Great Attractor

The Great Attractor (GA) is a gigantic mass in space which pulls our Milky Way galaxy, and many other galaxies towards it.Rees, Martin 1999. Just six numbers: the deep forces that shape the Universe. Weidenfeld & Nicolson, London.p60 

The Great Attractor is known by its effect on the movement of galaxies across hundreds of millions of light years (mly). Its mass is equivalent to the mass of tens of thousands of Milky Ways.

All the galaxies in the GA are redshifted, in accordance with the expansion of the Universe. They are receding relative to us and to each other, but the variations in their redshift show the existence of the Attractor. The variations in their redshifts  range from about +700 km/s to -700 km/s, depending on where they are in relation to the Great Attractor.


 Position 
The position of the Great Attractor was finally worked out in 1986. It is between 150 and 250 million light years (47–79 million parsecs) away. Objects in that direction lie in the Zone of Avoidance, which is the part of the night sky obscured by the Milky Way galaxy. Because of this, they are difficult to study with visible light. However, X-ray observations have revealed that the region of space is dominated by the Norma Cluster,R.C. Kraan-Korteweg 2000. Lecture notes in Physics 556. edited by D. Pageand J.G. Hirsch, p301 Springer, Berlin.One theory claims the Great Attractor is a supercluster (possibly the Shapley Supercluster), "with the Norma Cluster near its center". (NASA's Ask an Astrophysicist: The Great Attractor) a massive cluster of galaxies, with large, old galaxies, many of which are colliding with their neighbours, and/or radiating large amounts of radio waves.

In 2005, astronomers conducted an X-ray survey of part of the sky known as the Clusters in the Zone of Avoidance. The survey confirmed earlier theories that the Milky Way galaxy was in fact being pulled towards a much more massive cluster of galaxies near the Shapley Supercluster, which is beyond the Great Attractor.

 Related pages 
 Shapley Supercluster
 Great Wall

References

Further reading

Category:Galaxy clusters