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Black Holes: The Gravitational Monster

What is black hole? General relativity and black holes. As many types of black holes...

Starting with Newton; You know, gravity has something to do with black holes. When we talk about gravity, we have to remember Newton’s apple. Let’s not talk about Newton’s apple today; let’s talk about Newton’s cannon. The story of this cannon was told to us by the eminent scientist Newton.

Suppose there is a cannon on a hill. If they fired a cannon, what will happen? The bullet will go some distance and fall to the ground, somewhere in the plains. Thus, according to Newton’s first law of motion, the bullet is supposed to go straight. But the earth’s gravitational path is bending to the ground.

Now let’s shoot harder. But what will happen? I will go further. This time Marie fired the shot at an unimaginable speed, so loud that it covered hundreds of kilometers before falling to the ground. But the world is round. If you travel hundreds of kilometers, the round will go a little on the curved path of the earth.

Now let’s increase the speed of the bullet a lot more so that the bullet can travel around the world at once. But what will happen? Round the earth will come straight and push the cannon behind the cannon! But since it would take a long time for the shell to turn, we removed the cannon. What will happen then?

This time a funny thing will happen, the bullet will come right on the hill and go straight again. This will continue for life. (It is better to say that when firing, we assume that there is no obstruction of the wind in this way). thay sent artificial satellites into space following this principle. This is also the principle that the moon revolves around the earth.

Now again, a little gravity formula. If the mass of the earth were a little more, what would happen? The attraction of cannonballs would have increased. Then we had to apply a little more force to move the bullet so freely.

The question is if we shoot at a speed that is a little faster than the speed at which the ball is spinning around the earth? But what will happen? Then the ball will continue to revolve around the earth with a little up.

It is even possible that we fired the ball so hard that the earth could no longer pull it closer with its gravitational force. Rather, he will go straight into space, overcoming the illusion of gravity. Yes, it is possible. The speed at which the ball will not return to the gravitational pull at the lowest speed is called the speed of release of the earth.

A little calculation can show it, the greater the mass of the earth, the greater the speed of liberation. Again, the greater the distance from the center of the earth to the center of the earth, the lower the speed of release.

If you want to calculate, you will get a release velocity of 11.2 km / second on the surface of the earth. If we threw anything from the surface of the earth at this speed or more, it will go into space, not back to gravity. Spacecraft sent to other planets or moons are thrown at speeds a little faster than this.

Now let’s see the release velocity on the surface of Jupiter, 59.5 km / s. The velocity of release on the surface of the sun is 617.5 km / s. To get something out of the surface of the sun at least 618.5 km / s.

Need speed. Now let’s see the density of the sun. About one and a half times the density of water on earth. But what if its density was much higher? Then its mass would increase, or its radius would decrease.

Then the speed of release would be more.

Now suppose an object, be it a star or a planet, or a mere ball, whose mass is so much greater than its radius that the velocity of release is many times greater. Much more means more of the horrible kind. Suppose the speed of light is equal to or greater than. What will happen then?

Those who have little interest in physics know that, according to Einstein’s special relativity, an object that has mass cannot travel at speeds equal to or greater than the speed of light. Then if any other object comes close to a star or object with a speed of release equal to or greater than the light, someone will surely trap it for life.

You can’t get out because you don’t get the speed like light. The idea of ​​an object with a higher velocity of light than the speed of light has been around for so long, much like the idea of ​​a black hole.

But the idea of ​​a real black hole is not like that. For this, we need Einstein. Einstein did the next step in gravity. In the genuine sense of the word, black holes are far from explained, and I do not find the idea in Newton’s law of gravitation.

General relativity and black holes

Einstein did not see gravity the way Newton did. Einstein compared the gravitational field to the acceleration field. For this, he has to solve the field equation. Without going into the complexities of them, it can be simply said that heavy objects bend the surrounding space-time. This curved spacetime captures our senses as gravity.

The heavier the object, the greater the amount of bending. Suppose a train runs over a railway line. If the line is straight, the car will go straight. But if the line is crooked or bends in any direction, the car can no longer go straight. The curve must continue. The work of gravity is the same.

When the surrounding area bends, something has to bend to get out of that place. The very close spacing of the object bends too much. It also has to do with the momentum of the object that is moving in that curved path. We can compare the matter to a tight cloth curtain. If we place a heavy iron ball in the middle of the screen, the screen will move like a hole.

