 days identically to that of Earth, though the angle of rotation appears to be 22 degrees on its axis. The planet is orbited by one natural satellite, formally known as Selena (though curiously many adopt using 'lunar' as an adjective), but more commonly known simply as 'the Moon', but also by many different cultures through some variation - 'the Broken Moon'.
The meaning of this last title is plain enough. Visible either in day or night, the only natural satellite of Mobius is shattered. The main body is somewhat intact, retaining a mostly spherical shape, though is surrounded by innumerable shards of material that orbit at varying rates. This material has formed a rough ring that orbits the moon at two selenal radii. Larger materials have already impacted the moon at unknown times in the past, though smaller shards appear to have taken up somewhat stable orbits. It is unknown how the cataclysm that tore apart this body occurred, as the Lost Million reported it upon arriving in the planetary system in the early 23rd Century. Selena is generally not safe to approach, except for polar vectors where chance of impact is slimmer than equatorial regions.
Though broken, Selena has great importance for cultures on the planet, with many giving names to the largest of the shards. The moon as a whole seems to be a lesson that even destruction can result in beauty.
There is no evidence of what caused the destruction of the moon, as computer models are not able to guess at what may have caused such destruction, and whether or not it was linked to the disappearance of pre-historic Human society on Mobius. It continues to orbit on a stable, near circular trajectory around its host world every 30 days and rotates once every fifteen days, very much unlike Earth's moon, which gives rise to the idea that the destruction is linked to an impact event of massive scale, and could potentially be linked to the differing landmasses on Mobius' surface, though no conclusions could be drawn.
In terms of climate, Mobius appears to retain a surface temperature of around 283 Kelvin, making it cooler than Earth, which currently retains a temperature of 290 Kelvin. The reason for the disparity is under theory, with the leading hypothesis being that Mobius is preparing to enter an ice age, expected to be in full swing in five to ten thousand years. Warmer regions of the planet are quite comfortable to live in, with equatorial areas approaching and exceeding 300 Kelvin, equal to over 100 degrees Fahrenheit. Trade winds and jetstreams distribute these temperatures to areas that would otherwise be cold, such as the Great Gulf Stream keeping the Kingdom of Acorn warm.
It should be noted that Mobius' surface contains large islands that seem rather fractured when compared to Earth. For example, Southamer, the analogue of South America contains a massive archipelago on the eastern coast of the continent, containing tens of thousands of islands over thousands of miles, and each containing ecosystems unique to each island. In comparison, much of Yurop, Rus, and Asya having far greater surface area than Earth. However, the sea levels seem to have lowered over time, with both the Behring Landbridge being visible as well as well as a landmass connecting Northamer and Albion dubbed the Mariana Landbridge, or more scientifically, Marangia.
Approximately one hundred and four recognized nations call Mobius home with numerous other pre-industrial tribes, bands, collectives, and unrecognized states dotting the land. There is far more wilderness than there is colonized land, which makes the areas in between these states lawless and full of danger, though individuals are free to live their lives with no oversight should they be able to provide for themselves.
Aurora IV – Eros
1.54 Semi-Major Axis
24 Hour Rotation, 687 Day Orbit
6,794km diameter
A dusty red and brown world, Eros is the equivalent of the cool desert planet known as Mars. Eros, sometimes called 'New Mars' for its familiarity, is unable to support Mobian life on account of its thin atmosphere of less than 1% that of Mobius. Eros is a metal-cored world that is similar to other terrestrial worlds in the system, except that a majority of its crust and surface is composed of iron and iron oxides that have corroded into a substance that appears rusty red from a distance, giving it the nickname of 'The Red Planet'. Eros is thought of to be the planet that has the most in store for Mobians as it is logically the next step in colonization, though due to a lack of a global technology base, no long-term plans have ever been in place with the exception of probes and only one manned mission in the last two hundred years which nearly ended in disaster for the crew involved.
Contrary to the other planets in the system, Eros is dead in terms of geological activity, much like Mars is. However, three great peaks that indicated supervolcanoes dot the land. Each is of comparable size to Olympus Mons, which indicates former geological activity, and possibly to a greater extent.
Eros possesses three separate large-scale trenches across its surface, dubbed Valles Marineris, Valles Hadius, and Valles Abyssus, with Valles Hadius being the deepest of the three, reaching an average depth of 11 kilometers below 'sea level'.
Eros rotates every 24 hours nearly exactly on its axis, and revolves around Aurora every 580 days. This is a much shorter year than Mars, and is a result of the planet orbiting closer within the habitable zone, with a semi-major axis of approximately 1.41 Astronomical Units. While still eccentric in orbit (the closest the planet gets is 1.2 Astronomical Units), it is still too cold to support life on account of its thin atmosphere, which gives it an average surface temperature of 233 Kelvin, or -40 Fahrenheit. It is also noted that the Perihelion of Eros, the point where it is closest to the sun, does not affect the orbit of Mobius.
