Here are the supplies!
Put an undercoat on (optional!), and then paint your nails black.
Paint white onto the makeup sponge.
Dab the sponge across in a line on your nail (or any way you would like!)
Then add yellow onto the sponge, then dab inside the white. (my yellow wasn't too visible in this photo, my bad.)
Then, add pink onto the sponge, and dab it into the yellow (make sure the yellow still shows!)
Put purple onto the sponge, and dab it on the sides of the white, to blend it back into the black.
Put white onto a toothpick, and put stars around the galaxy and some in it.
(optional) you can put a clear sparkle coat ontop of your nail to make more stars.
Finished! Enjoy your galaxy nails :)