There are very few in the universe with the ability to challenge black holes for the attraction they exert on cosmology worshippers. Neutron stars are one of them. While astrophysicists have developed enough to provide us with valuable information about them, cosmologists have not yet fully understood the mechanisms that trigger their formation and govern their behavior.
Fortunately, we had a good plan for the best. And we owe one of them to a research group from the Oak Ridge National Laboratory in the United States of America, led by astrophysicist Kelly A. Chipps. In the article that these scientists have just published in the Physic Letters, they explain very well what the experiment was that allowed them to recreate something fascinating in their laboratory: one of the trade-offs in which a star devours neutrals. part of the mass of the star.
A few brushes with neutron stars to whet your appetite
Before we go on and investigate the work of these researchers, it is important for us to take a moment to understand what a neutron star is and what makes it special. This knowledge will help us to better understand the relevance of the work of these scientists. If you already know these concepts in detail, you can probably skip directly to the last part of this article. Otherwise, I encourage you to spend a few minutes reading the following paragraphs. Let’s go there.
Stars are formed due to the action of gravity on dense clouds of vapor and dust scattered through the interstellar medium. When the condensation of matter exceeds a certain threshold, the formation of protostasis begins, which can obtain its strength from gravitational contraction.
Approximately 70% of the mass of stars is hydrogen, 24-26% is helium, and the remaining 4-6% is a combination of chemical elements heavier than helium. The life of each star depends on its initial composition, but above all it is profoundly affected by its mass, which is nothing more than the amount of matter that gravity is capable of collecting and condensing in a part of space.
Radiation and gas pressure are necessary to counteract gravitational contraction and keep the star in hydrostatic equilibrium.
Once a protostar has accumulated enough mass, gravitational contraction puts the necessary pressure on its core to ignite the nuclear furnace. This is the moment in which nuclear reactions are allowed, which allows the star to start fusing the first hydrogen nuclei to produce a new helium nucleus. The energy released by these reactions manifests itself in the form of pressure and vapor rays, which are necessary against the gravitational contraction and keep the star in hydrostatic equilibrium.
This mechanism explains why stars remain in equilibrium for most of their lives, although they are constantly undergoing fusion reactions that trigger the production of all the chemical elements in the periodic table until iron is reached, so that nuclear energy cannot be obtained through fusion. In this process they now obtain an onion-like constitution, so that each of these layers is composed mainly of a chemical element.
When the core of a star is made up mostly of iron and the production of energy has stopped, the pressure of the gas radiation is not enough to counteract the gravitational contraction, so the iron core suddenly contracts under the enormous pressure exerted by all the layers. the material will be superimposed. Stella lost her balance. At this moment, it loses all that nuclear support, which is now much denser, and falls at a tremendous speed.
One cubic centimeter fragment of a neutron star weighs about a thousand tons. Degenerate matter, which is no longer composed of protons, neutrons and electrons, like ordinary matter.
When this material from the star reaches the surface of the core, a rebound effect is produced, which causes the energy to be ejected to the center of the star, spread out. A supernova just happened. Some of them are so intense that in a short time they emit more light than the entire continent of the galaxy. But the iron core does not come out intact from this process.
These processes are quantum mechanics in nature, which lead to important changes in the structure of matter.
The enormous pressure to which it is subjected changes the most important factors in its structure, so that it is no longer ordinary matter, with its protons, neutrons and electrons, but is evident from what astrophysicists call degenerate matter. If the object remaining after the star ejects its outer layers into the interstellar medium in the form of a supernova has more than 1.44 solar masses, a value known as the Chandrasekhar term after the Indian astrophysicist who calculated it, the remnants of the star will collapse once. many neutral stars arise.
A few moments before a supernova occurs, the iron core of our star is subjected to the enormous pressure of higher materials and also to the constant action of gravitational contraction. These processes trigger a mechanism of a quantum nature, which entails the greatest moments in the structure of matter, causing the iron in the stellar core, which is subjected to the hottest, to photodisintegrate under the action of high-energy photons, which Illi. They constitute a form of energy transfer known as gamma rays.
