Alternate Planets, Suns, Stars, and Solar Systems Thread

In the near-future, when the discovery of alternate Earths become the talk of nations, an unlicensed scientist had discovered one such alternate universe, categorized as #9, in which nine rocky planets have the following exact features:

  1. Set in a habitable zone in which liquid water is possible

  2. At least one large satellite to stabilize the axial tilt

  3. A predominantly iron core, which means each of the Nine Earths has a solid, active magnetic field

  4. The inner core measuring a radius of 760 miles (This doesn't change with any of the planets' outer diameters, especially Mars-sized Jotunheim, the smallest of the Nine Earths. So if planets of different sizes have such cores of these parameters and dimensions, would they affect radiation and climate in any way?)

  5. A predominantly silicon crust

  6. A predominantly silicon-magnesium mantle

  7. Atmospheric pressure no greater than one bar

  8. Clear, tangible evidence of life. (However, the lifeforms on all of the Nine Earths are microbial, which would be perfect for our criminal's first phase of his overall terraforming plan--dump pioneering colonies of photosynthetic cyanobacteria on the primeval oceans--if the two last of the Nine Earths didn't throw a monkey wrench at that.)
These Nine Earths orbit a complex series of stars--first, a binary of G-type main-sequence stars, or "yellow dwarves" (Bestla, 1.15 solar masses; and Borr, 0.84 solar masses), then a trinary of K-type main-sequence stars, otherwise known as "orange dwarves": Odin (0.8 solar masses), Vili (0.7 solar masses) and Ve (half a solar mass). The Nine Earths, in turn, orbit those two star systems in a habitable zone. But how wide of a habitable zone would such systems result in?

The Nine Earths are listed as following, in order of orbit:

  1. Alternate Earth 9a, "Muspellheim", Venusian in size, orbiting the pantheon from the inner boundary of the habitable zone. The oceans and continents are alive with volcanic eruptions of all types--low gas/low viscosity (quiet lava eruption), high gas/low viscosity (lava fountain), low gas/high viscosity (dome-building eruption) and high gas/high viscosity (classic Ring of Fire eruption). The oceans, in turn, have an average pH between 7 and 8.3, comparable to Yellowstone's Grand Prismatic Spring back home. Would our cyanobacteria colonists survive in such conditions? After oxygenation, would complex, multicellular life follow suit?

  2. Alternate Earth 9b, "Alfheim", Terran in size. Atmosphere is predominantly carbon dioxide and methane, but the clouds are so concentrated in sulfur particles that atmospheric albedo is 100%. Should the atmosphere ever be oxygenated, would the albedo drop? And would complex, multicellular life thrive in an atmosphere in which there is a lot of sulfur in the clouds?

  3. Alternate Earth 9c, "Jotunheim", Martian in size. The smallest of the Nine Earths. Would the lower gravity still hold a solid, breathable atmosphere?

  4. Alternate Earth 9d, "Vanaheim", Terran in size. In a certain respect, a real-live Abyssia.

  5. Alternate Earth 9e, "Asgard", Venusian in size. Earthlike in every respect except for its Venusian diameter and mass and therefore, its gravity.

  6. Alternate Earth 9f, "Midgard", Terran in size. The most Earthlike of the Nine Earths. Granted, like most of the others, it is Archaen in size and environment, so it's currently not hospitable for us, but that is why we have cyanobacteria as Phase I.

  7. Alternate Earth 9g, "Svartalfheim", Terran in size. We have now come to the point so far into the habitable zone that the climate is getting cooler. Its thinner atmosphere--1/12 the thickness of Earth's--coupled with the surface's black rocks give this the lowest albedo of the Nine Earths, 1%.

  8. Alternate Earth 9h, "Helheim", Venusian in size. Waters at the poles are frozen solid, but those at other latitudes are liquid oceans thickly veiled in clouds of steam. Colonization by cyanobacteria would be declared redundant for this one.

