Einstein was right again. Scientists capture a hungry black hole tearing at spacetime and feeding on a star.
Astronomers have witnessed a star wavering in its orbit as a colossal, ravenous supermassive black hole tears it apart and consumes its stellar material. This rare event illustrates Lense-Thirring precession, also known as frame dragging, where a rapidly spinning black hole drags the surrounding fabric of space and time along with its rotation.
This twisting of spacetime traces back to Einstein’s general relativity, which posits that mass warps spacetime, and that gravity emerges from this geometric distortion. The concept of a rotating mass dragging spacetime around it was formalized in 1918 by Josef Lense and Hans Thirring, building on Einstein’s ideas.
One of the researchers, Cosimo Inserra of Cardiff University, described the finding as the most compelling evidence yet for Lense-Thirring precession. He compared it to a spinning top pulling the water in a whirlpool around it. He noted that the discovery not only confirms a century-old prediction but also sheds light on tidal disruption events (TDEs), where a star is shredded by a black hole’s immense gravity.
Watching the wobble
To probe Lense-Thirring precession, the team studied a TDE labeled AT2020afhd, analyzing X-ray data from NASA’s Neil Gehrels Swift Observatory and radio observations from the Karl G. Jansky Very Large Array on Earth.
A TDE happens when a star ventures too close to a supermassive black hole—masses that can reach billions of suns. The intense gravity stretches and squeezes the star, a process nicknamed spaghettification, which creates a long, flattened stream of matter that forms an accretion disk around the black hole.
Matter from this disk gradually feeds the black hole, but these monsters are notoriously messy eaters. Some material is channeled along the black hole’s poles by strong magnetic fields and expelled as twin jets traveling at nearly the speed of light.
Both the accretion disk and the jets glow brightly across the electromagnetic spectrum, and since these emissions originate just outside the black hole, they should be influenced by frame dragging. This effect manifests as a wobble in the motion of material in the disk around the black hole.
Indeed, during AT2020afhd, the team observed rhythmic variations in both X-ray and radio signals that indicated the disk and jet were wobbling together, completing this cycle roughly every 20 Earth days.
Inserra explained that, unlike other studied TDEs which showed steady radio signals, AT2020afhd exhibited short-term fluctuations that could not be simply attributed to the energy release itself. This strengthened the case for a dragging spacetime effect and offered researchers a new method to study black holes.
By modeling the Swift and VLA data, the researchers confirmed the observed variations align with frame dragging. Further analysis could deepen our understanding of the physics behind the Lense-Thirring effect.
Inserra added that demonstrating a black hole’s ability to drag spacetime helps illuminate the mechanics of the process. He likened it to how a rotating charged object generates a magnetic field, noting that a massive, spinning black hole can produce a gravitomagnetic field that influences nearby stars and other cosmic objects.
This work serves as a reminder—especially as we look up at the night sky during the festive season—that our exploration of the universe continues to reveal extraordinary phenomena in all their diverse forms.
The study appeared on December 10 in Science Advances.
Rob Leane is a science journalist based in the United Kingdom, with articles in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek, and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Follow him on Twitter @sciencef1rst.
