These four dwarf galaxies are part of a census of small galaxies in the tumultuous heart of the hearby Perseus galaxy cluster.
The galaxies appear smooth and symmetrical, suggesting that they have not been tidally disrupted by the pull of gravity in the dense cluster environment. Larger galaxies around them, however, are being ripped apart by the gravitational tug of other galaxies.
The images, taken by NASA's Hubble Space Telescope, are evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter.
NASA/ESA/C. Conselice and S. Penny (Univ. of Nottingham)