The answer is yes, there are stars being born right now. In order to know at what stage of its evolution each star is, it is evident that we cannot follow one during its entire life because it lasts billions of years. What we do is observe the areas in which the birth of stars occurs. In these areas of our galaxy we can see from stars before they were born, before we can properly call them stars, to others in more advanced stages of their evolution. These star-forming regions are very dense clouds of dust and gas. They are so dense that we cannot observe them with optical telescopes, the most commonly used telescopes that we are all familiar with. For these areas we have to use radio telescopes because the radio signal is capable of going through those clouds and allows us to know what is inside them.
Star formation theories explain the different phases a star goes through when it is forming. What we do is detect stars in these different phases, which has helped confirm this theory.
A star is born from the condensation of matter in a certain region of a cloud of gas and dust. When the density is sufficient, the temperature increases until it reaches the point where the nuclear reactions that make stars shine begin, that is when we say that a star has formed. There are characteristics associated with this phenomenon such as jets of matter perpendicular to the newly formed star, which also has a disk around it. And since we are able to detect the radiation from the molecules and atoms that are in those structures, we can observe the protostars at this early stage. We can also observe stars in the following stages: when the jets of matter have practically disappeared and when planets begin to form in the disk around the star.
There are stars of very different sizes. There are medium ones like our Sun, there are smaller ones and there are much larger ones. We know that the formation process of a star is different depending on its size, and that large stars and small stars are born in the same star-forming cloud, but we do not know why each individual star ends up being one or the other size.
The process of star formation lasts several million years and is considered fast compared to what will later be the life of the star, which will be billions of years. Stars are always formed inside those clouds of gas and dust that we call star formation, because they are born from the matter that these clouds contain. A star cannot be born isolated because in a vacuum there is not the matter it needs to form.
The process of new star birth occurs within galaxies, as known matter clumps together into these huge assemblages of stars, gas, and dust. We are only able to detect the formation of stars in our galaxy, although we know that in the Universe there are some galaxies in which there are many stars in formation, because they are younger galaxies. There are galaxies that are older in which the gas that initially existed is already part of the stars that have formed and so very few new stars are born. In our own galaxy, the Milky Way, there are still many stars in formation because there is still a lot of gas and a lot of dust left.
The life of stars is a cycle. Stars form, are active for a few billion years, and then die. During their active life they will transform the hydrogen that originally composed them into other chemical elements. Towards the end of their lives, they expel the external material that formed them and from that material someday other stars will form. New stars are born from the remains of dead stars. Thanks to this process, human beings and everything we know also exist, because at the beginning of the cosmos the only thing there was was hydrogen, a little helium and a minimal amount of beryllium and lithium. The rest of the chemical elements that we know and that make us up have been produced inside stars. When our Sun goes extinct, the atoms that make us up today will become part of new stars and maybe even other planets.
Olga Suarez She is a doctor in Physics, a researcher in astrophysics and responsible for scientific dissemination at the Côte d’Azur Observatory, Nice (France).
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