Talk about Hot Jupiter! The Brown Dwarf system is interesting, I say. Are there any humans, and if so, where do they principally live?
Alternate Planets, Suns, Stars, and Solar Systems Thread
- Thread starter Pragmatic Progressive
- Start date
Starforce
Banned
They live on the planet known as Daeldrum. On the planet there are various races such as the 'locust men', the 'swamp men', the 'lizard men' and various others that live in their own areas of the planets and generally don't interfere with the other areas of the planet as to not cause wars as that has happened in previous times. The planet is home to various cryptids, and terrestrial life. It's first moon, Erina is Lunar mass but orbits half the distance of our moon and is quite volcanic, while the distant one Malmoa orbits slightly further than our moon does. These moons create tides 8 times that of our own, and the planet has a thin ring over the Eqator.
The planet Cari and it's trojan planet of Valcera eclipse the solar disk every 18 hours, roughly. Cari is what is known as a super-puff planet.
The planet known as Agarthanon was once home to human life but the biosphere was destroyed by various wars and disasters millions of years ago.
Your setting is very interesting.. Are the humans native to Daeldrum or do they come from someplace else?
Starforce
Banned
They fled to Agarthanon after the wars, but they didn't evolve independently on Agarthanon and were put there by some sort of ancient alien influence that nobody knows.
The planets of Luyten’s Star are named for the Triglav of Slavic myth. The first of these is Svarog, a hot, Mercurian world with a radius of 7026 km, and a surface gravity 97% that of Earth. Veles is more similar to Earth despite it’s tidal locking, as atmospheric circulation keeps most of the planet save for the most sunward and nightward extremes at temperatures humans would find liveable. This has allowed for the development of native life. Veles has a relatively complex biosphere loosely analogous to Earth’s during the late Devonian-Early Carboniferous period. Plants (or more precisely, sessile photosynthetic organisms, which interestingly seem to use a substance similar to retinal for photosynthesis) have made extensive progress colonizing the land and the seas contain a diverse menagerie. (Notably animals with vertebrae seem to be comparatively uncommon on Veles). Veles has a radius of 9304 km and a surface gravity of 112% Earth gravity. The last planet of the system is Perun, a purple-blue ice giant with a decent sized moon system. Perun is a small gas giant, slightly less massive than Uranus. The star system as a whole is relatively compact, with all three planets able to fit within Earth’s orbit.
Veles possesses a single moon, an oblong object the size of the asteroid Juno known as Devana after Veles’ wife and the goddess of the hunt. Perun has eight major moons (major moon being a satellite larger than 100 km in diameter) and fourteen unnamed minor moons. The major moons are all named after various kinds of Slavic spirits. They are Leshy, Vila, Dvorovoi, Rusalka, Bolotnik, Shubin, Likho, and Nav. Rusalka and Botoknik are considered two of the most interesting moons (though the others all have their quirks) as they both have subsurface oceans, with Rusalka possessing a highly complex ET ecosystem. An ecosystem that may contain signs of sapient life.
______
Here is another star system map I made. This one is within the same universe as my earlier Barnard's Star map, and like that one I hope to set a story here. Some notes on the map: Perun's orbit is far less elliptical than what depicted on the map, I just drew it that way so I could fit in the moons. The moons also do not share the same orbits. The moons are listed on the map by their distance from Perun, with the closest at the top.
Last edited:
I suspect that if we find habitable tidal locked planets, mostly it would be a matter of the subsolar zone being the habitable part, and a fair part of the sunward hemisphere iced over. The important thing is that the cold night side not become so cold that air starts to liquefy. Carbon dioxide and water freezing out on the cold side could be a problem but active geology bringing deposits into the day side might enable decent levels of both CO2 and water.
The trouble with trying to warm the limbs of a dayside at the cost of sacrificing the subsolar center to a hot zone is that the limbs will have a majr temperature gradient, and winds will be severe. This might be OK for native life, which just has to adapt to the fact of unending, relentless gale force winds. If instead we have a central warm zone under eternal noon, the immediate subsolar zone will be in the "eye of the storm" as it were with relatively gentle winds; by the time these build up to hurricane force we will have long before crossed the tundra and glacial boundaries.
