An artist's concept of the accretion disk around the binary star 
system WZ Sge

Dark Matter Discovered in Accretion Disks |  Suggests Major Revisions to Concepts of Disk Structure and Luminosity. Observations of the interacting binary star using telescopes at Kitt Peak National Observatory and NASA’s Spitzer Space Telescope suggest that the disks of hot gas that accumulate around a wide variety of astronomical objects—from degenerate stars in energetic binary systems to supermassive black holes at the hearts of active galaxies—are likely to be much larger than previously believed. Released at the 211th AAS Meeting in Austin. NOAO Press Release 08-02

Image Credit: P. Marenfeld and NOAO/AURA/NSF