Alternate Planets, Suns, Stars, and Solar Systems Thread

crossposting from the map thread
Earth 5,757,738,947 (Africa Uber Alles)
A strangely convergent world, where changes in paleotectonics have lead to the African continent being the only continent to rise fully above the ocean. Industrial advances in the Asian archipelagos have thrust the world into the modern age at last, and as it plunges into war, men fear what these new weapons will do.



The Central Solar System (once called the Inner Solar System, until people realized how crazy the space beyond Neptune really was) is defined as the region extending from the Sun to the Junoan orbit. Here are all the major planets and bodies that make up this place, in their natural state before human expansion (but I'll give a quick description of who colonized it and the culture of the places).

The most dominant body of the solar system is the sun, officially designated in the European continent as Sol, although everyone up until the expansion to the outer stars of the solar system called it the sun. Sol is a G2V type star, which is the largest in the system and bigger than 90% of other stars. It is a massive 1,392,700 kilometers across, much, much bigger than the rest of the solar system combined. The Sun was kinda/sorta colonized by weird sun worshiping cults, manufacturing companies in need of energy and daredevils from the rest of the solar system. They mainly live in orbital habitats.

Next to the sun, at around 0.05 AU is the Apollo Belt, a group of small, scorched planetoids orbiting very close to the star. The largest of them is the very small dwarf planet Apollo, which is about 761 km across, followed by Tonatiuh, Aetheon and Pyrois, each of which are less than two hundred kilometers across. The rest are very small, but are still home to resources rivaling the much bigger Kemtoid belt. These planetoids are believed to have come from an old planet breaking up near the sun or probably from Apollo itself. Like the sun, the belt was colonized mainly by companies from all over and gold diggers who heard about the materials there.

Vulcan is the first actual planet from the sun, and it is a pretty cool place. The planet is tidally locked to the sun, with a lava ocean known as Mare Pandoris facing the sun. It has a small atmosphere of choking hot carbon dioxide, along with some rock vapor. Yes, rock vapor, and this tends to rain as boiling hot rocks on the far side of the planet. The sun also squeezes Vulcan to immense degrees, causing volcanoes (no pun intended) to erupt regularly. Despite being a literal hell, Vulcan is home to immense resources beyond imagining, having massive amounts of diamonds, gold, platinum and many other goodies, making Vulcan worth the challenge to mine. Vulcan is a little bigger than Earth, at around 14,476 km, but is twice as massive. It zips around the sun having an orbit of only 25 days, and it lies 0.147 AU from the star that tortures it. Vulcan was colonized by Germanic Europeans, Mercurians and Selenites. Its culture really values toughness and respect, and the planet was subjugated by Mercurian corporations for a while. Oh yeah, Vulcanian humans are short and stocky due to the immense gravity of the planet, and think of themselves as dwarves.

Mercury is the next planet, and it is basically a calm version of Vulcan, although it is home to less resources and is much smaller. The planet is home to gargantuan cave systems, tunneling deep into the planet. Mercury has no atmosphere, which means that the planet is full of craters that cover it many layers deep. The planet is actually pretty small, at only 4,879 km, and orbits around 0.32 AU from the sun. Mercury has a bit of an eccentric orbit, generally wobbling around the sun more than the other planets. Mercury was colonies by the Chinese, Middle Easterners, Indians and Americans, and it is society is very <s>corporatist</s>, technophilic, superstitious and religious.

The next planet is Minerva (OTL Venus, ITTL Venus is up later), which is a roughly Earth sized planet covered in a thick layer of clouds made up of Carbon Dioxide. Minerva is home to intense pressures at its surface, and it is very hot, although not so much as Vulcan. The planet is geologically active, and has a very long rotation, and its day is longer than its year. Minerva orbits at 0.55 AU, and is 12,103 km in diameter, although it is half the mass of Earth. Minerva was initially colonized by a ragtag of groups from Mars, Luna and Mercury, and then was 'recolonized' by Africans who settled on the planet once the terraforming was complete (the terraforming was done entirely by African corporations, so there's that).