Eros posses three moons, all of which are asteroid size objects of varying diameters. The first two moons are still named Phobos and Deimos, with the third, a large carbonic rock measuring over eight hundred kilometers, known as Apollyon. All of these moons are believed to be captures from the asteroid belt, and all are in relatively stable orbit.
Orbital scans from the manned mission to Eros determined that structures are located beneath the surface of Eros as well as limited appearances above the sands. It can be surmised that the ancient pre-historic Human society had a presence on Eros to the point where cities were established. However, all of these have been abandoned long ago and are in various states of decay.
::The Auroran Asteroid Belt::
The asteroid belt is familiar to Human readers as an identical band of various rocks spanning from the size of golf balls to the some kilometers in a diameter spin around Aurora. Much like other asteroid belts, it is believed to be leftover matter from the creation of the star system in the distant past. A common thought to children who watch science fiction films of harrowing chases through asteroid belts is that rocks are constantly crashing against one another. In reality, it is possible for one rock never to encounter another for eons, drifting sometimes with no other rocks in visual distance for long periods of time. Probes can and have passed through the belt with no difficulty. It is believed that there is enough matter in the asteroid belt to produce another planet the size of the moon. The belt serves as the practical barrier to the outer star system, serving as the so-called 'frost line' of planetary development.
-Planets - Outer System-
Aurora V –Zeus
5.5 AU Semi-Major Axis
9.9 Hour Rotation, 11.92 Year Orbit
198,019km diameter
Zeus is the largest of the gas planets in the Aurora system, and the largest of all of the planetary bodies in the whole system. Zeus is a gigantic world, spanning over 100 times the diameter of Mobius and is composed mainly of hydrogen and helium, much like other gas planets in the system. Unlike its counterpart in HU, Zeus has a red tinge that is not present on the planet Jupiter. The atmosphere contains hydrocarbons that give it its crimson color. Zeus Is dominated by an amazing magnetic field that covers many of its moons. This also means that electromagnetic radiation from the star causes amazing aurorae to form at the poles of the planet.
In terms of diameter, Zeus is larger than Jupiter, stretching from end to end, almost two hundred thousand kilometers. It is not known why exactly this is the case, but it is assumed that during formation of the Aurora system, more material from other parts of the system must have made its way to the far more massive planet. Zeus is estimated to have almost two and a half times the mass of Jupiter, meaning that it is within the lower realm of becoming a Class Y brown dwarf, though it is not known why the process of fusion never began.
Storms are common across the surface of the planet, with numerous cloud bands stretching across the upper cloud layers. Where different storm bands meet, vortexes form, which commonly brings warmer layers up into the upper atmosphere. These storms take the form of spiraling 'eyes' that are dark red or brown in color, though white spots are not uncommon. In nearly all storm scenarios, mega lightning bolts are common, and are believed to stretch for thousands of kilometers with each strike. Currently, a massive storm, three times the size of Mobius is occurring in the Northern Hemisphere of Zeus, titled The Great Pale Spot due to massive ammonia clouds being brought up. Wind speeds are thought to achieve twice the speed of sound. This storm was first observed in 2350, when the Terra Nova expedition established permanent settlements and scientific observatories in the Apylacha region of Northamer. It is believed that water clouds exist, but at far deeper altitudes. Like all gas planets, Jupiter contains no solid surface, with gas becoming thicker and hotter the deeper one goes.
Zeus harbors a rocky ring of planetary materials that stretches to three planetary radii from the Roche Limit of the planet - the location where large planetary bodies would be torn apart by tidal forces. It is believed that this is the result of a planetary body being destroyed by said gravitational forces, distributing the material across the new ring system. Due to the fact that these rings are relatively bright, it is possible that this ring is less than two million years old.
The moon system itself has at least fifty confirmed bodies, many of which being under one thousand kilometers in diameter. However, there are a few of exception. The most notable is that of Europa, still named the same due to tradition. Attentive Terrans will note that the name is exactly the same, and will wonder why no doubt. The answer is complex and not quite clear, with ancient tribes noting the name insistently as Europa. Terra Novans also refused to change the name of the moons as well, which may have solidified into a trend, much the same how Phoebos and Deimos retained their names. [It is known to still harbor [remnants of subterranean prehistoric Human laboratories as well as massive power generation structures]] - [REDACTED]
[This facility is still operational as of the current date, though most of it remains inaccessible due to Frontier Corps intervention in 3234 against the hostile super-intelligence housed within. We don't want people digging into this one; the place is a tomb already. Come on, Antoine; you know better than this. The highlighted portions will not appear in final print.]
The other large moon is Ganymede, measuring well over the size of the Terran moon Luna. It is a dense, volcano-covered globe that retains a thin atmosphere of carbon dioxide, sulfur, and carbon monoxide. Surface gravity is measured to be at .25G, meaning that surface conditions are tolerable to Mobians and other bipeds that evolved in 1G standard environments. Zeus' massive magnetic field protects moons like these. Ganymede's surface is relatively flat, with parts of the globe directly facing Zeus being distorted by gravitational forces, creating taller mountain ranges.