  9. Alternate Earth 9i, "Niflheim", Terran in size. The last of the Nine Earths orbits the pantheon from the outer boundary of the habitable zone. As a result, the mean surface temperature is 0 degrees Celsius. 30% of the atmosphere is oxygen, but all hint of water is locked in ice, two miles at the thickest. Beneath the ice are rich sources of two factors of greenhouse gases--volcanoes and methane hydrates. Because of all this oxygen, colonization by cyanobacteria is deemed redundant. But our criminal would not settle for dark-loving germs, so he improvised by shooting one nuclear missile into the atmosphere which, upon contact, will detonate and release 100 megatons of methane into the atmosphere. Would this be enough to launch a global chain reaction?

More seriously:
a4: The very interiors of planets are... extremely odd. A smaller core for a more massive planet may mean the core's more dense, and that's likely to make the core at least a little hotter, but I don't think this would.

a9: Generally, habitable zones for close binaries are found by taking the luminosities of both stars- from there, simple worldbuilding tutorials like Artifexian's solar system videos should answer that question for you.

b1: You should be able to get a brand of cyanobacteria that thrives in such conditions- even if you had to guess how cyanobacteria lived on early Earth to do it.
b1b: Probably, eventually- barring catastrophic climactic change or a big solar flare?

b2: ...Possibly. I don't recall, but I think sulfur dioxide is pretty sucky for clouds.
b2b: If it was evolved for it.

b3: Again, possibly. If I recall correctly, its lack of a magnetic field is integral to the loss of Mars' own atmosphere- if it's younger, or if you find a way to get its core running longer (higher mass is an easy solution), it'll probably be fine.

b9: That probably involves complicated fluid dynamics calculations, but so long as the methane doesn't get messed up it should at least tip the temperature a little longer- though you certainly don't need to be above zero celsius to have liquid water, even if it's the same pressure as Earth's surface.
The Three Suns.jpg

I have here a trinary system of red giants. Judging from the size and luminosity, we can confer that each star has been a red giant for 542 million years, which means it has less than the same time to expire left. (Or perhaps far longer because apparently, some red giants can last up to twice as long as Earth's current lifespan!) If you think, judging from this map, that the binary is a little too close for comfort, this is not to scale. In fact, the first two stars orbit each other from a distance of four AUs (pretty much the distance between Jupiter and Saturn). What, then, would the resulting distance be for the third, solitary red giant? And in this system, how far from the third system will the habitable zone begin, and how far will it expand? How big and how bright, exactly, will a 542-million-year-old red giant be?

Isaac Beach


Erre; A world that in on the verge of tidal locking, with a day/night cycle lasting 9 of their years. Life has evolve three methods to survive the harsh nights and days that has resulted in three vastly different ecosystems. Life on Erre either lives within the underground aquifers, goes into a hibernation similar to waterbears, or migrates across the world to stay in the belt of temperature that allows water.

My map in this same thread, three pages back, and the base of an Inkscape map from one page ago :rolleyes::

Is there any Binar Star Systems out there? Can NOT find a way to make a planet in such a unstable enviroments.
These two videos might help:

They're on a channel called Artifexian, from an Irish guy who's doing a series on world-building. Starting from the star and working down into planets, climate, language, cultures, etc.
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These two videos might help:

They're on a channel called Artifexian, from an Irish guy who's doing a series on world-building. Starting from the star and working down into planets, climate, language, cultures, etc.
Heeeyy.... Thanks! These are great! I am creating a Planet Called Krenz for a series of Sci-Fi novels and Graphic Novels. This works nicely!
Tútídis is the third planet in the Laugus sub-system of Sábális system. It is a mid-sized world generally matching the concept of a desert planet, with a somewhat thin nitrogen-argon atmosphere with few clouds and an extreme temperature (daytime temperatures range between 50 and 120 degrees celsius) due to the increased size of its early-giant parent star. Despite this, it is the most habitable planet in Sábális system, with land capable of sustaining plants (given enough water) and, given the proper conditions (no humidity (easy on this world), as much exposed surface area as possible, and quite a lot of water) sustaining humans for extended periods of time. As a result it is the second-most populous world in the system, following Salúna's undersea cities. The most populous areas of Tútídis are the basins- the poles, and several other places where water and air have gathered. These places naturally have more mild weather than elsewhere, their thicker atmosphere and water keeping the temperature between 40 degrees in height of summer and 10-15 degrees in the depth of winter (depending on the position of the first and third stars in the system). These areas have been terraformed, as well- the nitrogen-argon atmosphere is complemented by a breathable amount of oxygen, so in the winters it's possible for a person to step out of their house and breathe in the cool fresh air. Most basins have rejected the assistance of a proposed orbital reflection ring to give them light during the winter- they believe that relying on a natural source of light separates them meaningfully from the habs in orbit.