The cold side, once we get a decent distance from the terminator, ought to be pretty uniform and fairly calm; there is no heat differential there.
Basically the warm zone air is lofted by eternal sunlight heating the surface; warm air absorbs moisture and rises, cooling and expanding thus forming clouds and rain, so the hot zone tends to retain moisture which wrings out of the air before it reaches stratospheric heights--the latent heat is released with condensation, thus driving the air up higher. Now the high altitude pretty dry air slides down the slope of lesser rising over cooler limb landscapes, over the sunset terminator, and falling, is heated and compressed. The cold surface is always absorbing heat from sinking air, which grows quite dense as it chills, and thus the nightside is at higher pressure on the surface as layers of air from the dayside accumulate. At the surface therefore, winds blow back into the day hemisphere, pouring over the terminator and converging on the warm zone. At some point it meets the warmed air and chilling it, a cold front sliding under a warm front, causes precipitation--beyond this rain wall, the air has been warmed and refills the air fountain.
So the habitable zone is within the rain walls, and wind speeds should be checked and air temperatures reasonably moderated, going from near freezing chilly to tropical warm at the center.
The warm zone might be only a small fraction of the whole globe, say a quarter its area maximum, but I think life could better establish itself in a subsolar Eden within say 30 degrees of the sun zenith point. It might help if the tidal locking is not perfect, and there is some revolution of the zenith point due to planetary spin axis being somewhat off the orbital plane, and some eccentricity of the orbit causing longitude variations, so we get an ellipse, causing seasons. The central tropical zone should be pretty consistently warm, the effect of the zenith revolving around is to give the limbs a summer as it passes nearer to one region then another. At any given time I suppose everything within 30 degrees of the zenith should be about full temperature. The major thing affecting habitability might not be temperature but wind intensity; a shifting zenith should stir up wind direction a bit.
Again going for a higher subsolar zone temperature and shifting the habitable zones outward puts those moderate temperature zones into the intense winds coming in from the cold hemisphere.
Veles of course is an alien world and its organisms can just bloody well adapt I guess. If we have life evolving in the seas they won't be directly affected by gale force winds in the air above them, except to the degree these make waves in the water; the oceans would be well aerated by this chop I guess. Organisms colonizing land have to just adapt somehow, with good grips on the ground I guess. The sunward zones can be pretty hot and biochemistry can just adapt to it, evolving higher temperature proteins and so forth; as long as water is liquid I would guess cytoplasm can adapt to tolerate near boiling temperatures--certainly there is plenty of solar energy to feed processes! On the cold side, there is no energy source but thermal vents, or preying on stray organisms wandering into the cold zones. By that same token, few organisms are consuming oxygen on the surface on the cold side; most life there would be under the sea at thermal vents and anaerobic.
Human visitors might be hard put to find any suitable spot for a base station; I suppose that even in a very windy temperate zone, landforms will create shelter here and there. And all that windpower does lie ready to hand to provide steady power in electric form.
Anyway odds are the planetary biochemistry is deeply incompatible with Terran biochemistry and humans would have to remain in sealed environments.
Thank you for the comments @Shevek23
I probably should have expanded more on how Veles works, but you're basically right about how the whole planet would constantly be experiencing winds as hot air circulates towards the cold hemisphere, keeping it just warm enough that the atmosphere doesn't freeze as that would cause the whole atmosphere to collapse.
As for Veles lifeforms, yeah I imagine the plant-esque lifeforms are deeply rooted and are rather squat. (I've been wondering if it would make sense for them to have photosynthetic cells evenly distributed across their who surface area rather than concentrating them in leaves that could snap off in the wind.)
And yes, the planetary biochemistry is completely incompatible with Terran life. Assuming I ever get to writing this story human colonization of the star system will mostly be concentrated on and around the moons of Perun for at least the first couple decades, with Veles mainly being of scientific interest.
