Astronomers have observed two supermassive black holes orbiting each other in an intense cosmic waltz, revealed by jets of matter exhibiting astonishing twists. The team used the Event Horizon Telescope to capture images demonstrating unprecedented helical structures within these ejections.
The quasar OJ287, located approximately 1.6 billion light-years away, likely hosts a pair of supermassive black holes. During an observation campaign in April 2017, the telescope network allowed for the distinction of two distinct shock waves propagating at different speeds in the jet.
Images of the twisted matter jet from OJ287 erupting from a distant black hole as seen by the EHT.
Credit: EHT Collaboration / E. Traianou
The Event Horizon Telescope, famous for its pioneering images of black holes like M87* and Sagittarius A*, thus demonstrates its utility beyond mere imaging. According to the researchers, this instrument allows for progress in the physics of jets, differentiating geometric effects from actual physical processes. This methodology allows for a more precise comparison between theoretical models and observed data.
Furthermore, the observations have highlighted Kelvin-Helmholtz instabilities. These are caused by the significant difference in speed between the jet, traveling nearly at the speed of light, and the much slower surrounding matter. These instabilities generate helical structures, producing a fluctuating polarization. Three distinct polarized components, exhibiting opposite rotations, have been identified.
A diagram showing the helical structure of the instabilities in the jet from OJ287.
Credit: EHT Collaboration / E. Traianou
These results challenge the simple precession models previously put forward to explain the jet's morphology. The motions that have been recorded indicate that the kinetic energy of the particles surpasses the magnetic energy in the inner regions.
The team has published its work in the journal
Astronomy & Astrophysics, offering a detailed view of the interactions between instabilities, shock waves, and magnetic fields.
An animation showing how the polarization of the jet from OJ287 changed over time.
Credit: EHT/E. Traianou Collaboration. Kelvin-Helmholtz instabilities
Kelvin-Helmholtz instabilities occur when two fluids with distinct velocities interact, generating waves and turbulence at their interface. For astrophysical jets, the matter ejected at relative speeds close to that of light encounters a much slower surrounding medium, which produces these instabilities. They materialize as deformations, visible in the structures observed by telescopes.
They play an important role in jet dynamics, as they can amplify light emissions and alter the trajectory of the matter. By compressing magnetic fields, they make certain areas brighter, thus helping astronomers map their properties.