Hello anons...

Hello anons, I am looking for the name of the type of habitable planet which is only habitable on the outer rim of the planet because of rotating sideways to the sun...?

>front is too hot
>rim is perfect
>back is too cold

Also, general habitable environment thread. All ideas are welcomed

The term you're looking for is "tidally locked."

Tidally locked?

Are you writing sci-fi, friend?

thanks anons here some earthboobs

similar, it's part of a story for a game

>because of rotating sideways to the sun
>"tidally locked."
Well, sorta.
Tidally locked would be like our moon, or how mercury was once thought to be.
One revolution around the parent body takes exactly as long as one rotation around it's own axis.
It's not "rotating sideways to the sun", but it does satisfy OP's requirement of "rim is perfect".

Spinning bodies don't work like that. A planet spinning on its side would have seasons where during the "Summer" (or whatever), one side would be sunbathed 24/7, "Fall" when the axis of spinning would point retrograde of the current orbit and day and night would be a thing. "Winter would be like summer but for the opposite pole.

Oh, whoops, you're right.

In that case, OP is asking for a planet with a "90 degree obliquity", and by "outer rim" he means "equator".

so... would a moon for that planet rotate around the 'outer rim'?

Yes, but consider the equator.

When the rotational axis was pointing towards/away from the Sun, the equator would be in perpetual twilight, like the "habitable" rim of a tidally locked world.

When it was perpendicular to the Sun, it would experience a day/night cycle once per rotation of the planet, just like Earth's equator.

So it ought to be notionally habitable, I think.

No, not necessarily. Our planet is at a 23° tilt, but our Moon doesn't orbit in the plane of our equator.

(However, the equator would get extreme storms during the "parallel" seasons, as air and moisture rushed from the increasingly scorching daylit North to the increasingly frigid shadowed South, and vice versa. It might actually be worse than a tidally locked planet, since it would never settle into a stable equilibrium.)

>living on jupiter

i better start doing some more squats before im ready for that

You mean a planet with a 90* axial tilt, and the equator is where the poles of most planets are? Like uranus?

IDK, good question, but rotation might not be stable that close to its star.

I think Jupiter's just there for the size comparison.

Planets like you are asking about don't actually exist. Any planet ordbiting at such a distance from it's sun would only be continuously habitable at the poles with a rotational axis approaching 0 degrees.

Tidally locked, a planet that was tilted 90 degrees like Uranus still has seasons.

so would a tidally locked planet have day and night cycles? Since the equator (habitable part) would always have to be on the sunny side of the planet for livable conditions? Ergo beings wouldn't sleep on that planet, or at least have a different type of regenerationsphase?

wheres KOI-4878.01? (to be confirmed i know)

Wouldnt they have eternal sunset?

The problem is that habitable as far as we know requires free water. On a tidally locked planet you will get evaporation from the day side and snow falling on the night side, a process that will run until the day side is bone dry and the night side is a huge glacier. Then no more life.

You call that tidally locked??

Perhaps but only near the edge of daylight and then only due to librations, which requires a non-circular orbit. This is why we see 59 percent of the lunar surface and not just 50 percent of it.

What kind of seasons do you want, senpai?

Just lock my shit up

You could have an Avatar-system: a mail planet, possibly tidally locked to the home star. Orbiting the planet is a tidally locked moon, that is, tidally locked to the planet.

On this moon you would still have a hot zone, away from the planet, and a cold zone, facing the planet as it would be eclipsed by the planet instead of getting noon time sun.

Weather would be far less extreme and you would avoid the problem of locking up all free water on the far side and you would also have days and night.

Pic. related.

OK, so I managed to put in the wrong picture.
While waiting for the countdown: the colour coding is to indicate heating received from the central sun.

As you will see the dark blue gets very little sunlight, never noon sun, only from the sides.

not op here, but neat. It would also have pretty bright nights, i suppose.
Depending on how elliptic the orbit is, it could also have some weird "tides" and volcanic activities.
I think I'm going to reinstall SpaceEngine, you guys made me want to check out interesting systems

op here, I also say neat. Never thought of that, interesting idea.

I need day and night, this helps :^)

Almost there.

For a rocky planet in the traditional habitable zone, the difference in temperature would result in a pressure difference between the hot and cold sides. This means that the atmosphere in both the hot and moderate zones would rush to the cold side. However, if Mercury is any example, the cold side will be cold enough to condense any atmosphere that gets to the cold end, lessening the amount of gas on that side and lowering the pressure again in a runaway vacuum effect that eventually causes all the atmosphere of the planet to rush to the cold side where it condenses and falls to the ground. This means that no matter how close or far a tidally locked planet is from its star, its moderate temperature zone will never be habitable in the traditional sense because it will have little to no atmosphere that isn't trapped in rocks.

