darthmunky said:
ben_danger said:
a moon with a moon! i guess it is possible.
Haha, I meant a planet acting as a moon to Endor.
Planets go around stars and moons go around planets, you can't have a planet going around a moon.
As posted above you can have moons with moons the orbital mechanics involved are weird, especially with the Death Star factored in but that's Ok because it Star Wars and not Science Fiction so it doesn't have to work scientifically.
The question you want to ask is why?
If it's to make the sky look more interesting I can't help but think it would make more sense to give the moon of Endor an interesting planet to be the moon of rather than giving a moon a moon which isn't refererred to once in the film.
Moons have to go around a planet rather than directly go around a star on it's own, it can be any size and have an atmosphere but it needs to go around a planet. Though it isn't necessary for Star Wars, in terms of planets we know about an Earthish sized moon with an atmosphere would have to go around a gas giant and be far away enough from it to not be ripped appart by the mass of the planet (in the EU the planet Endor was lost and only the moon remains but that doesn't make sense, that would make the moon not a moon anymore).
It would also have to be near a star which used to be thought to be a problem as in our Solar System the gas giants are all relatively far away from the sun and it was generally assumed to be the case with most stella systems. We have recently discovered gas giants orbiting other stars very closely indeed (not that this is necessary for Star Wars but it adds a bit of colour to my explanation).
So for the forest moon to work scientifically (not that it has to) you would need a large gas giant close to a star with a forest moon orbiting it from a safe distance (ergo my green ringed gas giant).
The forest moon's nearest Solar cousin is Saturn's moon Titan :
http://en.wikipedia.org/wiki/Titan_(moon)
If it was as close to the sun as the Earth it could possibly support human life but that would mean moving Saturn nearer to the sun too.
Here's a nice artistic representation of what Titan looks like in it's current position :

Having a moon going around the moon adds a whole level of complexity (scientifically speaking, compounded by having the Death Star going around it as well).
But really we don't have to worry about that sort of thing, just ask does it make narrative sense and does it look interesting those are Star Wars sort of questions.
If you stick a larger yellow sun and a forest into the above picture of Titan you get a general idea what a ringed Endor looks like from it's forest moon.
