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The image shows an accretion disk surrounding a black hole, with its inner regions swinging around. |Image source: NASA
Astronomers have observed a star wobbling in orbit around a ravenous supermassive black hole that is tearing it apart and devouring its stellar material. The observation is evidence of a rare and elusive phenomenon called “lensing-Teering precession,” or “frame drag,” in which a rapidly spinning black hole drags the surrounding fabric of space and time with its motion.
This hovering time and space Originally appeared in albert einsteinTheory of 1915 general relativitywhich predicts that objects with mass “distort” the fabric of space and time (unified into a single entity called spacetime), and that gravity results from this geometric effect. The greater the mass of an object, the greater its impact on space-time, and therefore the greater the impact of gravity. In 1918, Austrian physicists Josef Lense and Hans Thirring used general relativity to solidify the concept of giant rotating objects dragging space-time.
However, scientists have had difficulty observing this effect since then, meaning the new study could provide scientists with a new way to study spin. black holethe way they feed on, or “accretion,” material ripped from stars during tidal disruption events (TDEs), and how TDEs create powerful outflows, or jets.
“Our study shows the most compelling evidence yet of Lens-Tirling precession – that black holes drag space-time like a spinning top dragging water in a vortex,” team member Cosimo Inserra of Cardiff University in the UK said in a statement. “This is a real gift for physicists because we confirm predictions made more than a century ago. Not only that, these observations tell us more about the nature of tidal disruption events – when a star is torn apart by the immense gravitational pull exerted by a black hole.”
Watch for shaking
The team began studying Lense-Thirring precession by studying a TDE named AT2020afhd by using X-ray data collected by the NASA spacecraft Neil Gehrels Swift Observatory (Swift) and radio wave observations from Earth’s Karl G. Jansky Very Large Array (VLA).
Tidal expansion occurs when a star gets too close to a supermassive black hole, and the cosmic titan’s massive gravitational influence – which has a mass equivalent to billions of suns – creates tidal forces inside the star that squeeze it horizontally while simultaneously stretching it vertically. This process, known as “spaghettification,” creates a wisp of stellar spaghetti that twists around the black hole like noodles around a fork, forming a flat cloud called an accretion disk.
Material from the accretion disk is gradually funneled toward the black hole, but these galaxy-dominating titans are notorious swallowers of chaos, with some material being channeled away from the black hole’s poles by powerful magnetic fields. From there, the material is ejected in the form of twin jets of near-light speed plasma.
The accretion disks of the black holes produced by these TDEs and the jets they erupt from both emit bright radiation across the entire electromagnetic spectrum, and since this radiation comes directly from outside the black hole, they should be affected by Lense-Thirring precession. This effect translates into a “wobble” in the orbits of matter in the accretion disk around the supermassive black hole. In fact, while observing AT2020afhd, the team saw rhythmic changes in X-rays and radio waves from this TDE, meaning the accretion disk and jets oscillated in unison, a motion that repeated every 20 Earth days.
“Unlike previously studied TDEs that had stable radio signals, AT2020afhd’s signal showed short-term changes that we could not attribute to the energy released by the black hole and its surrounding components,” Inserra continued. “This further confirms the drag effect in our minds and gives scientists a new way to detect black holes.”
By modeling data from Swift and VLA, the team was able to confirm that these changes were the result of frame dragging. Further analysis of these results could help scientists better understand the physics behind the lens-Teering effect.
“By showing that black holes can drag space-time and create this frame-drag effect, we are also beginning to understand the mechanism of this process,” Incerra said. “So, just like a charged object creates a magnetic field as it spins, we see how a massive rotating object, in this case a black hole, can create a gravitational magnetic field that affects the motion of nearby stars and other cosmic objects.
“It’s a reminder that, especially during the holiday season, when we look up at the night sky in wonder, we have the opportunity to recognize even more extraordinary objects in the variety and flavor that nature produces.”
The team’s findings were published in the journal on Wednesday (December 10) Scientific progress.
