Dark matter distribution
Dark matter distribution. Image 3 of 4. Supercomputer simulation, known as the Millennium Run, showing the distribution of dark matter in the local universe. The frame is 63 megaparsecs (206 million light years) in distance across. Dark matter is a form of matter that cannot be detected by telescopes as it emits no radiation. It is thought that cold dark matter first formed after the Big Bang. This matter then collapsed under its own weight to form vast halos (bright yellow) which sucked in normal matter to form visible matter, such as galaxies. This simulation was created in 2005 by the Virgo Consortium of international scientists using supercomputers at the Max Planck Society, Germany. For complete sequence, see images R980/209 - R980/212
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A Cosmic Magnifying Glass
Scanning the heavens for the first time since the successful December 1999 servicing mission, NASA's Hubble Space Telescope imaged a giant, cosmic magnifying glass, a massive cluster of galaxies called Abell 2218. This hefty cluster resides in the constellation Draco, some 2 billion light-years from Earth. The cluster is so massive that its enormous gravitational field deflects light rays passing through it, much as an optical lens bends light to form an image. This phenomenon, called gravitational lensing, magnifies, brightens, and distorts images from faraway objects. The cluster's magnifying powers provides a powerful "zoom lens" for viewing distant galaxies that could not normally be observed with the largest telescopes. The picture is dominated by spiral and elliptical galaxies. Resembling a string of tree lights, the biggest and brightest galaxies are members of the foreground cluster. Researchers are intrigued by a tiny red dot just left of top center. This dot may be an extremely remote object made visible by the cluster's magnifying powers. Further investigation is needed to confirm the object's identity. The color picture already reveals several arc-shaped features that are embedded in the cluster and cannot be easily seen in the black-and- white image. The colors in this picture yield clues to the ages, distances, and temperatures of stars, the stuff of galaxies. Blue pinpoints hot young stars. The yellow-white color of several of the galaxies represents the combined light of many stars. Red identifies cool stars, old stars, and the glow of stars in distant galaxies. This view is only possible by combining Hubble's unique image quality with the rare lensing effect provided by the magnifying cluster
Stephan's quintet. Optical image of Stephan's quintet. This group of galaxies is 300 million light years from Earth in the constellation Pegasus. It consists of NGC 7320 (upper right) NGC7319 (lower right), NGC7318A and B (centre left) and NGC7317 (upper left). The galaxies are so close together they are tearing each other apart with gravitational tidal forces, leaving trails of dust and gas. The red areas are hydrogen clouds and sites of star birth. It is argued that NGC7320 is not actually part of the cluster, but lies in the foreground.
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