The last moon of note is Io, which is far larger than its Terran counterpart, estimated to be half the size of Mobius, but with equal density. It is hypothesized that this version of Io may have collided with other moons in the past that increased the surface area of the moon and in addition to which, also increased the mass. Its orbit is nearly circular around Zeus because of its mass, and it also seems to exhibit some degree of rotation, believed to be from its ancient impact. It is believed that Io has a surface pull of about half of Mobius standard, though its atmosphere is far from hospitable being sulfur heavy, with other major gasses being hydrogen sulfide and hydrogen cyanide. Massive lava flows cover huge plains and valleys, creating seas of constantly replenishing molten material, with gasses flowing into the atmosphere. It is possible that Io is in the process of becoming a greenhouse world, where temperatures will soar even higher after a few hundred thousand years. Io is also unique in the fact that it possesses a small moon itself, only three hundred and forty kilometers in radius, a large asteroid named Hesiod that orbits fairly close to the body, likely a capture from the asteroid belt. There are no plans as of now to explore Io, as the atmosphere is rather poisonous and can affect electronic equipment without proper protection.
Lastly is Callisto, a moon much like Europa, and in fact shares a similar diameter, though its surface is covered with a far denser sheet of ice. It is believed that there is a subsurface ocean beneath Callisto, though no proof as of 3239 for its existence. In the time of its discovery, no less than three administrations attempted to form such a mission, though funds could not be secured for such an endeavor. In the end, only a mission to generally survey the Zeusian system was conducted, and Callisto seemed to be left out of much of the equation. Only surface telescopes from Mobius can determine the general composition and surface features of the body: its surface is covered by numerous cracks much like Europa, unlike its Terran counterpart. However, its surface is covered in impact craters, many of which are fresh, only a few thousand years old. This is believed to be because of its outer orbital position, where it at times catches asteroids drawn in by Zeus' strong gravitational pull. Its color is believed to be light to dark grey depending on surface composition. Otherwise, there are no surface features of note that make the moon stand out. Despite it being a possible harbor of life, it is far more interesting to shift attention to Europa.
The remaining moons are little more than large asteroids that clumped together in roughly spherical shapes. These are more or less similar to Terran counterparts, and many of them have high-inclination orbits, meaning that they do not appear on the same planes as the four largest Zeusian moons, making them hard to observe without strong telescopes. As of 3238, the Frontier Corps have discussed a mapping project, set to commence in 3241.
Aurora VI – Cronus
10 AU Semi-Major Axis
11 Hour Rotation, 31 Year Orbit
120,536km diameter
A familiar sight to many in the world - Cronus. This planet has dazzled poets, dreamers, and astronauts alike for many centuries. Cronus is of similar composition, mass, and diameter to Saturn, and seems to share the same beautiful ring system that Terrans experience on a daily basis. However, there is a difference noted. There are numerous gaps in Cronus' ring system, measuring thousands of kilometers in distance. The reason for this are large shepherd moons that exist within the system itself, believed to form from material building up. The B-ring, and the A-ring are where these major divisions exist, and as such, cause the ring to appear more as hoops from Mobius. Despite the missing material, Cronus has always appeared beautiful to observers. Unlike Zeus' ring system, Cronus' rings appear to be ice-based, with some rocky material occasionally spotted. Because of this, the rings reflect light far more than Zeus does, making them far more visible.
Cronus is made of hydrogen and helium, though contains more ammonia than its Terran counterpart, which has resulted in a bright white band across the equator that seems to complement the orange-yellow tinge of the greater planet. Unlike Zeus, Cronus does not appear to have notable cloud banding that can be seen from Mobius outside of the equatorial ammonia clouds. However, most unusual in the planet is what is known as a hexagon storm, which is located on both the north and southern poles of the planet, whereas Saturn in the Sol system appears to have a persisting storm only at the northern pole. It seems that these hexagonal storms are linked to Cronus' radio emissions from deep within the structure of the gas giant. From a distance, these odd formations are rather beautiful and do not appear to be out of the ordinary. On the contrary - The Unified Colonial Administration Authority Factbook - a supplementary work to the Codex, mentions that many gas giants that resemble Cronus have hexagonal storms. The planet also seems devoid for the most part, of large storms on the level of the Great Pale Spot, however, there are small vortexes in both the northern and southern hemisphere that are only several hundred kilometers at the widest point. Wind speeds are lower than that on Zeus, perhaps only reaching a thousand kilometers an hour.
The moons however are a point of difference when comparing Cronus to Saturn, especially since many of them do not seem to exist. Saturn is confirmed to have well over 70 moons, however, it appears that Cronus appears to lack many of the smaller objects, and instead seems to have had the matter consolidated into twenty larger objects. This has puzzled UEG scientists greatly and serves as a point of major divergence from the Sol system. From the lack of debris surrounding Cronus, it appears that the moons, if there were smaller moons at all, merged into these larger bodies millions of years prior. Some are recognizable, while others are something unique entirely.
