Great tutorial! Is there a way that you could motion blue the stars to help simulate motion when the ship is moving faster?
Sure, but to apply motion blur, you'll need to code a fragment shader. That's something we actually cover in the Shader Secrets course, which I noticed you bought already. Here's the corresponding lesson: https://gdquest.mavenseed.com/lessons/gaussian-blur
To turn this gaussian blur into a motion blur, you animate its blur_scale property from GDScript in the desired direction.
If you need more details don't hesitate to ask under the gaussian blur lesson.