For people who like puzzles, a little astronomy for your afternoon. Apparently a huge cluster of galaxies and dwarf galaxies rotate around Andromeda like they are painted on the surface of a very flat plate. Our own solar system, which seems like it ought to be more gravitationally connected than an entire largish neighborhood of the universe, has a sloppier plane of the ecliptic. The abstract’s final aside puts a nice exclamation point on the story.
Here we report the existence of a planar subgroup of satellites in the Andromeda galaxy (M 31), comprising about half of the population. The structure is at least 400 kiloparsecs in diameter, but also extremely thin, with a perpendicular scatter of less than 14.1 kiloparsecs. Radial velocity measurements reveal that the satellites in this structure have the same sense of rotation about their host. This shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way’s disk and with the vector between the Milky Way and Andromeda.
Maybe it’s a glitch in the matrix?