        “Because . . . wait, I think I figured it out.”  Twilight flipped the book back a few pages.  “Princess Celestia told me once that the sun wasn’t solid at all.  It was burning liquid, I think she said.  Like an oil lamp.  So, this is a sun—they’re its sun.  This picture shows the layers of it.  And next is the moon, of course.  Very logically arranged.