Here's the gradient I used in the "star" layer:

  And here's the gradient I created for the "star enhancement" layer:

 
For the "star enhancement" layer's gradient, I moved the leftmost node, which begins the transition from black to white, to the left. Then, slightly to its right, I inserted a node of navy blue between the black and the white nodes, so that the transition from black to white in the part of the image where those nodes apply goes through progressively lighter shades of blue.

There's another change, but that came later. When I applied the gradient with just the changes I have described, I got the coloring I wanted, but all sorts of large, jagged patterns appeared where the screen had previously been solid black.

I then moved the rightmost node further right and added a second white node, very close to it, widening the area of white and making the white-to-black transition at the right side of the gradient very steep. This pushed the unwanted patterns outward from the star. I decided that I'd use a clipping mask to hide all but the star, in the center of the screen.
 

 
This will cause the Gradient Editor to appear, displaying the current gradient of the "star enhancement" layer.

The image should now look like this:

 
The hues are good, and the tonalities. The wide spread of white in the gradient got the black spot out of the center of the star enhancement, but now the star enhancement, even at 85% opacity, is too prominent. It's too large.

We're going to reduce the size of the "star enhancement" layer from a magnification of approximately 700 to a magnification of approximately 550.