Enrique Nácher and Sergio Pastor, CSIC scientists at the Institute of Corpuscular Physics (IFIC), located in the scientific-academic area of the Science Park of the University of Valencia (PCUV), write the latest issue of the collection What do we know about? Researchers describe the physical processes responsible for the origin of the elements in the periodic table
All the matter around us is made up of atoms of some chemical element. Where and when were these elements generated? How, for example, was the oxygen we breathe or the lithium used to make batteries created? Why is there so much carbon on our planet and so little gold? The latest book in the collection What do we know about? (CSIC-Catarata) makes a journey through the history of the cosmos to tell how the atoms that shape our world were forged. Written by researchers from the Institute of Corpuscular Physics (IFIC), which is located in the scientific-academic area of the Science Park of the University of Valencia and joint center of the Superior Council for Scientific Research (CSIC), Enrique Nácher and Sergio Pastor, The formation of chemical elements begins its story in the first moments of the universe, when the simplest elements appeared, such as helium, and ends with the artificial synthesis of superheavy elements, such as hasio or nihonium, in laboratories and large experimental facilities. In this tour, the authors also describe the types of elements and their classification through the periodic table.
Nucleosynthesis is the key word in this text, a term that refers to the set of physical processes responsible for the different elements. "These processes cannot happen anywhere or at any time, because, among other conditions, they require very high temperature values," say the scientists of the Spanish Scientific Research Council (CSIC). In addition, "they are responsible for whether there is more or less abundance of each element," they add.
The beginning of all
The first elements formed long before stars existed. The early universe was dense and hot, and still did not contain the structures we easily recognize, such as galaxies, stars, planets and other stars. According to the cosmological model of the Big Bang, the universe began its expansion after it originated some 13.8 billion years ago. During its first few minutes, as the universe cooled and expanded, there was a stage called primordial nucleosynthesis. Some of the lighter elements, such as hydrogen and helium, were created at that time, which are "the building blocks for star formation," say experts.
A few hundred million years later the first stars were born, "the true cosmic cauldrons where the lightest elements are cooked to make heavier ones". According to the authors, "one of the great discoveries of the last century was to confirm that stars generate their energy through thermonuclear fusion reactions, and as a result of this discovery, it was established that nucleosynthesis takes place in the stellar interior.".
The life of stars and elements
The life of a star goes through a series of phases, and in each one a type of element is formed. "Hydrogen fusion defines the initial stage of stellar evolution, and is the first link in the chain of nucleosynthesis in stars," say the scientists. "The main feature of this process is that the elements that are created in each stage are the initial for the next," they indicate.
However, not every star can create all the chemical elements. "The production of nuclei in a given star is determined by its evolution, which in turn depends on its mass, temperature and composition," they point out. There are light stars where nuclear fusion processes transform hydrogen into helium, which later gives rise to elements such as carbon, and more massive stars that take us one step further by synthesizing heavier elements.
"The Sun will burn hydrogen to produce helium for several billion years, then enter a red giant phase, and in its last 100 million years of life, transform part of its helium into somewhat heavier nuclei like carbon, to end its existence turned into a white dwarf, a remnant of a not very massive star that has exhausted its nuclear fuel", Enrique Nácher and Sergio Pastor, IFIC scientists
The IFIC researchers use as an example the Sun, a medium-sized star that is neither very light nor very massive and which is now in the main sequence phase. "The Sun will burn hydrogen to produce helium for several billion years, then enter a red giant phase, and in its last 100 million years of life, transform part of its helium into somewhat heavier nuclei like carbon, to end its existence as a white dwarf, a remnant of a not very massive star that has run out of nuclear fuel", they explain. On the other hand, "stars larger than ours can create many more elements until they reach the iron environment," they underline.
About the authors
Enrique Nácher González is a CSIC scientist at the IFIC. His research focuses, on the one hand, on the beta decay of exotic nuclei of great relevance in nucleosynthesis in neutron stars through X-ray explosions, and on the other hand, in medical applications of nuclear instrumentation and in measures of climate change affecting marine ecosystems using radio tracers.
Sergio Pastor Capi is a CSIC researcher at the IFIC, of which he is its deputy director. His field of research is theoretical astroparticle physics, a discipline that straddles elementary particle physics, astrophysics and cosmology. In particular, it studies aspects related to the role of neutrinos in different astrophysical and cosmological scenarios. Author of the book Los neutrinos (2014) in this same collection.
Source: Comunication CSIC Comunitat Valenciana Delegation
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