The curvature of this screen can be called the curvature of two-dimensional spacetime. If something may roll over this screen, we will force it to fall into that curvature.

With gravity, this game of curvature takes place in three-dimensional space. We associate it with time or period. Together we say four-dimensional spacetime.

Einstein explained gravity in this way, which removed some limitations of Newton’s theory. The beauty of this theory, however, is that Newton’s gravity is applied only to objects that have mass, but Einstein’s gravity is also applied to weightless particles.

Because where the road is crooked, the light has to follow the same path. This fancy scene (curvature of light) from Einstein’s theory was observed in 1919, led by Sir Eddington.

In 1918, Schwarzschild came to an extraordinary conclusion in solving Einstein’s equations. There is a limit to the density of a heavy object, the excess of which will cause the side path of the object to bend so much that nothing can come out of that curvature. In Einstein’s theory, something means all particles. No light can come out as he is.

Within that limit, we will create a special condition, which is called a singularity. Singularity is a fancy arrangement. Because, in this, the formulas we know of physics are broken. We don’t even know how the four balls other than gravity exist.

It has nothing to do with Newton’s theory of gravitation that I found something like a black hole. Even if no object could come out through that black hole, light could come from inside.

So it does not create special problems in physics. But the idea of ​​a black hole that came from Einstein’s general relativity is so strange, and everyone thought it was a theoretical thing.

For almost half a century, there was no such discussion. However, the possibility that arises from the black hole is extra incomprehensible, beyond imagination. When an object falls into a black hole, the total mass of the black hole increases slightly.

As he limits his curvature, the Schwarzschild radius also increases slightly. Since no one will ever be able to get out, will it swallow up the universe as it grows bigger little by little?

The matter does not end here. The singularity of gravity is like the singularity of the moment of the Big Bang or the Big Bang. The laws of physics do not work before Planck’s time, at the moment of the Big Bang.

We do not know how the four basic forces were then. Then when the idea of ​​a black hole was found, the question arose, is the black hole the beginning of an alternative universe?

Since we know not much about black holes or black holes, then the popular culture started with this. It created a place of great interest in everyone. Whatever happens in this case, various rumors spread in the market.

Such a black hole is a wormhole. Through this, one can reach the other end of the universe in a moment by piercing space-time. If you search, you will find that there is sci-fi science fiction in Ganda about going into a black hole. But is the matter limited to science fiction? No. The research went further.

Stephen Hawking on stage

If it ends here, we have left the matter to science fiction. But then Stephen Hawking appeared on the stage. Hawking said, “No, nothing can come out of the black hole. That’s not true.” As can be seen from quantum theory, radiation can also come out of there, which is called Hawking radiation.

Does that mean black holes aren’t really black? Like the black body, it also has radiation? Everyone sat motionlessly. If this theory is correct, not only can a black hole disappear by radiation slowly but also between quantum mechanics and the theory of gravitation.

Thus, in various experiments, all the predictions of Einstein’s theory of general relativity have come true. The latest found is the gravitational wave. But with Hawking radiation, quantum mechanics itself conflicts with the theory of relativity. But there is no chance to throw away quantum theory.

Because, in all other cases, this theory is also quite successful. So what solves this dispute? Scientists do not know yet. Because they don’t know the details of the gravity ball yet. The gravitational force seems to differ from the other four balls, and its value is very low. Only this ball actually works in an immense space. Even fancy black holes originate.

Black holes and dark matter

Dark matter accounts for 28% of the total mass of the universe. But we do not know what it is. But we see it shows the effect of a gravitational ball like an object. Meanwhile, in popular culture, black holes are just as popular as dark matter. So many people sometimes confuse black holes and dark matter.

So far, scientists have no evidence that black holes and dark matter are the same. Recent hypotheses, however, suggest that dark matter may be a primordial black hole. However, scientists have no evidence to confirm this.

However, if it is proven, the number of black holes must be considered. Because only 5 percent of the total mass-energy of the universe comprises matter we know, the remaining 26 percent is dark matter, the rest (6 percent) is dark energy. If Dark Matter is actually a black hole, then 32 percent of the Earth will be the universe of matter we know.

