Eyeball Planets

[ysabetwordsmith]

Tidally locked planets tend to have very different conditions on the hot and cold sides.  This isn't a new idea, but the nickname is new and amusing.  It comes from the circular pattern of zones that can make a bullseye design.  This can have various configurations depending on how close the planet is to its sun.  The article includes several illustrations to show how they might look.

I would love to write this kind of setting.  It sounds like so much fun.

Comments

[neonvincent]

I know Larry Niven wrote about two tidally locked worlds in his Known Space stories. However, they're both exceptions to the rule. The first was Mercury in "The Coldest Place." That was when astronomers thought the planet was tidally locked. We now know it's not. The other was Jinx, a moon of a gas giant around Sirius. Niven did his best description of it in "Borderland of Sol," describing it as a giant Easter egg. However, it was tidally locked to the gas giant, not Sirius, so it wouldn't be an "eyeball planet."

[we_are_spc]

Hi. I'm Tana. I live on Target... xd

Oh gods, I'd love to see the illustrations now.

-T~

Thoughts

[ysabetwordsmith]

I have far more writer friends than artist friends, and it's been a long time since anyone did fanart of my original writing.

[heron61]

Fascinating article. I have seen one recent novel that dealt with a tidally locked world exceptionally well Charlie Jane Anders' brilliant The City in the Middle of the Night

[siliconshaman]

Hmm.. they'd have a perpetual weather system too.. the air circulation would be as fixed as the planet, without rotation. There would be a storm in the 'eye' of the planet, and somewhere round the twilight zone it would rain forever, as the hot wet winds hit the cold air.

Come to think of it, coriolis forces would cause the clouds to form eyelids at the upper latitudes.

Well ...

[ysabetwordsmith]

With such extremes, there would be permanent drivers of weather. I think it could go different ways, though:

* Some planets would probably evolve a relatively stable set of weather systems in different places.

* Others would be prone to violent weather roaming all over the place.

This would likely depend on the type and amount of atmosphere along with the amount of heat received from the sun.

Less atmosphere and/or heat would mean less churn. More atmosphere would mean more church due to having more space to move around in, while more heat would drive the whole system with greater force. It would also depend on the amount of water (or other liquid) available. Less liquid, less churn; more liquid, more churn.

Another possible driver of erratic weather would be volcanic action. (On a dark side covered in ice, then ice volcanoes are yet another option.) If the planet has active tectonic plates, then volcanoes on the dark side could create a whole different ecosystem there, much as like the black smokers undersea have done here. You could actually have a first-contact scenario if a different sentient species arose on the cold side and the hot side.

And that's just with things we already know about. Eyeball planets might devise their own way of passing energy around, that we haven't seen here because Earth doesn't need it. But we do have analogs: consider certain systems for mass transfer of biological material from water to land (salmon runs) or land to water (herd animals drowning during migrations).

Re: Well ...

[(Anonymous)]

Atmo or hydrosphere rivers, like we used to use for trade? Heat rises, cool sinks would still move some things...

As would moons...

Re: Well ...

[ysabetwordsmith]

Those seem likely.

Really, you're just looking for energy inputs and stuff to move. Heat from the sun, geothermal, tectonic pressure, thermohaline cycle -- there are all kinds of options.

It is dead certain that eyeball planets will have a batch of standard mobilizations that we haven't thought of because they don't happen here. How would someone who only knows freshwater understand a thermohaline cycle?

[kengr]

Yeah, I've got a planet like that that needs a lot of fleshing out. Mostly figuring out the weather patterns.

What I'd *like* is for there to be enough atmospheric circulation to keep the "hot pole" not *too* much worse than the deep parts of the Sahara (if it's land). And the cold pole not too much colder than the colder parts of Antarctica.

Rising air at the hot pole sucks in air from areas around it. The rising air flows away from the hot pole at upper levels and sinks at the cold pole.

It might be possible to have several rising/sinking flows in rings around the hot & cold poles. But that would mean the temperatures wouldn't be moderated as much except in those rings.

I want global circulation because it'd not only even out the temps a fair bit, it'd also get water transported.

Of course, once you have enough ice at the cold pole it'll flow towards dayside. Unless it gets too cold to flow.

While Coriolus force will have an effect on the circulation, it will be *much* less than on earth due to the slow rotation of the planet (once a year).

I have a scene where someone new to the planet has been outside for *hours* and asks how long it is til sunset. Someone who's been there long says "About three thousand miles. I think the closets part of the terminator is *that* way..."

