*Description*: Astronomers assembled this photo by combining a visible-light image of the Abell 901/902 supercluster taken with the MPG/ESO 2.2-meter telescope in La Silla, Chile, with a dark matter map derived from observations with NASA's Hubble Space Telescope. The magenta-tinted clumps represent a map of the dark matter in the cluster. Dark matter is an invisible form of matter that accounts for most of the universe's mass. The image shows that the supercluster galaxies lie within the clumps of dark matter. Hubble cannot see the dark matter directly. Astronomers inferred its location by analyzing the effect of so-called weak gravitational lensing, where light from more than 60,000 galaxies behind Abell 901/902 is distorted by intervening matter within the cluster. Researchers used the observed, subtle distortion of the galaxies' shapes to reconstruct the dark matter distribution in the supercluster. Technical facts about this news release: About the Object Object Name: Abell 901/902 Object Description: Space Telescope A901/902 Galaxy Evolution Survey (STAGES) Position (J2000): The STAGES area spans a quarter square degree centered on the Abell 901/2 supercluster at roughly R.A. = 10h and Dec. = -10 Constellation: Leo Dimensions and Distance: The STAGES area covers 0.5x0.5 degrees which corresponds to an area of 5x5 Megaparsecs at a redshift of z = 0.16. About the Data Data Description: The image was created from HST data from proposal 10395: M. Gray (University of Nottingham) The science team is being led by C. Heymans (University of British Columbia). The full list of team members is available at the STAGES team [ http://www.nottingham.ac.uk/~ppzmeg/stages/team.html ] webpage. Instrument: ACS/WFC Exposure Date(s): June and July, 2005 Exposure Time: 1.6 days Filters: F606W (V) About the Image Image Credit: NASA, ESA, C. Heymans (University of British Columbia), M. Gray (university of Nottingham), and the STAGES Collaboration Release Date: January 10, 2008 Orientation: Dark Matter Distribution in Supercluster Abell 901/902 [ http://imgsrc.hubblesite.org/hu/db/2008/03/images/b/formats/compass_large_web.jpg ] What is an American Astronomical Society Meeting release? A major news announcement issued at an American Astronomical Society meeting, the premier astronomy conference. Astronomers are using NASA's Hubble Space Telescope to dissect one of the largest structures in the universe as part of a quest to understand the violent lives of galaxies. Hubble is providing indirect evidence of unseen dark matter tugging on galaxies in the crowded, rough-and-tumble environment of a massive supercluster of hundreds of galaxies. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Hubble's Advanced Camera for Surveys has mapped the invisible dark matter scaffolding of the supercluster Abell 901/902, as well as the detailed structure of individual galaxies embedded in it. The image, taken by NASA's Hubble Space Telescope, shows the supercluster. The magenta clumps throughout the image reveal the distribution of dark matter in the cluster. The galaxies lie within the clumps of dark matter. The image was assembled by combining a visible-light image of the supercluster taken with the MPG/ESO 2.2-meter telescope in La Silla, Chile, with a dark matter map derived from Hubble observations. Read more: * The Full Story [ http://hubblesite.org/newscenter/archive/releases/2008/03/full/ ] *News Release Number:*: STScI-2008-03b
