Lately, I've been working a lot with a character who is an astronomer--Niela from Of Gods and Dragons, specifically, a woman whose knowledge of the stars gave rise to the campaign in the first place. It struck me that I've carefully mapped my world, created an accurate globe for it, and written about it in detail here, and yet I've never looked beyond. The one thing I know is that the planet that is my homebrew setting is called Izar. That said, I should know more, especially given that I have a regularly featured character who specializes in astronomy--she knows what she's talking about, so I need to.
When it comes to scientific knowledge in my setting, things are deliberately incomplete. I teased in both Listen Check and Lethanin's intro session in Of Gods and Dragons that there was more to the world than people know, and so this accurate information is known only by a few leading experts willing to delve into esoterica and theorize on their own. And since Niela is just such an expert, this will be information she has and can talk about. All of this said, here's a guide to the solar system Izar resides in.