Let's understand the Universe

Mankind has always been curious about the night sky. In ancient times representations of the universe have been created, with objects that could represent stars and planets. Humans saw the stars not only to guide themselves as navigators, but also to elaborate the first calendars.

Astronomy is one of the first sciences. With the invention of the telescope and the development of new techniques, astronomers were able to enter the universe more and more.

^{Seyfert Galaxy. Credits:NASA/ESA-Hubble}

So that they can understand the concept of one of the greatest enigmas of the universe we must return to the past and review the most important theories.

^{Issac Newton. credits:Wikipedia}

Isaac Newton

^{Científico Británico}

In the seventeenth century he wrote his work of Universal Gravitation, his famous story of the accidental fall of the apple, was what gave him the idea.

Newton, defined the gravitation as:

"The force that a body exerts on another body with mass"

^{John Michell. credits:Ecured}

John Michell

^{Geologist and English astronomer}

In the eighteenth century, in a lecture he delivered a theory in which he claimed that the rays of the sun and other stars reach the earth only because light is able to escape its gravitational attraction . Applying Newton's laws, he calculated that a star could become so dense that it would not allow its own rays of light to escape and that's why they appeared black. He called these types of objects, black stars.

^{Pierre Laplacecredits}

Pierre Laplace

^{Mathematician, Astronomer and French Physicist}

He thought that in the universe there could be stars with a gravitational force so big that even light could not escape it , although he could not develop the concept there is the precursor idea of the black hole.

^{Albert Einsteincredits}

Albert Einstein

^{German physicist}

One of the most famous scientists of the twentieth century, revolutionized the world of physics with its General Theory of Relativity that replaced the gravitational physics of Newton. He discovered that time and space were inseparable , and combined them under his theory called Space-Time .

Gravity instead of being considered as a force, can be understood as a deformation of space-time, that is, objects with mass deform space-time modifying the trajectory of other objects. That is why the planets orbit the sun, for example.

^{Karl Schwarzschildcredits}

Karl Schwarzschild

^{Physicist and German astronomer}

This scientist set out to solve the so-called field equations proposed by Einstein and found something very surprising.

As we can notice, when jumping we fall again, when we throw a ball upwards, it falls again. This is because he does not have enough momentum to leave the planet. A rocket needs 11.2 km / s to escape from our planet, this is called escape velocity.

Karl discovered that the speed of escape depends mathematically on the mass as the size of the object that you want to escape The larger the mass or the smaller the radius, the greater the escape velocity. If the object is small enough, more than 300,000 km/s would be needed, so that even light could not escape. This theoretical phenomenon was called black hole.

First contact...

^{Cygnus constellation}

In the 1960s a powerful signal was received near the Cygnus Constellation. This discovery became the first case of detection of a black hole, Cygnus X1 a binary system.

One of the two stars collapses forming a black hole and orbits around its cosmic neighbor while devouring it slowly. The attracted matter revolves around the black hole and generates a very intense radiation, meanwhile two jets of plasma are projected towards the universe.

Often these jets outnumber the same galaxy. The so-called active nuclei of galaxies are super massive black holes located in the center of the galaxies that feed on matter, some are so luminous that it could be compared with quasi-stellar stars hence the name with which they are currently known, Quasar.

^{Cygnus X1 binary system. Credits: NSA/Hubble}

^{Cygnus X1 binary system. Credit: Gif Hubble}

The Cygnus X1 event is a way to create a black hole. But there are other ways, one of which is what I will explain next...

^source

Imagine a star much larger than the sun, with its extremely large gravitational attraction but also the atomic forces that push the mass outward.

That makes the size of the star remain stable, but after several million years the star consumes all its atomic fuel.

There is nothing that pushes out and then, suddenly... BUUM!! it collapses on itself. First it explodes in the form of a supernova to later become a black hole, then everything that passes through the event horizon never comes out.

^source

But... what happens in the Event Horizon?

Imagine now that in the event horizon an astronaut falls, inside a black hole it would accelerate until reaching the speed of light when all the effects of general and special relativity would come into force. So time would slow down and the astronaut would increase more and more in mass.

For an external observer, time would pass so slowly that it would seem an eternity, because when the astronaut arrives at the horizon of events, time almost stops. In addition, radiation in the form of X-ray and gamma rays emitted by the black hole would cause the astronaut to die long before reaching the event horizon.
^{Werner Zeilinger}

^{gif source}

If the hole is black, how can they detect it in the universe?

A black hole would be almost invisible in the dark background of the universe, but it is not impossible to detect it. When black holes are born they produce gravitational waves that are possible to detect them, also when they pass close to a celestial body deforming their light, also when these black holes are "devouring" they produce X-rays that are also detected by space telescopes.
^{Gif Source}

^{Gif Source}

In the galactic center of our Milky Way, there is also a black hole of about 2.6 million solar masses that astronomers called Sagittarius A. It was possible to detect it from the observation of a group of stars that turned to a dark point to more of 1500 km/s.

^{Heart of the Milky Way Galaxy. Credit: NASA - Hubble}

Undoubtedly, black holes are one of the most destructive, fascinating and mysterious phenomena of our universe.

In our universe could there be another a phenomenon similar to a black hole that can teleport us to another place in the Universe? Wormhole?

Gif Wormhole

Sources:
^{1. Milky Way - Wikipedia 2. Cosmos - Black Holes 3. Institute of Theoretical Physics 4. Black Hole 5. Documentary-Black Holes 6. ABC.es 7. Black Holes - Wiki}

Let's understand the Universe | Black Hole