Proposed concentration of mass, equivalent to tens of thousands of galaxies, that influences the movement of many galaxies, including the Milky Way Galaxy (see galaxy ).
In 1986 a group of astronomers noted that the Milky Way and neighbouring galaxies exhibit systematic deflections from the motion predicted by expanding universe . One possible explanation is a large collection of galaxies exerting a gravitational pull on the clusters of galaxies around it; its centre would lie in the direction of the constellations Hydra or Centaurus in the southern sky, about 200 million light-years from Earth.