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
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
Location of the Great Attractor
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
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