The round, bright, yellow objects near the center of the Hubble image below are part of a massive galaxy cluster. If you look closely, several blue galaxies seem to form a wide circle around the cluster, and they all look strangely similar. That’s because they’re actually reflections of the same galaxy.
The smaller blue galaxy is much more distant than the bright yellow galaxy cluster, so light from the blue ring galaxy has to pass the cluster to reach Earth. Gravity exerts a pull on light just like it does on matter. When light passes through the gravitational field of something massive, like a galaxy cluster, the light bends just like it would if it passed through a curved glass lens. Physicists call this gravitational lensing.
So when the light from the blue ring galaxy passes through the bright yellow galaxy cluster to reach is, it gets bent and scattered into multiple images of itself. You can see those images in a ring around the galaxy cluster at 4 o’clock, 10 o’clock, 11 o’clock, and 12 o’clock. There’s another, less distinct image near the center of the cluster.
Astronomers say this image shows 11 different background galaxies, but thanks to gravitational lensing, they appear as 33 images. Can you find any reflected duplicates? [NASA]