Hey

I've got one tip for you. A while back I did a storyboard for a short film set in space, where I figured a good way of getting stars. you've got the right idea with using noise, but as it is here the stars are far too dense and 'flat'. What you need to do is edit the levels, move the grey up very very close to the white, then move the white all the way down to the edge of where the markings start. Also make sure that while you're doing this that you are viewing the image at 100% as being zoomed out will affect the look of the noise. once the white is at the edge of the markings, just play around with the grey and black to get a good variation of bright and faint stars.

one last thing, lens flare happens inside the camera lens, meaning the lens flare wouldn't be behind the planets. Put the lens flare on a solid black layer and then set the blending mode to lighten or screen.

The planets them selves are done very nicely though. For my storyboard I just made the planets in a 3D program and rendered them, didn't look half as good as yours though!