dark flow

Dark flow is a particular pattern observed in the movement of some nearby galaxy clusters suggesting some force other than whatever powers Hubble expansion, such as could be the gravity of a relatively compact but extremely massive object. Evidence was announced in 2008 based upon Wilkinson Microwave Anisotropy Probe (WMAP) data as well as galaxy cluster data, and has since been debated. The concept has inspired exotic explanations from astrophysicists and others. The general direction of the dark flow is somewhat toward the Great Attractor, but they could be independent.