Markarian 501: Imminent Black‑Hole Merger?

Astronomers report two supermassive black holes orbiting each other in the galaxy Markarian 501 with a 121‑day period and a separation of a few hundred astronomical units. Depending on their masses, the pair could merge within decades to a century and would emit low‑frequency gravitational waves that pulsar timing arrays could track as a steadily rising signal. — If confirmed and monitored, this would be a rare case of a foreseeable, multi‑messenger supermassive‑black‑hole merger—shifting how observatories, funding agencies, and the public prioritize gravitational‑wave detection and long‑term monitoring.