An illustration shows a black hole causing a “plunging” warp in spacetime. (Image credit: Robert Lea (created with Canva))
Scientists have confirmed, for the first time, that the very fabric of spacetime takes a “final plunge” at the edge of a black hole.
The observation of this plunging region around black holes was made by astrophysicists at Oxford University Physics, and helps validate a key prediction of Albert Einstein’s 1915 theory of gravity: general relativity.
The Oxford team made the discovery while focusing on regions surrounding stellar-mass black holes in binaries with companion stars located relatively close to Earth. The researchers utilized X-ray data collected from a range of space telescopes, including NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR)and the International Space Station’s mounted Neutron Star Interior Composition Explorer (NICER).
This data allowed them to determine the fate of hot ionized gas and plasma, stripped from a companion star, taking a final plunge at the very edge of its associated black hole. The findings demonstrated that these so-called plunging regions around a black hole are the locations of some of the strongest spots of gravitational influence ever seen in our Milky Way galaxy.
“This is the first look at how plasma, peeled from the outer edge of a star, undergoes its final fall into the center of a black hole, a process happening in a system around 10,000 light years away,” team leader and Oxford University Physics scientist Andrew Mummery said in a statement. “Einstein’s theory predicted that this final plunge would exist, but this is the first time we’ve been able to demonstrate it happening.
“Think of it like a river turning into a waterfall – hitherto, we have been looking at the river. This is our first sight of the waterfall.”
A “normal” star is in a binary system with a black hole with mass following from the former to the latter (Image credit: ICRAR)
Where does the black hole plunge come from?
Einstein’s theory of general relativity suggests that objects with mass cause the very fabric of space and time, united as a single four-dimensional entity called “spacetime,” to warp. Gravity arises from the resulting curvature.
Though general relativity operates in 4D, it can be vaguely illustrated through a rough 2D analogy. Imagine placing spheres of increasing masses onto a stretched rubber sheet. A golf ball would cause a tiny, almost imperceptible dent; a cricket ball would lead to a larger dent; and a bowling ball a massive dent. That’s analogous to moons, planets and stars “denting” 4D spacetime. As an object’s mass increases, so does the curvature they cause, and thus, their gravitational influence increases. A black hole would be like a cannonball on that analogous rubber sheet.
With masses equivalent to tens, or even hundreds, of suns compressed into a width around that of Earth, the curvature of spacetime and the gravitational influence of stellar-mass black holes can become quite extreme. Supermassive black holes, on the other hand, are a whole other story. They’re hugely massive, with masses equivalent to millions or even billions of suns, dwarfing even their stellar-mass counterparts.
Returning to general relativity, Einstein suggested this curvature of spacetime leads to other interesting physics. For instance, he said, there must be a point just outside the boundary of the black hole at which particles would be incapable of following a circular or stable orbit. Instead, matter that enters this region would plunge toward the black hole at near-light speeds. […]
Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.
More: Right again, Einstein! Scientists find where matter ‘waterfalls’ into black holes
