Stunning transformation: a star was born from the cold void of space | Space void

The same thing happened to us with the stars as with the Universe: when we began to understand how it works, we learned that they were not always there. Our own Sun testifies to its perishable nature. It consumes hydrogen in thermonuclear reactions at a rate of 100 million tons per second, which is why it glows. Despite the large mass, it is not infinite. The conclusion is obvious: the sun has not always shone and will not always shine.

Therefore, stars have a beginning, just as we can say that they experience something resembling an end. Starting with what we know as the interstellar medium, the process of its formation involves a stunning transformation: tenuous and very cold material, whose temperature is about 363 degrees below zero, turns into a red-hot fireball with temperatures reaching millions of degrees inside, and so density. increase many, many zeros.

The first thing we need to understand is that this is a process that takes time. Not as much as they shine, but quite a bit, even on a cosmic scale this is not an instantaneous process. If the right conditions are met, a star could form in space within tens of millions of years.

The mechanism is chaotic and full of uncertainties. Hundreds, thousands of stars are formed simultaneously in dusty gas shells, speckled with bubbles, scattered and held together by those solid particles that we call interstellar dust. In order for this to happen, it takes time, as we have already said, but first of all it is necessary to transform the environmental conditions several times so that it passes from moderate and almost empty to very cold and dense. So over time it becomes even more dense, so much so that it can continue to collapse under the influence of gravity.

The filamentous and tenuous low-density material eventually breaks down into thousands of clumps, which over time form the densest structures in space. Some of them are hundreds of times the mass of our star, most of them are located in pairs, in so-called binary systems, and others, most of them, are shaped like stars almost similar to the Sun, but slightly less massive.

We don’t know the process of formation of massive stars that are, say, more than 20 times the mass of the Sun. It is not yet clear to us whether they are formed as a result of the monolithic collapse of a very large cloud or, conversely, become large as a result of the addition of smaller stars. Gravitational wave detections or discoveries such as a black hole 33 times the mass of the Sun recently discovered by GAIA show that we still don’t have all the details clear.

What is surprising is that the birth of the largest stars is associated with the birth of the smallest stars and with the same formation of stars throughout the galaxy. Massive stars, through their winds and supernova explosions, inject enormous amounts of energy into the interstellar medium, thereby reducing the rate of formation of other stars. Without massive stars, our Milky Way would have used up all its gas in a huge, short burst of formation, but thanks to them, it continued to slowly form stars over billions of years.

For stars like the Sun, we generally know the procedure well; they are easier to see in telescopes. We know that clouds of a certain size, about 3-30 light-years, break up into fragments that are about 10,000 times the distance between the Earth and the Sun. This occurs in a very cold environment, possibly with turbulence and eddies where the material is located. concentrated, in some places becoming more and more dense. This is where the mass falls. There is not just one, there are many, and as material coming from far away approaches the center, the point of destruction, or the edge upon which it presses, there is a certain rate of rotation associated with it, which increases as we approach. to the center It is this conservation of angular momentum that leads to the formation of a disk that performs two functions: on the one hand, it feeds the star with material so that it can continue to grow, and on the other, it represents the very structure associated with the formation of the star itself that allows planets to form.

What makes the spark ignite? The condition for us to consider them as such and call them stars is that at the moment they are capable of initiating nuclear fusion reactions within themselves. This is when a protostar becomes a star. Some fail, though very small ones that are neither star nor planet: brown dwarfs.

With time and gravity, stars will explode as supernovae, collapsing as neutron stars, white dwarfs and even black holes. But before that, no matter how incredible it may seem, cold is simply necessary for the formation of the hottest structures of the Universe. And it’s cold there, there’s everyone we need there.

Space void This is a section in which our knowledge of the Universe is presented qualitatively and quantitatively. Its purpose is to explain the importance of understanding space not only from a scientific point of view, but also from a philosophical, social and economic point of view. The name “cosmic vacuum” refers to the fact that the Universe was and remains largely empty, with less than one atom per cubic meter, despite the fact that our environment, paradoxically, contains quintillions of atoms per meter. cubic, which invites us to think about our existence and the presence of life in the Universe. The section has been compiled.

Pablo J. Perez Gonzalezresearcher at the Astrobiology Center, and Eva VillaverDirector of the Space and Society Directorate of the Spanish Space Agency and Research Professor at the Institute of Astrophysics of the Canary Islands.

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