4
$\begingroup$

Hello! I've put together my first planetary system, but as I'm not a scientist (and bad at maths) I'm reaching the limits of my brainbox and would really appreciate some fact checking! I have questions, but I'll post them in separate questions.

I know that tidally locked red dwarf planets are getting a bit overused, but quite frankly I really love the look, and as this world is going to be the backdrop of a webcomic, aesthetic is very important. Anyway, here are the specs I have so far;

Kereiol is a 2 billion year old quiescent carbon-rich M star with a temperature of 3,100 kelvins. If it flares at all they are tiny. It has four orbiting planets, only one of which, Liskuel, is within the goldilocks zone. Liskuel is 0.15 AU from Kereiol and has an orbital period of 35 days.

Liskuel is a tidally locked wet, rocky carbon-born planet with an active core. It is 1.5 times the size of earth, but with a similar mass and gravity as unlike our planet which is dominated by oxygen and silicates, it is rich in aluminium, titanium, silicon, carbon, and lithium and mostly comprised of quartz or diamond. 70% of the surface is covered in water, with especially deep oceans on the nightside.

At the substellar point high temperatures vaporise water whilst in the nightside low temperatures condense it. This condensation creates a vacuum that sucks in hot air and water from the substellar point, therefore creating a global air circulation cell. Water circulates, too – rain from the substellar point flows across the land and through the oceans to the nightside where it freezes. At the same time, frozen water is melted by the heat of the earth and flows around to the substellar side. Intense cloud formation on the nightside also minimises thermal flux, and trapped water on the nightside helps prevent the runaway greenhouse effect.

All this means that the substellar point would be baking hot with perpetual hurricanes and permanent torrential rain. The nightside would be in perpetual darkness, and a permanent ice age. The substellar hurricane would generate freak ocean waves which could be dangerous for the habitable equatorial belt where the sun never sets but hovers in a perpetual twilight. Due to rain runoff from the nearby storm, the land in the terminator belt would have large networks of river deltas and swampland. Deserts would exist, but in the rain shadows of mountains, and would be long and narrow. The crust would be largely composed of graphite and would be dark in colour. Because water absorbs red light fast and M stars don’t produce a lot of blue and purple light, photosynthesis in water may be limited to the top 10m or less. This means there are no photosynthetic reefs or deep kelps but there is a lot of floating microbial biomass.

There is a huge variety of plants. Because light only ever comes from one angle, tree foliage is perpendicular to the sun, and only grows on one side of the tree. Because Kereiol is a relatively weak source of light, the plants maximise a far wider portion of the EMR spectrum than they do on earth, meaning they present in colours we can’t see and don’t have names for. All dark colours, however, like dark red, yellow and orange, with the occasional dark purple. We see a very small fraction of the spectrum of light, which enables us to perceive the difference between night and day – but because there is no such difference on Liskuel animal species have adapted to see much more of the EMR spectrum than we can. Others have evolved without eyes.

Due to tidal locking, the only change in the amount of sunlight comes from the slight variation in distance from the sun due to the orbit being slightly elliptical. Therefore, although there is no day-night cycle in any given location, there are cycles of temperatures accompanying Kereiol’s height over the horizon. This acts as a natural clock – a morning beginning with a cold winter, followed by a pleasant spring, then a hot summer afternoon, autumn in the evening and another winter morning. This ‘day’ spans the length of Liskuel’s rotation around the sun (35 earth days.) Depending on the ‘latitude’ there may be a completely dark night in between or no night ever.

Are there any holes or issues with the system above?

P:S I've edited this to remove some questions, as I now know that those should be in separate posts. I'll put those other questions in a list below as I post them. Thanks again!

