[Space/Thaumatology] Stargate: Fantasy - Worldbuilding thread

[adm]

Another issue I would note is that large gas giants hoover up a lot of asteroids and comets etc. Note the number of impact caters on many of those moons, or on the "outside face of Earth's moon.

Not a lot of fun.

[ehrbar]

If you assume the star is the Sun, the gas giant is the mass of Jupiter, the orbital distance is 1 AU, and the orbital radius of the gas giant is near enough to circular as makes no difference, you get a Hill sphere radius of about 0.07 AU, or 10 million km (assuming I didn't screw up my calculations). In practice, stable satellite orbits are generally closer than half of the Hill sphere radius, or in this case about 5 million km of the gas giant. Of course, the further out you are from the gas giant, the more variation you get in solar distance during the time going around the gas giant, and the longer it takes (giving more time to cool off when far from the Sun, and more time to heat up near the Sun).

You can play some tricks, of course. Drag the gas giant's orbital radius out to Martian distances, then give the planet-moons atmospheres thicker than Earth's (for more greenhouse forcing, more insulation, more convection, and more shielding from the gas giant's magnetosphere-related radiation), for example.

Keeping the planet-moons spinning at roughly once per 24 hours rather than getting tidally-locked to the gas giant could help a lot, and magic could do that. Sure, it'd be big and powerful magic, but you can have it operating down at the solid inner core of the planet-moons where nobody can get at it or examine it. Giving the planet-moons their own powerful magnetic fields as a consequence of the magical rotation of their cores to help shield them from charged particles interacting with the gas giant's magnetosphere, too.

[Fred Brackin]

Originally Posted by ehrbar

I have it operating down at the solid inner core of the planet-moons where nobody can get at it or examine it. Giving the planet-moons their own powerful magnetic fields as a consequence of the magical rotation of their cores to help shield them from charged particles interacting with the gas giant's magnetosphere, too.

If the cores are solid rather than molten you can run an iron bar from pole to pole and magnetize that. Leave a few meters sticking out at each end and paint them candy-stripe red and white if you have dubious sense of humor like mine.

This would give you a much bigger and stronger magnetic field than Earth's and no rotation would be required. With the GG's magnetic field to feed them the Van Allen belt-equivalents would be much more intense than Earth's.

You would get he fantastic view back in the form of polar auroras though.

[ehrbar]

Originally Posted by Fred Brackin

If the cores are solid rather than molten you can run an iron bar from pole to pole and magnetize that.

True.

I was assuming Earth-type geology complete with a molten outer core and a solid inner core, but that's of course not the only possible arrangement.

[Prince Charon]

Poll remains open for now, partly because the discussion is interesting, and might be ongoing. That said, the votes so far (if I'm counting correctly) are four for 6, two for 1, and one each for 2, 3, and 4.

[TGLS]

6) But also one of the "moons" is an ancient (not necessarily capital A ancient) space station that deflects hazardous asteroids and comets.

[ericthered]

Originally Posted by Fred Brackin

Over a few million (or maybe tens or hundreds of) years any moons of the polar-centric GG would end up in that planets equatorial plane and with their poles pointed in the same direction. So they'd have perpetual brigthsides/darksides and you'd really have to have that atmospheric superrotation.

I don't think that gives you bright-sides and dark-sides though. You do get the tide locking effect, but it locks to the planet, not to the star, and I think planets are generally far enough away from their moons that the moon still gets a lot of light from the star.

[Fred Brackin]

Originally Posted by ericthered

I don't think that gives you bright-sides and dark-sides though. You do get the tide locking effect, but it locks to the planet, not to the star, and I think planets are generally far enough away from their moons that the moon still gets a lot of light from the star.

The moons would be in the same situation as the planet with one pole perpetually pointed at the star just like the planet (which i am still not sure is possible).

[ericthered]

Originally Posted by Fred Brackin

The moons would be in the same situation as the planet with one pole perpetually pointed at the star just like the planet (which i am still not sure is possible).

I don't think its possible either: Uranus gets full sun coverage over the course of its year. You would get some pretty extreme seasonal cycles though. Normally I'd say extreme seasons is a downer, but these are supposed to be desert elves, and I think they're nomadic? So it could be a fun bit of color.

[Keysh]

Originally Posted by Fred Brackin

The moons would be in the same situation as the planet with one pole perpetually pointed at the star just like the planet (which i am still not sure is possible).

It's not possible -- that would massively violate the conservation of angular momentum.