Einstein's Theory of Relativity Verified The 'Plunging Region' of Black Holes Discovered

On May 28th, TapTechNews reported that an international team led by scientists from the University of Oxford has confirmed a key prediction of Einstein's General Theory of Relativity regarding black holes, proving for the first time the existence of a 'plunging region' around a black hole, that is, a region where matter no longer swirls around the black hole like a vortex but directly falls into it.

In addition, they also found that this region exhibits the strongest gravitational force currently known in the Milky Way. The relevant paper was published in the latest issue of the Monthly Notices of the Royal Astronomical Society (TapTechNews attached DOI: 10.1093/mnras/stae1160).

Scientists from the Department of Physics at the University of Oxford conducted a study titled 'Continuous Radiation in the Downstream Region of a Black Hole Disk' and used a series of X-ray data to study a relatively nearby small black hole on Earth, including NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) installed on the International Space Station.

It is worth noting that as part of a multi-million-euro European project, another Oxford University team plans to make a film about black holes later this year, involving black holes that are much larger and farther away than the aforementioned one.

Einstein's General Theory of Relativity proposes that objects with mass cause the structure of space and time to distort. Simply put, 'pacetime' is a four-dimensional entity formed by the unification of space and time, and gravity is the 'fruit' resulting from this distortion.

Although the General Theory of Relativity belongs to a theory in four-dimensional spacetime, we can use a rough two-dimensional analogy to help everyone understand. Imagine placing a ball on a stretched rubber sheet, and this sheet will create a depressed region due to the increase in the mass of the sphere, similar to how the Moon, planets, and stars 'dent' four-dimensional spacetime. The greater the mass of the object, the greater the curvature of spacetime they cause, and the stronger the gravitational influence, and black holes are currently the known celestial bodies with the largest mass in the universe.

Returning to the General Theory of Relativity, Einstein believed that such spacetime curvature would lead to some interesting physical phenomena. For example, due to the existence of angular momentum, matter will not directly fall into a black hole but will rotate around it, so there will be a flat, rotating cloud around a black hole, which we generally call an accretion disk. Starting from the accretion disk region, matter will inevitably be gradually sucked into the black hole.

According to Einstein's prediction, there must be a point outside the boundary of a black hole where particles can no longer maintain a stable circular orbit. Instead, matter entering this region will fall towards the black hole at nearly the speed of light.

The lead researcher of this study, Dr. Andrew Mummery from the Department of Physics, said, 'This is the first time we have observed how plasma is stripped from the outer edge of a star and eventually falls into the center of a black hole, a process that occurs abou t 10,000 light-years away from us. And the most exciting thing is that there are many black holes in the galaxy, and we now have a new technology that can be used to study the known strongest gravitational fields.'

Dr. Mummery added, 'Einstein predicted this final collapse, but we are the first to confirm this theory. Imagine a river turning into a waterfall - so far, we have been observing this river, and this is the first time we have seen the waterfall. We believe this is an exciting progress in the history of black hole research that allows us to explore the final region around a black hole. And only by understanding this final collapse can we fully grasp the gravity.'

In fact, astrophysicists have long been studying the 'accretion disk' that orbits around black holes to understand the situation near the surface of such celestial bodies, and there has always been controversy about whether this 'plunging region' can be detected. The Oxford University team spent years developing models and finally used the data from X-ray telescopes and the International Space Station to confirm it.

The black hole (MAXIJ1820+070) studied by the research team is about 10,000 light-years away from the Earth and has a mass of about 8 solar masses. It is currently continuously sucking matter from its companion star and ejecting two jets at nearly 80% of the speed of light, and at the same time, it emits strong X-rays.

The research team found that the X-ray spectrum of MAXIJ1820+070 in the 'oft state' outburst period represents the radiation emitted by the accretion disk around a rotating black hole (Kerr black hole), which means that we have observed a complete accretion disk, including the 'plunging region'.

Researchers said that this discovery is the first obvious detection of radiation from the 'plunging region' near the inner edge of the black hole accretion disk. They call this signal 'emission within the innermost stable circular orbit'. These 'emissions within the innermost stable circular orbit' verify the accuracy of the General Theory of Relativity in describing the area around a black hole.

Although this research only focuses on small black holes near the Earth, another research team in the Department of Physics at the University of Oxford is participating in the African millimeter Telescope project. This telescope will greatly enhance our ability to directly obtain images of black holes. Currently, this project has received more than 10 million euros (TapTechNews note: currently about 78.7 million yuan).

Scientists believe that the African Millimeter Radio Telescope will be the first to observe and photograph large black holes located in the center of our galaxy and farther away. Like small black holes, large black holes also have an 'event horizon'. These black holes represent unimaginable energy sources, and the research team hopes to be the first to observe and photograph their rotation.