I was reading an article that, among other things, discussed the expansion of the universe. It described the cosmological event horizon, a quality of our universe of which I was aware, and I considered an exotic phenomenon that may arise from it.
Consider a galaxy that is a nice round spiral and it is oriented to us so that one side of the spiral is 5,000ly closer to us than the other side. Now consider that galaxy's position to be such that the "line" that is the cosmological event horizon bisects that galaxy.
Ought there not be a subset of galaxies, admittedly on the ragged edge of what can be observed with the largest instruments, that are part invisible and part visible? A fraction galaxy if you will.
It is not clear to me the speed at which the "disappearing event" will occur from our perspective but I think it would be slow so that in the example galaxy it would require 5,000-ish years from first contact with the horizon to total disappearance. Even if it was fast, then there should be the possibility of observing a galaxy disappear.