The cosmos has delivered a remarkable discovery for a team of scientists, unveiling one of the most elusive phenomena in the night sky. Their study, published today in Science Advances, details the first observations of a swirling vortex in spacetime caused by a rapidly rotating black hole.
This phenomenon, known as Lense-Thirring precession or frame-dragging, describes how black holes twist the spacetime around them, affecting nearby objects such as stars and causing their orbits to wobble. The research team, led by the National Astronomical Observatories at the Chinese Academy of Sciences and supported by Cardiff University, focused on AT2020afhd, a tidal disruption event (TDE) where a star was torn apart by a supermassive black hole.
Unveiling the Cosmic Dance
During this event, a swirling disk formed around the black hole, composed of the star’s remnants, from which powerful jets of matter were ejected at nearly the speed of light. Through rhythmic changes in both X-ray and radio signals emanating from the event, the team observed the disk and the jet wobbling in unison, repeating every 20 days.
First theorized by Einstein in 1913 and mathematically defined by Lense and Thirring in 1918, this observation confirms a prediction of general relativity, providing scientists with new opportunities to study black hole spin, accretion physics, and jet formation.
Expert Insights and Implications
Dr. Cosimo Inserra, a Reader in the School of Physics and Astronomy at Cardiff University and one of the paper’s co-authors, emphasized the significance of these findings:
“Our study shows the most compelling evidence yet of Lense-Thirring precession – a black hole dragging spacetime along with it in much the same way that a spinning top might drag the water around it in a whirlpool.”
Dr. Inserra further explained, “This is a real gift for physicists as we confirm predictions made more than a century ago. Not only that, but these observations also tell us more about the nature of TDEs – when a star is shredded by the immense gravitational forces exerted by a black hole. Unlike previous TDEs studied, which have steady radio signals, the signal for AT2020afhd showed short-term changes, which we were unable to attribute to the energy release from the black hole and its surrounding components. This further confirmed the dragging effect in our minds and offers scientists a new method for probing black holes.”
Methodology and Analysis
The team utilized X-ray data from the Neil Gehrels Swift Observatory (Swift) and radio signal data from the Karl G. Jansky Very Large Array (VLA) to identify the frame-dragging effect. Further analysis of the composition, structure, and properties of the cosmic matter with electromagnetic spectroscopy enabled them to describe and identify the process.
Dr. Inserra elaborated on the mechanics of the process:
“By showing that a black hole can drag spacetime and create this frame-dragging effect, we are also beginning to understand the mechanics of the process. So, in the same way a charged object creates a magnetic field when it rotates, we’re seeing how a massive spinning object – in this case, a black hole – generates a gravitomagnetic field that influences the motion of stars and other cosmic objects nearby.”
Looking Ahead
This discovery marks a significant milestone in astrophysics, opening new pathways for understanding the universe’s most mysterious objects. As Dr. Inserra reflects, “It’s a reminder to us, especially during the festive season as we gaze up at the night sky in wonder, that we have within our grasp the opportunity to identify ever more extraordinary objects in all the variations and flavors that nature has produced.”
The paper, titled ‘Detection of disk–jet coprecession in a tidal disruption event’, is now available in Science Advances, offering a comprehensive look at this groundbreaking research.
