One of the biggest galaxy collisions ever observed is taking place at the center of this image. The four white blobs in the middle are large galaxies that have begun to tangle and ultimately merge into a single gargantuan galaxy. The whitish cloud around the colliding galaxies contains billions of stars tossed out during the messy encounter. Other galaxies and stars appear in yellow, orange and red hues. Blue shows hot gas that permeates this distant region of tightly packed galaxies.
NASA's Spitzer Space Telescope spotted the four-way collision, or merger, in a giant cluster of galaxies, called CL0958+4702, located nearly five billion light-years away. The dots in the picture are a combination of galaxies in the cluster; background galaxies located behind the cluster; and foreground stars in our own Milky Way galaxy.
Infrared data from Spitzer are colored red in this picture, while visible-light data from a telescope known as WIYN are green. Areas where green and red overlap appear orange or yellow. Since most galaxies in the cluster contain old stars that are visible to Spitzer and WIYN, those galaxies appear orange. Blue represents X-ray light captured by NASA's Chandra X-ray Observatory. The colliding galaxies appear white because they are in areas where all the colors overlap.