[Space] GURPS Handbook of the Planets

[Nemoricus]

Originally Posted by Whill

A gas giant can only have a moon system that totals no more than .4 Earth masses? If that is in the GURPS Space system, I missed it. Or is that in reality based on current science?

So does this mean I can't have even 1 Earth-massed moon around my gas giant? If these more massive major moons just can't form there, are there any plausible migration/capture scenarios that could account for them being there?

It's a general rule that a gas giant will have a total mass of moons equivalent to about 1/10000 of its own. However, it's not a hard and fast rule, and in our own solar system it varies from about 1/1000 to 1/4000. Since it's possible that this could vary more, I'd say that as long as your gas giant has at least 1000 Earth masses, you could probably have an Earth sized moon without raising too many eyebrows.

Originally Posted by Brett

My grasp of physical chemistry is weak, but perhaps it would be possible to use a weighted average of the the specific heats of the chief constituents.

As an approximation, that should be fine.

• I replaced the method for resoving the Ocean/Garden ambiguity, which multiplies the age of the system by the level of visual illumination on the planet, and then compares that to a randomly determined expected time of oxygen catastrophe.
  
• I coded a modifier to temperature for worlds with water oceans and active volcanoes or tectonics, to reflect stabilisation of the temperature at about 15 C by the carbonate-silicate cycle.
  
• Instead of using Space's "habitability" score I determine factors.

What's the general formula you use for these?

Originally Posted by Brett

No? Well, I guess that being a good and reliable writer and easy to work with is an acceptable substitute for formal qualifications. I'm not any of those things, and besides I don't want to design a pencil-and-dice star system generator. For one thing I don't feel sufficiently confident of my own expertise.

No writer is perfect, especially when they first start out. Still, my impression is that you could write a fairly good star system generator and accompanying explanation, based on the posts I've seen from you. And as a star system generator will necessarily include simplifications and approximations for the sake of usability, imperfections in understanding are not a particularly problem. Especially since our understanding of extrasolar planetary systems is quite rudimentary as it is. Verisimilitude is therefore the primary goal.

However, it would be quite a lot of work to design a star system generator, and it serves a very niche market....