With Photoshop (but probably works with any application)
1. Make new layer (I make a new layer because the background layer is limited) and color it black
2. Make new layer and airbrush and/or watercolor a purplelish-blue for those novas (I think that's what they are). Once you're done, reduce the opacity to what
you see fit.
3. Make new layer and draw a bunch of white speckles for stars.
4. Duplicate that layer and make it an "add" layer and gaussian blur it to what you see fit.
5. Make a new layer and airbrush bluish, purpleish, or pinkish (space colors) dots (size depends on how big the big stars are)
6. Duplicate that layer, make it an "add" layer, and gaussian blur it.
7. Make a new layer and draw the big stars. They should look like + signs.
8. Duplicate that layer, make it an "add" layer, and gaussian blur it.
This is what I got in 5 minutes:http://i231.photobucket.com/albums/ee97/Xeele/starrycopy.jpg