 Ultraluminous X-ray source

An Ultraluminous X-ray Source (ULX) is a type of astronomical object that emits an extraordinary amount of X-ray radiation, significantly more than typical X-ray binaries. ULXs are defined as having luminosities greater than 10^39 erg/s (or about 10^36 watts), which exceeds the Eddington limit for a stellar black hole (a theoretical maximum luminosity based on the balance between the outward radiation pressure and the inward gravitational force).