  1. What plant colours other than black could be available on a red dwarf planet?
  2. Would having more mass and gravity make a tidally locked red dwarf more habitable?
$\endgroup$
  • $\begingroup$ That's not why we see a narrow range of the electromagnetic spectrum. You can still distinguish day and night just fine even if you perceive the entire EM spectrum with no color discrimination. There are terrestrial animals which can see more of the spectrum than we can (we are limited by our relatively recent evolutionary history as small nocturnal mammals), but all are limited by what wavelengths can be efficiently captured by biomolecules, what can pass through the physical structure of the eye, and what light is actually present in the environment, and thus useful to be able to see. $\endgroup$ – Logan R. Kearsley Jul 11 at 14:39
  • $\begingroup$ Quartz and diamond don't really go together very well here. If there is lots of quartz, graphite, and diamond, I would also expect lots of silicon carbide. $\endgroup$ – Logan R. Kearsley Jul 11 at 15:57
2
$\begingroup$

1) Due to the fact the star does not emit light in the blue to violet ranges, your plants may not look blue or green at all since those wave lengths are not even present. The plants will maximize its use of yellows and reds. The result would be dark colors of the remaining spectrum or unabsorbed useful spectrum, so dark reds, yellows and oranges. Any blue light produced by the sun may make leaves look a dark purple.

2) For the oceans, again, water is absorbing the red light wave lengths, and in the absence of higher wave lengths, the seas would look dark as its absorbing all available wave lengths. The sky would be mostly the same, blue, due to scattering of light. It would be influenced by the red star above and some chemical interactions with the atmospheric gasses, but it would be not be too influential.

3)I cant say too much for certain, but you cannot have a constant wind blow from day side to night side in all directions without some air coming back. I would imagine there would be a prevailing wind that would constantly blow in one direction with returning cool air from the opposite direction. This would not be driven by the planets rotation, but the shear pressure built by the winds. Id imagine if there is a possibility of a flow reversal, which would be catastrophic for the planet, but would happen occasionally.

5) That's a simple plug and chug equation. You stated the diameter is 1.5 that of the Earth, so that would make the surface area 1147.5 million square km.

6) This would be difficult to say to any degree of certainty, since this kind of thing is highly debated by planetary scientists. I would imagine at the point were the sun is directly above you, the temperature would be pretty unbearable as all the wind is trying to blow away from you, so no real cooling, and there would be very little to no moisture. The antipode location would not be too opposite, as all the air is trying to rush to you. The pressure induced prevailing winds would regulate it some what, but the opposite sides would be fairly unlivable. With a sufficiently thick atmosphere, and the prevailing winds, vast majority of the world would potentially be habitable.

$\endgroup$
  • $\begingroup$ I forgot 4, but I have no clue how to answer that $\endgroup$ – Sonvar Jul 11 at 3:49
  • $\begingroup$ Thank you so much!!! Haha, no worries. Just one thing; from what I gather all the cold air rushing towards the substellar point is at ground level while the hot air is higher up. Does this mean that no matter where you are the prevailing wind would be cold? Thanks again! :) $\endgroup$ – MissMermaid Jul 11 at 3:57
  • $\begingroup$ The air goes back at the top of the global convection cell. At ground level, winds pretty much all blow in the direction of the antistellar point, although the Coriolis effect will have an influence. $\endgroup$ – Arkenstein XII Jul 11 at 4:06
  • $\begingroup$ unless the planet is rotating perpendicular to the star, Coriolis effect wouldn't have very much effect, or at least 1/35 of the effect of that on earth due to its orbit. There would have to be some return winds in the troposphere due to convection and pressure since the upper layers of the atmospheres would be more susceptible to the solar effects on winds than the lower layers would be. I would imagine a sort of swirling effect as the stellar side winds fight the antistellar return winds. After millions of years, som semblance of balance would develop between these competing forces $\endgroup$ – Sonvar Jul 11 at 4:39
  • $\begingroup$ our general advise is to answer only well asked questions, and to address improvements for the other. Now you have answered questions which are no longer there $\endgroup$ – L.Dutch Jul 11 at 4:50
2
$\begingroup$

Given the large amounts of heat-transporting surface water and an atmosphere, your assumption of significant nightside ocean freezing and a permanent hemispheric ice age may be wrong:

Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea-ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, night-side sea ice remains O(10 m) thick and night-side water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete day-side dessication. Only planets with a geothermal heat flux lower than Earth's, much of their surface covered by continents, and a surface water reservoir O(10 %) of Earth's would be susceptible to complete water trapping.

Without a map, including elevations, showing the continents in relation to the sub- and antistellar point, it's impossible to know for certain the extent of oceanic freezing, ice caps, etc. but deep and extensive oceans is an argument against it.

$\endgroup$
  • $\begingroup$ That's wonderful information, thank you so much! You have a really good point - this is very useful. Thanks again! $\endgroup$ – MissMermaid Jul 12 at 5:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.