Mimas is the innermost moon of note. However, what makes it notable is what it lacks. In the Sol system, Mimas is known for its impressively large impact crater that covers a considerable portion of its geography. However, in this system, it appears that the impact crater is absent, and as a result, the moon seem to retain more mass, measuring in at over two hundred and fifty kilometers. It is also fifty percent more massive than the Sol variation of the moon. Aside from that, it is rather plain with no distinguishing marks. It is airless, though its very small gravity seems to grab particles from the extended G-ring every now and again.
Enceladus is the next out from the ring system, however, its size and mass is far greater than expected. It measures over twelve hundred kilometers in diameter and maintains a smooth, icy, and cracked exterior, similar to Europa. Like Europa, there are believed to be oceans under the ice, and telescopes have captured what appear to be icy geysers rising into space measuring several dozen kilometers above the surface. The cracks in the icy crust are caused by tidal forces acted upon it by Cronus, though it appears the forces are not as strong as Europa's. Enceladus is marked as a possible source of water ice on long intrasystem journeys.
The next moon of note is Rhea, which under normal circumstances would be unusual, were it not for the ring system that it exhibits. Rhea possesses three thick and icy rings in orbit around the moon. A hypothesis is that somehow Rhea managed to steal ring material from Cronus, but that hypothesis is cast into doubt considering that it is the third body from the ring; far less likely to grab particles. However, given the fact that a sizable portion of Cronus' ring material is missing, some of it may have been found by Rhea's gravitational field. An object the size of this tiny moon is not likely to maintain a spherical shape, yet it does, despite not being particularly dense considering the material it is made out of.
The next moon is Titan, which is rather unusual for a moon as it retains a thick atmosphere around it. It is larger than the Broken Moon, and more massive than it, and appears notable for being the only other moon in the Aurora system that retains a form of liquid on its surface. Because of the extreme distances from Mobius, Titan is cold, not even 100 Kelvin, almost -180 Celsius. Water, even salt water, would freeze instantly on the surface of the moon. However, what Titan does possess in abundance is liquid hydrocarbons - carbon chain materials that we would recognize as butane, gasoline, ethane, propane; all of these exist as liquids on the extremely low temperature surface of Titan. The atmosphere is almost fifty percent thicker than Mobius'. If one were to strap wings to their arms, they would be able to fly in the thick atmosphere by flapping.
Titan's natural cycles are very similar to those found on Mobius. Storms have been observed to occur on the surface, complete with hydrocarbon rain that seems to form larger spheres that fall to the ground at only a tenth of the gravity of Mobius. Any sign of heat causes sublimation of the local liquids to gas. A popular myth is that if one were to light a match on Titan, the entire atmosphere would be burned at once. This is untrue as there is virtually no oxygen in Titan's atmosphere. Oxygen is crucial for keeping a flame lit; despite the large amounts of nitrogen in the moon's atmosphere as well, which also makes up most of our breathing air.
There are signs that Titan may have been settled, or at the very least, visited by the Human civilization of eons past. Probes flying over the moon's surface made observations that what appeared to be structures were located on mountainous plateaus, however, no communication was ever returned, signifying that it was an abandoned or destroyed structure, lost during whatever cataclysm wiped the old civilization from Aurora.
Past Titan, there are two moons that do not correspond to the Saturn system. These moons are massive, easily the largest in the system, and they appear to orbit one another, making it the only binary moon in the Aurora system - Dione, and Iapetus. These two moons are rocky, airless, but are nearly the size of Mobius. As such, it is debated whether or not to call them planets instead of moons, though because their center of gravity is still well inside of Cronus, they remain moons. Iapetus is 10,400 kilometers in width, and Dione, the smaller of the two, is 11,120 kilometers in width. They orbit each other at a distance of only thirty thousand kilometers, and are tidally locked to one another to the point where each side will always face the other. For objects this close, it seems unlikely that this would be the case, but Dione and Iapetus have stable orbits, and each appears massive in the other's skies.
The remaining moons are small and un-noteworthy. Despite their size, they are only asteroids with very little to set them apart from other rocks.
Aurora VII – Caelus
19.18 AU Semi-Major Axis
17.02 Hour Rotation, 84 Year Orbit
50,600km diameter
Caelus is an oddity, as it is the only major planet in the Aurora system that bears a Roman name. This is ironic, as the counterpart in the Sol system, Uranus, is already Greek to begin with. The Terra Novans, thrown for a loop, decided to continue following the conventions that they did for the planets before it. It is also rumored that another reason was to avoid an overplayed joke common to Terrans. Caelus is the Roman god of the sky, and it is an appropriate name. Caelus appears sky blue in the inky darkness of space, the color, some have noted, like a robin's egg. However, this is not what makes Caelus interesting. It is the fact that Caelus' rotation is perpendicular to its orbital path. While many planet's equators face the sun, Caelus' north pole faces Aurora, while the equator faces away. This is thought to be because of an impact event that took place in Caelus' ancient past. A body, the size of Eros if not larger, struck Caelus and knocked it so that its axis was struck off balance. This means that its northern pole is warmer than its southern pole and that its wind patterns have changed noticeably, but also that its ring system as also moved along with its new axial tilt.
