Panoramic view of the entire near-infrared sky — location of the Great Attractor is shown following the long blue arrow at bottom-right. (Graphic by Thomas Jarret,IPAC) The Great Attractor is a gravity anomaly in intergalactic space within the range of the Centaurus Supercluster that reveals the existence of a localised concentration of mass equivalent to tens of thousands of Milky Ways, observable by its effect on the motion of galaxies and their associated clusters over a region hundreds of millions of light years across. These galaxies are all redshifted, in accordance with the Hubble Flow, indicating that they are receding relative to us and to each other, but the variations in their redshift are sufficient to reveal the existence of the anomaly. The variations in their redshifts are known as peculiar velocities, and cover a range from about +700 km/s to -700 km/s, depending on the angular deviation from the direction to the Great Attractor. Location The first indications of a deviation from uniform expansion of the universe were reported in 1973 and again in 1978. The location of the Great Attractor was finally determined in 1986, and is situated at a distance of somewhere between 150 million and 250 million light years (the latter being the most recent estimate) from the Milky Way, in the direction of the Hydra and Centaurus constellations. That region of space is dominated by the Norma cluster (ACO 3627),[1][2] a massive cluster of galaxies, containing a preponderance of large, old galaxies, many of which are colliding with their neighbours, and/or radiating large amounts of radio waves. Attempts to further study the Great Attractor and other phenomena are hampered due to line of sight obstruction by its location in the zone of avoidance (the part of the night sky obscured by the Milky Way galaxy). Further reading * Dressler, Alan. Voyage to the Great Attractor: Exploring Intergalactic Space. New York, Alfred A. Knopf, 1994. References 1. ^ R. C. Kraan-Korteweg, in Lecture Notes in Physics 556, edited by D. Pageand J.G. Hirsch, p. 301 (Springer, Berlin, 2000). 2. ^ One theory claims the Great Attractor is a supercluster (possibly the Shapley Supercluster), "with Abell 3627 near its center." (NASA's Ask an Astrophysicist: The Great Attractor) Retrieved from "http://en.wikipedia.org/"
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