How do I make a space themed video intro?
First up you'll have to upgrade to a different Video Editing program that has more support for the custom effects that you'll need to create an intro. For professional-looking video intros, I recommend using Adobe After Effects. Premiere Pro, Sony Vegas Pro and Pinnacle Studio are also viable options.

Since you're new to video editing, I recommend looking for some tutorials on what you're trying to achieve. I found this tutorial on YouTube which seems to fit your description:

                
            

Take what you learned from watching tutorials, and use it to create the intro you that suits you.