As many types of black holes

How can black holes be divided? We do not know their taste and smell! Since the information does not come out, it is difficult to give a definite hadith of how much of a substance it was before we made it.

Again, since it sometimes eats nearby stars or objects, it is not possible to say when it played. The substance can not divide the origin of the black hole. However, based on how the black hole was formed, scientists have the idea that there are three types of black holes.

These are primordial, stellar, and supermassive black holes in the center of the galaxy. Apart from this, there are some theories about intermediate-mass black holes in the middle of stellar and supermassive black holes.

Primordial black hole

In gravitational contraction, the density has to be much higher if there is to be a singularity (black hole). The density of the universe was much higher at the time of the Big Bang.

So it is possible to make a black hole. Hawking showed in 1971 that the mass of a black hole might be much less than that of the Sun. As a result, it is possible to create a black hole of 106 kg to several thousand solar masses during the Big Bang.

However, according to estimates, all black holes weighing less than 1,011 kg have already disappeared through Hawking radiation.

The mass of black holes that were discovered in Ligo a few days ago is much larger than the mass of stellar black holes. So they created these black holes just after the Big Bang. That means there are also primordial.

One month after the first announcement in March 2016, a team of three separate researchers claimed they formed these black holes at the beginning of the universe.

As mentioned earlier, this primordial black hole solves the problem of dark matter. Many researchers have blamed black holes of this nature for the origin of supermassive black holes inside the galaxy.

Stellar black holes

The most well-known type of black hole in the black hole developed from them. The gravitational objects that produce helium in hydrogen fusion are called stars. With stars, hydrogen is the fuel, and helium is the product. The star’s gravitational force causes the temperature to rise a lot.

Once that temperature has reached the temperature required for the nuclear fusion reaction. Then the hydrogen nuclei attach. In this way, they emit tremendous energy from inside the stars.

This again creates an outward pressure on the gas. Again the star pulls the gravitational force towards the center for its own mass. By maintaining the balance of these two balls, they get a fairly stable shape and continue to emit energy at a constant rate. In such cases, the star is called the main sequence star (Main sequence star).

Under normal conditions, helium no longer fuses inside stars. As a result, at some point, they run out of fuel. For this reason, the pressure of the exhaust gas can no longer withstand gravity.

As a result, gravity causes the star to shrink. The stars below 0.5 solar eclipses gradually turn into white dwarf stars. At 0.5 to 10 solar stars, the temperature rises considerably during the contraction, and the fusion of helium begins. The stars are called red monsters. Our sun will also turn into a red monster.

Fusion of red monsters can go up to iron. It then turns into a planetary nebula and turns into a white dwarf. With heavy stars, most of the outer layer disappears into space under the pressure of their radiation. And the fusion inside continues. Once iron was made infusion.

The fusion can no longer continue. Then, usually, supernovae explode and most of the stars spread out into space.

If the mass of a star remaining after a supernova explosion exceeds the lunar limit (1.4 solar masses), the degeneracy pressure of the electrons in the middle of the star cannot prevent contraction because of gravity. As a result, electrons and protons are added and converted into neutrons.

Only neutrons remain in the star, so this type of star is called a neutron star. Now, if the mass of neutron stars exceeds the TOV or Tolman-Oppenheimer-Volkov limit (also known as the LOV or Landau-Oppenheimer-Volkov limit), the neutron star becomes a black hole in further contraction. The value of the TOV range is between 2 to 3 solar.

If a star has a mass of 15-20 solar masses in the main sequence star, it may exceed the TOV limit even after a supernova explosion. A black hole results from a star with a mass greater than 15-20 solar masses. The mass of the black hole thus developed is usually about 5-20 solar masses.

Supermassive black hole

These are truly massive or massive. The mass of the sun is about 3 lakh 33 thousand times the mass of the earth. The mass of the sun is called solar mass. The mass of supermassive black holes can range from a few million to a few hundred billion solar masses.

We mainly found them inside the galaxy. Each galaxy (also called the center) is thought to have one supermassive black hole. The traces of these black holes can be found by observing the motion of stars in the center of the galaxy. But there is an interesting thing, what is the density of the black hole? It may seem so, of course, too much. But in the case of black holes, the density is disproportionate to the square of the mass. So the density of supermassive black holes can be even lower than water!

