Pandora's Cluster: A galactic crash investigation

By abe10tiger
Jun 23, 2011
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  1. Science News

    When huge clusters of galaxies crash together, the resulting mess is a treasure trove of information for astronomers. By investigating one of the most complex and unusual colliding clusters in the sky, an international team of astronomers has pieced together the history of a cosmic crash that took place over a period of 350 million years.

    This image combines visible light exposures of galaxy cluster Abell 2744 taken by the NASA/ESA Hubble Space Telescope and the European Southern Observatory's Very Large Telescope, with X-ray data from NASA's Chandra X-ray Observatory and a mathematical reconstruction of the location of dark matter. The galaxies in the cluster, while they are the only part that is visible in the optical part of the spectrum, actually only provide around 5 percent of the mass in the cluster. Hot intracluster gas (shown in pink) is visible through its X-ray emissions, observed by NASA's Chandra satellite. The blue overlay shows a map of the mass in the cluster. This is reconstructed based on detailed analysis of the way that the cluster bends light from galaxies in the distant background. Evidence of this light bending can be seen in arc-like distortions in parts of this image. Since dark matter makes up the lion's share of mass in the cluster -- around 75 percent -- this blue overlay reveals the location of the otherwise invisible dark matter. Analysis of this data has allowed scientists to observe some strange phenomena in Abell 2744, including a pocket of dark matter with no gas or galaxies, and a clump of galaxies with no associated gas. Astronomers believe that Abell 2744 formed from the simultaneous pile-up of at least four separate clusters. (Credit: NASA, ESA, ESO, CXC, and D. Coe (STScI)/J. Merten (Heidelberg/Bologna))

    Source:Science Daily

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