2021-11-10 15:24:26
During the initial moments of the formation of the Universe, just three minutes after the Big Bang, the first atoms, the smallest, hydrogen (H) and helium (He) were formed. If the Universe had remained like this, nothing we know would exist, not the carbon that makes up our tissues, not the oxygen we breathe, not the calcium in our bones, not the silicon in the rocks we walk on… Actually, except for those two Primordial elements, the more than one hundred different atoms that make up everything that exists around us, and ourselves, would never have been created.
But luckily for our very existence, the story had only just begun. Those initial atoms formed enormous clouds of gas that in some places were compressed by gravity and heated up. This concentration of mass reached such a point that the nuclear furnace that gave life to the first stars was turned on inside. And it was there, in the extremely hot core of stars, that heavier atoms began to be forged. The extreme conditions of pressure and temperature existing in the stellar interior allowed the hydrogen nuclei to unite to generate more helium and, later, after the hydrogen was exhausted, the stars were further compressed, generating new fusions that gave rise to heavier atoms. . Some stars, like the Sun, barely manage to create atoms of low atomic weight, up to carbon, but others, much more massive, became the true forges of everything we know. Inside these giants, tens or even more than a hundred times more massive than the Sun, the pressure and temperature conditions are so dramatic that the chain of fusions continues and generates heavier atomic nuclei, up to iron. The process is so energetic that they are stars that usually live for a very short time and end their existence with a huge release of energy. When their nuclear fuel runs out, they explode with tremendous violence, creating new atoms even heavier than iron and scattering a large portion of them into interstellar space.
The Universe, throughout its 13.7 billion years of existence, has contemplated the life and death of many generations of massive stars that have been seeding the host galaxies with radiation and matter, a matter loaded with metals (astrophysicists speak of ” metals” in a broader sense than used in chemistry, referring to all atoms heavier than H or He).
Understanding how the Universe has evolved since its formation is a huge challenge. One way to investigate what happened in the early days is to search for and study massive stars with low metallicity, such as those that existed at a time when the Universe had not yet been “contaminated” with atoms heavier than hydrogen and carbon. helium. This is the research path chosen by our guest in Speaking with Scientists, “Miriam García:https://cab.inta-csic.es/personal/miriam-garcia-garcia/, researcher at the Center for Astrobiology.
Miriam García explains that, as the Cosmos was enriched in metals, the new stars that formed agglutinated part of the matter generated and dispersed by previous generations of stars and, as a consequence, they were enriched in these heavy elements. Thus, the study of metal-poor stars opens a window into the past of the Universe. Where can these stars be found and observed? Logically, existing observing instruments have limited resolving power and, when focused on very distant and therefore older galaxies, are unable to see individual stars. For that reason, current knowledge about metal-poor stars comes primarily from one place: the Small Magellanic Cloud.
The Magellanic Clouds are two dwarf galaxies close to the Milky Way and given the distance at which they are, the stars that compose them can be observed. The Small Magellanic Cloud is located an average of 200,000 light years from Earth and has traditionally been used to study massive stars with low metallicity. Miriam García and her colleagues have published in the scientific journal Experimental Astronomy an article that summarizes the current knowledge about extremely metal-poor massive stars and proposes the need to expand current knowledge by studying nearby galaxies that are extremely metal-poor and other than the Small Cloud. of Magellan. Of course, to achieve this, new projects are needed, such as the launching of a 10-meter-diameter telescope that operates in the optical and ultraviolet ranges. Another proposal mentioned in the article is that the ESA join their efforts to NASA to realize the concept of the mission LUVOIR that improves on and surpasses the great achievements achieved by the Hubble Space Telescope.
I invite you to listen to Miriam Garcia, astrophysicist and researcher at the Center for Astrobiology, a mixed center of the WHILE y CSIC
Reference:
Garcia, M., Evans, C.J., Bestenlehner, J.M. et al. Massive stars in extremely metal-poor galaxies: a window into the past. Exp Astron 51, 887–911 (2021). https://doi.org/10.1007/s10686-021-09785-x
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