An all-sky map of half a million supermassive black holes

The Sloan Digital Sky Survey's Data Release 20 has mapped over 500,000 supermassive black holes by combining optical observations with X-ray data from the eROSITA space mission. The release reveals that rapidly growing giant black holes were surprisingly common in the early universe, and that 70–90% of all black hole growth happened hidden behind dust and gas. All data is freely available to researchers and the public worldwide.