The ring of Caelus is thinner than that of Zeus, with approximately half of it being composed of icy materials while the other half is composed of rocky debris such as silicates, iron, and carbon deposits. To an observer, Caelus seems to have some bright bands around it, but similar to Cronus, it has numerous gaps filled in by shepherd moons that siphon materials away from it. These moons are smaller than any other gas giant in the system, no larger than one hundred kilometers in width. Unlike Cronus though, Caelus seems to retain a large number of its moons comparative to the Sol system, yet many of them are small and insignificant to the system. Just as with other systems, nearly all of them are asteroids.
On the composition of Caelus itself, the planet's gaseous atmosphere is primarily made up of hydrogen and helium, just as any other gas giant, however, the planet is notable for its robin's egg blue color. The reason for this is because of high concentrations of methane and ammonia, when viewed together, absorbs red light and reflects blue and white. At times, the upper atmosphere of Caelus appears to be featureless on its calm days, though when it is more active, Caelus had white bands of clouds in its upper atmosphere, whipped around by 1500 kilometer per hour winds. Because of its distance from Aurora, these winds are not generated by solar activity as they are on Mobius, which means that they are powered by forces within the atmosphere. It is possible that heating from the hotter and denser lower layers travelling up through the colder layers causes high and low pressure differences. On more than one occasion, a small band of water ice clouds has been spotted on the top of the methane layer. However, these are quickly scattered by the winds of Caelus.
It should be noted that because Caelus is oriented with its pole towards Aurora, and thus rotates perpendicular to its orbital path, one side of the planet never sees daylight, with the night-time side in well below freezing conditions.
The moons of Caelus are much the same as they are in Sol, however, in Aurora, they appear smaller than they are before. Because of the slightly more robust ring system, it is believed some of the moons have been starved of material. The planet itself has 27 moons in orbit around it with many of them orbiting within its ring system. The largest of them appear to orbit on the outskirts of the field.
Miranda is one of the innermost major moons, and is widely regarded as the ugliest of all the moons in the Aurora system. The reason for this particular distinction is a result of its heavily scarred surface, with a notable amount of deep crevices, canyons, and cracks tearing away at the misshapen ball. Because of its heavy deformity, it is believed that Miranda is not able to achieve a state of hydrostatic equilibrium, where it can return to a spherical shape under its own gravity under what's called the Square Cubed Law. This particular law was touched on in the Laws of the Universe section of the Codex.
Miranda is tidally locked to Caelus, which is not unusual for a moon of its size and distance from the host planet – it only orbits 129,000 kilometers from the planet – yet the moon also has a relatively highly inclined orbit for its position. While 4.2 degrees does not appear to be a lot on paper, the result is that the moon orbits on an angle, while many of the other major moons are more or less coplanar. Because of its synchronous rotation, Miranda is subject to tidal heating, which may have been the cause of its escarpments and coronae on its surface – some of which are two hundred kilometers wide. However, the moon does not appear to be geologically active as of the current date.
Ariel is the next major moon, which like all of the moons, orbits perpendicular to the orbital path. It is a tiny thing, roughly a tenth the size of the Broken Moon were it whole. It is equally composed of rocky and icy material, with the ice showing major cracks in the northern and southern hemisphere. Because of the mixed surface, it appears to have in equal distribution icy planes as well as craters, most of which are less than one hundred kilometers in diameter, with the exception of Yautzee Crater, which measures 119 kilometers in diameter, taking up almost a tenth of the surface area. It is possible that this is how Ariel obtained its icy content.
Like many other moons, Ariel is tidally locked, with an orbital period of only 2.5 days. The sun appears looking north from the equator travelling in a tight circle only slightly dipping below the horizon before rising again. Because of its shifted rotation, just as with everything in the Caelus system, one side of Ariel never sees sunlight.
Umbrial is a dark and rocky moon measuring only 1169 kilometers in diameter. It was thought that this was icy material, but subsequent Frontier Corps observations confirm that unlike Uranus, this is a rocky and craggy moon of Caelus. The moon is airless and like everything else in the planetary system, orbits perpendicular to the orbital path. There is indeed icy composition to the moon, but these are relatively few, and they are dirty, making Umbriel the moon with one of the least albedo on its surface, which makes it easy to see on transits. A bright impact crater is located on the top of Umbrial, dubbed the Laika Crater by Mobian astronomers. This was not observed by Terra Novans as it was located slightly behind the moon's curve. Only on subsequent viewings from probes were the features made apparent. This crater is almost eighty kilometers in length, and exposes bright icy surfaces that are present on the poles. It is unknown how a large impact like this did not knock the moon off its orbital path which has remained fairly non-eccentric.
Because it is mainly composed of rock, it is more massive than the moon that orbits Uranus, possessing .056 G of surface pull. It is tidally locked, and travels around Caelus in 4.2 days.