For such a planet to have any atmosphere, that atmosphere would have to be thick enough to allow an undercurrent of gases that replaces the gases on the hot end from underneath and allows the condensation on the cold end to heat up due to both the friction of falling through the atmosphere and the existing undercurrent bringing heat with it. Such a planet is a gas planet, again not traditionally habitable.

For, say, a planet with a thick layer of water, you may have some luck, though further away than the traditional habitable zone, where the heat energy on the hot side may exceed the enthalpy of formation of water, causing it to split into hydrogen and oxygen. If it's far enough away from its star, the low pressures would cause sublimation, allowing for no liquid water. However, if it's a planet with a large collection of moons, tidal friction may allow liquid water and trapped gases to coalesce underneath the surface.

If it's a binary planet or a planet with a large enough moon, the planet is likely to become tidally locked with its partner before the system as a whole becomes tidally locked with the star.

>It would also have pretty bright nights, i suppose.
True, as the reflections from the planet would illuminate the moon well. We see this on the Moon too when sunlight reflected from the oceans add to the illumination of the Moon.


Make the planet a gas giant (like in Avatar) and you get even brighter nights (still cool though) and tidal effects. Io, in orbit around Jupiter, is pretty brutally kneaded.

Good points. On Earth the South Pole in winter is cold enough to be below the freezing point of CO2. If you balance the pressure right with lots of water you can get a mad heat pipe effect going though the weather is going to be something awesome, and not quite in a good way.

You might have a permanent cyclone going though.

The highly NSFW web comics Off World: the Crease is based on the premise of a tidally locked planet with a giant permanent cyclone going.

>thick atmosphere with an undercurrent of gases to keep some hot air going to the cold side and some cooler air trapped beneath the hot side

Sounds like it just needs a thick atmosphere like Venus. It'd be a really windy life, though.

Also windy, though not as bad. Except the "hot" side is the habitable side, and the "cold" side would be more like a band of ice that runs from its north pole to its south pole, since those parts would also be icy in this model. The planet's reflection would keep the cold side from approaching dark-side-of-Mercury-cold, and if you want the habitable side's day/night cycle to be short enough to not roast it by day and freeze it by night, it'd need to orbit close to its planet, meaning that the planet cannot be a gas giant, because orbiting close enough for a short day would rip it to shreds.

I mean, if the "hot" side is supposed to get inhospitably hot, just make its day long enough for that to happen. the habitable zone will just move to the two zones that are on either side of the ice band. But still, lots of wind, very windy.

>You call that tidally locked??

reading comprehension

>front is too hot
>rim is perfect

>reading comprehension
Mor elike Physics comprehension.
Line was:
>Tidally locked, a planet that was tilted 90 degrees like Uranus still has seasons.

Uranus is a rather large gas planet spinning around an axis that twice per year points at the sun. Not continuously. Were you to force the orbital axis to precess at a rate of 360 degrees per year you will have to dispose of enough angular momentum to completely destroy the entire planet.

Have you ever seen a gyro??

I remember Asimov called that sort of planet a "ribbon world" in Foundation.

tidally locked

it's a fucking you dumb cunt

a fucking what?

>huh? huh? whut?
dumb cunt

If you have a binary star system where your planet is in orbit around star A and tidally locked to A, and start B was in a wider orbit around A and the planet, you could get a long day time at the far side of the planet.

This could be used to solve the problem of ice buildup on the night side.

I remember reading some time ago when we began discovering tidally locked super-earth exoplanets in the habitable zone that a sufficiently thick atmosphere could distribute temperatures across the planet rather evenly, volcanism would probably also could help keep the night side warm as well.

it's not likely that this would be possible, the B component would not only significantly disrupt materials beyond the snow line that are vital to planetary habitability but also likely make a stable orbit for such a planet impossible in the first place, provided it could even form in that kind of environment

It will still have convection and with that heat transfer so no ice locked habitat with no place to live. Given eons of time, life developing at the rim will most likely creep into the sun areas using methods to block the sun. Thus, upsetting any stable weather balance as you suggest.

>a sufficiently thick atmosphere could distribute temperatures across the planet rather evenly
I am sceptical. This would be a purely convective heat transfer system. The heat pipe solution above relies on phase transitions and is capable of far, far greater heat transfer.

So you would have a tropical warm side with a mother of all cyclones to raise a whole lot of steam. Such permanent cyclones have been discussed seriously (and not just as a premise for the NSFW web comics Offworld: the Creas). At the same time the cold side would have the mother of all rainfalls, a permanent torrential rain to release enough latent heat to balance the radiation loss into space. A huge cloud cover would help.

This planet now sounds a whole lot pleasant than earlier.

>make a stable orbit for such a planet impossible
Perhaps but I have not looked at the numbers. This would be comparing the radiative powers with gravitational forces (and gradients), and it is possible a distant blue supergigant would to the trick.

Again weather on this planet would have pretty brutal climates.