Astronomers have recently spotted a star wobbling in its orbit around a supermassive black hole. This black hole is tearing the star apart and gobbling up its material. This rare event is linked to something called “Lense-Thirring precession” or “frame dragging,” where a fast-spinning black hole pulls space and time along with it.
The idea of frame dragging comes from Albert Einstein’s theory of general relativity from 1915. Einstein proposed that massive objects warp space and time. The more massive an object, the stronger its gravitational pull. Years later, in 1918, physicists Josef Lense and Hans Thirring expanded on this by describing how rotating objects can drag spacetime with them.
Despite the theory being over a century old, scientists found it hard to see this effect directly. However, the new research sheds light on how black holes consume stars and create energetic jets. According to Cosimo Inserra from Cardiff University, this observation provides strong evidence for frame dragging, likening it to how a spinning top pulls water around it in a whirlpool.
The study focused on a star designated AT2020afhd, using data from NASA’s Neil Gehrels Swift Observatory and radio observations from the Karl G. Jansky Very Large Array (VLA). A tidal disruption event (TDE) happens when a star gets too close to a supermassive black hole. The intense gravitational forces stretch it vertically and squeeze it horizontally, a process known as spaghettification. This creates an accretion disk, a swirling mass of debris around the black hole.
Matter from the accretion disk feeds the black hole, but it’s not a tidy process. Some material is ejected as high-speed jets, creating a dynamic environment. Both the accretion disk and the jets emit bright signals across the electromagnetic spectrum, which are influenced by frame dragging. During their observations of AT2020afhd, the researchers noted rhythmic changes in X-rays and radio waves, indicating the accretion disk and jets were wobbling together in 20-day cycles.
Inserra noted that unlike previous TDEs, AT2020afhd showed rapid changes in its signals, suggesting the frame-dragging effect is at work. By analyzing data from Swift and VLA, the team confirmed these variations were caused by this gravitational dragging.
This discovery allows scientists to explore how a spinning black hole creates a gravitomagnetic field that affects nearby celestial bodies. It highlights the connection between massive objects and their influence on space and time. Inserra emphasized that as we look up at the night sky, we are reminded of the wonders waiting to be discovered.
For those interested in understanding more, the research was published in Science Advances on December 10. You can find the full study here.
