For the first time, astronomers have directly observed that a rapidly spinning black hole is "dragging" the surrounding space-time, causing it to undergo measurable periodic oscillations. This phenomenon confirms a key prediction made by Einstein's general theory of relativity more than a hundred years ago.This breakthrough comes from the long-term monitoring of a tidal disruption event in which a star is torn apart by a black hole. It provides a new window for the scientific community to study the rotation of black holes, the structure of accretion disks, and the formation mechanism of jets.
The research was led by the National Astronomical Observatory of the Chinese Academy of Sciences and participated by Cardiff University and other institutions. The observation target was the tidal disruption event code-named AT2020afhd - a star was torn apart after breaking into the "death radius" of a supermassive black hole, and its remains formed a bright accretion disk and ejected material jets approaching the speed of light. By analyzing the X-ray and radio signals emitted by the event, the team found that both the accretion disk and the jet were swinging synchronously, with a cycle of about 20 days, showing a stable coordinated "swing" rhythm.
Research points out that this wobble is the "Lense-Thirring precession" predicted by general relativity, also known as the "reference frame drag effect": a rotating black hole will distort and drag the surrounding space-time, causing the orbital direction of nearby matter to slowly change. Previously, scientists mainly inferred the existence of this effect through indirect methods, but this time it is the first time that a clear signal of the co-precession of the disk and the jet has been directly captured in the black hole accretion disk-jet system.
In this event, material from the torn star quickly fell into the black hole, forming a high-speed rotating accretion disk and driving high-energy jets ejected along the black hole's axis of rotation. Observations show that the disk and the jet do not point stably in a single direction, but "nod" as a whole in space. This coordinated change is difficult to explain by traditional fluctuations in energy release, but it is highly consistent with the precession characteristics caused by the dragging of space and time.
Cosimo Inserra of Cardiff University's School of Physics and Astronomy, a co-author of the paper, said that this study provides the strongest evidence yet of Lens-Tilling precession. "Like a spinning top churning out eddies in water, the black hole is dragging the space-time around it." He pointed out that unlike previous tidal disruption events where the radio signal was relatively stable, the radio signal of AT2020afhd had short-term changes that could not be simply attributed to fluctuations in energy output, further strengthening the explanation of space-time drag.
To identify this effect, the scientific research team comprehensively utilized data from multiple telescopes, including space telescopes in the X-ray band and radio observations from the ground-based Karl Jansky Very Large Antenna Array (VLA), while conducting a detailed analysis of the electromagnetic spectrum of the event. Spectral studies help scientists clarify the composition and structure of the accreted material, thereby testing in theoretical models whether the geometric configuration and dynamic behavior of the disk-jet system are consistent with the predictions of frame drag.
The researchers emphasized that this discovery not only once again verifies the validity of general relativity in extreme gravitational environments, but also provides new tools for measuring the spin of black holes, understanding how matter falls into black holes, and how high-energy jets are formed. Tidal disruption events like AT2020afhd are expected to become natural laboratories for systematically detecting the "space-time vortex" of black holes in the future, helping humans to further describe the true appearance of the most extreme celestial bodies in the universe.
Relevant results have been published in the journal "Science Advances" on December 10, 2025. The paper is titled "Detection of disk-jet coprecession in a tidal disruption event" (Detection of disk-jet coprecession in a tidal disruption event). The research team believes that with the new generation of multi-band sky surveys and high-sensitivity telescopes put into operation, humans are expected to capture similar signals in more tidal disruption events and systematically depict the "gravitational vortex" of black holes dragging space and time.
Compiled from /ScitechDaily