Felix Anholt

First visited in 2123 by the Ibn Battuta (Mahex corporation) 31 light years from Earth, the system was lifeless, home to a single planet in the habitable zone, one Jovian giant and one Superjovian. The system was already uninteresting, but it was made worse by the planet only had a few percent water. There was no interesting alien biochemistry to explorer and exploit, the planet was too marginal for terraforming, and the Superjovian had been captured two billion years ago, cleaning up much of the asteroid of the system. Mahex still set up a claim to the system, in hope that someone would buy it, the Superjovian at least had industrial potential, and while poor in asteroids, it still had enough to feed any local industry for a billion years. Several moons of the Jovian were interesting, but ironic as two was captured planets, they was simply too big to use for extraction and to cold for surface terraforming, through the Earth sized moon had large seas under a relative thin layer of ice, no more than tens of meter thick at equator. The habitable planet also had a small but extremely metal rich moon, believed to be a captured inner planet.

To the luck of Mahex the Ymir Terraforming Cooperative was looking for a desert planet for experiment in terraforming, and the system was only seven light years from Hydra Idun the center of the cooperative in the spinward sector. They bought the system cheaply in 2130 and named it Felix Anholt. The “Felix” (happy) was used by cooperative from system with only an arid world in the habitable zone and “Anholt” was an old Scandinavian island known for its desert-like landscape. The habitable planet was named Balar after the Celtic God of drought.

The Ymir Cooperation believed that while early in colonization only first-rate worlds was colonized or terraformed, as they were taken second-rate worlds would increase in value this close to Earth itself and wished to develop useful terraforming technics. As such they were not interested in increasing the planet hydrosphere but develop a stable and functioning ecosystem with the limited water resources.

The Ymir Cooperation were known for its technic of seeding worlds in waves with more and more complex life and simply leaving them fallow between seedings, could see that a more active terraforming was needed, and permanent orbital industry and settlement was placed above the planet early on. Only after half a century of terraforming, a significant part of the population settles on the colony. Until 2297 it stayed a sleepy backward of Ymir’s possession in the region with less than a hundred million living in the system. Most resources came from the continued development of Balar, and the local industry was limited in size. But in 2297 the pirate warlord Jim Chun conquered Hydra Idun and the Ymir Cooperation was thrown into chaos with the spinward part of the cooperation cut of from support from elsewhere. This forced Felix Anholt to fend for itself, this lasted until one of Chun’s navies arrived in 2301, and Felix Anholt was given the choice between paying tribute or face orbital bombardment.

The next 78 years Felix Anholt was a vassal of Chun Dynasty, early on the poor system was forced to pay the tribute in corvée, delivering workers and soldiers to the Chun Dynasty. This was widely hated, and the space industries was expanded so that the tribute could be paid in good and money. The small moon of Balar with its vast richness and low gravity was very helpful in this. The pride of Felix Anholt was the shipyards, while the system lacked the infrastructure to produce their own Alcubierre drive, they were able to import those and build interstellar freights and warships. Of course, Chun and his descendants kept an eye on Felix Anholt to ensure, they didn’t build their own navy. But even with its shipyards it was still a backwater.

But an empire kept together with force often run into problems, in 2379 a succession crisis threw the Dynasty into a decade long civil war. For Felix Anholt this meant they was left alone for the first time in almost a century. From the moment the local naval garrison left for the civil war, the shipyards shifted to mass producing gunships, warship meant for in system use and unable to go FTL, while large orbital fortification was built. This was an opportunity, which maybe would not come in lifetime again. As such when the civil war ended in three successor states and large chumps of the Chun Dynasty eaten by its rivals. There were several attempts by the different successor states to vassalize Felix Anholt again. The result was several beaten fleets.