These extremely high-energy photons manage to dissolve the iron and helium accumulated in the star’s core, producing alpha particles, which are helium nuclei that lack an electron shell and therefore have a positive electrical charge. and neutrons. In addition, there is a mechanism known as beta capture in which we are not going to investigate so as not to spoil the article too much. The most we know is that the electrons of iron atoms interact with the protons of the nucleus, neutralizing their positive charge and causing more neutrons to be produced.
In this process, the initial matter, which is composed of protons, neutrons and electrons, is made only of neutrons, because, as we have just seen, electrons and protons give rise to more neutrons by capturing electrons. From which time the star is no longer made of common matter; A kind of crystal waste is made only of neutrals.
However, when the star reaches this state, we can find out what mechanism allows this neutron ball to resist and resist the pressure of the tireless contraction of gravity. The phenomenon to keep the neutron star in equilibrium is Pauli’s exclusion principle, a result of quantum nature, which it is not necessary to go into to avoid a much more complicated article.
The phenomenon of observing a neutron star in equilibrium is the principle of Pauli’s exclusion.
Strictly speaking, this principle, which was stated by the Austrian physicist Wolfgang Ernst Pauli in 1925, states that two fermions of the same size of a system cannot remain in the same quantum state. Quarks, which are the elementary particles that make up the protons and neutrons in the atomic nucleus, are fermions. Yes, and CNN. To approach simply what it means that two fermions cannot acquire the same state and understand, hence the equilibrium of neutral stars, it is known that the impossibility of two neutrals occupying the same place generates the necessary pressure to maintain equality. star
And that brings us to the undoubtedly most surprising characteristic of neutron stars: their density. The average radius of one of these objects is about ten kilometers, but the mass is enormous. Compared, for example, to main sequence stars, or even white dwarfs, neutron stars are very small, and packing so much mass into such a small space makes a 1-cubic-centimeter chunk of a neutron star weigh about billions of tons. It is surprising that a small particle of matter like a sugar cube can have such a monstrous weight.
Understanding these stars helps us understand the nature of matter
The review that we have just done will help us to understand a little better what exactly the experiment was done by the scientists from the Oak Ridge National Laboratory. For astrophysicist Kelly A. Chipps, “neutral stars are fascinating both from the point of view of nuclear physics and astrophysics. A deeper understanding of their dynamics can be useful in revealing the cosmic recipe of the chemical elements that make up everything from humans to planets.” “This, in short, is the purpose of your inquiry.
Chipps and his team are using JENSA (Jet Experiments on Nuclear Structure and Gas Jet Target Astrophysics), a highly sophisticated experimental equipment loaned by the US Department of Energy to the University of Michigan. It is not necessary to investigate the operation of this technique, but it is important to know that these techniques use a very high density of helium gas in the experiments. And they do this with an ambitious goal: to simulate nuclear reactions very similar to those that take place on the surface of neutron stars that are close to another star that is passing through its main sequence.
Consequently, the helium that the neutron star “steals” from the adjacent star interacts with the degenerate material deposited on its surface.
This simply means, this is the second time this star gets its energy from nuclear hydrogen fusion. The gravitational pull of the nearby neutron star causes it to lose mass, so that the hydrogen and helium that the neutron star “steals” from the nearby star interacts with the degenerate material on its surface, triggering a series of nuclear-producing reactions. new chemical elements. This natural process is very intense because of the great power that it is, but also exciting. And it’s amazing.
The JENSA team allowed Dr. Chipps and his team recreate in their laboratory one of the nuclear reactions that take place under the conditions described above on the surface of neutral stars. neither more, nor less. The reason why this experiment is so valuable is that it helps these researchers to better understand the dynamics of neutron stars, the complex nucleosynthesis processes of stars responsible for the creation of chemical elements, and ultimately the nature of matter. Who knows what exciting new experiments this knowledge will give us in the future.
Images: Xataka with Midjourney | NASA | NASA Goddard Space Flight Center | NASA/JPL-Caltech
More information: Physical Review Letters
In the Xataka: From clouds of dust and vapor to black holes: this is how stars are born, grow, die and return.