The penultimate major moon of Caelus is Titania, adequately named as it is the most massive moon in the Caelus planetary system. While it does contain sizable amounts of water-ice and other frozen gasses, Titania is mostly a rocky world with a rocky core. It has a diameter of 1570 kilometers and is covered in many scars of impact events, some of which are larger than 250 kilometers in width. Smaller and more regular impacts dot the terrain, with new craters less than a hundred years old appearing to astronomers daily. Titania has a density of nearly twice that expected, and unlike many other moons in the gas giant systems, has a tentative atmosphere, one hundredth that of Eros'. It is believed that this atmosphere is formed from volcanic activity deep within the mantle, as slightly white and yellow patches being seen on the surface. It is believed that this activity is formed from the tidal activity between the tidally locked Titania and its parent planet.
It is confirmed that unlike many of the other moons in the Caelean system that Titania does indeed rotate, albeit at a very slow rate with a day estimated to take twelve Mobian days. The orbital period is 8.7 days to completion, making Titania similar to Aphrodite in its day-year relation. This makes it a relative oddity to the system, though in almost all other respects it is fairly typical of moons in this region of the system.
The last moon of note is Oberon, which is a mix of ice and rock. It is 1500 kilometers in diameter, though is the second most massive moon after Titania. What is immediately interesting is that Oberon is tidally locked to Caelus, which spites Titania that has a slight rotation. While both are natural satellites of Caelus, formed in the same accretion disk, it is presumed that whatever struck Titania did not have a similar fate for Oberon. Its orbital period is appropriately longer, measuring at just over 13 Mobian days to complete.
Most of Oberon's mass is in its core, which composes almost sixty percent of the moon's mass, with the remainder being in thick mantle, crust, and generous ice layered on top of it all. Impact events have exposed parts of this frozen covering, making Oberon take the appearance of a golf ball, with startlingly geometric patterns appearing to astronomers. Several of these craters are quite large, measuring up to and even exceeding 200 kilometers in diameter. The ejacta from this event rains out in rays like the Aurora itself on a bright day, which has led the most prominent to be called Sunny, measuring at 206 kilometers in width.
Aurora VIII – Poseidon
30 AU Semi-Major Axis
17.25 Hour Rotation, 164.8 Year Orbit
50,000km diameter
The next planet is the gas giant named Poseidon after the Greek god of the sea. It is named as such because of its deep blue color with is just as eye-catching as the brightness of Cronus or the dark red of Zeus. However, there is no water on Poseidon, as it is very much a gas giant mainly composed of hydrogen and helium. The deep blue is thought to be composed by compounds of methane with white streaks in the atmosphere caused by ammonia compounds as well as water ice which is in surprising abundance in the upper atmosphere.
Poseidon is properly aligned to its orbital plane; its equator is pointed towards Aurora, though at this point the sun is becoming smaller and smaller, barely indicating the 164 years it takes for the planet to make its journey around it. At almost fifty thousand kilometers exactly in diameter, it is the fourth largest planet in the system. Unlike Caelus, the features on the planet are shockingly clear given the distance. The most shocking and beautiful features on the surface are the Great Dark Spot, which covers a sizable portion of the lower hemisphere, several shades deeper than the surrounding cloud layers. This is a massive storm that has continued to rage ever since it was first observed in the late 23rd Century by Terra Novan explorers. It has actually increased in size to nearly be the size of the Earth. The deep blue is thought to be lower layers of the methane clouds visible through the gap caused by the storm. The pressure differences have created white clouds that persist around the storm. These clouds are the second feature of the planet that seem to have a form that harkens to Mobius' own skies. These clouds are thought to be made mainly of ammonia, though they also contain water ice. They seem to take on a cirrus form that tend to be visible at higher altitudes and whip across the surface of the planet at speeds of over five hundred kilometers an hour, with internal speeds reaching over 2100 kilometers per hour.
The rings of Poseidon are very faint and are composed mainly of dusty materials. They do not reflect much light and are thus hard to observe.
Poseidon retains 14 moons, most of them irregular satellites, though there are some that are of particular note, and they are moons that are not native to the planet, classifying them as what's known as irregular moons. Many of the inner moons are dark and have low reflectivity.
The first of which is Triton, a captured body that is notable for its orbital pattern, Triton orbits around the planet opposite to the rest of the moons around it. This is because of the origin of the moon. However, as impressive as the revolution is, this works against the 2700 kilometer object, as the tidal forces between Poseidon and its moon cause Triton to slow down slightly over each year. Eventually, Poseidon will steal enough energy from Triton to pull it into its Roche Limit and tear the moon apart. Even now, geological stresses have been seen acting upon the moon with cracks, and shifts in wide spreads of land. However, this expected destruction is set to happen over three billion years in the future, leaving Triton an oddity that will amuse Mobians for quite a whole to come. Due to the retrograde motion, Triton takes -5.8 days to orbit around Poseidon, though it is synchronous to the planet.
