The Milky Way and Andromeda galaxy are each surrounded by a thin plane of satellite galaxies that may be corotating. Cosmological simulations predict that most satellite galaxy systems are close to isotropic with random motions, so those two well-studied systems were interpreted as rare statistical outliers. We tested this assumption using the kinematics of satellite galaxies around the Centaurus A galaxy. Our statistical analysis revealed evidence for corotation in a narrow plane. In standard cosmology simulations, less than 0.5% of Centaurus A-like galaxies show such behaviour. The immediate conclusion is that corotating satellite systems are more common in the Universe than previously expected, seriously challenging small-scale structure formation in the prevailing cosmological paradigm. To scrutinise the universality of the disk of satellites phenomenon, the study of dwarf galaxy populations around other nearby large galaxies is of fundamental importance. We propose a systematic search for faint satellite galaxies and disks of satellites around all Local Volume galaxies brighter than MV=−20 mag in the northern hemisphere, in the distance range 8-11 Mpc.
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