MOST of the small satellite galaxies around the Andromeda galaxy are lined up in a single plane that slices through its spiral disc, an alignment that suggests the satellites are floating on a river of dark matter.
Using the Hubble Space Telescope, Eva Grebel of the University of Basel in Binningen, Switzerland, and her colleagues found that nine of Andromeda’s 14 satellite galaxies lie in a relatively thin plane about 52,000 light years wide.
“It’s unlikely such a plane would arise by chance,” Grebel says, who presented the results at a meeting of the American Astronomical Society in Washington DC. The satellites in the plane also have similar characteristics – most…
