the TIE and the explosion were first composited without motion in a separate after effects composition. it was then added to the other elements and the motion path then added so that the explosion & TIE would have the same trajectory & scale. This is why the explosion looks like it is remaining central and because the camera is panning right and shrinking it quickly would make the explosion look very odd but it does shrink in scale to match the TIE (because it is on the same compositing track). I have tweaked the shot now so that the explosion moves slightly to the left.