Tar,
The diagram has not been represented as an explosion and it's not the universe, nor is it referencing the big bang in any way.
We do have knowledge of the stellar movement in all directions. From observations the universe seems to be expanding non-uniformly into a tube. Granted, a tube is not an elliptical shape. Due to the enormous amount of mass interacting in the universe it is difficult for us to see what is actually occurring.
Think of the cannibalization of two galaxies on a much larger scale. Do the two galaxies not stretch? If we were inside one of the galaxies and only able to see a portion of it what would we see? We would see stars wildly moving away from us while others seemed to be moving closer or not at all.
Regards,
Pleader88