Centaurus A, the nearest giant elliptical, hosts a satellite system that moves like a disciplined formation. Of its well-measured satellites, those with velocity data show a coherent kinematic pattern: satellites on one side of the galaxy systematically receding, those on the other approaching, the signature of a co-rotating planar arrangement. Mueller et al. (2018, Science; extended 2021) quantified the arrangement: roughly 80 percent of the measured satellites participate in the coherent motion, and matching configurations occur in well under 0.5 percent of comparable ΛCDM simulated hosts. Centaurus A thereby joined the Milky Way and Andromeda as the third consecutive nearby host whose satellites orbit in an organized plane, with the joint probability of three-for-three under the model dropping toward one in a million.
The model's defense for any single plane, a transient chance alignment caught at a fortunate viewing epoch, weakens combinatorially with each addition and was constructed for the Milky Way specifically (Sawala et al. 2022); it does not export to Centaurus A's independent geometry. Group infall and filamentary accretion produce mild anisotropies in simulations, never the thin, kinematically coherent, high-participation planes observed, and the satellites' co-rotation requires not just correlated positions but a shared orbital angular momentum that random subhalo accretion does not deliver. Every adequately sampled host showing the same forbidden structure converts an anomaly into a law the model lacks.
The standing is decisive in trajectory: distance and velocity campaigns on additional hosts (Sculptor group, M81, M101 systems) are extending the census, and SAGA/ELVES statistical samples will fix the incidence rate. Either the planes are universal, falsifying isotropic accretion outright, or sample completeness will dilute them.