Credits for the photos used:
“NGC 6992 Eastern Veil Nebula” by Astrobond (via Wikimedia) is licensed under CC BY-SA 4.0 (first image used)
"Center of the Milky Way Galaxy IV" by NASA/JPL (via Wikimedia) is licensed under Public Domain (second image used)
"Antennae galaxies" by NASA/ESA/Hubble Heritage Team (via Wikimedia) is licensed under Public Domain (third image used)
"Andromeda Galaxy" by Adam Evans (via Flickr) is licensed under CC BY 2.0 (fourth image used)
"Cartwheel Galaxy (MIRI)" by NASA (via Wikimedia) is licensed under Public Domain (fifth image used)
“Example book cover” by VicEdu13 (me via Wikimedia) is licensed under CC BY-SA 4.0 (my custom book cover example)