Alternate Planets, Suns, Stars, and Solar Systems Thread

[BrobDingnag]

How far can one twin orbit the other without putting either one at risk of tidal locking?

You can calculate it provided you know the parameters. Finding out where they will tidally lock lets you kick up the semi-major axis to beyond that, which nets you various orbital resonances. An orbital distance above the tidal lock distance but within the Hill Sphere is what you’re after, right?

Would both still have the axial tilts needed for seasons, or would the gravity from either side straighten them up?

Solved easily by simply giving the barycenter of the system an axial tilt. Then you can even have them have no tilt relative to one another.

How will orbiting each other affect the seasons themselves?

The Moon orbits the Earth and seasons are still seasons. Having the barycenter that far outside the Earth is going to more greatly affect the weeks, rather than the seasons. And even then, not by much. The Earth-Moon system diameter is smaller than the variation in the annual Earth-Sun distance, and though this would be larger, I can’t see it being significantly larger.

Will a year still last months as our Earth does, or will it last weeks, as is the case with moons?

A year will be a year, because it’s a year. Axial tilt defines that.

Will a binary planet render the use of a moon moot?

I’m not sure how you’d get one stably around either planet. Assuming no tidal locking as you said, you’d still have tides on each planet like a regular moon would provide… provided that the shared resonance is high enough for that. You could have slower tides, I suppose.

How bright will a binary planet be on the night sky?

Easily calculable as a direct function of finding out the first calculation above. We know the absolute magnitude of Earth, so all you have to do is plug in the distance you need from above and calculate the relative magnitude at that distance.

Workable can correct me, of course.

 

[Epsilon Tauri]

If Earth were just the one twin of a binary planet system, then the following questions are as such:

Without giving away too much, I've been working on a binary planet scenario for the MotF, so I might be able to give some insight here that hasn't already been mentioned.

How will orbiting each other affect the seasons themselves?

<snip>

This explanation is for a tidally locked pair. The actual seasons are going to be similar, as mentioned, but there are interesting phenomena that arise during each of them. If they're not tidally locked, it's probably not too different from Earth.

Will a binary planet render the use of a moon moot?

If the planets are tidally locked and relatively close, then you could probably fit a moon stably within their hill sphere. This would be helpful, because with tidal locking, you don't get a monthly/daily tide cycle. As already mentioned, if they're not tidally locked, you probably can't get a moon.

1. How bright will a binary planet be on the night sky?

Earth is 2.5 times as reflective as the moon (moon = 0.12 albedo, earth = 0.30). 2.5 * r^2/a should give you a good answer. r = planetary radius in lunar radii, a = distance between planets in lunar distances. This tells you the brightness of a full *planet, compared to a full moon.

 

[Epsilon Tauri]

---

From a letter sent by the Acalsha Regent on behalf of the League before negotiations in Xayin began, 1306:
To His Highness the Celestial Emperor, who makes his worldly home in Matfin, He who speaks to the Gods themselves, Climber of Mountains, Conqueror of Countries, that he may recieve our message in peace and in good health, and in a disposition to humor this humble request.
The great armies of the Celestial Empire have taken vast swaths of land from our common rivals in Talitun, and now as I see them preparing in Xayin I must wonder if the great Celestial Emperor would turn on our own humble nation next. Not since the last Acalsha Imperial Pretender fell in the northern slopes of Anxulin in the 1284th year since the revelation have any from Calshan stood against an army from great Matfin, and as these vast armies grow stronger by the minute, with more and more soldiers joining the gods' cause, it would be wise to keep it that way. Calshan and her few satellites have thus deemed it prudent to reaffirm our loyalty to His Highness the Celestial Emperor of Matfin and of all places above the sea. The court stands eager to humble itself before the Celestial Emperor and avoid any of the unnecessary bloodshed that war - especially war with the Celestial Empire, as their armies are so brave and coordinated that all enemies before them are decimated - always causes.

Though rumors should never be trusted, some claim that the gods themselves shine heavenly light from their home in the Shuru upon the great city of Matfin and all those which lie within the Empire, a true proof of her legitimacy. There would be no greater honor than to become another part of the one true Blessed Celestial Empire.

May the Gods grant this letter swift passage along the roads and the seas, that it may find its recipient unharmed.