Because of its size and mass, Trition dominates other moons in terms of sheer weight, which is all the more impressive as it is a foreign object. Triton is a capture, which means that orbiting coplanar is extremely unlikely. Triton's orbit is inclined 129 degrees relative to the solar plane. However, it is unusual in that its orbit is virtually circular with very little if no eccentric at all. It does maintain an atmosphere, if a very thin one of only 1.5 pascals. To compare, the atmosphere of Mobius is 101325 pascals. However, it has been noted that thin clouds have been seen in Triton's atmosphere, and subsequent comparison with the Sol system has confirmed that this is a point of convergence.
The surface features are interesting in that there is a slightly red tinge to the surface. The reason for this is a material known as tholins. Tholins are icy compounds of carbon, methane, and ethane that is usually in combination with nitrogen. Several dwarf planets in the outer reaches of the system have the same composition on their surfaces which helps determine the origin of Triton. Other levels of materials have been determined to be caused by the active cryovolcanism on the surface. Massive eruptions of nitrogen gas and dust from within the surface have been noted to extend from the surface up to eight kilometers. These geyser contents form a sharp turn as the planet's high velocity winds carries it away, creating strange and unique 90 degree turns. It is believed that these geysers are caused by the tidal forces between the planet and the moon, heating it up on the inside and forcing the material out to the near absolute zero surface of Triton.
The other moon that can be noted is the largest regular moon of Poseidon, which bears the name Proteus. It is roughly 400 kilometers in diameter, though it is not spherical. It is not even ovoid, instead being polyhedronic, meaning that its shape is rather indeterminate. Some portions of the body rise twenty kilometers over others. It takes over a day to orbit around Poseidon, and is synchronous to the planet. Despite being a regular moon of the planet, it likely didn't form until after Triton was captured. The fact that it retains an irregular shape though suggests that it is mainly made of ice with no core, similar to a very large asteroid. The gravitational pull is very light which supports that claim.
The surface is heavily cratered, possibly as a result of its accretion, but it still continues to be struck by debris even today.
There is very little of note on the surface even though it is the largest of Neptune's regular moons, and the second largest orbiting body aside from Triton.
Aurora IX – Thantos
39.4 AU Semi-Major Axis
9.20 Hour Rotation, 248 Year Orbit
950km diameter
Thantos is a small planet that is smaller than Hermes. It orbits very far away from the core of the Aurora system with the sun appearing as only a small dot in the sky. Thantos, named after the god of death, is a cold world that takes 248 years to orbit once, and its eccentric orbit takes it within the slot of the eighth planet in the system. For a time, it switches positon with Poseidon for furthest in the system, but for the most part, it is ninth in position. This is a point of divergence with Sol as Humanity does not consider their version of Thantos, Pluto (officially 134340 Pluto), a proper planet after a ruling of the International Astronomical Union in 2006 to relabel it a dwarf world due to failing to be the dominant gravitational force in its system. Terra Novans, in an attempt to help differentiate Aurora from Sol, decided to reverse the decision, even though by the definitions of the IAU, Pluto still does not qualify as a planet.
Thantos only measures 2376 kilometers in diameter, with its core taking up most of its mass. It takes 6.39 days for the planet to rotate on its axis. However, it can be seen where the IAU came to their decision, as Thantos shares its rotation with its largest moon, named Charon. Charon is half the diameter of Thantos, yet it exhibits enough of a gravitational pull to be tidally locked to its host planet. However, this type of tidal locking goes far beyond what is common between the Broken Moon and Mobius, as Thantos itself is just as locked to Charon as Charon is locked to Thantos. This type of phenomenon is known as mutual gravitational locking, where Thantos always presents the same face towards Charon and Charon always presents the same face to Thantos, each one eternally in the other's skies. This relationship between planet and moon is important because it is believed that at the current retreat of the Broken Moon, it and Mobius are eventually set to end up in the same position, though not for a very long time.
Thantos itself retains a surprisingly thick atmosphere for its position and size, managing to hold on to one pascal of pressure, consisting mainly of nitrogen and methane. The light gravitational pull of Thantos, averaging around 1/12th that of Mobius, holds onto the particles if lightly, causing the atmosphere to appear to blossom distantly around the globe. The term 'average' is used here because Thantos exhibits another phenomenon known as a gravitational anomaly over a large plain surface, which depending on the source, appears as a heart or as a dog, the connection of which has been lost to history. This large plain, called Planitia Corus, after the heart-like appearance, is a regularly refreshing area of the surface that is composed of ice mountains. Planitia Corus is thought to be evidence that Thantos is evidence of geological activity of the planet, and supposed sightings of cryovolcanics may support this idea.
The other notable area on the planet is a large darkened area likened to appear as a whale named Dagon Regio, which has prompted some to wish the change of the name, though over the centuries the name continued to stick. For reference, Dagon refers to an entity within the works of H.P Lovecraft, an early science fiction writer from the 20th Century to describe an ancient being of great power resting at the bottom of the ocean. The region is dark and is rich in tholins, materials that give the icy surface a reddish hue to it, but this area in particular is dark, signifying a heavy concentration of them. This region was dubbed Mordor in the Sol system and is still named such. Mordor being a region in the ancient writer J.R.R. Tolkein's fantasy setting, the 'Lord of the Rings', which still finds popularity with Humans to this day.