Of course, I'm having the planet orbit a brown dwarf which throws in a lot of other fun "local color".

Thoughts

[ysabetwordsmith]

>>What I'd *like* is for there to be enough atmospheric circulation to keep the "hot pole" not *too* much worse than the deep parts of the Sahara (if it's land). And the cold pole not too much colder than the colder parts of Antarctica.<<

You need at least as deep an atmosphere as Earth, maybe more. Which means you need a planet with enough mass to hold onto that much: this much or bigger/denser.

>> I want global circulation because it'd not only even out the temps a fair bit, it'd also get water transported. <<

Consider adding local features to facilitate that. It would absolutely benefit the biosphere to transfer energy and temperature to modulate the extremes. I would predict for 'terraformers' to emerge in the most temperate region first, which is most likely to happen on a planet whose habitable zone circles the twilight perimeter, and migrate outward from there. On a planet whose habitable area faces the sun, life would probably start at the sunward center, but the margin once colonized would probably become a lively place just because margins tend to do that.

See elsethread my ideas about a dual biosphere where the cold side has its own driver via volcanoes. I don't know how well that would fit your plan.

>> Of course, once you have enough ice at the cold pole it'll flow towards dayside. Unless it gets too cold to flow.<<

... or something else moves it.

>> While Coriolus force will have an effect on the circulation, it will be *much* less than on earth due to the slow rotation of the planet (once a year). <<

True. So instead of weather that changes from day to day, each weather system would act more like a season. That would be more variable in terms of when it could happen, but much less variable once it started. Meaning species would not have a timed trigger but rather a weather event trigger. Cold system = winter = hibernate. Rain = spring = reproduce. Or whatever.

>>I have a scene where someone new to the planet has been outside for *hours* and asks how long it is til sunset. Someone who's been there long says "About three thousand miles. I think the closets part of the terminator is *that* way..." <<

ROFL I love this! You should definitely write it.

>> Of course, I'm having the planet orbit a brown dwarf which throws in a lot of other fun "local color". <<

That probably aids moderation.

See my observation that Earth is NOT orbiting a best-bet star.

Can you imagine the reaction if the norm is actually eyeball planets around cooler stars? This place would look insane to them. The sun is broiling hot, the planet is spinning like a berserk top, everything is all messed together, the weather is chaotic, and the light blinks on and off all the time.

I am now tempted to explain Drake's equation that everyone who's come here intending to conquer the place has taken one look at the freakazoid planet and gone "Oh HELL no!" so they all just decided to pretend it doesn't exist while they go about their galactic geopolitics without us.

Re: Thoughts

[kengr]

Well, brown dwarfs are not good choices for life-bearing planets. Since they run on deuterium or even helium fusion, their lifespan is *much* shorter than most stars.

Add in the fact that their output changes a *lot* over their lifespan (so the already narrow Goldilocks zone *moves* much more than its width) and the conditions for life get even less suitable.

I'm doing a lot of handwaving with theories put forth about perturbations in the system moving the planet closer to the star as the star cooled, and other even weirder ideas.

And I'm planning on the indigenous lifeforms being very primitive (middle to late Devonian). That gives the humans pretty much free reign on the land.

Oh yeah, because of it being a brown dwarf, the planet's year is something like six-and-a-half *days*. Which means any Coriolus effects will be more pronounced, but still nothing like Earth's.

I'm considering a number of ideas for climate moderation. Higher water to land ratio, or the land being more broken up. Strategic placement of bodies of water, etc.

Heck hills or mountain ranges might direct the flow of weather to a greater extent.

Re: Thoughts

[ysabetwordsmith]

>>Well, brown dwarfs are not good choices for life-bearing planets. <<

Depends on who you ask. There are competing theories.

>>I'm considering a number of ideas for climate moderation. Higher water to land ratio, or the land being more broken up. Strategic placement of bodies of water, etc.

Heck hills or mountain ranges might direct the flow of weather to a greater extent.<<

Those are all promising.

Re: Thoughts

[kengr]

Well, the problem with brown dwarfs is that they are just barely stars. They aren't massive enough to start the Bethe cycle, so they can only fuse deuterium and lithium which are a lot less abundant and don't release nearly the energy that p-p fusion does.

Estimates for the "lifetime" of a brown dwarf are in the millions of years, not billions. Which is why Whereisit is of interest. It *might* be as much as a billion years old. so how does it already have life?

And since brown dwarfs are cooling from day one, the life zone is steadily shrinking.