Light echoes reveal invisible mass around supermassive black holes

Supermassive black holes are the heaviest objects in the universe, often weighing millions or billions of times more than the sun. While their immense gravity pulls in glowing clouds of gas and dust, recent measurements suggest they are also surrounded by vast, invisible reservoirs of dark matter. Because dark matter does not emit light or experience friction, it remains hidden from traditional telescopes, revealing itself only through its gravitational pull on the space around it.