The fastest-growing black hole in the Universe

Abstract Quasars are supermassive black holes feasting on surrounding matter, which make them outshine their host galaxies. Around a million quasars have been cat- alogued in the Universe by probing deeper and using new methods for discovery. In this work, we study the properties of the most luminous of all quasars found so far. It has been overlooked until recently, which demonstrates that modern all-sky surveys have much to reveal. The black hole in this quasar accretes around one solar mass per day onto an existing mass of 15 billion solar masses. In this process its accretion disc alone releases a radiative energy that is equivalent to the output from between 365 and 640 trillion Suns. The range is mostly due to the unknown viewing angle of the disc, which radiates more intensely near its polar sight lines than at grazing angles to the disc.