The supermassive black holes found at the centers of galaxies are known for their extreme X-ray emission. This emission is associated with the massive hot disks of gas and debris that circle these monstrous black holes before it is consumed.
However, X-ray observations of distant galaxies have also uncovered additional luminous X-ray sources that aren’t associated with the galactic centers (where supermassive black holes are found). These are ULXs, or ultraluminous X-ray sources. ULXs hav