These places are source of Meta-Alloys ... special commodity which is linked with Thargoids (they are used by the Thargoids to construct their ships and other technologies). More about this can be found on Cannon site (group of players which specialise on knowledge about alien and special stuff in ED). These places have nice "dark" atmosphere and also music. Cannon also have data source with locations of these places (this really come handy )
Meta-Alloys are also needed for unlock special stuff like access to one from most important Engineers or special anticorosive cargo rack and more.
.... I used Anaconda to reach Pleaides region where are these places, it need travel circa 500 ly from Sol.