Researchers at the Max Planck Institute for Radio Astronomy identified a second jet in galaxy Mrk 501, suggesting a binary black hole system that could merge within a century.
By Hermes-Vector AI Desk
Astronomers have identified compelling evidence of two supermassive black holes orbiting each other at the center of the galaxy Mrk 501. The findings, led by Silke Britzen of the Max Planck Institute for Radio Astronomy (MPIfR), suggest the pair could merge in as little as 100 years. The study has been accepted for publication in Monthly Notices of the Royal Astronomical Society.
For decades, scientists have known that the central black hole in Mrk 501 produces an intense jet of particles moving at nearly the speed of light. However, an international research team analyzing radio observations collected over approximately 23 years discovered a second jet. This newly identified jet points in a different direction from the primary jet, which explains why it had remained hidden.
The observations provide what the researchers describe as the first direct imaging evidence of such a system at the center of a galaxy. While the black holes themselves are too close to be individually resolved, the movement of the second jet offers strong indirect evidence of a companion 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 Silke Britzen.
By tracking the position of the second jet over several weeks, astronomers observed it sweeping counterclockwise around the larger black hole. This motion suggests a regular orbital rhythm. "Evaluating the data felt like being on a ship. The entire jet system is in motion. A system of two black holes can explain this: The orbital plane sways," explains Silke Britzen.
The team calculated that the two black holes complete an orbit around each other approximately every 121 days. Their estimated separation is between 250 and 540 times the distance between Earth and the Sun. Given their masses, which range from 100 million to a billion times that of the Sun, this proximity is remarkably tight.
The study also highlights an unusual event in June 2022, when radiation from the system formed a ring-like appearance known as an Einstein ring. This phenomenon occurs when gravity bends light, creating a lensing effect. One possible explanation is that the two black holes and Earth were briefly aligned, allowing the foreground black hole to act as a lens for the second jet behind it.
The tight orbit of the black holes in Mrk 501 could lead to a merger in as little as 100 years, a short timeframe by astronomical standards. While current instruments like the Event Horizon Telescope (EHT) lack the resolution to distinguish the two black holes individually, the system is a promising target for detecting gravitational waves.
As massive objects orbit one another, they generate low-frequency gravitational waves. These waves could be detected using pulsar timing arrays (PTAs), which use the regular radio pulses of neutron stars as cosmic clocks. Supermassive black hole binaries are already considered the leading explanation for the gravitational wave background, a signal reported by collaborations such as the European Pulsar Timing Array in 2023.
"If gravitational waves are detected, we may even see their frequency steadily rise as the two giants spiral toward collision, offering a rare chance to watch a supermassive black hole merger unfold," notes co-author Héctor Olivares.
This discovery addresses a long-standing gap in astrophysics: the difficulty of identifying pairs of supermassive black holes in close orbit. While galaxy collisions are common, direct evidence of the resulting binary black hole systems has been elusive. Mrk 501 provides a unique laboratory for studying the final stages of black hole mergers. If gravitational waves are detected from this specific source, it would allow scientists to measure the orbital evolution of the pair and confirm theoretical models of how supermassive black holes grow and merge.
Sources
This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
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