To understand how black holes twist the universe, it helps to first understand spacetime. Spacetime is the four-dimensional fabric of the universe that combines the three dimensions of space with time. According to Albert Einstein’s theory of general relativity, massive objects bend and shape the spacetime around them. The more massive an object is, the more it curves spacetime, affecting the motion of matter and how time flows around it.
This theory predicts a phenomenon known as Lense-Thirring precession, also referred to as frame dragging, in which a rotating black hole pulls on nearby matter and even twists spacetime around it. Near a black hole, spacetime becomes so warped that time slows down and space curves dramatically. When a star is pulled apart by a black hole, its debris forms a fast-spinning disk around the black hole, while powerful jets of material shoot outward at nearly the speed of light. Due to many observational challenges of these phenomena, including the transient nature of the disk and jet, viewing angle effects, and contamination from other sources of variability, the Lense-Thirring precession is extremely difficult.
Recently, in a paper published in Science Direct, astronomers reported the observation of AT2020afhd, a tidal disruption event (TDE) that occurred when a star was torn apart after wandering too close to a supermassive black hole. By tracking X-ray and radio patterns for twenty days, astronomers saw the accretion disk and jets from the destroyed star “wobble” together in a quasi-periodic variation. This finding provides one of the strongest pieces of evidence yet of the Lense-Thirring precession. It also deepens the scientific community’s understanding of disk-jet physics and offers a new way to measure black hole spin, allowing scientists to measure how much black holes warp spacetime.
Dr. Cosimo Inserra, one of the paper’s co-authors, says, “It’s a reminder to us, especially during the festive season as we gaze up at the night sky in wonder, that we have within our grasp the opportunity to identify ever more extraordinary objects in all the variations and flavors that nature has produced.”