Chapter 406： : Swamp, Traces of the Dragon【Anti-theft (1/2)

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Sina Technology News, August 27, Beijing time, in all astronomical concepts, black holes may be the most bizarre one. The density of the black hole is so high that even the light cannot escape, just like a dark and terrifying behemoth. Since the general laws of physics are not applicable to black holes, black holes seem to be created for science fiction. However, numerous direct and indirect evidences show that black holes do exist in the universe.

Einstein's prophecy

Black holes are the inevitable result of Einstein's theory of general relativity.

German astronomer Karl Schwarzschild first predicted the existence of black holes in 1916, and believed that this was an inevitable result of Einstein's theory of general relativity. In other words, if Einstein's theory is correct (all evidence points to this), then black holes must exist. The research of Roger Penrose and Stephen Hawking further consolidated the theoretical basis for the existence of black holes. Its research shows that after any celestial body collapses into a black hole, a singularity will be formed, and the laws of traditional physics all fail at this point.

Gamma Ray Burst

Observing equipment on Earth has detected some gamma-ray bursts that were generated during the birth of black holes.

In the 1930s, Indian astrophysicist Subramanyan Chandrasekha conducted research on the outcome of the star's nuclear fuel exhaustion. He found that the final result depends on the mass of the star. If the star is very large, say 20 times the mass of the sun, the dense core of the star (the mass of the core alone can be as high as two or three times the mass of the sun) will collapse inward until it becomes a black hole. The stellar core collapses extremely fast, only a few seconds before and after, during which it will release amazing energy in the form of gamma-ray bursts, which is equivalent to the sum of the energy released by an ordinary star in a long lifetime. Telescopes on Earth have detected multiple gamma-ray bursts, some of which were emitted by galaxies billions of light-years away, indicating that we have really observed the birth of black holes.

Gravitational waves

The picture shows the conceptual drawing of gravitational waves drawn by the artist. The gravitational action between the two black holes will form ripples in time and space and spread outward in the form of gravitational waves.

Black holes are not always alone, and sometimes they appear in pairs and revolve around each other. The gravitational action between the two black holes will form ripples in time and space and spread outward in the form of gravitational waves. This is also one of the predictions put forward by Einstein's theory of relativity. With the help of observatories such as LIGO and Virgo, we now have the ability to detect gravitational waves. In 2016, scientists first announced the discovery of gravitational waves caused by the merger of two black holes. Since then, we have detected multiple gravitational wave events. As the detector's sensitivity continues to increase, scientists have also detected gravitational waves generated by events other than black hole mergers, such as the collision of black holes and neutron stars.

Invisible companion

The picture shows the imaginary orbits of several celestial bodies in the Samsung system HR6819.

What can produce gamma-ray bursts or gravitational waves are high-energy events that occur in a short period of time, perhaps half of the universe can be seen. But considering their nature, most black holes are undetectable. Black holes do not emit any light or radiation, so they can hibernate in space silently, and astronomers are unaware of their existence. However, there is a way to detect their existence: using the gravitational effect of black holes on other stars. In 2020, when astronomers were observing the seemingly ordinary binary star system HR6819, they found that the trajectories of the two stars are somewhat strange, unless there is a completely invisible celestial body in the system to explain this phenomenon. After calculating its mass, the researchers realized that there is only one truth: this celestial body must be a black hole. It is only a thousand light-years away from the earth and is located within the Milky Way galaxy. It is the closest black hole to the earth discovered so far.

X-ray

The black hole CygnusX-1 is sucking the huge blue companion star on the side.

In 1971, when scientists were studying a dual star system called CygnusX-1 in the Milky Way, they first observed evidence of the existence of black holes. The X-rays produced by this system are extremely bright, but these rays do not come from the black hole or its visible companion, but are produced by the accretion disk formed when the black hole absorbs the stellar material. Just like the binary star system HR6819 just mentioned, astronomers can also use the trajectory of the visible star to estimate the mass of the invisible celestial body in the CygnusX-1 system. The final calculation result is about 21 times the mass of the sun, and considering that the space occupied by the celestial body is small, it can only be a black hole, and there is no need to consider other possibilities at all.

Supermassive black hole

There is also a supermassive black hole in the center of the Milky Way.