First evidence that ‘submersible regions’ exist around black holes in space

An international team led by researchers at Oxford University Physics has proved that Einstein was correct about a key prediction about black holes. Using X-ray data to test Einstein’s theory of gravity, their study provides the first observational evidence that a “submergence region” exists around black holes: an area where matter stops spinning around the hole and instead falls straight in. Additionally, the team found that this region exerts some of the strongest gravitational forces yet identified in the galaxy. The findings are published in Monthly Notices of the Royal Astronomical Society.

The new findings are part of a wider investigation into the extraordinary mysteries surrounding black holes by astrophysicists at Oxford University Physics. This study focused on the smallest black holes relatively close to Earth, using X-ray data collected by NASA’s Spectroscopic Space Telescope Array (NuSTAR) and Inner Composition Neutron Star Telescopes. Explorer (NICER). Later this year, a second Oxford team hopes to get closer to recording the first videos of larger and more distant black holes as part of a European initiative.

Unlike Newton’s theory of gravity, Einstein’s theory states that close enough to a black hole it is impossible for particles to reliably follow circular orbits. Instead, they “plunge” toward the black hole at the speed of light. The Oxford study assessed this region in depth for the first time, using X-ray data to better understand the force generated by black holes.

“This is the first look at how plasma, stripped from the outer edge of a star, undergoes its final collapse into the center of a black hole, a process that occurs in a system about ten thousand light-years away,” said Dr. Andrew Mummery. , of Oxford University Physics, who led the study. “What’s really exciting is that there are many black holes in the galaxy, and we now have a powerful new technique to use them to study the strongest known gravitational fields.”

“Einstein’s theory predicted that this final dip would exist, but this is the first time we have been able to demonstrate that it is happening,” continued Dr. Mummery. “Think of it as a river turning into a waterfall so far we’ve seen the river. This is our first view of the waterfall.”

“We believe this represents an exciting new development in the study of black holes, allowing us to probe this final region around them. Only then can we fully understand the gravitational force,” added Mummery. “This final plunge of plasma occurs at the edge of a black hole and shows matter responding to gravity in its strongest possible form.”

Astrophysicists have for some time tried to understand what happens near the surface of a black hole, and do so by studying disks of material orbiting around them. There is a final region of spacetime, known as the sink region, where it is impossible to stop a final descent into the black hole and the surrounding fluid is effectively doomed.

The debate among astrophysicists has been going on for decades as to whether the so-called submerged region would be detectable. The Oxford team has spent the past two years developing models for it and, in the newly published study, demonstrates its first confirmed detection using X-ray telescopes and data from the International Space Station.

While this study focuses on small black holes closer to Earth, a second research team from Oxford University Physics is part of a European initiative to build a new telescope, the Africa Millimeter Telescope, which would greatly improve our ability to directly image black holes. . Over €10 million in funding has already been secured, part of which will support several first PhDs in astrophysics for the University of Namibia, working closely with the University of Oxford Physics team.

The new telescope is expected to make it possible to observe and film, for the first time, the supermassive black holes at the center of our galaxy, as well as far beyond. As with small black holes, large black holes are expected to have a so-called “event horizon,” pulling material from space toward their center in a spiral as the black hole spins. These represent almost unimaginable sources of energy, and the team hopes to observe and film them while spinning for the first time.

The study, “Persistent emission from within the submerged region of black hole disks,” is published in Monthly Notices of the Astronomical Society.