As such Felix Anholt entered the 25th century as free but fortified world. They reestablished contact with the Ymir Cooperation which by this time had ended up centered around the Jotuns a trinary star system almost 350 lightyears from Earth coreward. A reunification was impractical, but friendly relationship was established, and information flowed freely. Several other former Ymirian worlds in the region, who had also regained their freedom, also established contact with Felix Anholt, but no one wished a union, instead they organized themselves in a loose alliance (SYTA) with a small unified alliance navy, and strong local interplanetary gunship navies.

SYTA would keep the local peace for centuries, strong enough to deal with pirates and help the members defending against invasions. But too weak to conquer its neighbors, its only aggressive wars it entered was the liberation of Hydra Idun and the rest of the local occupied Ymirian Worlds in the region in 2435-39. So, the local region returned to sleep and Felix Anholt could focused on the continued terraforming of Balar, while having been habitable for centuries, the ecosystem was still not fully stable, and the process continued. The system returned to be a sleepy backwater even with a population in the hundreds of millions.

Terraforming of the Earth-size Jovian moon (Trymheim) was begun, it was never expected it would be fit for major human settlement, but a breathable atmosphere would enable a better use of the planet, even if it would never become hospitable than the Antarctic Peninsula on Earth at least not above water.

By the early 27th Century a new empire was rising, and it was clear that it couldn’t be stopped. The Terran Commonwealth wished to unite mankind under one state. It offered equality under the banner of Terra. The SYTA discussed whether, they should fight Terra, but in the end, they saw Terran hegemony as inevitable, and they negotiated a peace with Terra.

The next part includes a spoiler to Castle Federation by Glynn Stewart, whose universe I borrowed to write this idea into.

This was the end of being a backwater, Felix Anholt turned out soldier for the Terran navies and armies, its shipyards rose to prominence again. The Superjovian became a major industrial hub. This lasted for more than a century until the Terran Q-net was destroyed in the war with the Alliance of Free Star and chaos reign again. But the spinward Ymirians knew that Terran Hegemony was still inevitable, and they stayed loyal to the new military Junta.

At this point Felix Anholt are still a lightly populated system, home to only a little above 1,5 billion people with 2/3 living on Balar, 5 million on Trymheim and the rest in orbit and on non-terraformed worlds, but it’s far more industrialized than its relative low population indicates.

I would like to thank slimysomething for having used his planet building template to make this map.
I don't have map making capabilities right now. I hope this is fine.


Earth-sized planet, 98% Earth's radius, fourth planet in the [REDACTED] system and one of two Human-habitable worlds[1]. It orbits a main sequence Type A star. Ammonia is present in the atmosphere.

Flora and fauna is Earth-derived, genetically engineered to survive the cold climate. Most photosynthesizing plants are black instead of green.

There is a large swathe of rocky, barren permafrost in the middle of Hob's single continent. This area, resistant to terraforming due to its altitude, is approximately the size of North America, and looks like a Mars-red splotch when the planet is viewed from space.

The planet has two moons, both about the size of Pluto. The closer one is 50% closer to Hob than Luna is to Earth.

The current year is 7778 'AC' (After Colonization), or approximately 9970 in the Gregorian calendar[2]. It should be noted that most languages on Hob use hexadecimal.

Population is 2.2 billion. Technology level resembles the early 22nd century.

The supercontinent covering half of Hob resembles four large peninsulas shoved together, and they are in fact separate tectonic plates (Hob is more geologically active than Earth).

Attar is a 'peninsula' approximately the size of continental Europe (including Russia west of the Urals and part of Kazakhstan). It resembles a gardening trowel with a sharp end. On the eastern 'tip' there is a shallow straight approximately 100km long, and a narrow landmass shaped like a really crooked Cape Cod, which is connected by an isthmus to an island of similar shape and size to Norway. The northeast of Attar has a hammerhead-shaped mountainous peninsula, on which sits a volcano the size of Olympus Mons; a deep trench sits vertically to the east, on the other side of which is a very large, swampy river delta. Attar is connected to the rest of the continent by a landmass the size of Spain, with a shape similar to the country of Georgia. Below the 'spade' of Attar is an island with a similar size and shape as India[3].

