(when someone thinks of the same title to your campaign and publishes something before you do, you're in trouble).
Every religion has one, every one has a view of the universe. In our case, it's a solar system. Better get down the physical side rather than the spiritual, since every religion -- Christianity, Orc Shamanism, the Sacred Light, Hinduism, Elven Paganism, Massalian Monotheism, etc; have their own spiritual Cosmology.
But for now we will deal with the Cosmology of my campaign setting as it pertains to the Physical.
The solar system of my Campaign World consists of a G2 type star with a luminosity of 1 in a different Galaxy. The Sun is a G2 yellow star.
Their are 10 planets in the Solar System -- Hermes, Aphrodite, Earth, Ares, Zeus, Hera, Neptune, Charon, and the Destroyer
Hermes is a rocky, terrestial world.
Aphrodite is a rocky, terrestrial world covered by cloud cover.
Earth is the campaign setting planet.
Between Aphrodite and Earth is an Asteroid Belt, the remains of a planet destroyed by a collision with the Destroyer.
Ares is a desert world.
Zeus is an Blue Gas Giant.
Hera is a red Gas Giant
Neptune is a dark blue gas giant.
Charon is a Kupier object.
The Destroyer is a brown Dwarf star that never ignited.
There is one moon that orbits Earth. Ares has no moons. Zeus has twenty moons, and Hera has thirty moons, and a brilliant set of rings. Neptune has nine moons, and Charon has none. The Destroyer has no satellite planets or moons.
Whew! There we go! The physical Cosmology of the Campaign Setting! :D