Cosmography of our cos mic neighborhood At the centre of the Hydra supercluster there is a gravitational anomaly, known as the Great Attractor , which affects the motion of galaxies over a region hundreds of millions of light-years across. These galaxies are all redshifted , in accordance with Hubble's law , indicating that they are receding from us and from each other, but the variations in their redshift are sufficient to reveal the existence of a concentration of mass equivalent to tens of thousands of galaxies. The Great Attractor, discovered in 1986, lies at a distance of between 150 million and 250 million light-years (250 million is the most recent estimate), in the direction of the Hydra and Centaurus constellations . In its vicinity there is a preponderance of large old galaxies, many of which are colliding with their neighbours, and/or radiating large amounts of radio waves. In 1987 Astronomer R. Brent Tully of the University of Hawaii ’s Institute of Astronomy identified what he called the
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