Chandra Release - March 2, 2012

Visual Description: Abell 520

The image features the colliding galaxy cluster Abell 520. The dominant colors in the image are a wash of green, blue, purple, and peach, which create a mesmerizing watercolor effect.  The overall appearance of Abell 520 resembles a colorful, swirling cosmic dance, reminiscent of a kaleidoscope, with dots of bright lights packed throughout.  The bright lights are mostly galaxies with some large foreground stars. Data from NASA's Chandra X-ray Observatory show the hot gas in the colliding clusters colored in green. The gas provides evidence that a collision took place. Optical data from NASA's Hubble Space Telescope and the Canada-France-Hawaii Telescope (CFHT) in Hawaii are shown in red, green, and blue. Starlight from galaxies within the clusters, derived from observations by the CFHT and smoothed to show the location of most of the galaxies, is colored peach-orange.  The blue-colored areas pinpoint the location of most of the mass in the cluster, which is dominated by dark matter. Dark matter is an invisible substance that makes up most of the universe's mass. The dark-matter map was derived from the Hubble observations, by detecting how light from distant objects is distorted by the cluster galaxies through an effect called gravitational lensing. The blend of blue and green in the center of the image reveals that a clump of dark matter resides near most of the hot gas, where very few galaxies are found.