I probably should have expanded more on how Veles works, but you're basically right about how the whole planet would constantly be experiencing winds as hot air circulates towards the cold hemisphere, keeping it just warm enough that the atmosphere doesn't freeze as that would cause the whole atmosphere to collapse.
As for Veles lifeforms, yeah I imagine the plant-esque lifeforms are deeply rooted and are rather squat. (I've been wondering if it would make sense for them to have photosynthetic cells evenly distributed across their who surface area rather than concentrating them in leaves that could snap off in the wind.)
And yes, the planetary biochemistry is completely incompatible with Terran life. Assuming I ever get to writing this story human colonization of the star system will mostly be concentrated on and around the moons of Perun for at least the first couple decades, with Veles mainly being of scientific interest.
Caribbean Salinity Crisis
The Caribbean Salinity Crisis
A butterfly flaps its wings, and geology is altered slightly. The Lesser Antilles and Puerto Rican subduction zones are a bit more active, and the volcanic activity opposing them a bit more frequent and extending slightly more to the northeast. About three million years ago, the volcanism had advanced to the point where North America connected to South America, first at Panama and shortly thereafter at Trinidad. The cutoff of the Central American seaway dramatically cooled the global climate, while the landlocked Caribbean Sea, located in dry latitudes, quickly drained. Within a few thousand years, it had reached an equilibrium with three large seas located two to three kilometers down, which has been maintained for the past three million years.
The seas were initially highly saline, much as the Messinian era Mediterranean was, but the Mississippi and Magdalena rivers have flushed out most of it by now. The northern Sea, the Mexican Sea, lies 2.1 km below sea level, the middle Cayman Sea lies 3.4 km down, and the southern Caribbean Sea lies 2.9 km down. Air pressure ranges from 25% higher at the Mexican sea to 40% higher at the shores of the Cayman sea. Ecologically, they’re like nothing else on Earth. The mouth of the Amazon averages 28 C, the mouth of the Congo 26. The mouth of the Mississippi averages 33, the mouth of the Magdalena 42 C. The life that has crept down from the highlands into the Mesozoic rainforests and scorching deserts tends to be small and gracile, and tremendously weird.
Early humans killed nearly all the megafauna in the American uplands, but the sunken Caribbean basins are hardly habitable for unadapted humans, and over the thousands of years it took for them to descend to the shores, the animals got wise to these strange new predators. Scimitar cats, Camelids, dwarf Elephants, giant teratorns, ground sloths, gompotheres, and more still range about the Carib seas. Some six thousand years, early agricultural efforts began in the Jamaican midlands, and a quite sophisticated civilization developed in the basin. Mexico is much more of a desert than in our world, as is the Mississippi basin, and so the city states of the sunken seas had little contest except from the strange Incans.
For millennia, they developed in their own strange bubble, domesticating some of the megafauna and killing others, sophisticating agricultural techniques, waging wars and mining the metals with which to fight them. For someone born and raised in the deeps of the Cayman or Caribbean, sea level feels as high as Lhasa Tibet would to us. The air is breathable, but only barely, and any serious mountain above sea level is potentially fatal. Their material wealth and sophisticated technology allowed them to enlist highland sepoys in the Bahamas, Mississippi, and Mexico to serve as explorers and in trade networks, and through these networks and a few brave explorers some corners of civilization are aware of most of the Americas, but there is little of note outside the deeps. Lake Titicaca is 7 km above the Cayman sea, and so the Incans and the Sách̀ Shum cannot even visit the others homelands, and both regard the lands around sea level as generally undesirable.
And then one day in the fall of the 1492nd year after the birth of Christ, a foolhardy Italian explorer sailing Spanish ships lands on the shore of a Bahamian island, and the world changes forever.
(not much of an alternate, but I thought it'd be interesting).
The Caribbean Salinity Crisis
A butterfly flaps its wings, and geology is altered slightly. The Lesser Antilles and Puerto Rican subduction zones are a bit more active, and the volcanic activity opposing them a bit more frequent and extending slightly more to the northeast. About three million years ago, the volcanism had advanced to the point where North America connected to South America, first at Panama and shortly thereafter at Trinidad. The cutoff of the Central American seaway dramatically cooled the global climate, while the landlocked Caribbean Sea, located in dry latitudes, quickly drained. Within a few thousand years, it had reached an equilibrium with three large seas located two to three kilometers down, which has been maintained for the past three million years.
