Astronomers have found two supermassive black holes orbiting each other at the core of galaxy Markarian 501, about 500 million light-years away.
The black holes, each up to a billion times the Sun's mass, are expected to collide within 100 years, producing powerful gravitational waves.
This is the first direct evidence of such a close binary system, offering a rare opportunity to study supermassive black hole mergers.
With a black hole merger expected in 100 years, what signs will astronomers look for first?
If supermassive black holes merge this often, how does that rewrite the history of galaxy growth?
Could this black hole duo also be the source of mysterious high-energy neutrinos hitting Earth?
Is a dueling black hole pair the only explanation for Markarian 501's bizarre, looping jet?
How was an 'Einstein Ring' the smoking gun that confirmed two black holes were at play?
How does this discovery finally offer a solution to astrophysics' long-standing 'final parsec problem'?
First Direct Detection of a Supermassive Black Hole Binary Orbiting Every 121 Days in Markarian 501
Overview
In April 2026, astronomers at the Max Planck Institute discovered two supermassive black holes orbiting each other in the galaxy Markarian 501, about 500 million light-years away. This binary system was revealed through decades of radio observations showing two distinct jets, indicating the presence of two massive black holes orbiting every 121 days at a close distance. These orbiting giants generate low-frequency gravitational waves, which pulsar timing arrays are now monitoring. Predicted to merge within about 100 years, this event offers a unique chance to test Einstein's theory, study black hole growth, and understand galaxy evolution, while current technology limits direct imaging, making gravitational wave detection essential.