Research Article

A whirling plane of satellite galaxies around Centaurus A challenges cold dark matter cosmology

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Science  02 Feb 2018:
Vol. 359, Issue 6375, pp. 534-537
DOI: 10.1126/science.aao1858

Dwarf galaxies move in unexpected ways

Massive galaxies like our Milky Way are orbited by satellite dwarf galaxies. Standard cosmological simulations of galaxy formation predict that these satellites should move randomly around their host. Müller et al. examined the satellites of the nearby elliptical galaxy Centaurus A (see the Perspective by Boylan-Kolchin). They found that the satellites are distributed in a planar arrangement, and the members of the plane are orbiting in a coherent direction. This is inconsistent with more than 99% of comparable galaxies in simulations. Centaurus A, the Milky Way, and Andromeda all have highly statistically unlikely satellite systems. This observational evidence suggests that something is wrong with standard cosmological simulations.

Science, this issue p. 534; see also p. 520