X-ray observations by the Chandra X-ray Observatory appear in blue and are overlaid upon a yellow-colored optical image by the Digitized Sky Survey. The blue regions contain shock-heated gas that has a temperature of about 6 million degrees Celsius. The heating is produced by the rapid motion of a spiral galaxy intruder located immediately to the right of the shock wave in the center of the image.
X-ray: NASA / CXC / INAF-Brera / G.Trinchieri et al.; Optical: Palomar Observatory / DSS