Scientists from the Department of Physics at Oxford University have confirmed a major prediction of Einstein’s theory of gravity, providing the first observational evidence of a ‘plunging region’ around black holes. This region is characterized by some of the strongest gravitational forces known in the galaxy.
Published in the Monthly Notices of the Royal Astronomical Society, the study utilized X-ray data from NASA’s NuSTAR and NICER telescopes to examine smaller black holes relatively close to Earth. Titled “Continuum Emission from Within the Plunging Region of Black Hole Discs,” this research marks a significant advancement in understanding black holes. Later this year, another team from Oxford plans to create the first movies of larger, more distant black holes as part of a multi-million euro European initiative.
Einstein’s theory predicts that particles near a black hole cannot maintain stable circular orbits. Instead, they rapidly plunge toward the black hole at nearly the speed of light, creating the so-called plunging region. The Oxford researchers have now studied this region in detail, using X-ray data to better understand the gravitational forces at play.
“This is the first look at how plasma, peeled from the outer edge of a star, undergoes its final fall into the centre of a black hole, a process happening in a system around 10,000 light years away,” said Dr. Andrew Mummery, who led the study. “What is really exciting is that there are many black holes in the galaxy, and we now have a powerful new technique for using them to study the strongest known gravitational fields.”
Dr. Mummery added, “Einstein predicted this final plunge, but we are the first to demonstrate it. It’s like seeing a river turn into a waterfall for the first time. We believe this is an exciting development in black hole research, allowing us to explore this final area around them. Only by understanding this final plunge can we fully grasp the gravitational force at play.”
Astrophysicists have long studied discs of material orbiting black holes to understand what happens near their surfaces. The plunging region is the final area where descent into the black hole is inevitable. There has been much debate about whether this region could be detected. The Oxford team spent years developing models, and their study confirms its detection using X-ray telescopes and data from the International Space Station.
While this study focused on small black holes close to Earth, another team from Oxford’s Department of Physics is part of a European effort to build the Africa Millimetre Telescope. This new telescope, funded with over 10 million euros, aims to make direct images of black holes. The project will also support several PhD students in astrophysics from the University of Namibia, working closely with Oxford’s Department of Physics. The new telescope is expected to capture images and film large black holes at the center of our galaxy and beyond.
