Gravitational Lensing

The distorted circular image of galaxies in the center is caused by a phenomenon called Gravitational lensing.

The galaxy in the front is so massive that its gravity distorts the space-time fabric, meaning that the light from the faraway galaxies gets bent due to the intense gravity of the foreground galaxy.

As a result, it produces several images of the same galaxy in a lenslike structure.

Image from Hubble