Einstein predicted it over a century ago. In 2020, a star got torn apart near a black hole, and for the first time, we watched the prediction come true.
When a rotating black hole spins fast enough, it doesn't just pull on matter around it — it actually twists spacetime itself, like water spiraling around a drain. Physicists call this frame-dragging, and catching it in action has been one of astronomy's white whales. Now, a team led by researchers at China's National Astronomical Observatories has done it.
The breakthrough came from an event called AT2020afhd, where a supermassive black hole shredded a star. As the star's remains formed a disk around the black hole, intense jets of material shot outward at nearly the speed of light. The researchers tracked the X-ray and radio signals from this cosmic wreckage using NASA's Swift Observatory and the Karl G. Jansky Very Large Array, watching for patterns that would reveal the black hole's gravitational grip on spacetime itself.
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Start Your News DetoxWhat they found was a wobble — a repeating cycle every 20 days, visible in both the X-ray and radio data. The disk and jet were swaying together, dragged along by the spinning black hole's twisting of spacetime around it. It's exactly what Einstein's general relativity predicted, and exactly what physicists have been hoping to see.
"This is a real gift for physicists," says Dr. Cosimo Inserra from Cardiff University, one of the paper's co-authors. "We confirm predictions made more than a century ago." But the implications go deeper. By watching this frame-dragging effect in action, researchers can now measure how fast the black hole is spinning, understand how accretion disks work, and figure out how black holes launch those relativistic jets into space.
Think of it this way: a spinning charged object creates a magnetic field. A spinning black hole, it turns out, creates something similar — a gravitomagnetic field that influences everything nearby. Now we have proof.
The findings, published in Science Advances, represent the kind of moment that reminds you why people spend careers staring at the sky. A century-old prediction, confirmed by a star's violent death millions of light-years away, observed by instruments on Earth. What comes next is the harder part: using this technique to study dozens more black holes and understanding the mechanics of how these cosmic engines actually work.
