Coma Cluster: A collection of thousands of galaxies about 320 million light years from Earth.
Enormous arms of hot gas have been revealed in the Coma galaxy cluster in data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton. A specially processed Chandra image (pink) has been combined with optical data from the Sloan Digital Sky Survey (white and blue) to highlight these spectacular arms. Researchers think that these arms -- which span at least a half million light years -- were most likely formed when smaller galaxy clusters had their gas stripped away by the head wind created by the motion of the clusters through the hot gas.
Scale: Image is 23 arcmin on a side (about 2 million light years).
Image credit: X-ray: NASA/CXC/MPE/J.Sanders et al, Optical: SDSS
Note: For more information, see Coma Cluster: Clues to the Growth of the Colossus in Coma