The seas were initially highly saline, much as the Messinian era Mediterranean was, but the Mississippi and Magdalena rivers have flushed out most of it by now. The northern Sea, the Mexican Sea, lies 2.1 km below sea level, the middle Cayman Sea lies 3.4 km down, and the southern Caribbean Sea lies 2.9 km down. Air pressure ranges from 25% higher at the Mexican sea to 40% higher at the shores of the Cayman sea. Ecologically, they’re like nothing else on Earth. The mouth of the Amazon averages 28 C, the mouth of the Congo 26. The mouth of the Mississippi averages 33, the mouth of the Magdalena 42 C. The life that has crept down from the highlands into the Mesozoic rainforests and scorching deserts tends to be small and gracile, and tremendously weird.
Early humans killed nearly all the megafauna in the American uplands, but the sunken Caribbean basins are hardly habitable for unadapted humans, and over the thousands of years it took for them to descend to the shores, the animals got wise to these strange new predators. Scimitar cats, Camelids, dwarf Elephants, giant teratorns, ground sloths, gompotheres, and more still range about the Carib seas. Some six thousand years, early agricultural efforts began in the Jamaican midlands, and a quite sophisticated civilization developed in the basin. Mexico is much more of a desert than in our world, as is the Mississippi basin, and so the city states of the sunken seas had little contest except from the strange Incans.
For millennia, they developed in their own strange bubble, domesticating some of the megafauna and killing others, sophisticating agricultural techniques, waging wars and mining the metals with which to fight them. For someone born and raised in the deeps of the Cayman or Caribbean, sea level feels as high as Lhasa Tibet would to us. The air is breathable, but only barely, and any serious mountain above sea level is potentially fatal. Their material wealth and sophisticated technology allowed them to enlist highland sepoys in the Bahamas, Mississippi, and Mexico to serve as explorers and in trade networks, and through these networks and a few brave explorers some corners of civilization are aware of most of the Americas, but there is little of note outside the deeps. Lake Titicaca is 7 km above the Cayman sea, and so the Incans and the Sách̀ Shum cannot even visit the others homelands, and both regard the lands around sea level as generally undesirable.
And then one day in the fall of the 1492nd year after the birth of Christ, a foolhardy Italian explorer sailing Spanish ships lands on the shore of a Bahamian island, and the world changes forever.
(not much of an alternate, but I thought it'd be interesting).
The topography file I was at 80m intervals and I was too lazy to fix it for the great lakes. They're basically as OTL, generally a few meters lower actually.
Really great stuff here. I especially like the fact that Hellas Panitia (that crater that is usually just an inland sea) is connected to the ocean in the maps above.
This really looks like a map of planet with proper shorelines due to erosion and the like. Is Mars here the same size, or has it grown?
So I’ve been working on a hypothetical system featuring a gas giant roughly the size of Saturn orbiting in the habitable zone. This gas giant has three main moons - the closest is similar in size to Earth and is intended to be the Earth analogue of this system, while the outer two are roughly the size of Luna and roughly the size of Europa, respectively (all of these are terrestrial moons). Because of alt-Earth (let’s call it Moon I)‘s position between the primary body and the other two moons (Moon II and Moon III), however, it is possible and probably likely that Moon I will experience a lot of volcanism due to the competing gravitational influences of the primary and Moons II and III; what would be the best way to reduce this volcanism down to levels comparable, if slightly higher, than those of our Earth? I’ve been thinking that a thicker crust might help to dissuade volcanism, although for all I know that could just end up in a Venus-type situation where the entire surface is recycled in a moon-wide volcanic event every hundred million years or so; the relative size difference between Moon I and Moons II and III might have an effect as well (Io, the closest equivalent to Moon I in our solar system, is much smaller than Earth, and the size ratios between Io, Ganymede, Europa, and Callisto are fairly different compared to those between Moon I, Moon II, and Moon III, so less gravitational effects on Moon I due to a different size ratio could lead to less subsequent volcanism).
