Scientists Spot Black Hole Twisting Space-Time While Devouring Star

Astronomers have witnessed a rare and powerful event in space where a star is being ripped apart by a supermassive black hole while wobbling in its orbit. This wobble has given scientists clear evidence of a phenomenon known as Lense-Thirring precession, also called frame dragging. In this effect, a fast-spinning black hole pulls and twists space and time around itself as it rotates. The observation not only supports a key prediction made over a century ago but also opens a new window into understanding how black holes behave, reported Space.com.

The concept of massive objects' effects on space and time stems from Albert Einstein's theory of general relativity, presented in 1915. According to this theory, massive objects bend space and time, and this bending is felt as gravity. The greater the mass of an object, the stronger its effect on space-time.

In 1918, Austrian physicists Joseph Lenz and Hans Thirring further developed this idea. Based on Einstein's theory, they demonstrated that if a massive object rotates rapidly, it drags space-time along with it. However, directly observing this effect, especially around black holes, has been difficult for scientists until now.

New research has provided strong evidence of this frame-dragging effect. This study opens a new avenue for scientists to understand how black holes rotate, how they pull surrounding matter, and how tidal disruption events, or TDEs, create extremely powerful jets.

Cosimo Inserra of Cardiff University explained that this study provides the most convincing evidence yet of Lense-Thirring precession. It showed that a black hole drags space-time along with it, much like a spinning top pulls water into a vortex. He said this confirms predictions made over a century ago and also helps understand how TDEs occur when a star is destroyed by a black hole's extremely powerful gravitational pull.

Researchers studied a tidal disruption event named AT2020afhd. They used X-ray data from NASA's Neil Gehrels Swift Observatory and radio waves from the Karl G. Jansky Very Large Array on Earth.

TDEs occur when a star comes very close to a supermassive black hole, which can be billions of times heavier than the Sun. The black hole's gravity compresses and pulls the star together. This process is called spaghettification. The star then collapses into a flat cloud of matter called an accretion disk, which continues to revolve around the black hole.

Some of this material is absorbed into the black hole, while the rest is ejected from its poles in the form of powerful jets emanating at nearly the speed of light.

Both the accretion disk and jet shine brightly in X-rays and radio waves. Because they form very close to the black hole, the effects of frame-dragging are clearly visible. This causes a slight wobble in the motion of the disk and jet.

While studying AT2020afhd, scientists observed regular fluctuations in the X-ray and radio signals. These changes repeated every 20 days, suggesting that the disk and jet were moving in sync.

Inserra explained that while previously studied TDEs had stable radio signals, AT2020afhd showed short-term variations that could not be explained by normal energy emissions. This strengthens the evidence for frame-dragging and opens a new way to understand black holes.

After modeling data from Swift and the VLA, the team confirmed that the observed variations were caused by frame-dragging. Further research could further elucidate the physical processes behind this effect.

Inserra explained that just as a rotating charged object produces a magnetic field, a massive, rotating black hole produces a gravitational-magnetic field that affects the motion of surrounding stars and matter. He said that such discoveries remind us that the universe still holds many extraordinary mysteries that remain to be understood.

The study was published on Wednesday, December 10, in the journal Science Advances.