This addon adds Hyperborea, a completely FICTIONAL planet with a pair of binary moons.
Each planet/moon uses level 8 textures, but they load fairly quickly on my computer. If anyone wants lower-res textures just ask and I'll upload them.
As for the addon itself, Hyperborea is a planet which is slightly larger and more massive than Earth. It has a nitrogen atmosphere.
It's moon, Crete, has a smaller atmosphere, about a third of the way between Mars' and Earth's.
Crete's "moon," Minos, is a somewhat-small atmosphereless rock.
Installation instructions are included in the file.