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This very violent supernova is our best candidate to be the result of an exciting phenomenon: the merger of a massive star and a neutron star.

Identifying a supernova is an event that astronomers often celebrate with enthusiasm. And it is not for less if we take into account that they are one of the most violent events with which we can run into in the cosmos. Knowing them better is very important because it can help us to understand more precisely what the last stages of the life of massive stars are like, and also the mechanisms that explain how the material originated by stellar synthesis can give rise to new stellar systems.

The mathematical tools currently used by astrophysicists describe supernovae as the inevitable result of the exhaustion of nuclear fusion processes that take place in the nuclei of massive stars. During the stage known as main sequence stars get their energy from the fusion of hydrogen nuclei. As this chemical element is consumed, the star begins to produce helium nuclei, and, of course, its composition begins to evolve.

During this process an enormous amount of energy is released and the star is forced to continually readjust to maintain hydrostatic equilibrium, a phenomenon that is the result of the coexistence of two opposing forces capable of compensating each other. One of them is gravitational contraction, which compresses the matter of the star, squeezing it relentlessly. And the other is the pressure of radiation and gases, which is the result of the ignition of the nuclear furnace and which tries to make the star expand.

This is the life of massive stars until they collapse and trigger a supernova

If the star is massive enough it will begin to consume its helium reserves and produce new carbon nuclei, maintaining at all times the hydrostatic equilibrium we have talked about. And if the star is massive enough, it won’t stop producing carbon. When this element is exhausted in the core, it will readjust, compressing and increasing its temperature once more to slow down gravitational collapse.

During stellar nucleosynthesis, stars acquire a layered structure similar to that of an onion. In the core resides the heaviest element, and from there we go up through layers finding ourselves increasingly lighter elements.

From this moment on, the carbon nuclei will ignite through the nuclear fusion process and the production of even heavier chemical elements. While in the core of the star the fusion of carbon is taking place, in the immediately superior layer the ignition of helium is maintained. And above this, hydrogen.

During stellar nucleosynthesis, stars acquire a layered structure similar to that of an onion. In the core resides the heaviest element, and from there we go up through layers finding ourselves increasingly lighter elements. If the star has accumulated enough mass, there will come a time when the nucleus will be made up essentially of iron, and of this chemical element it is not possible to get more energy through nuclear fusion processes.

At that time the radiation and gas pressure is not enough to counteract gravitational contraction, so the iron core contracts suddenly under the enormous pressure exerted on it by all the layers of material above it. The star has lost hydrostatic balance. At this moment all that matter loses the support exerted by the nucleus, which is now much more compact, and falls on it with enormous speed.

When all this material from the star touches the surface of the core, a rebound effect is produced that causes it to be thrown with enormous energy towards the stellar medium, being scattered. A supernova has just occurred. Some of them are so energetic that for a few seconds they emit more light than the entire galaxy that contains them. However, scientists have long suspected that this is not the only mechanism that can trigger the production of a supernova.

Astrophysicists believe they have found a new type of supernova

Cosmologists have considered for many years the possibility that supernovae may also originate in a different way than the one we have just described. The laws of physics allow that this violent discharge of energy that involves the projection through space of an enormous quantity of matter can be the result of premature fusion of a massive star and a neutron star or a black hole. The problem is that until now astronomers had not observed anything like it. But this has changed recently.

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A group of astrophysicists has published in the scientific journal Science a very interesting article in which they defend that they have solid evidence of the appearance of a supernova that seems to come from the merger of a massive star and a neutron star. The radio signal you have studied was picked up by the VLASS radio telescope network (Very Large Array Sky Survey), and its intensity appears to be unusually high. After thoroughly analyzing the signal and hypothesizing what could be its origin decided to verify that their observation was correct before moving on.

The amount of information carried by a signal like the one supported by this research is staggering. Thanks to it, these scientists have managed to shape solid evidence

What they did was contact NASA to ask them to consult the records of the MAXI instrument (Monitor of All Sky X-ray Image), a highly sensitive camera installed on the International Space Station that scans the cosmos for the purpose of collect X-ray signals that go unnoticed by other instruments and identify their origin. And … bingo! There was that same sign. And, indeed, it seemed to come from a supernova with unusual characteristics.

The amount of information carried by a signal such as the one supported by this research is astonishing, and thanks to it these scientists have managed to shape solid evidence that points to the possibility that, as I mentioned a few lines above, this supernova has been triggered. by the merger of a massive star that it had not yet consumed all its fuel and a neutron star. Or even a black hole.

The mechanism that explains how the mass transfer of the star that has been engulfed could have been carried out is not yet known with precision. These researchers also do not know how the collapse that produced the supernova was triggered, and there is even the possibility that, in reality, this phenomenon was not caused by the merger of a binary system. In any case, this research is an extraordinary starting point that invites us to investigate further into the nature of the most energetic and amazing phenomena of how many take place in the cosmos.

Imagen de portada | NASA/ESA/JHU/R. Sankrit & W. Blair

More information | Science