I've already suggested this on the MCForum, but here goes. Some things here aren't in the mod, such as stars or black holes or wormholes, but if you want I can try to explain them further as of to how I personally think they should be. I love astronomy, I was going to do a mod like this myself, but I didn't. I have some ideas you can try to fit in if you want. For example, instead of planets, there's another "overworld" you can go to, which is just space, you can travel to galaxies, which is like a mid-overworld, and from there you can find planets and stars and black holes and wormholes and nebulae and stuff. Also, a Constellation Maker, which will create beams between stars to form a constellation on a stargazing map, which is basically a 3D map of space. Also, a diamond spacesuit, which will let you survive on stars, gas planets, black holes, nebulae, or supernovas. Those were some things I was going to add on my mod, unfortunately it wasn't completed, so I just wanted to see if some of these ideas that I would love to see in Minecraft could be added.