---

The Reflector Networks were a perfect example of the idea of Mutually Assured Destruction. After contact was established with the Ashuro, the early experimenters tried to collaborate to bounce messages between the worlds. This was done in the name of science, a field still in its infancy at the time. Soon, permanent retroreflectors were set up to bounce light between cities on the other world; the earliest route went from Xungcin to Matfin. More and more routes were set up on both worlds, for a simple reason; they held complete power over each others' communications. If either planet decided, for any reason, to shut off the retroreflectors, the other could freely knock out all of their own retroreflectors as revenge. Of course, this meant that both had a rather strong incentive not to displease the other. The system was a house of cards at best, and it's frankly a surprise that it lasted as long as it did.

---

The invention of the Reflector Networks was the biggest factor in ending the Three Empires period. The continent had been split in three for most of a century, but when the Amatfe were the first to develop Reflectors, the balance was tipped. The first major military maneuver coordinated through the reflectors was the Amatfe invasion of the southern Edalito territory. It was a huge success. The communication between Shlikun and Naculayn, located in the only two major passes in that area of the Heavenly Mountains, was instrumental in the entire operation. The Emperor in Matfin continued with the new technology, conquering most of the northeast. It was at this point that the Acalsha joined forces with the Amatfe. Their own throne had been vacant for twenty years, and with their reports of "the gods themselves" flashing "heavenly light" in Matfin, there was little they could do to reclaim legitimacy.

Talitun had an advantage over Calshan in its isolation from Matfin, over the Heavenly Mountains and the great jungle. They even began a small Reflector Network of their own , but too little, too late. The public had already been convinced that the Emperor in Matfin had been chosen by the gods who lived on the Shuru, and that their own was a pretender.

---

This map was fun! I've had a vague idea for something along these lines for months now, but this MotF gave me the chance to really flesh it out. Some notes:
The Shuru is the twin planet. This is a binary planet. The religion of this area holds that the gods live on the Shuru, so needless to say when somebody figured out they could actually talk to the gods using mirrors, this was important beyond just "oh cool, the telegraph a little bit early".
Speaking of which, this world's tech is early 1600s level (except for optics and astronomy, which is much more advanced).
I think that's it!
Edit: Oh, and Amatfe, Acalsha, and Edalito are the demonyms of Matfin, Calshan, and Talitun, respectively.

---

Since I'm finally getting around to crossposting this MOTF after like a month, I figure this thread is another good place to share it, given the obvious "alternate planet" aspect.
Link back to the (identical) original.

 

[Neoteros]

I've already posted the premise on the ASB thread, but this thread seems more appropriate:

A K-type main sequence star, 0,5 times the mass of the Sun and a surface temperature of 3.900 K.

Near the center of the habitable zone of this star, a rocky planet with a mass 2 times that of Earth, with a radius 1.3 times that of Earth; the atmosphere is richer in oxygen than Earth's, but nonetheless very similar to ours - it'd resemble the atmosphere Earth had during the Carboniferous period. The surface would be covered by a shallow ocean peppered with several flat island chains.

Near the outer edge of the habitable zone of the same star, a small rocky planet with a mass equal to 2,7% that of Earth, and a surface between those of Ganymede and Mars; despite its small size, being more distant from its sun might allow it to retain liquid water and a thick atmosphere, leading to it being a low gravity water world; life could almost float in water and sky alike, and perhaps land-based life could colonize continent-sized chunks of ice, if actual land is scarce.

Both of these planets would have moons of their own, to help with tides and so on, and several gas giants on the outer edge of the system could protect them from asteroids and comets; lifeforms would be squat and stocky on the first planet, that would have a higher average temperature than Earth, but lanky and spindly on the second planet, that would have a lower average temperature than Earth.

Would such a system be plausible?

 

[da Racontor]

A different plausibility check that I've been thinking about for a while for a fantasy-esque idea. Could a star system's barycenter be stretched out far enough to be located in the star's habitability zone? And if so would there be any gravitational side-effects for an object located there?

 

[Epsilon Tauri]

I've already posted the premise on the ASB thread, but this thread seems more appropriate:

A K-type main sequence star, 0,5 times the mass of the Sun and a surface temperature of 3.900 K.

0.5 solar masses fits more with an M1V-type star; the smallest K-type stars will be around 0.60 solar masses.
Some stats for the star (with 0.5 solar mass, 3900 K):
It should have about 6.61% the luminosity of the sun (=mass^(3.5)).
The habitable zone should extend from around 0.24 to 0.35 AU from the star, using the 0.95-1.37 estimate for our own solar system which is most common - proportional to the square root of luminosity.
The star's radius will be roughly 0.60 solar radii.

