Glowing galaxies crowd this Hubble view of the galaxy cluster Abell 3192. Like all clusters of galaxies, this one is full of hot gas that emits powerful X-rays, and it's also enveloped in a halo of something called dark matter – which is like the invisible scaffolding of our universe. All this matter, though not visible, has a huge effect on Abell 3192. That enormous amount of mass, combined with the mass of all these galaxies as well, is strong enough to curve spacetime around it. This is calle