The southwest has a mountain range that curves to the east in a C shape, creating an icy desert in the center of Attar about the size of Ukraine. Further east, towards 'Norway' is plains and permafrost steppe.

The population is Human, but genetically engineered. The most novel difference between Homo sapiens hobs and Homo sapiens terra is their feminine appearance. They lack almost all sexual dimorphism and almost no male secondary sex characteristics. In some cases women are taller than men. Hobbsians have extremely high metabolisms, zero body and facial hair, dense muscle fibers, and have antifreeze enzymes in their blood. The ethnic groups of the Attar resemble Russians or Northern Europeans. The Attar (the largest ethnic group in the region, hence the name) are most commonly blonde, while the closely related Shi'an have black hair.

One of the staple crop on the Attar is a genetically engineered grass called kaff. It's a short, thorny bush, designed to survive the extreme cold. Grains resemble quinoa, and have hard black shells that have to be milled similar to rice. It tastes like quinoa, suggesting it was originally engineered from that plant. The population of the Attar is entirely vegan. Other crops grown in this region include a plant resembling soybeans, and a plant resembling jackfruit.


[1] Though Hob, originally given the nickname Hoth when it was discovered in the late 21st century AD, required 200 years of terraforming.
[2] The exact year of colonization is unknown, but it's believed to be 2192 AD.
[3] I lost my maps and I don't have the ability to make new ones.
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So @tungsterismapping's making Space Equirectangulars. I decided to convert two of those (Io and Callisto) into Worldas. Feel free to use them!
This is rotated 180 degrees from what is shown on the space equirectangular, partially because it looks less awkward and partially because I think it's now aligned with the other Callisto map I uploaded way back when.
A solar system I am working on. None of these pictures made by me, the planets and moons aren't to scale.
Are the stars also to scale with the planets? If so, those are small red dwarfs. The smallest we’ve found is EBLM J0555-57Ab, which is only the size of Jupiter and is a damn small anomaly. Yours would have to be red dwarfs, too. And that giant at the end must have been thrown out of its place in the system by interactions with the inner giant. I mention this only because I’m in love with the IRL Five Giants hypothesis and the implications regarding Planet Nine.

It’s a neat setup. Seems like those super-earths managed to coalesce early enough that instead of becoming a smaller set of giants, they were able to divvy up outer system mass between a larger number of smaller bodies.
Are the stars also to scale with the planets? If so, those are small red dwarfs. The smallest we’ve found is EBLM J0555-57Ab, which is only the size of Jupiter and is a damn small anomaly. Yours would have to be red dwarfs, too. And that giant at the end must have been thrown out of its place in the system by interactions with the inner giant. I mention this only because I’m in love with the IRL Five Giants hypothesis and the implications regarding Planet Nine.

It’s a neat setup. Seems like those super-earths managed to coalesce early enough that instead of becoming a smaller set of giants, they were able to divvy up outer system mass between a larger number of smaller bodies.

No they are not. The main star is a G type star and the other one below it is an M class star orbiting in a tight binary, think orbiting in 3-5 days or so. I'll give a quick run-down of the planets in the system.

The 1st planet is supposed to be a 1.1-1.6x times the mass of Earth, with a Venus type atmosphere with a different composition.

The 2nd planet is 0.1-0.2 times the mass of Earth. Think Mars but with oceans, a thicker atmosphere and warmer. With a single large moon.

The 3rd planet is an Earth mass world with 2 moons. Quite Earth like.

The 4th planet is a gas giant with different chemicals in its Atmosphere that make it a blue Jupiter type, similar to Jupiter in mass and radius.

The 5th planet is a frozen over planet, with snow and ice everywhere. It's a super Earth type planet.

The 6th planet is similar to Uranus.

The 7th planet is like Neptune but with a more of an Oxygen - Nitrogen Atmosphere. Imagine a gas planet with our Atmosphere.

The 8th planet is very Neptune like with an Earth mass binary companion.

The 9th planet is like Saturn in terms of size though it has different chemicals in its atmosphere that make it a dull red.

The 10th planet isn't even a planet at all, it's a brown dwarf that orbits extremely far out from the system, probably 400-500 AU out.