Near the center of the habitable zone of this star,

You may want to go a little further in with this; Earth is near the inner edge of the Sun's habitable zone, and you don't want to interfere with the stability of the other planet.

a rocky planet with a mass 2 times that of Earth, with a radius 1.3 times that of Earth;

This is just slightly denser than Earth. It will probably have a smaller core. Gravity will be 1.18 g (=m/r^2).

the atmosphere is richer in oxygen than Earth's, but nonetheless very similar to ours - it'd resemble the atmosphere Earth had during the Carboniferous period.

Around 35% oxygen, then.

The surface would be covered by a shallow ocean peppered with several flat island chains.

Sounds like there wouldn't really be much height variation. The planet would then probably be less geologically active than earth.

Near the outer edge of the habitable zone of the same star, a small rocky planet with a mass equal to 2,7% that of Earth,

This is quite small - just a little larger than Ganymede. The star is smaller too, though, so I think it would be able to clear its orbit. It could be difficult to maintain stability with the narrow habitable zone, as I mentioned earlier; perhaps set up a resonance between the two planets.

and a surface between those of Ganymede and Mars;

what do you mean? in terms of temperature? composition?

despite its small size, being more distant from its sun might allow it to retain liquid water and a thick atmosphere,

Being within the habitable zone, it should definitely be able to hold liquid water. A thick atmosphere is also definitely possible; how many atmospheres do you mean?

leading to it being a low gravity water world;

Given your mass, for a water world (specifically, a world where H2O covers a large fraction of the planet's mass), according to my reference chart (figures 4, 5; pages 21, 22), the radius should be between 0.33-0.45 earth radii. Err on the lower end of this for a larger core and silicate mantle, which I think you'll want for habitability.

life could almost float in water and sky alike, and perhaps land-based life could colonize continent-sized chunks of ice,

Sounds cool! The continent-sized chunks of ice will probably take the form of polar ice caps which shrink and grow yearly (assuming you have seasons).

if actual land is scarce.

Actual land will be nonexistent on such a world.

Both of these planets would have moons of their own, to help with tides and so on,

Makes sense. This is rather unlikely for terrestrial planets; there are only 3 moons, and only one major enough to cause tides, out of four terrestrial planets in our solar system. However, tides are likely important for habitability.

and several gas giants on the outer edge of the system could protect them from asteroids and comets; lifeforms would be squat and stocky on the first planet, that would have a higher average temperature than Earth,

Maybe add a bit of a greenhouse effect to ensure higher temperatures, or else keep the planet close to the inner edge of the habitable zone.

but lanky and spindly on the second planet, that would have a lower average temperature than Earth.

Would it be beneficial to be spindly, on a world where heat loss is a major concern?

Would such a system be plausible?

Seems pretty plausible overall to me.

A different plausibility check that I've been thinking about for a while for a fantasy-esque idea. Could a star system's barycenter be stretched out far enough to be located in the star's habitability zone? And if so would there be any gravitational side-effects for an object located there?

You mean like, a multi-star system? It's possible for the barycenter to be in the habitable zone, but if you tried to put a planet at the barycenter, it would have a very unstable orbit.

 

[da Racontor]

You mean like, a multi-star system? It's possible for the barycenter to be in the habitable zone, but if you tried to put a planet at the barycenter, it would have a very unstable orbit.

Either multi-star or what I was also wondering was a small star with a relatively large amount of large gas giants in the outer section of the system. From you answer though, I would assume adding more bodies to the system would only make it worse.

 

[Epsilon Tauri]

Either multi-star or what I was also wondering was a small star with a relatively large amount of large gas giants in the outer section of the system. From you answer though, I would assume adding more bodies to the system would only make it worse.

Adding more bodies would indeed worsen the instability.
You might have more luck placing something at the L1 Lagrange point, either in a binary star or between a star and a giant planet. There should be no other planets, to ensure stability.

 

[Neoteros]

*snip*

Sounds good; as I was reading up on low gravity water worlds and superhabitable planets, I tried to come up with a compromise that'd allow both kind of planets in the same system. I was originally going to have the smaller planet be the moon of the bigger one, but that way there was a serious risk of all the water on the smaller planet, not to mention its atmosphere, just going away because of the heat.