The black hole in the center of our Milky Way is called Sagittarius A *, with a mass of about 4.1 million solar masses. There is no definitive explanation for how black holes of this species are formed.

However, if there is a black hole at the beginning of the formation of the galaxy, it can increase its mass over time by taking mass from nearby stars or by combining it with other black holes.

According to many scientists, these black holes formed during the Big Bang. Because the size of the universe was much smaller, it is possible to create such a huge black hole. Or at least create a black hole of moderate mass, which can later take on such an immense size with more mass.

The black hole in the middle mass

So far, scientists could not identify too many black holes—only about 120. There is no black hole in the middle mass (100 to 10 thousand solar masses).

Tal Alexander of the Weizmann Institute of Science in Israel and Ben Bar-Or of Princeton University offer some explanations why there is no mass between supermassive and stellar black holes outside of the above three types of black holes.

A study published in the June 19 issue of the journal Nature Astronomy showed that the fact that they found it did not mean that there were no such massive black holes. Maybe there are, but their numbers are much less likely. As black holes take mass from other stars their mass increases day by day.

According to them, a black hole consumes about one solar year of food every 10,000 years or increases its mass. So even though primordial black holes have formed in the middle, they have become supermassive for hundreds of millions of years.

However, if there is a massive black hole in the middle, it can be found in very dense regions of the universe. The problem in these areas is that it will be difficult to find them in the crowd of other stars. But the hope is that day by day; the technology is getting better; it sounds like the message of hope.

In search of black holes,

Some say from the beginning that the black hole allows nothing to come back. It also eats light. It is difficult to find in such a situation. Yet scientists have come up with some ideas to find out. They found the first black hole in 1974 from X-ray radiation of the accretion disc. Its name is Signus X-1.

There were three ways to identify black holes before. Seeing the motion of the surrounding stars, the radiation of the accusation disk, and the gravitational lensing. Now added gravitational waves.

Black holes from stellar motion

The black hole tried to hide by blocking the light, but gravity caught it. The gravitational field of the black hole is naturally quite strong. As a result, when found in the scope, it forces itself to orbit by twisting the path of another star in the vicinity. The mass of the central object can be determined only by identifying the light of those bright stars and determining the orbit. This is how all the dimensions of the star at Sagittarius inside our galaxy have been determined.

Radiation of the accus disc

Larger stars use gravity to absorb mass from a nearby star. As a result, we form accretion disks around the heavy stars from those stars.

Because of intense friction, the temperature of the accretion disk rises so much that it continuously emits black body radiation, most of which is emitted as X-rays. In this way, about 40 percent of the total mass is converted into energy (whereas infusion between stars, only about 0.6 percent is converted into energy).

Such pairs are called X-ray binary. Such X-rays examine the signals from the binary to see what kind of central star it is. Usually, the central object is a neutron star or a black hole.

Again, such an accus disc can be created next to a supermassive black hole. In that case, the radiation emitted is much higher. According to scientists, the quasars and active galactic nuclei are actually radiation from the action disks formed next to supermassive black holes.

Read More: Galaxies from Laniakea

Currently located outside the Earth (because the atmosphere blocks X-rays), NASA and Harvard University’s Lunar X-ray Observatory identify such black holes by observing X-ray sources from different parts of the universe.

Gravitational waves

The previous two methods require bright stars in the vicinity to detect black holes. But if there is a black hole, it will have a star with it or it will have an accusation disc.

So they needed another method to catch such a lonely black hole. They can use gravitational waves in this case. In 2015, for the first time, Laigo received a gravitational wave in this way.

Then they found two more gravitational waves. We created these gravitational waves by the joining of two black holes.

Gravitational lensing

This is another fun method. Light bends space-time for gravity. So when the light goes in this way, its path also goes crooked. So if something bright passes right behind a black hole, the light catches our eye as if it were coming from a distorted lens. It is called gravitational lensing.

The gravitational field of a black hole is so strong that it is possible to capture a black hole directly through gravitational lensing. However, no black hole has been identified in this method yet.

We have to look at space in search of light. That light does not give any information about the black hole. Yet, we can find black holes. Constantly giving all the new information about the universe. This black hole may solve cosmology in the future.

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