Dark matter structure observed for the first time as scientists discover a dark matter filament between two clusters of galaxies about 2.7 billion light-years away.
For something that makes up an estimated 84% of the universe (1), dark matter is a pretty elusive substance: until now, that is. Scientists have observed a filament of dark matter connecting galaxy clusters Abell 222 and Abell 223, almost 2.7 billion light-years away. The presence of dark matter has been detected by monitoring the way large clumps of it, located in galaxy clusters, bend light. This phenomenon is more difficult to observe with the filaments which are thought to connect the various clusters, much like a spider's web, as they have a much smaller mass.
The observation published in Nature Magazine this week - which was made by Jörg Dietrich, a cosmologist at the University Observatory Munich in Germany, and his colleagues - was of a massive filament which was "oriented so that most of its mass lies along the line of sight to Earth." (2) In the published Abstract we are told that "[i]t is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments." (3) Dietrich goes on to say that the discovery "'is the first time a dark matter filament has been convincingly detected" and that it is "a resounding confirmation of the standard theory of structure formation of the universe...and a confirmation people didn't think was possible at this point." (4)