Are you talking about the ring around the star or the general illumination? I made that by using the Supernova filter in Gimp and then set the Layer Mode to Grain Merge. I thought it sort of washed out the colors a little, but without it the map would be very dark. I turned down the Opacity on that layer a little to diminish the wash out, but it still tends to show the rays. And as a neat little side effect, that ring around the star pretty well marks where it would be a less than stellar* idea to travel. I was thinking about trying a Foreground to Transparent Gradient with a near white color to see if that has a less "ray-like" effect.
Not really a crit on the map, since I think it looks just fine as-is, but aren't the "rays" on stars a product of seeing them through atmosphere? Again, I'm not suggesting you take them off, I think they add something artistically that would be lost without them. Just musing.