Merging galaxy clusters can generate enormous shock waves, similar to cold fronts in weather on Earth. This system, known as Abell 665, has an extremely powerful shockwave, second only to the famous Bullet Cluster. Here, X-rays from Chandra (blue) show hot gas in the cluster. The bow wave shape of the shock is shown by the large white region near the center of the image. The Chandra image has been added to radio emission (purple) and visible light data from the Sloan Digital Sky Survey showing galaxies and stars (white).
Image Credit: X-ray: NASA/CXC/Univ. of Alabama/S.Dasadia et al, Radio: NSF/NRAO/VLA, Optical: SDSS
Explanation from: https://www.nasa.gov/mission_pages/chandra/abell-665.html