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We now know that there are about 40 billion billion black holes in the observable universe.

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Black holes, these supermassive cosmic bodies, which allow neither matter nor light to escape, fascinate the whole world. However, it remains, to a large extent, a mystery to physicists. In an effort to understand it a bit more, researchers from Scuola Internazionale Superiore di Studi Avanzati (SISSA) in Italy have been able to determine the number of stellar black holes in the observable universe. Verdict: There are about 40 trillion (billion billion) stellar black holes in the observable universe.

Published in Astrophysical JournalThe study has developed an ingenious computational approach to counting the number of black holes in our observable universe – a massive ball 90 billion light-years across. They also made the startling discovery that roughly 1% of ordinary matter will be contained in so-called stellar black holes.

These black holes, born from the collapse of stars greater than 20 to 25 solar masses, will contain a large portion of the matter that makes up everything around us (ordinary baryonic matter). This first demographic discovery of stellar black holes is part of Applying big data to studies of black hole evolution (BiD4BESt) and paves the way for further discoveries in the future.

Multidisciplinary achievement

Dedicated primarily to studying the evolution of black holes, as its name suggests, the BiD4BESt project requires several disciplines at once. According to Professor Andrea Labbe, Sicilia Supervisor and PhD Coordinator in Astrophysics and Cosmology at SISSA, the research mobilizes expertise in stellar astrophysics, galactic formation and evolution, gravitational waves and other more specific branches of science. Astrophysics.

To achieve their results, the Italian researchers applied a methodology that combines the latest codes of stellar and binary evolution called SEVN, with an approach based on probability calculations. Dr. Mario Spira, one of the SISSA researchers, developed SEVN specifically for the project.

Most of the calculations were then made taking into account the properties of galaxies, the rate of star formation in each of them, the amount of stellar mass and the metallicity of the interstellar medium (the non-helium part of its mass). and hydrogen).

Once these components were listed and brought together, the team of researchers applied a self-consistent approach, that is, taking into account each component that made up all the structures. Their new and very advanced computational method, which combined all this data, made it possible to determine all three black stars in the observable universe, as well as their mass distribution.

« The innovative character of this work lies in the coupling of a detailed model of stellar and binary evolution, with advanced recipes for star formation and mineral enrichment in individual galaxies. This is one of the first and most powerful preliminary calculations of the mass function of stellar black holes throughout cosmic history. Alex Cecilia, a doctoral student in astrophysics and cosmology at SISSA and lead author of the study, explains in a press release.

Focus on the origin of the largest stellar black holes

SISSA’s research didn’t stop at just estimating the number of stellar black holes. In fact, the study looked at many other fascinating questions, such as the formation of black holes of different masses, individual stars, binary star systems, and star clusters. Among other things, it has been shown that massive stellar black holes come largely from dynamic events within stellar clusters.

These results, obtained through the collaboration of two researchers from the University of Padua, show that these dynamic events will be useful in explaining the function of the masses of black holes that have merged, or three of the united blacks. These masses are estimated by measuring gravitational waves with the international scientific collaboration LIGO / Virgo – a giant gravity observatory located near Pisa.

Italian researchers think they’ve made good progress creating the light seeds of supermassive black holes, which emit at the top of red wavelengths. These “seeds” will be intermediate black holes, which play a major role in the formation and evolution of galaxies, and more specifically in the formation of supermassive black holes. Thus the SISSA study will open the way for determining the origin of the “heavy seed”.

Source: Astrophysical Journal

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