Mars is the next planet, and it is probably the most Earth Like of the main planets, with oceans and land. It is home to some very primordial life, such as bacteria and some more evolved creatures, which are basically like Jellyfish on Earth. Mars is well known for its red oceans, which are full of iron and other chemicals. The planet is similar to Earth in pressure, is a little hotter than Earth in temperature but is home to toxic chemicals in the atmosphere. Mars is 11,788 km in diameter and is 0.85 AU from the sun. The planet has two moons, Phobos and Deimos. They are 1,316 and 1,406 km in diameter respectively, and they are both generally made up of rock and ice, with no atmospheres unlike Luna. I made a post on colonial Mars which you can check out here:, but as of 2361, they have turned out very conservative in nearly every aspect.

Earth is the fifth planet from the sun, and the homeworld of humanity and the majority of other races. It is home to oceans, land, ice sheets and a vast diversity of life, more than any other planet. The planet is 12,742 km in diameter and orbits 1 AU from the sun (the AU is based off of this measurement). Humanity evolved on Earth, and formed many great empires, and first took to the stars here. Earth was cool until WW6 caused Kessler Syndrome and the Selenites got involved in ruining it.

Orbiting Earth is the moon Luna, a bizarre but surprisingly habitable world. Luna is covered in a dense layer of mist and clouds, giving it a whitish appearance from Earth. Under the mist, lies many mountains and small lakes, although underneath them is a massive biological network made up of fungal like organisms tunneling deep into the planet. Luna's atmosphere is fine for humans, although there is too much oxygen. The moon is tidally locked to Earth, with days and nights 15 days long, orbiting 413,399 km from Earth. The moon is 3,514 km in diameter, although the layered fungal canopies give it a lot of land area. Luna was mainly colonized by North Americans, Europeans and East Asians.

Venus is the next planet from the sun, covered in a massive ice sheet, as it had been for billions of years. The planet is intensely reflective, appearing as a bright star from Earth, even more so than Mars, which Earth is closer to. Venus is home to a decent atmosphere, although its pressure is a little weak, and its atmosphere does not have much oxygen. The planet is still cold, at around Antarctic temperatures. It has some very basic bacterial life, although this still is not enough for oxygenation. Venus has two moons, Adonis and Cupid. Adonis is the smaller one, orbiting closer to Venus, and it is basically a captured object from the kemtoid belt. Cupid is the bigger one, orbiting farther out. Venus is 10,753 km in diameter and orbits 1.86 AU from the sun. Venus was mainly colonized by the American-Chinese lead Pacific Sphere alliance, and they became one of the nicest places to live in the system.

Juno is the next planet in, and it is quite an interesting world. The planet is a gas dwarf, with an immense atmosphere making up half of its mass, greatly decreasing its density. The atmosphere is mainly made up of hydrogen, and looks green and yellow from space. Juno orbits at 2.21 AU, right next to the Kemtoid belt. It has several moons, most of which are captured Kemtoids, the biggest ones being Bellona, Hebe, Eris, Eileithyia and Enyo. These are no more than 400 km across. Juno was colonized by a lot of random groups which each took a moon for themselves, and decided to coexist.

Orbiting ahead and behind Juno, the Ceres and Vesta fields act as Lagrangian companions to the planet. These fields are made up of many captured planetoids centered around a large planeload, those being Ceres and Vesta themselves, each of them being 1,300 km across (bigger than any object in the Kemtoid belt). They are considered to be disjointed from the belt, although they regularly overlap. Ceres was colonized by former Soviet countries and Vesta was colonized by the Japanese and South Americans.
Oh, this is really neat! I appreciate that you kept Venus intact, and of course the updated tally of 6 and a half (up from 2 and a half) major female names in the inner system. I find the minor moon masses a little odd- I think some of them suggest a mainly icy composition for places where ice would sublimate away quickly. I also think Eris is massive enough to be spherical, but it's definitely marginal. Juno reminds me of a thing @deleonism and I did- we also had a green gas dwarf named Juno!

