An international research team led by Silke Britzen of the Max Planck Institute for Radio Astronomy (MPIfR) has detected a pair of supermassive black holes at the center of the galaxy Markarian 501. The team utilized an international network of radio telescopes to image two distinct particle streams, or jets, emanating from the galactic core.
This discovery provides long-sought evidence of two massive black holes orbiting one another in close proximity. Scientists believe the duo is in the final phase of a merger, a process that could be completed in as little as 100 years.
A milestone in galactic evolution
While current models suggest that almost every large galaxy hosts a supermassive black hole, researchers have struggled to explain how these objects reach such extreme masses. The prevailing theory suggests that black holes must merge with other massive counterparts to grow, a process that follows the collisions of their host galaxies.
Despite the frequency of galaxy collisions in the universe, scientists had never reliably detected a close-orbiting pair of supermassive black holes before this study. The observations at Markarian 501 offer a rare look at the mechanics of this final, high-energy stage of coalescence.
"The black hole at the centre of Mrk 501 ejects a powerful jet of particles traveling at nearly the speed of light into space," the researchers noted in their report. By analyzing these jets, the team determined that the curved trajectory of one stream likely originates from a second, previously unobserved black hole.
This work, which has been accepted for publication in the Monthly Notices of the Royal Astronomical Society, confirms that these black holes act as individual “motors” for their respective particle jets. The findings provide critical data for astrophysicists working to refine theoretical models of how massive black holes interact and eventually combine.
