Whoa!! Goooood questions! :) "...rather large accordion..." HEE HEE!!
The note on the side - yeah! The "white hole" to the next-door universe. Good one, Rapaire. Some kind of an inverse note. I have NO idea what that means.

Re how they detected all this: supposedly via "sound wave" ripples in the galactic gas. / But yeah: I've always wondered about the sound effects in all the movie & TV scenes of mighty battles in the vacuum of space. Phaser blasts, explosions, crashes, engines, whooshing spacecraft, etc. Hm.