When creating the cover for my first scifi novel, I was so excited to learn that Hubble/Nasa images are in the public domain. Reaching out to Nasa to make sure and getting a human response was equally exciting! The outside border of the book is the Andromeda Galaxy, and the other images are nebulas!

https://bit.ly/3ltgzG9 via /r/spaceporn https://bit.ly/3A2hBwJ