The information between the two horizontal lines reproduce a handout I gave to players with characters from Oerth (The World of Greyhawk ™) in my old Spelljammer ™ campaign. It tells them everything a reasonably-educated groundling knows about the planets and stars. (I'd probably delete third paragraph of the cosmography section if printing this out for non-scholarly types.
For the record, the pronounciation of "Oerth" is from a Frank Mentzer article in Dragon Magazine issue 93. Also, "Oerthian" (not "Oerthling") is actually TSR's preferred nomenclature for a native of Oerth, but I changed it in my campaign for strictly idiosyncratic reasons.
GENERAL KNOWLEDGE -- OERTH
As a native of the Oerth, your character knows the following common facts about the sky.
Your Home: The center of the Universe is the Oerth (preferably pronounced "ayrth", although "orth" and "urth" are acceptable). It is a round (spherical) planet.
Nomenclature: A native of the Oerth is an Oerthling. The adjectives for something from Oerth are oerthish or oerthian.
Cosmography: Sages are now quite sure that the other planets orbit around the Oerth (A rival theory once held that the Oerth went around the Sun, but has since been revealed as idiotic speculation). Thus the definition of "planets" includes the Sun and Moons.
The Sun and Moons, of course, are the closest to Oerth, being the only planets that appear larger than the stars. The Moons are also the only planets that can cause eclipses of the Sun. Oerth's smaller blue moon is called Celene. The larger white moon is Luna.
Working outwards from the Oerth, the planets are Celene, Luna, the Sun, Edill, Gnible, and Conatha.
History/Lore: There is very little folklore or legend involving the planets. Occasionally, old myths say there should be an extra planet between the Sun and Edill, or even a second Sun.