File:MACS J0717-dark.jpg

This is a NASA/ESA Hubble Space Telescope image of the galaxy cluster MACS J0717.5+3745. Shown in blue on the image is a map of the dark matter found within the cluster. This cluster was part of a study of 72 galaxy cluster collisions which determined that dark matter interacts with other dark matter even less than previously thought.

Credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey