Galaxies that move together have cosmologists stumped about dark matter
Astronomers have discovered that the smaller satellite galaxies around Centaurus A are engaged in a coordinated dance that seems out of sync with our understanding of the large-scale structure of the universe.
The discovery, described in the journal Science, could push physicists to redefine our understanding of dark matter, that mysterious stuff that forms the universe's cosmic web.
Unlike normal matter, dark matter doesn't interact with other matter. It can't be seen or touched. And yet we know it must be
