On the Habitability of Sel

[Firesong she/her]

So, one thing I was concerned about is how habitable Sel would be at 1.5R and 1.2G, but it actually wouldn't be that bad, is what my research concluded. 

Okay, so first, the mass of such a planet would have to be 2.696246M to get the proper gravity at that radius, and the density would be 4.4044746136 g/cm3 (0.799 Earth's).

This falls within the range of believably terrestrial and Earth-esque planets, with a rocky composition and liquid surface, at 0.5 < Planet Radius ≤ 1.6 Earth radii or 0.1 < Planet Minimum Mass ≤ 3, according to several sources. 1.5R and 2.69M puts it in the right range. It would also have an Earth Similarity Index (ESI) of 0.858578643763 (assuming equivalent stellar flux). So, it being as Earth-like as it is is reasonable with the known parametres. 

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The mass of a potentially habitable exoplanet is between 0.1 and 5.0 Earth masses. However it is possible for a habitable world to have a mass as low as 0.0268 Earth Masses. The radius of a potentially habitable exoplanet would range between 0.5 and 1.5 Earth radii.

-Wikipedia

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The Habitable Exoplanets Catalog is a database of potentially habitable worlds discovered by ground and space telescopes in the last decade. The exoplanet data comes from the NASA Exoplanet Archive and includes planets up to 2.5 Earth radii or 10 Earth masses orbiting within the optimistic stellar habitable zone to be as inclusive as possible. The conservative sample includes those that are more likely to be rocky up to 1.6 Earth radii or 3 Earth masses.

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This is a list of the exoplanets that are more likely to have a rocky composition and support surface liquid water (i.e., 0.5 < Planet Radius ≤ 1.6 Earth radii or 0.1 < Planet Minimum Mass ≤ 3 Earth masses). They are represented artistically in the top image.

-Habitable Exoplanets Catalogue 

We can assume the atmosphere is fine, the higher gravity would still keep in the atmosphere, and as we can see, it does have the proper composition for life, so not much issue there. 

Gravity is also, in fact, okay. From what I can find, the maximum assumed gravity one can survive is 4G. 2G is also known to be survivable, but could have some issues if you don't properly adapt to it. But 1.2 is a lot less than that, and also, we know evolution happens very fast in the cosmere due to Investiture, and Sel is very Invested, so I can believe that they would, over the generations, adapt to be able to withstand the gravity of the planet. So that one is actually pretty fine. Not much issue with it.

It would be rather uncomfortable, it would be around double to 3.6x the force you feel when a downward moving elevator starts slowing down, if I did the math correctly. But it would be survivable. 

Basically, I feel that the planet would be habitable from what we know about it.

And I am excited to see what Brandon changes in Elantris 2 to better reflect the higher gravity, as he now has said gravity planned out when he probably didn't before. So I feel he would do things like clarify that the mountains aren't that tall, and the like. Would be neat.  

[Firesong she/her]

Stormlight info

Spoiler

Oooooo, using the Artefexian Worldsmith calculator, I found the exact Iron Core Mass Factor of Roshar, it would be 12.472%. Much less than Earth, but it would give 5663 for the radius, which is exact to the given circumference, around 0.889 standard, which was given in a WoB. Plus it would have gravity of 0.699 g, close enough to 0.7g.  This all working with its 0.551908908238 Earth Masses. Overall for a density of 4.330 g/cm3. 

Not sure how good of a magnetic field that would produce, though. But they do have the benefit of Stormlight healing them constantly, which would probably protect them from solar radiation. It also technically is made by Adonalsium, so they could have just used magic to produce a field maintained by Investiture instead of by natural means. 

The mass factor is less than the moon, and the moon's is to small to make a field. But also, Roshar's would still be much bigger than the moon's. Given it is 3.25x the radius of the moon, and 44.85x the mass. So it might be able to make a magnetic field.

Looking into atmospheric conditions with its rotational speed, it should have 3 atmospheric cells in the same longitudes and latitudes as Earth. At the same 0-30, 30-60, 60-90 ranges. 

 

Sel on the other hand... yeah, that doesn't seem like it would work out. The calculator turns out with you needing like, -30 something for the CMF. Which, needless to say, is not what is happening.  

 

Okay, I read that planets above 2 Earth Masses would be likely to retain too much of their primordial helium and hydrogen. But I actually don't feel that this would be the case with Sel, who only has a gravity of 1.2 due to a lower density. Whilst the source of this information was thinking of more traditional density and makeup. 

So I feel that isn't too much of an issue. We just have to imagine Sel has a really weird crust that is low density. 

Edited October 9, 2023 by Firesong