Starburst galaxy UGC 6697, combined optical and Chandra X-ray telescope image. The optical parts, mainly stars, are red, the X-ray parts are blue. This galaxy is part of the large galaxy cluster Abell 1367. The cluster's gravity accelerates the galaxy towards bottom left. The galaxy's motion through the gas in the cluster compresses the gas inside it. This leads to a burst of star formation producing massive, short-lived stars that explode as supernovas after around ten million years. These heat the gas in the galaxy, causing it to emit X-rays. This accounts for the lag between the front edge of the galaxy and the X-ray region. The galaxy lies some 300 million light years from Earth in the constellation Leo.