Distant Worlds addresses and explains many of the issues being discussed here. I suggest picking up at least the PDF and giving it a read. It's really cool. For each point of interest in the solar system it offers adventure hooks that can draw even low level characters off world.
As far as interstellar travel via magic, it must be possible given where Desna makes her home. And I suspect a Starsoul Sorcerer could use their own ability to enter the void. Just be careful about what might be sleeping in the void with you.
