how much does it matter for the density wheather the core is liquid or not?
Shouldn't matter too much. I'm not familiar with the behavior of iron at thousands of K and hundreds of gigapascals, but liquid/solid transitions in general don't tend to make a whole lot of difference (you see differences between substances, with normal ice being *less* dense than water, as opposed to other substances being more dense when solid, and also differences between different parts of the same substance's phase diagram, with the properties of high-pressure water ice being very different from "normal" ice.
In any case, the difference in density between solid and liquid iron would be dwarfed by the difference between rock and iron.
From what I've seen so far, yes, but I'll take another look at how water and ice are actually calculated. I'll pass you a patch with an updated planet display as soon as possible.
Edit: confirmed, no "trinitarian" composition. The water covering seems to be estimated from the volatile gas inventory and temperature. Haven't quite understood it yet, but ices definitaly don't have an influence on the density calculation.
I had the same thoughts, actually. I think the program currently has only "accreted" atmospheres, not self-generated. I'm not quite certain about this, but I haven't seen anything indicating otherwise so far. There is also the question of how old the system is. The program calculates the decay of Helium and Hydrogen.
At the temperatures in question, it shouldn't matter.
There is a flag for "resonant spin locked", but I think that's meaning that the planet rotation is locked in a ratio to its orbit,
Yes, it does, such as Mercury's 3:2 spin lock with its orbit or the Moon's 1:1
Keep in mind that spin-locks have can influence on orbital parameters, and vice versa. Mercury's spin lock and the eccentricity of its orbit are related, and the Moon is slowly backing away from Earth as a result of its lock.
Also, for close orbits around stars/planets, a non-1:1 spin lock can create quite a bit of tidal heating (or a 1:1 spin lock combined with an orbital resonance with another moon/planet, such as Io and its 1:2:4 resonance with Ganymede and Europa). This is primarily a concern for moons, but will also be important for planets of red dwarves.
and not the relationships of the orbits of two planets. Might be tough to implement...
Well, it's pretty closely tied with the problem of migration, and the solutions to the two problems will probably go hand in hand. A very rough algorithm would be:
Figure out the planets that have more than a certain amount of gravitational influence on a given planet. (In terms of mass and similarity of orbital elements).
Give a random "kick" to the orbital elements based on the existing elements.
After repeated iterations, some situation should result that results in the "kick" becoming less and less: Either: A) The planet migrating to another part of the system. B) The planet leaving the system, colliding with another body, or diving into the sun. Or, C) The planet's orbital parameters settling into a stable resonance (the combination of certain period resonances like 2:3 or 3:2 with certain inclinations and eccentricities, such that the planets never come near each other, and such that imperfections in the resonance (say 201:300) tend to lead to the orbit being pushed back in the direction of a perfect resonance, rather than away from it (back to 2:3 instead of to 202:300)).
You'll need a fairly full set of orbital parameters to make this work.
That wouldn't be a problem. In fact, my code currently deletes moons above a certain mass on purpose, because I thought them too unrealistic. I can remove that and see what comes out.
Edit: I pushed the mass limit up to one earth mass,
I wouldn't put explicit limits on mass (for one thing, a reasonable upper mass limit for an Earth-sized world's moon will be different than for a 10-Jupiter mass planet). Rather than a hard limit, your algorithm should have a given probability of outputting various masses, and that should go to zero for absurdly high masses.
and habitable moons seem to have become fairly common around Gas Giants around F-stars that have left main sequence (For having them in Main Sequence stars, I'd have to put in orbital migration first, I'm afraid). However, they're all showing up around Sudarsky III giants, looks like something with the temperature classification isn't quite alright...
and yet another Edit: I took the temperatures for the classifications from Wikipedia, which sets a Sudarsky II at somewhere around or below 250 K. That's about 40 K too low for a habitable planet, so they show up around the colder Sudarsky III in the generator. Should I just put up the classification of a Sudarsky II to 300 to 320 K?
Well, something that has to be kept in mind here is that the temperature of a planet is not necessarily the temperature of its moons. (Though the 250K in Wikipedia appears to be a typo, because the Wikipedia article leaves a 100K gap between the top of Sudarsky II and the bottom of Sudarsky III (which it gives as 350K))
The big question I have WRT the Sudarsky classification is where they're measuring from.
Are they measuring the temperature of the re-emitted black-body radiation?
The layer where light is absorbed/reflected (IE, the cloud deck)?
Are they measuring the temperature at one bar atmospheric pressure?
They certainly *aren't* measuring the temperature at the solid surface, but for a terrestrial planet, or a moon of one of these gas giants, this would be the temperature one would be most likely to measure.
And on Earth or Venus, all three temperatures are different. Venus, being more reflective than Earth (like a Sudarsky II would be), is actually *colder* in re-emitted blackbody (I believe both are below freezing). Both planets are warmer at the 1 bar line than their blackbody temperature (because the average height at which radiation is emitted, reflected, and absorbed is higher than the 1 bar line, and also because the average absorption/reflection height is lower than the emission height. This is what the greenhouse effect is), and both planets actually have quite similar temperatures around the one bar line.
So even though we've established that the Wikipedia article is in error, the fact that the temperature at the cloud deck (or wherever they're measuring from) of a Sudarsky II is around 250 K does not preclude the temperature at the surface of a less beclouded and more begreenhoused moon being above 273K.
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I also took the opportunity to look at the Gas Dwarfs. The code currently classifies a gas dwarf if it has a mass lower than 10 earth masses and more than 5% of its total mass is in gas. So the very low density Gas dwarf you observed must have quite a small core. It seems still justified to classify them as gas dwarfs, but you tell me if you think I should set the ratio higher.
Actually, the super-low-density planets I observed were rocky worlds in hot orbits.
The gas dwarves I'd been talking about just had insanely low amounts of gas. I'll try looking through the compositions on the Gas dwarves once there's a patch up with gas/rock ratios in it (The latest patch I see in the release thread is 0.52 with the keyboard fix, or am I looking in the wrong place?).
) might use two or three separate images: One for stellar density, and then one or two for stellar age and star formation related parameters. 
