by Scientists have confirmed, for the first time, that the fabric of space-time takes a “final beginning” at the edge of a black hole.
Astrophysicists at the University of Oxford Physics have observed this submerged area around black holes, and it helps validate a key prediction of Albert Einstein’s 1915 theory of gravity: general relativity.
The Oxford team made the discovery while focusing on the regions surrounding stellar mass black holes in binaries with companion stars located relatively close to Earth. The researchers used X-ray data collected from a range of space telescopes, including NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Probe (NICER) mounted on the International Space Station.
These data allowed them to determine the fate of the hot ionized gas and plasma, extracted from a companion star, entering the final reaches of the associated black hole. The results showed that these so-called flooded regions around a black hole are the locations of some of the strongest spots of gravitational influence ever seen in our Milky Way galaxy.
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“This is the first observation of how plasma, peeled from the outer edge of a star, about its final fall in the center of the black hole, a process occurring in a system about 10,000 light years away,” team leader and Oxford University Physics. said scientist Andrew Mummery in a statement. “Einstein’s theory predicted this final collapse, but this is the first time we have been able to demonstrate that it was happening.
“Think of it as a river turning into a waterfall – until now, we’ve been looking at the river. This is our first view of the waterfall.”
Where does the collapsing black hole come from?
Einstein’s theory of general relativity suggests that objects of mass cause the fabric of space and time, united as a single four-dimensional entity called “space-time,” to compact. Gravity arises from the curve as a result.
Although general relativity works in 4D, it can be vaguely illustrated by a rough 2D analogy. Imagine placing a sphere of increased mass on a stretched rubber sheet. A golf ball would cause a tiny, almost imperceptible dent; a cricket ball would result in larger teeth; and a giant tooth bowling ball. That is analogous to the moons, planets and stars “denting” 4D spacetime. As the mass of objects increases, so does the curvature they create, and so their gravitational influence increases. That analog rubber sheet would have a black hole like a cannon ball.
With masses equal to tens, or even hundreds, of suns compressed into a width about the width of Earth, the curvature of space-time and the gravitational influence of stellar-mass black holes can be enormous. Supermassive black holes, on the other hand, are a whole other story. They are enchanted massive, with masses equal to millions or even billions of suns, dwarfing even their stellar mass counterparts.
Returning to general relativity, Einstein proposed that the curvature of spacetime would lead to another interesting physics. For example, he said, there must be a point just outside the boundary of the black hole at which particles would not be able to follow a circular or stable orbit. Instead, matter entering this region would fall towards the black hole at near-light speeds.
Understanding the physics of matter in this hypothetical region of a black hole has long been a goal of astrophysicists. To address this, the Oxford team looked at what happens when black holes exist in a binary system with a “normal” star.
If the two are close enough, or if this star is puffed out a bit, the black hole’s gravitational influence can pull stellar matter away. Because this plasma carries angular momentum, it cannot fall straight to the black hole — so instead, it forms a flattened spinning cloud around the black hole called an accretion disk.
From that accretion disk, material is gradually added to the black hole. According to black hole feeding models, there should be a point known as the most eccentric and stable circular orbit (ISCO) – the last point where matter can remain spinning stably in an accretion disk. Any matter beyond this is in the “immersion region,” and it begins its inevitable descent to the maw of the black hole. The debate over whether this submerged region could ever be detected was settled when the Oxford team detected emissions from just outside the ISCO of accretion discs around a Milky Way black hole binary called MAXI J1820+070.
Located about 10,000 light-years from Earth and about eight suns in mass, the black hole component of MAXI J1820+070 is pulling material from its companion star as it blasts out jets at about 80% the speed of light; it is also producing strong X-ray emissions.
The team discovered that the X-ray spectrum of MAXI J1820+070 is in a “soft-state” burst, indicating emission from an accretion disk around a rotating black hole, or “Kerr,” – a full accretion disk, with its n -includes the dive. region.
The researchers say this case represents the first strong detection of emission from a submerged region on the inner edge of a black hole’s accretion disk; they mean such signals as “emissions within the ISCO.” The emissions within this ISCO confirm the accuracy of general relativity in describing the regions immediately surrounding black holes.
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To follow up on this research, a separate team from the Department of Physics in Oxford is collaborating with a European initiative to build the African Millimeter Telescope. This telescope should increase scientists’ ability to capture direct images of black holes and allow the more distant regions of collapsing black holes to be examined.
“What’s really exciting is that there are a lot of black holes in the galaxy, and we now have a powerful new technique to use them to study the strongest gravitational fields,” Mummery said.
The team’s research is published in the journal Monthly Notices of the Royal Astronomical Society.
