I've seen people doing space nails all over the place, and it inspired me to try it out for myself. All in all I'm pretty happy with it!
I didn't really use a tutorial for this, I basically just looked at a bunch of examples and pictures of galaxies and took a makeup sponge with random nail polish colors to my nails. The base color was Zoya, Dovima. I then sponged on NYC "Empire State Blue," orchid "Barely There," essie "Allure," a tiny bit of Nubar "G188," and Sally Hansen "Twinkle Twinkle." Phew, that was a mouthful. I probably didn't have to use that many polishes but I was basically just having fun sponging the colors all over my nails!