Always a pleasure to see a space map here
The result is pretty neat, that's an agitated system with all those orbits! The stars you draw in the background are really well done, same thing for the planet shadows.
Small critics\advises from a space map addict: i would have worked a bit more the nebula background and the lights on the sun. I often use real nebula pictures that i recolor and distort in photoshop for the background, and play wit some lense flare pictures blended with the sun to depict sun ray, you can also use the halo effect from photoshop (i guess the same effect exist in gimp) to improve the lights from your sun.