The Great

Detailed observations of the galaxies around us indicate that there is superposed on the Hubble flow a large-scale streaming motion of about 600 km/s in the general direction of the constellation Centaurus.

A River of Galaxies

This mass migration includes the Local Group, the Virgo Cluster, the Hydra--Centaurus Supercluster, and other groups and clusters for a distance of at least 60 Mpc up and downstream from us. It is as if a great river of galaxies (including our own) is flowing with a swift current of 600 km/s toward Centaurus.

Location of the Great Attractor

Calculations indicate that ~1016 solar masses concentrated 65 Mpc away in the direction of Centaurus would account for this. This mass concentration has been dubbed the Great Attractor. Detailed investigation of that region of the sky (see adjacent image of the galaxy cluster Abell 3627) finds 10 times too little visible matter to account for this flow, again implying a dominant gravitational role for unseen or dark matter. Thus, the Great Attractor is certainly there (because we see its gravitational influence), but the major portion of the mass that must be there cannot be seen in our telescopes.

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