What is a black hole?
The Minister of Racial Equality, Anielle Franco, stated this Wednesday (1st) that the term “black hole” is a racist word. The statement was made on the EBC program “Bom Dia, Minister”.
But what is a black hole within the scientific context and what is the explanation for the name given to that region of space from which nothing, not even light, escapes?
In a nutshell, a black hole is a kind of cosmic abyss that sucks into itself everything that comes close – within a certain distance – to it.
As we said, not even light escapes being attracted to these objects. And that’s why black holes are, in fact, black. And this happens for a reason: the gravitational attraction of these bodies is extremely strong.
Albert Einstein first predicted the existence of black holes in 1916, but it was only in 1967 that the term was coined by American astronomer John Wheeler, and has since become popular.
The term refers to the fact that everything that is attracted by the force of gravity to a black hole becomes trapped “inside” it and seems to disappear, just like in a hole.
“[Nos buracos negros] We have a situation where not even the light escapes. Then, the matter will be attracted and will fall as if it were falling into a hole, into a pocket. Therefore, this name hole was given metaphorically”, says astrophysicist and FEI professor, Cássio Barbosa.
In this report you will understand, in 10 questions, what we know about these phenomena.
1 – What is a black hole?
A black hole is a kind of cosmic abyss that sucks into itself everything that comes close – within a certain distance – to it.
Not even light escapes being attracted to these objects. This is why black holes are, in fact, black.
And this happens because the gravitational attraction of these bodies is extremely strong.
“A big misunderstanding is that black holes ‘suck in’ their surroundings. This doesn’t happen: things can fall into a black hole, but only when they are close to it”, he explains to g1 Jakob van den Eijnden, astrophysicist and researcher at the University of Oxford.
2 – What are the types of black holes?
There are three types cataloged by astronomers: stellar black holes, intermediate black holes It is supermassive black holes.
Stellar black holes are the smallest. They are formed when a massive star dies, in an explosion called a supernova. They generally have a mass (the amount of matter in an object) between 10 and 100 times greater than the Sun.
Finally, supermassives inhabit the center of most galaxies in the Universe, and generally appear after the formation of their galaxies, swallowing everything they see in front of them. As their name suggests, they are one of the heaviest objects in space, with masses ranging from millions to billions of solar masses.
3 – Is the black hole really a hole?
NO, a black hole is not a hole.
Albert Einstein first predicted the existence of black holes in 1916, but it was not until 1967 that the term was coined by American astronomer John Wheeler.
The term refers to the fact that everything that is attracted by the force of gravity to a black hole becomes trapped “inside” it and seems to disappear, just like in a hole.
“[Nos buracos negros] We have a situation where not even the light escapes. Then, the matter will be attracted and will fall as if it were falling into a hole, into a pocket. Therefore, this name hole was given metaphorically”, says astrophysicist and FEI professor, Cássio Barbosa.
4 – Why do we say that black holes defy the laws of physics?
When any object crosses the event horizon From a black hole, that is, their “edge”, there is no longer any escape.
Gravity is so intense at this point that this object goes through a process known as spaghettification: it is torn apart by the gravitational field of the black hole in a shape that resembles spaghetti, in thin and elongated shapes.
This happens because at the center of the black hole we have a point so small and massive that its density reaches infinity, which is something inexplicable by current physics and mathematics.
This heart of the black hole, called singularityis where space and time cease to exist as we currently know them.
“What defies the laws of nature are not black holes, which are well described by general relativity, but singularity”, highlights George Matsas, professor of Physics at UNESP.
5 – How many black holes are there in the Universe? How many do we have in the Milky Way?
According to the Space Telescope Science Institute, the scientific operations center for the Hubble and James Webb telescopes, there are so many black holes in the Universe that it is impossible to count them.
It’s like counting the grains of sand on a beach. The bill is unimaginable. To give you an idea, scientists estimate that a stellar black hole is born every second.
And “around here”, Sagittarius A* is not alone. It is estimated that there are 100 million black holes in the Milky Way.
6 – What is the most distant black hole ever discovered?
According to NASA, the most distant supermassive black hole ever discovered is part of a quasar called J0313-1806, an object as luminous as a star, which is why it is called “quasi-stellar”.
It is 13 billion light years away from Earth and is about 1.6 billion times larger than our Sun.
“Observing a very distant quasar means not only indirectly seeing a black hole, but also a very old black hole, since light has a finite speed. If J0313-1806 is 13 billion light years away from Earth, it means that the photo we recorded today is what the quasar looked like 13 billion years ago”, says Matsas.
7 – What’s inside a black hole?
This is one of the great mysteries of science. In the words of scientist Andrea Gehz – who investigates black holes and was one of the winners of the 2020 Nobel Prize in Physics for her work – nobody knows.
“We have no idea what’s inside black holes – they are the collapse of our understanding of the laws of physics,” Gehz said.
Astrophysicist van den Eijnden explains that many things remain unknown when it comes to black holes. An active field of study, for example, is that which investigates what happens to a material when it falls into a black hole: what it looks like, what its properties are and why part of this material is launched into space in the form of jets.
“Indeed, these processes that take place close to the event horizon are difficult to observe and, therefore, poorly understood”, notes the researcher.
8 – What is Sagittarius A* and where is it?
Sgr A* is a supermassive black hole, 4 million times larger than the Sun, with an even larger diameter, about 18 times larger than our star (see infographic above).
It is stationed in the constellation Sagittarius, which is visible in both the northern and southern hemispheres (the constellation, not the black hole).
Its discovery was revealed to the scientific community by astronomers Bruce Balick and Robert L. Brown in the 1970s, initially as a bright radio source in the center of the Milky Way.
Van den Eijnden explains that Sagittarius A* is relatively quiet: there is not a large amount of material being drawn into it. Therefore, we can only study it because it is in our own Galaxy.
“If an exact copy of Sagittarius A* were located in another distant galaxy, it would be too silent and faint to study,” he says.
“For the most part, this black hole is not active. Therefore, we cannot draw any conclusions about it, because it is simply not sending information”, adds FEI astrophysicist, Cássio Barbosa.
9 – Can the Earth be swallowed by a black hole? Would Sgr A* be a threat?
Holes don’t wander around in space, swallowing everything they come across.
NASA explains that, like other objects in space, they follow the laws of gravity.
Therefore, one’s orbit would have to be very close to our solar system to affect life here on Earth, which does not happen, not even with Sgr A*.
10 – What can we learn by studying Sagittarius A* and the image of supermassive black holes?
The astrophysicist and researcher at the University of Oxford explains that because Sgr A* is so close to us (when compared to other black holes), we can study it even if only small amounts of material are falling into it.
And that is precisely what happens with this object at the center of our Milky Way. By way of comparison, the M87 has a much higher rate of material that is absorbed.
Therefore, Van den Eijnden emphasizes, we can study what happens around this black hole in a way that we cannot observe anywhere else in the universe.
“Studying black holes in general allows us to study physics in the most extreme circumstances, which are so extreme that we cannot recreate them in a laboratory on Earth.”
(VIDEO: Telescope records star being swallowed by black hole.)
Telescope records star being swallowed by black hole
