Astronomers using the Event Horizon Telescope (EHT) have captured the most detailed observations yet of a binary system of supermassive black holes, located 1.6 billion light-years away in the quasar OJ287. The study reveals never-before-seen behavior in the jets emitted by these cosmic giants, providing a new window into the complex physics governing these extreme environments.
Twisted Jets and Shockwave Dynamics
The EHT, famous for imaging the first black holes (M87 in 2019 and Sagittarius A in 2022), has now turned its focus to understanding black hole jets—powerful streams of energy and particles ejected at near-light speed. Observations of OJ287 revealed two shockwaves racing down the jet at different velocities. The key finding: these shocks interact with instabilities in the surrounding magnetic fields, creating a twisted, highly structured jet unlike anything previously observed.
This is significant because jets are not just random outbursts; their structure holds clues to the black hole’s behavior and the physics around it. The observed twisted shape, combined with variations in polarization, confirms that the jet is permeated by a helical magnetic field—a fundamental property that has been theorized but never directly visualized until now.
Rapid Changes and Unexpected Motion
The team captured snapshots of OJ287 just five days apart in April 2017, revealing substantial changes in the jet’s structure and polarization. This is the shortest time interval such changes have been observed, offering an unprecedented look at how these systems evolve. The observed changes do not align with existing models based on jet precession, suggesting that shocks and instabilities play a more critical role than previously understood.
The data implies that kinetic energy dominates over magnetic energy in the jet’s inner regions, driving Kelvin-Helmholtz instabilities—vortices that twist and distort the jet’s flow. This explains the observed non-ballistic motion of particles within the jet, meaning they don’t move in straight lines as expected by simpler models. Instead, they follow a chaotic, yet predictable, path shaped by magnetic fields and shocks.
A Unique Laboratory for Black Hole Physics
OJ287 is an ideal system for these observations because its supermassive black holes periodically erupt in violent outbursts. This makes it a natural laboratory for studying black hole dynamics. The EHT’s findings confirm that shocks interact with instabilities, illuminating the helical structure of the magnetic field, and generating the observed polarization oscillations.
“These rotations in opposite directions are the smoking gun,” said research team leader José L. Gómez. “When the shock wave components interact with the Kelvin-Helmholtz instability, they illuminate different phases of the helical structure of the magnetic field, producing the polarization oscillations we observe.”
The study highlights the EHT’s growing ability to move beyond imaging and into the realm of detailed physical analysis. It confirms that high-resolution data can visualize jet instabilities, shocks, and magnetic fields in action—solidifying our understanding of these powerful phenomena.
These new observations will refine theoretical models of black hole jets, offering insights into how energy is released from these cosmic engines and how galaxies evolve.
