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Fascinating facts about black holes that you probably don’t know

Fascinating facts about black holes that you probably don't know

Black holes are considered one of the most mysterious objects in the universe and trap almost all the light in the surrounding environment in their strong gravitational field. But such an event does not mean that astronomers and researchers can never observe it.

Ever since Albert Einstein discovered the presence of black holes by solving the equations related to general relativity in 1915 AD/1294 AD, astronomers and astrophysicists have been looking for them until finally in recent years we were able to find direct evidence of their existence.

Until today, researchers have been able to describe the behavior of black holes at birth and understand their characteristics. Also, astronomers know that supermassive black holes live in the heart of galaxies, and some of them swallow a large amount of material around them, and explosions occur that continue for thousands of light years in space.

In 2019/1398, the Event Horizon Telescope (EHT) recorded the first direct image of the central black hole of the galaxy M87. Just this year, astronomers with this telescope were able to achieve a great achievement and record an image of the central black hole of our galaxy. The image taken of Alpha Centauri was one of the greatest goals of astronomers and physicists.

What is a black hole?

Albert Einstein was able to predict the existence of black holes for the first time with his theory of general relativity. He also discovered that matter can bend the fabric of space-time and have an effect on it. Before the introduction of relativity, astronomers thought that space is the place where phenomena in the world occur. But Einstein redefined this sentence and space played a big role in natural events.

John Wheeler has described space in the simplest possible way: “Space causes mass to move and mass causes space to bend.” If we want to have an image of space-time, we can imagine a cloth with several balls of different weight on it. Just as a basketball bends this fabric more than a tennis ball, a star bends the fabric of space-time more than a planet.

Black holes bend space-time in such a way that any matter passing by is deflected. But as these descriptions tell us, black holes are not actually a “mass” like stars and planets. It is better to call them “spacetime events”.

How are black holes born?

The birth of black holes is one of the life stages of very massive stars. When these stars are in the middle of their lives, a period known as the main sequence, they burn the hydrogen inside them and turn it into helium. This nuclear fusion creates an outward pressure equal to the inward pressure of gravity, keeping the star in equilibrium.

When the star’s hydrogen burning ends, this outward pressure also decreases and the star collapses under its own gravity. With this, the outer layers of the star become larger and a red giant is created. After that, the outer layers are scattered into space, and only the core of this star remains, known as a white dwarf. This is the life course of low-mass stars.

But when massive stars lose their helium and collapse in on themselves, enough pressure is created to produce heavier elements. This process continues until iron is produced in the core of the star.

Stars can’t make elements heavier than iron, so a supernova explosion occurs that throws all the layers of the star into the surrounding space, leaving only a core. However, for some more massive stars, this collapse stops and becomes so dense that a teaspoon of it weighs 4 billion tons. Such a mass is known as a neutron star.

Of course, this does not happen to most massive stars, and no phenomenon can stop the gravitational collapse of the star, and eventually, black holes with the mass of one star are created.

Facts about black holes

In the rest of this article, we discuss five interesting scientific facts about black holes that you probably don’t know about.

1. Our sun will never become a black hole

In about 4.5 billion years, our star will run out of hydrogen and expand to become a red giant. The outer layers of the Sun expand until they reach the orbit of Mars and engulf all the inner planets, including Earth.

But since our star is low-mass compared to other stars, it follows the evolution trajectory of normal stars and eventually becomes a white dwarf.

2. Supermassive black holes are at the center of galaxies

Black holes with the mass of stars have a mass of 3 to 10 times the mass of the Sun, but supermassive black holes are millions or even billions of times the mass of the Sun. Of course, medium-sized black holes also exist, but finding them has been difficult until now.

Since there are no stars of such mass in nature to create supermassive black holes, their existence has been a puzzle to astrophysicists until now. Of course, they suggest that such objects are created by a hierarchy of merging black holes.

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Image of the central black hole of the Milky Way (Sgr A) and M87

Researchers hypothesize that black holes of the same mass will merge and form larger black holes. Of course, what we know well until today is that supermassive black holes live in the center of galaxies.

3. Light cannot escape from black holes

When you approach a black hole, the first boundary you see around this singularity is the event horizon. The event horizon is the boundary from which the black hole’s gravitational effect becomes so strong that even light cannot escape.

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This feature of black holes makes them invisible to us and no light is reflected from them. If you understand the escape velocity well, you will also understand the reason for this happening. If any object wants to escape from the gravitational field of a mass, it must reach a certain speed. This escape velocity for Earth’s gravitational field is approximately 11.5 km/s.

The heavier the mass, the faster it escapes. Now we know that the gravitational field of a black hole is so great that even light with a speed of 300,000 kilometers per second cannot escape from it.

4. The laws of physics do not work at the center of black holes

When the solution of an equation tends to infinity, physicists wonder if something is missing in those calculations or not known at all. Until today, all the calculations made by researchers to measure the singularity of the center of a black hole have ended in unknown answers.

Such an occurrence shows that we should not look at a singularity as a physical situation. A singularity is a point where the volume of matter has shrunk so much that an infinite density is created at its center and strongly bends space-time.

Of course, it is better to say that the laws of modern physics fail to describe such a phenomenon and we need a newer physics for that. Besides, to explain such a phenomenon, we need the combination of two important theories of today, general relativity, which is used to describe the world in cosmic dimensions, and quantum mechanics, which describes the subatomic world, are not compatible and are not combined until today.

Until we get a quantum theory of gravity, we cannot describe gravity on a very small scale like inside black holes.

5. What would happen if we fell into a black hole?

Suppose an astronaut approaches a black hole. By the time this astronaut reaches the event horizon, there will most likely be nothing left of his body, and if he does, it will disappear into the center of the black hole, where we don’t know what’s going on.

Of course, even before the astronaut reaches the event horizon, his life is endangered by “tidal disruption events”. These gravitational or tidal forces are so strong that black holes can tear apart stars.

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When the astronaut approaches the black hole, the part of his body that is closer to the black hole is affected by these forces and is simultaneously compressed in the direction perpendicular to it. This is a process known among astronomers as spaghettification, and it’s not as funny as it sounds!

If a group of astronauts watch the fall of their astronaut friend from inside their spaceship, they will never see it cross the event horizon. Since light can never escape the event horizon, they will never see their friend cross this boundary, and he will be seen there for a very long time.

Things we don’t know about black holes

One of the most pressing issues in cosmology today is what happens at the center of black holes, in that mysterious singularity? Do black holes die? And if this happens, why and how?

Before his death in 2018/1397, Stephen Hawking realized that black holes emit something from themselves into the outer space and, in other words, “evaporate”. He explained that after a long time, perhaps even longer than the life of the universe, black holes will emit infrared radiation, which was later known as Hawking radiation.

Of course, such an event leads to a case called the Hawking paradox. According to the laws of quantum mechanics, information is not lost, but something must have happened to the material that carried this information into the black hole.

Until today, many studies have been done to understand this phenomenon, but these studies must continue to get the information we don’t have about black holes today.

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