Accretion Disk
A rotating disk of gas, dust, and other matter that spirals into a central massive object like a black hole. The material heats up due to friction and gravitational forces, emitting radiation across various wavelengths.
Source: nasa.gov
APODs including "Accretion Disk"
The X-ray Sources of M31
31/12/1995
Just like our own Milky Way Galaxy, the nearest major galaxy M31 has many star systems spewing high energy radiation. High energy X-radiation is visible to certain satellites in Earth orbit such as ROSAT - which took the above picture. The X-ray sources in M31 occur in globular clusters, the spiral arms, and near the galaxy's center. Probably most of these sources are accretion disk binary star systems. M31 has more X-ray sources near its center than our Galaxy, and the reason for this is currently unknown.