A Universe of births
Our journey through Birth, Luce della Vite’s monographic book, continues. While last month we focused on the birth of a vineyard, inspired by the words of Luigi Veronelli who said that “Wine is the song of the earth to the sky”, here we are now, looking up at the sky. And at the stars.
So how are the stars born? And how about the planets? Tommaso Belloni, the current Research Director at INAF’s Osservatorio Astronomico di Brera, explained this in his article in Birth. He told us how, starting from the Big Bang, a constant process of birth commenced in the Universe, so that stars (and planets) are born from other stars. Just like the vineyard which, after the wineter, is born again with the arrival of spring, starting a new vegetative cycle, so the universe, with its stars and its planet, is made of births and rebirths.
Everything surrounding us is made of “heavy” chemical elements, such as iron, oxygen, silicon, nitrogen, carbon. But how were these born? If we start from the beginning, from the primordial Big Bang from which the Universe was originated some 14 billion years ago, we find out that despite it being a spectacular event, the only elements that were produced once the Universe cooled down were hydrogen and helium, the stars’ main combustible materials. The first stars to be born, therefore, were only made of hydrogen and helium, and were probably much larger and massive than current stars. They were very different from the Sun, even though less than 1% of the mass of the solar system is made of heavier elements. For sure, you cannot make a planet with just two elements. So the elements that make everything that surrounds us must have been produced later.
Of the stars, the very massive ones have a short life and become supernovas: they explode and expel a large part of their gas. This matter is much richer in heavy elements, produced both during the life of the star and during the supernova event itself. This is when our elements are born, though they’re still In the form of gas.
At the core of the explosion, an exotic voracious object like a black hole or a Neutron star can be born. The gas expelled, on the other hand, comes in contact with the surrounding gas, like an interstellar cloud. The gas becomes more dense and from the cloud new stars are born, made of other elements too: a stellar nursery originates from the end of a star. This is when new planetary systems are also born.
The more massive stars in turn will also end as supernovas, and repeat the process. One of the less massive stars is our Sun with its planets. This happens constantly, both in our galaxy and in the others, Even though the time scale is much longer than human time (the last supernova to be recorded in our galaxy was in 1604). The Universe is made of continuous births: one of these produced the solar system and hence the Earth and us too of course.
We were born from stardust.