In comparison, Charon also possesses tholins, but mainly present in the norther cap regions. It also orbits close enough to Thantos to share particles of atmosphere with it, though it does not retain an atmosphere of its own. It is thought to possess organic molecules that are vital to the formation life, though Charon is too far away for life to form.
Another geological aspect that is notable about Charon is a massive jagged ridge that travels from the south to northern hemisphere, called the Great Cliff. This geological feature stretches over a thousand kilometers and is thought to be a result of extreme tidal forces affecting the surface of Charon.
There are additional moons of Thantos, but they are otherwise plain except for a few startling facts. The first of which is Nix, a moon that is in 3:2 resonance with Charon, that is, it takes three revolutions to match two of Charon. Nix is special in that it is in a constant and erratic tumble in orbit. Its day and axial tilt varies daily, with Nix rotating 50 hours retrograde, which means that the moon is spinning backwards roughly. Since its first observation in the 23rd Century, Frontier Corps analysis has confirmed that the moon's tumbling has accelerated by twenty percent. In addition, the fifty kilometer rock is on an inclined orbit of 132 degrees versus the equator of Thantos.
The other moon of note is Hydra, measuring 65 kilometers. It orbits in a 3:2 resonance with Nix, and rotates even more erratically than Nix does, with a day length of only ten hours, but this is only averaged when direct observation is possible. It has been known to flip completely end over end at times on is 32-day orbit.
The remaining two moons are Kerebos and Styx, both of which are small and ovoid shaped rocks that, just as before, rotate oddly around the planet, 20.2 days and 32.16 days respectively. These two objects are natural satellites which suggests that they originate from an impact event.
Aurora X – Asteria
750 AU Semi-Major Axis
10.14 Hour Rotation, 17,000 Year Orbit
51,200km diameter
The tenth and final planet of Aurora is Asteria, an ice giant that orbits far beyond the outer reaches of the system. Direct observation has only become possible with the Frontier Corps providing vessels for explorers to visit the planet in question. Before this point, it was believed to exist from trying to discover its radial motion and reflectivity. However, the object orbits well beyond the point where regular telescopes would be useless. It is a cold and dark world with a deep green color to it which suggests that in addition to its hydrogen and helium, one of the more dominant forms of atmospheric gas is xenon. The planet takes just over ten hours to turn on its axis, but takes seventeen thousand years to travel around Aurora.
Asteria is a relatively small world, only slightly larger than Poseidon, though it is three times as massive. The density is believed to be from a rocky core that rests within the slushy interior. Observations of the planet itself have also reported storms on its surface, which suggests that the disturbances are created by the planet's interior heat, which even as far as it is, would still retain its original heat, but given the apparent age of the planet, this raises the mystery on how planets retain their creation heat over long periods of time.
Curiously for a gas giant, Asteria has no moons in orbit around it, remaining alone as it proceeds on its 17,000-year orbit through the Kuiper Belt of the system, with Aurora only appearing as a faint prick in the sky, barely larger than any of the stars around it. Some of that light appears to reach Asteria, though the planet for the most part is dark.
In addition to the darkness, there is the extreme cold to consider. The distance means that all heat produced is exothermic versus how planets usually work. The surface layers are near absolute zero in temperature, but subsequent studies of the deeper atmosphere suggest that the internal layers produce heat in excess of 800 Kelvin if not higher with the core estimated to be close to 2400 Kelvin. If the planetary model follows the other giants in the system, the deeper fusing regions are possibly even warmer than this, assuming that the planet has held onto is thermal energy. This internal energy is seen with the magnetic field of Asteria which extends to nearly five solar radii of the planet, which indicates that the core is metallic and is still spinning.
Asteria's orbit is highly eccentric, with its closest pass still being far beyond Poseidon's orbit, and its farthest point being deep within the expanse beyond. With all of these factors taken into account, it is believed that Asteria is a rogue planet – a phenomenon where a planet is forcibly ejected from its old star system and is deposited in a one. Given the lack of a circular orbit, and the fact that its path has not affected the circular nature of the planets closer to the star, this capture may have occurred a significant time in the past, possibly when the Aurora system was still forming. It is possible that Asteria may have even aided the creation of the system, though this is speculation on the part of astronomers.
Asteria is a major point of divergence with Sol, as there has been no reported ninth planet (Pluto's demotion being taken into account) beyond the orbit of Neptune.
-CLOSING-
Beyond this, there is very little. The stellar medium grows thinner and thinner, with unknowable objects still within the Kuiper Belt and the father Oort Cloud, which are simply asteroids and comets that occasionally stray close enough to be snagged by the gravitational pull of the sun. The objects out here are so distant and so cold that it is impossible to chart them all. After this, there is interstellar space and the stars beyond, light years distant.
This is Aurora, and with all of its beauty, wonder, and natural and unique phenomena, is our one and only home.
