Two supermassive black holes detected in Mrk 501 may merge within 100 years

Max Planck-led astronomers reportedly detected two supermassive black holes in the blazar Mrk 501 after analyzing decades of radio data. Each is estimated at roughly 100 million to 1 billion solar masses. The pair is described as 250–540 astronomical units apart, orbiting roughly every 121 days. They may merge within about 100 years, potentially offering a chance to detect gravitational waves with pulsar timing arrays.