Thinking about the "Mars as big as Moon" hoax, I was wondering what the actual effects would be of a Mars-sized body orbiting roughly twice as far from Earth as the Moon. Would this have any significant effects on Earth and the Moon (such as increased volcanism and convection, higher tides, etc) or would the distance be enough to effectively cancel out any gravitational effect of alt-Mars on Earth? Additionally, what if rather than appearing to be the same size as the Moon, alt-Mars orbited out far enough to appear only half its size, or a quarter, or an eighth?
This tide calculator seems to think the tides would be comparable, even a little weaker!
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Ea, Our Second Chance

Background for a speculative biology/future history project I've been working on for a while. I've been posting it on the SpecEvo forum, though I'm considering parallel-posting it here on AltHistory as well.

The solar system of Utu, Ea's star. Mass measures are given in the picture as Earth's-masses (Me), 1 Me being about 6.0 million billion billion kg; distances are given in astronomical units (AU), 1 AU being equivalent to Earth's average distance from the Sun, or about 150 million km. Body sizes are proportional to each other, as are distances between bodies, but sizes and distances are not proportional to each other (if they were, even the star would be just barely visible).

As a G4-class star, Utu is somewhat smaller and colder than our Sun, which is a G2-class star (Utu has a radius of 650,000 km and a surface temperature of 5530 K, whereas the Sun has a radius of 700,000 km and a surface temperature of 5778 K).
In broad strokes, Utu's system is similar to our own, if slightly smaller, with a number of rocky planets surrounded by gas giants on wider orbits. The outer gas giants protect the inner planet from major meteorite impact by absorbing or deflecting most objects on irregular orbits, or by capturing them as moons.

Asherah (0.38 Me, 0.64 AU) is the closest planet to Utu. In its formation it was closer still; as the high temperatures slowed the consolidation of its crust, its surface is now covered in crystals, mainly quartz, that make it highly reflective. After the moons Nanna and Ereshkigal, it's the brightest object in Ea's night sky.
Ea (0.64 Me, 1.03 AU) is the only planet in the system with liquid water oceans and an oxygen-rich atmosphere. As such, it was chosen for human colonization. Its native red flora is well visible from space.
Attis (0.18 Me, 1.9 AU) and Cybele (0.31 Me, 1.9 AU) are twin planets that orbit around each other as they revolve around Utu. The tidal forces due to each other's gravity deform and fissure the crust (compare Jupiter's moon Io). They are being considered for mining because of the deposits of heavy radioactive metals brought to surface by this process.
Dagon (0.79 Me, 2.6 AU) is the farthest rocky planet. Like Venus, it has a hot core but no significant tectonic activity; instead, pressure builds up for hundreds of millions of years until it is released in a planet-wide eruption that melts most of the crust. Today the surface is frozen and static, but the immense scars of the last eruption are still visible. Thanks to the periodic outgassing, it's the only rocky planet in the system other than Ea with a significant atmosphere.
Bel (256 Me, 6.1 AU) is the first gas giant, and the only planet of Utu's system with visible rings. It's mostly composed of hydrogen, helium, and ammonia, and its surface, like Jupiter's, is divided in parallel belts of alternately rising and falling gases (similarly to what occurs in Ea's own atmosphere).
Marduk (298 Me, 13.2 AU) is the largest planet in the system. Its atmosphere appears bluish due to a presence of methane, which glows where it's ionized by electric storms. A counterclockwise cyclone, known as the Eye of Marduk, persists in the northern hemisphere.
Ashur (156 Me, 21.8 AU) is the farthest planet of Utu's system. At the present is poorly studied.
The orbit of Ashur was reached just before the Planetary War by the Hanno 3 probe. The further regions of Utu's system, containing a large number of dwarf planets, comets, and other such objects, are to date relatively unknown.

