Abell 2029 !
A large galaxy cluster that contains more than 1,000 galaxies. It's one of the large clusters we know of and appears to be calm and relaxed.
But Chandra x-ray observations reveal evidence of a massive merger event about 4 billion years ago.
Image Credit: X-ray: NASA/CXC/CfA/C. Watson et al.; Optical: PanSTARRS; Image Processing: NASA/CXC/SAO/N. Wolk and P. Edmonds