I think you can make it out safely- if you break the resonance, that'll solve nearly everything; and given your first moon is much heavier than its sisters then it's more likely to be the one with the main effect.
Breaking resonance with the other moons’ orbits, with the parent body, or both?
Moon orbits. Tidelocking the moon to the parent will also cool the moon down, unless it has a high inclination or eccentricity.
The moon will probably be tidally locked to the parent if it's close enough, and from what you've described it seems like it is. Definitely need a negligible eccentricity for orbital stability and to avoid too much tidal heating. To get no eccentricity, there probably can't be any orbital resonance.
I don't know too much about giant planet magnetospheres, but I think that it would probably make sense to have this moon within its parent's magnetosphere, not having its own. That said, I also hear Jupiter has a lot of radiation in its magnetosphere that would pose a big threat to any life within, so maybe it isn't such a good idea after all. I don't know much about the radiation, though, and Earth has a magnetic field too that doesn't kill off the life on its surface with radiation - in fact, the magnetic field protects us from radiation.
Google and Wikipedia tell me the Jovian radiation belts are largely thanks to Io's volcanism (though I have no idea why that might be), and we have just figured out how to stop Io-level volcanism on this moon, so maybe there wouldn't be any problem? Somebody who knows more about this than me should probably give an opinion on the radiation situation.
Interestingly, I believe gas giants in the habitable zone are likely to have water vapour clouds (or at least, it's possible), which means that instead of tan or cyan, they would appear white.
When you're deciding on an exact size for this moon, err on the smaller side. It's unrealistic for a gas giant smaller than Jupiter to have a habitable moon in a non-eccentric, close orbit that's tidally locked in the first place, but the suspension of disbelief is easier if the moon is very small and its parent is very large. This is because, for an orbit like I've described above, the moon needs to have alongside its parent, and not have been captured. It has been estimated that the moon:gas giant mass ratio is unlikely to exceed 1:10000 in non-captured satellites (if memory serves) - only Titan exceeds this in our solar system at roughly 1:4200, and its formation is uncertain and probably an outlier -, but Saturn is less than 100 Earth masses. Some suspension of disbelief is permissible, but I think the gas planet should be at least Jupiter-sized and the moon roughly a third of Earth's mass for it to be believable.
I don't know too much about giant planet magnetospheres, but I think that it would probably make sense to have this moon within its parent's magnetosphere, not having its own. That said, I also hear Jupiter has a lot of radiation in its magnetosphere that would pose a big threat to any life within, so maybe it isn't such a good idea after all. I don't know much about the radiation, though, and Earth has a magnetic field too that doesn't kill off the life on its surface with radiation - in fact, the magnetic field protects us from radiation.
Google and Wikipedia tell me the Jovian radiation belts are largely thanks to Io's volcanism (though I have no idea why that might be), and we have just figured out how to stop Io-level volcanism on this moon, so maybe there wouldn't be any problem? Somebody who knows more about this than me should probably give an opinion on the radiation situation.
Interestingly, I believe gas giants in the habitable zone are likely to have water vapour clouds (or at least, it's possible), which means that instead of tan or cyan, they would appear white.
When you're deciding on an exact size for this moon, err on the smaller side. It's unrealistic for a gas giant smaller than Jupiter to have a habitable moon in a non-eccentric, close orbit that's tidally locked in the first place, but the suspension of disbelief is easier if the moon is very small and its parent is very large. This is because, for an orbit like I've described above, the moon needs to have alongside its parent, and not have been captured. It has been estimated that the moon:gas giant mass ratio is unlikely to exceed 1:10000 in non-captured satellites (if memory serves) - only Titan exceeds this in our solar system at roughly 1:4200, and its formation is uncertain and probably an outlier -, but Saturn is less than 100 Earth masses. Some suspension of disbelief is permissible, but I think the gas planet should be at least Jupiter-sized and the moon roughly a third of Earth's mass for it to be believable.