 

[Sardar]

Question: what are some additions to the solar system that could be somewhat significant, but also not change human history very much at all pre-1900/1800? Maybe like Mars having one larger moon instead of two, or Venus having a moon?

 

[BrobDingnag]

Question: what are some additions to the solar system that could be somewhat significant, but also not change human history very much at all pre-1900/1800? Maybe like Mars having one larger moon instead of two, or Venus having a moon?

Anything invisible from antiquity isn’t going to change history much, so just keep it at a low enough apparent magnitude, whatever it is, or obscured by a brighter body. Aside from Planet Nine (I hope it’s real), there’s talk of the potential for an Earth-size body or several Mars-sized bodies out at the Kuiper Cliff. Anything that size is significant, no matter where it is. But that’s less “history” and more “potential future”…

 

[Rosella]

0.5 solar masses fits more with an M1V-type star; the smallest K-type stars will be around 0.60 solar masses.

To be fair, there's a lot of variability and fuzziness between late-K and early-M stars especially. I'd probably go with somewhere between K9 and M3.

Question: what are some additions to the solar system that could be somewhat significant, but also not change human history very much at all pre-1900/1800? Maybe like Mars having one larger moon instead of two, or Venus having a moon?

Pretty much anything involving moons, yeah. So long as said moons are fairly small and relatively dim- I wouldn't try my luck with anything larger than Ceres- I imagine even relatively large inner system changes are doable.

 

[Zackzona]

Caribbean Salinity Crisis

@Ten Thousand Red Lakes I was wondering how did you make this topographic map or where did you might get this from? The color scheme used is almost the one used in this link here http://ahstat.free.fr/2-topography/monde1000-1024.html, it has a similar topography to this map.

 

[TheShah]

I know this has probably been asked to death, but does anyone know of a ice age worlda map with climate already superimposed? If not, I'll make one. Just don't want to have to reinvent the wheel if there's already one out there.

 

[Jürgen]

An new experiment in a different way to represent a space colony (inspired by Overheaven)

Elara one of the major settlements in the solar system of the Danish diaspora. Elara is 16-cylinder habitat placed around the minor Jupiter moon of Elara.

Name: Grand Duchy of Elara

Denonym: Elarian

Status: Member of the Jovian Confederation; in Personal Union with the Danish Commonwealth, Associated Status in the EU, Member of the UN

Government: Parliamentary constitutional monarchy

• Monarch: King and Grand Duke Christian XIV
• Stadtholder: Prince Erik
• Prime Minister: Olaf Elyouseff
• Speaker of the Alting: Christian Frederik Johnny Christensen

Official language: Danish

Population: 14,714,607 (January 2161)

Area:

• Habitats: 12,800 km2
• Elara: 23,200 km2

History: Elara started 2071 it was established as a Danish public-private enterprise to develop the Danish space industry. Original only a Torus habitat place close to Elara, it would be expanded into two large, closed O’Neill Cylinder a few years later, strife on Earth and global warming resulted in many Danes leaving Earth around 2100 and the Elara Colony offered a new home far from the strife of Earth. In 2121 the status of the colony was official changed and it became an independent member of the Danish Commonwealth. In the years after it established with the other Independent Jovian states the Jovian Confederation and slowly began to buy out external actors in the Jovian system or even in one case conquering the colony of Carpo.

Economy: Elara is a relative minor economy, which sell a mix of consumer product and have a respectable shipyard and stationyard industry. But it’s mostly famous for being one of the major exports of timber and agricultural products in the Jovian System.

Geography: Elara is made up of 16 major habitats connected to the minor moon of Elara, all the 16 habitats are 8 kilometers in diameter and 32 kilometer long. The major habitat is Elarastaden which is home to 8 million people. 6 million people live in the other 15 habitats and close to a million live in minor minjor orbital habitats. 7 habitats are mostly used for agriculture, while 8 habitats are used to grow timber. Elara itself have major mining operation.

Demography: Elara population are 91% Danish Elarian. The biggest minority are Marjki at 3% of the population. The Marjki are a mixed population of different Sunni Muslim immigrants from the late 20th century to Denmark who has intermarried with each other and with Danish converts. 85% of them speak their own dialect of Danish, while the rest speak an Arabic-based creole. Outside the low level of intermarriage and different religion, the Marjki are cultural the same as other Elarians and suffer little discrimination.

