In the Bullet Cluster, we have two well defined galaxy clusters that exhibit gravity lensing. Between them is a mass of gas (mostly hydrogen and helium) that is roughly eight to nine times the stellar (observable) mass of the two galaxies. The mass of gas doesn't exhibit any lensing. My question is, why do we expect the gas to act like a lens? For a lens to work, no matter how massive, it needs to focus the rays of light coming from behind it in a coherent way. Since this cloud could be shaped like a box, or a cone or have any shape at all, why are we so convinced that it can focus light? There's no question it can bend light, the question is how is it able to focus light. Here's the X-Ray contour map of the Bullet Cluster. From this it's easy to see that we're not dealing with a relaxed system (there's absolutely no symmetry). I don't see any possible way to de-project the surface brightness to a 3D density profile without an assumption of a relaxed system. Without a density profile, I don't see how you can make any predictions at all about how this mass should bend light. What am I missing?