I would guess, Rob, that this occurred because you made the mistake of shooting this shot as your intergalactic vessel jumped to light speed on your way home. However, there are other potential reasons for this occurrence. I have a "lazy" left eye that tends to drift. To compound the problem, part of my left eyelid was blown off during WW2 when I singlehandedly wiped out a Nazi machine gun nest and won the coveted Navy Cross. When I close my left eye, all of your shots look like this. The only other possible explanation is that your camera drank some electric Cool-Ade when you weren't looking. Now you know why the locals call me Sherlock Roger.
To me, it looks like the back half of a focal plane shutter that never made it all the way across. Have to admit it's been 50 years since I've seen anything like it :-).