Editing Skein of Worlds:The Material Plane (section)

=== Planetary Systems ===
As previously mentioned, spheres tend to clump together into small systems. There's almost always at least one of each type of sphere in a system, and usually several more. (Planets tend to be about 3 times as numerous as either suns or black holes.)

Suns are easily visible from anywhere within a system, and even from other systems (as stars). Planets are usually visible from within the same system, although the further planets may require a telescope to see as more than a bright star. Black holes are rarely visible unless they eclipse something else.

''Note: I have no idea how spheres move within systems. Simply rotating in place isn't enough, but they have no particular reason to orbit each other in any simple way.''