Double Einstein Ring Photographed by the Hubble Telescope

NASA/ESA Hubble Telescope photographed a phenomenon called "Einstein ring" where, predicted by Einstein a long time ago, gravity can "bend" light rays:

The phenomenon, called gravitational lensing, occurs when a massive galaxy in the foreground bends the light rays from a distant galaxy behind it, in much the same way as a magnifying glass would. When both galaxies are exactly lined up, the light forms a circle, called an “Einstein ring”, around the foreground galaxy. If another more distant galaxy lies precisely on the same sightline, a second, larger ring will appear.

And you get a Double Einstein Ring: Link (Photo: NASA/ESA, R. Gavazzi, T. Treu, SLACS team)