Three hundred years have passed since we've last heard of Earth.

We don't know where to look or listen in the night sky, and all our radiotelescopes haven't caught so much as a whisper from any direction. As far as we can tell, every single human that lives, lives here on Ea, where the starship brought us so many generations ago. And when one considers the state of our former planet at the time of our departure, this statement is likely to be true in the most literal sense.

We don't even know how far it traveled, or in what direction. How many centuries did it spend cruising through the void with its irreplaceable cargo, before its thousand sensors told it of the presence of an Earth-like planet in this corner of the galaxy? The navigation centers, consumed by the rigors of space, were of little use; and once the pods descended on the parched surface, quickly sacrificed by the travellers to survive those first terrible years, the starship was a distant concern. For centuries it hovered silently over Ea, burning red at dawn and sunset, shining with reflected light in the night-time, watching over us as it had during our long sleep.

But this is no cause for sadness; as much as our ancestors loved their green world, we have found reason to love our own red one.

We know much about Earth, of course – we saved the records, the documents, the encyclopedias, the art catalogues. We know about the Sun, the Moon, and Mars. We know about the Sahara, the Amazon, and the Great Barrier Reef. We know about elephants, whale sharks, and hummingbirds. We know about Jesus, Buddha, and Muhammad. We know about Napoleon, Hitler, and Genghis Khan. But few of us know Earth, the world that was. Very few, those ten thousand who first stumbled out on the yellow sands of Ea, still dazed from cryopreservation – or the even fewer who remain, some living quietly in unknown corners of the planet, some guiding our societies with their peerless wisdom.

We had hoped that none of the tragedies of Earth would repeat. Yet before the pod shields had cooled we began to argue about the best way to live, and words quickly gave way to weapons. The most honorable solution we found was to part ways with each other: there was a whole planet to fill, beautiful and untouched, and we were few, then. People were allowed to pick what sort of society they would rather join, and eventually great nations formed. Some built themselves a paradise of earthly pleasures, others find fulfillment in industry and creation; some placed their trust in the Creator of all worlds, others sharpen their minds to carve truth out of confusion; some find comfort in the protection of a wise leader or in the provisions of bountiful nature, others take pride in tracing their own path in the world.

Most of us, sitting here, remember well the horrors of the Planetary War. But a greater number of us, I hope, remember the promise we've all made afterward. Seven powers shall share this world as equals, each managing its domain after its own conscience, each agreeing to let the others do the same.

We may not know Earth anymore, but we have begun knowing Ea. Much of it we have lost, replaced with what we remember of Earth. This was a cold and arid place, we were told; so we blasted apart the polar caps, drilled boreholes through the crust, and scattered to the wind all sorts of seeds, spores, and eggs, to make it more like the world that was. We were anxious to overcome the new challenges, from the ruthless global winter to the marine eruptions that troubled our fleets. We were adrift and alone, and we clung to whatever reminded us most of home. Only recently we've started truly to appreciate the world that is. The world of red forests and blue flesh, the world of floating jungles and living stones that once baffled us so much. This too was a mistake of our forefathers; this too is a pledge to do better.

Here we are on Ea, second planet from Utu, our second chance, perhaps not yet definitively wasted. We have all made a leap of faith through the unknown, searching for the deepest unity of our species, for a responsible place in the universe, for a deeper understanding of the cosmos we share, to pursue growth and excellence, to experience happiness without compromise, to exercise our capacity to live and create, to honor the memory of our ancestors; any of these things, and all together, depending on what is in our heart and our mind.

Let us toast these three centuries of life, then, and let the next ones be better still.

– First Speaker Irene Järvinen, address to the Planetary Assembly, Landing Point, opening toast for the Third Centenary (300 AL)