Astronomers observed a star wobbling around a spinning black hole, revealing rare evidence of Einstein’s frame-dragging effect. X-ray and radio signals show spacetime twisting every 20 days.
Astronomers have seen the orbit of a star wobbling around a black hole—a spectacular dance in the cosmos that serves as one of the very few direct confirmations of Einstein's general theory of relativity made over 100 years ago. The result, derived from periodic changes in X-ray and radio emissions in a tidal disruption event, is essentially a new window onto the workings of a spinning black hole that warps space and time around it.
Spacetime Twisted: How the Wobble Was Seen
According to the study, researchers analysing the tidal disruption event AT2020afhd noticed that both the swirling disk of stellar debris and the black hole's powerful jets were wobbling in unison, repeating roughly every 20 days. This motion matches a phenomenon called frame-dragging, where a rotating black hole literally drags spacetime around with it—an effect first described by Einstein and later quantified by Josef Lense and Hans Thirring. The wobble was detected by combining X-ray data from NASA's Swift Observatory with radio observations from the Karl G. Jansky Very Large Array.
Why This Matters for Gravity and Black Hole Physics
This is one of the most compelling pieces of evidence so far that real black holes follow the laws of general relativity even in very strong gravity regions. By confirming frame-dragging, scientists will be able to understand more clearly the spin of a black hole, the behaviour of the accretion disk, and the formation of the jets. Tests of relativity, like the detection of gravitational waves that confirmed Einstein's theory during black hole mergers, support the idea that relativity still applies, even in the most extreme conditions.
