http : //creativecommons.org/licenses/by-nc-sa/4.0/ cover image adapted from : vst images the lagoon nebula by eso/vphas+ team http : //en.wikipedia.org/wiki/file : vst_images_the_lagoon_nebula.jpg engraved printing plate by edinburgh city of print http : //commons.wikimedia.org/wiki/file : engraved_printing_plate.jpg prologue look .