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Right, lets try this again.

I'm making a planet for a book I'm writing. I want to know if the planet I outline here is scientifically probable, able to support life, and what the climate would feasibly be like, compared to Earth.

First off, the planet is a terrestrial world, about 1.1 Earth masses and 1.04 Earth radii, giving it a surface gravity of 1.144, comparable to Neptune. It orbits a K-Type star, at a distance of 1.2 AU. It has an Albedo of 0.088, lending to a rich ash colored geology. It's axial tilt is 12 degrees, and its orbited by a moon around 0.0268 Earth masses, and a radius of 0.22 Earth radii. Said moon's Bond Albedo is about 0.20. Overall, I'm going for something along the lines of a mini Arakis in terms of look for the moon. Its orbit is 384,400 km from the planet.

Now, things get complicated with this last feature - a silicate debris ring, about the mass of Ceres (0.00016 Earth masses). It's inner edge being 2.56 Earth Radii from the surface, and 3.48 Earth Radii at its outer edge, making it 0.92 Earth Radii long. Since I'm bad at math, lets say its about 9.5 km thick. Their Bond Albedo is about 0.03.

I also have some more specific questions, along with my general ones above:

  • Would black body radiation from the ash-colored deserts lead to the planet becoming warmer than Earth, or would dust being kicked up in the upper atmosphere make it cooler? Or would the two factors cancel each-other out?
  • Would the rings cause an annual oscillation between antarctic temperatures and tropical temperatures where their shadow is cast upon the planet? Would this lead to massive storm-fronts and a general lack of plant-life around the tropics?
  • Apart from more mild seasons, how would a 12 degree axial tilt affect climate on the planet's surface?
  • Do I have to reduce the size of the moon to allow the rings to exist along geologic time-scales?
  • If plant-life can exist on the planet, what color would they be to maximize energy absorption from a K-Type star?

Please also let me know if any other glaring problems become obvious from what I've outlined here. I want this to be as scientifically accurate as possible, so I can have a better idea of what needs to change and what's working well. Thank you in advance for your help!

Additional Info:

Sun Characteristics): The Sun is a K-Type Star, with a Luminosity of 0.79 L and a temperature of 5518 K. According to the calculator Sonvar provided (thanks, by the way!), its Inner Habitable Zone is 0.845 AU, and Outer Habitable Zone is 1.49 AU. It's Stellar Flux on the inside of the HZ is 1.107, and on the outside is 0.356.

Water on the planet): Ideally, I was hoping the planet would have comparable amounts of water to Earth, maybe about 72%? If it means anything, I was thinking it'd have two main continents: one in the northern hemisphere, about the size of Eurasia, and one near the equator, about the size of Central America. It'd have a chain of islands comparable to South-East Asia in size off of the latter continent.

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  • $\begingroup$ If you include some basic stats of the star beyond k-type star, then a calculation can be made on the generic habitability. You can us this calculator to determin the "goldilocks zone." depts.washington.edu/naivpl/sites/default/files/… $\endgroup$
    – Sonvar
    Dec 1, 2021 at 22:13
  • $\begingroup$ How common is water on the main planet? Is it also Arrakis-like? $\endgroup$
    – Alexander
    Dec 1, 2021 at 22:44
  • $\begingroup$ I've addressed both of your comments in an addendum. Thanks for asking for clarification! $\endgroup$ Dec 1, 2021 at 22:56
  • $\begingroup$ @Alexander Arrakis has plenty of water, most of it is inaccessible but it is there. $\endgroup$
    – Ash
    Dec 2, 2021 at 1:38
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    $\begingroup$ @Arthur Lawrence if you have a lot of surface water, you will have a lot of at least one of the two - clouds and ice. Which means having albedo 0.088 is problematic. $\endgroup$
    – Alexander
    Dec 2, 2021 at 5:25

2 Answers 2

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OK, let's talk about the planet's estimated temperature. The estimated temperature takes into account star luminosity, bound albedo and distance from star. The estimated temperature given by this calculation was - 39°C. By comparison Mars estimated temperature is -63°C and Earth -18°C. This is known as the equilibrium temperature where theoretically the planet is warmed only by it's star. This means at this temperature the energy emitted balances the energy received. Of course, this is not the actual temperature, as Earth is considerably warmer, due to the greenhouse effect and other factors but even with a similar greenhouse effect your planet would still have an average surface temperature of -39°C.

https://www.astro.indiana.edu/ala/PlanetTemp/index.html

I still think your planet would be very cold even with the ameliorating effects of low albedo.

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For plant life around a reddish star, your plants could have evolved upshifting organelles around their chloroplasts that upconvert the reddish incoming light into a frequency range useful for chlorophyll or an analog to work.

I think the debris ring, 434 million cubic kilometers of materials spread as described across about 216 million square kilometers, won’t be making much difference to the light on the surface. But let’s check. If the ring is less than 2 kilometers wide, and the volume of material is evenly spread, then that volume of material is nearly solid. Not sure how stable that is. It would shade part of the planet.

There are a lot of tools available to warm up your world — You can bring it a little closer, put any of countless heat-trapping gasses (https://physics.stackexchange.com/questions/101017/how-do-greenhouse-gases-trap-heat) in your upper atmosphere, have the ground trap heat, internally generated heat from deep fissionables, or still coasting on leftover heat from planetary formation (or whatever put that debris ring in the sky).

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