First close pair of supermassive black holes detected
by Nina Brinkmann, Max Planck Society
edited by Lisa Lock, reviewed by Robert Egan
Supermassive black holes at the centers of galaxies are one of the most active fields of research in astronomy. In order to accumulate their enormous masses, they must merge with each other. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn has found direct evidence of two supermassive black holes in the galaxy Markarian 501, which orbit each other very closely. This could be the first time that a pair has been detected that is about to merge. This provides a unique opportunity to better understand a central process in galaxy evolution.
The findings suggest that there is a supermassive black hole at the center of almost every large galaxy, with a mass millions or even billions of times greater than that of our sun. It is still unclear exactly how they can reach such enormous masses. Collecting (accreting) gas from the surrounding area alone would take too long, so it is likely that they have to merge with other massive black holes. Galaxy collisions have been observed throughout our universe. It is thus very likely that the supermassive black holes at the centers of these colliding galaxies also merge, first orbiting each other ever closer and ultimately coalescing into one.
Telltale particle beam
However, theoretical models cannot yet accurately describe this final phase. Complicating matters further, no close pair of massive black holes has yet been reliably detected, despite collisions between galaxies being commonplace on cosmic timescales. The recent study of the galaxy Markarian 501 (Mrk 501) in the constellation Hercules has changed that. The work has been published in the Monthly Notices of the Royal Astronomical Society.
The black hole at the center of Mrk 501 ejects a powerful jet of particles traveling at nearly the speed of light into space. For the study, the team analyzed high-resolution observations of the region. These cover various radio frequencies and were collected on dozens of days over a period of approximately 23 years. This long-term data reveals not only a single jet, but a second one as well. It is the first direct image of such a system at the center of a galaxy, and a clear indication of the existence of a second supermassive black hole. "We searched for it for so long, and then it came as a complete surprise that we could not only see a second jet, but even track its movement," reports Britzen.
Article link:
https://phys.org/news/2026-04-pair-supermassive-black-holes.html
Pic Description:
The artistic rendering shows the center of the galaxy Markarian 501, from which two powerful jets emanate. The radio observations are visible as contours in the background. Credit: Emma Kun / HUN-REN Konkoly Observatory
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