Elarian are almost universal Caucasian and outside the Marjki who have visual Middle Eastern and Subcontinent ancestry, they’re standard North Europeans.

Religious half the population are Lutheran, around 10% are Other Christian (Catholic and Orthodox), 10% are neopagan, 3% Muslim and 2% Buddhist.

To visualize how these habitats function, they're connected with a ring between the habitats and with large pillars to Elara.

 

[Ekg]

Question :is a planet with only poles habitable possible ?

 

[Workable Goblin]

Question :is a planet with only poles habitable possible ?

Sure, depending on what you mean by "habitable". It's easy to imagine a planet which has an average temperature which is too high for unprotected habitation, but near the poles the cooler climate means that you can live there, for instance. Of course, the kind of technology you would need to get there means that you could build artificial habitats even in the hotter areas, though a native species would be more limited. You could also imagine unusual geographical arrangements, for example the equator could be entirely oceanic and all of the land could be near the poles; again, the technology you would need to get there would probably mean that you could build floating or underwater habitats, but I think it would be fair to say that only the polar areas would be habitable.

 

[Epsilon Tauri]

Question :is a planet with only poles habitable possible ?

I would give you the example of Dorozhand's Teotlale, presented along with the rest of the Huitzilopochtli system in the first few pages of this thread. For further context, the average surface temperature was later given as 48ºC.

Teotlale - The first world within Huiztilopochtli's habitable zone, though barely. Bombarded by UV radiation, the harsh blue disc in the sky is an unmerciful mistress. The baked sand is nearly lifeless on the surface, but underground bacteria thrive. Multicellular life tightly hugs little oasis ponds which spring from the earth, and large plants with orange fan-like leaves are as big as life gets even there. The only significant area of surface water are two small lakes almost on top of the north and south poles, each less than about 500 km in surface area and .5 km deep. They are the only places which host significant permanent animal life. Tiny herbivores and shelled, gelatinous cephalopods which evolved in geothermal vents, slowly creeping to the surface over a billion years. Teotlale has no plate tectonics, which probably saved the life as volcanism would have belched forth CO2 and the world may have ended up like Venus.

 

[roderickgibsono]

https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/f/a62babb8-68ed-4fce-a2a2-10de3780d484/de0umzw-1ad14fd5-d60b-4771-97f1-e8337b2d7f6e.png?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1cm46YXBwOiIsImlzcyI6InVybjphcHA6Iiwib2JqIjpbW3sicGF0aCI6IlwvZlwvYTYyYmFiYjgtNjhlZC00ZmNlLWEyYTItMTBkZTM3ODBkNDg0XC9kZTB1bXp3LTFhZDE0ZmQ1LWQ2MGItNDc3MS05N2YxLWU4MzM3YjJkN2Y2ZS5wbmcifV1dLCJhdWQiOlsidXJuOnNlcnZpY2U6ZmlsZS5kb3dubG9hZCJdfQ.Exi0593G6Xd_JnQAABT0McQHz8mP_tqsPMO7Z_R91R4

https://images-wixmp-ed30a86b8c4ca887773594c2.wixmp.com/f/a62babb8-68ed-4fce-a2a2-10de3780d484/de0un0m-c8edaf37-c423-4760-94be-9b6d7fd437b6.png?token=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ1cm46YXBwOiIsImlzcyI6InVybjphcHA6Iiwib2JqIjpbW3sicGF0aCI6IlwvZlwvYTYyYmFiYjgtNjhlZC00ZmNlLWEyYTItMTBkZTM3ODBkNDg0XC9kZTB1bjBtLWM4ZWRhZjM3LWM0MjMtNDc2MC05NGJlLTliNmQ3ZmQ0MzdiNi5wbmcifV1dLCJhdWQiOlsidXJuOnNlcnZpY2U6ZmlsZS5kb3dubG9hZCJdfQ.CkJBMlB1iyGmepGr7NAf1dxyYSXe14XRuBRlcceR_TA

How do you make this??????

 

[Ten Thousand Red Lakes]

@Ten Thousand Red Lakes I was wondering how did you make this topographic map or where did you might get this from? The color scheme used is almost the one used in this link here http://ahstat.free.fr/2-topography/monde1000-1024.html, it has a similar topography to this map.

It's the standard Wikipedia color scheme.