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

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The black holes, these ultramassive cosmic objects, which let neither matter nor light escape, fascinate the whole world. Yet they still remain, to a large extent, a mystery to physicists. In an effort to understand them a little more, researchers from the Scuola Internazionale Superiore di Studi Avanzati (SISSA), Italy, have managed 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.

Posted in The Astrophysical Journal, the study has developed an ingenious computational approach to calculating the number of black holes in our observable universe — a huge 90 billion spherelight years of diameter. They also made a fascinating discovery, according to which nearly 1% of ordinary matter would be contained in these so-called stellar black holes.

These black holes, born from the collapse of stars exceeding 20 to 25 solar masses, would contain a large part of the matter that makes up everything around us (ordinary baryonic matter). This first demographic finding of stellar black holes is part of the Big Data Application for Black Hole Evolution Studies (BiD4BESt) and paves the way for other discoveries to come.

A multidisciplinary feat

Dedicated mainly to the study of the evolution of black holes, as its name suggests, the BiD4BESt project requires several disciplines at once. According to Professor Andrea Lapi, supervisor of Sicilia and coordinator of doctorates in astrophysics and cosmology at SISSA, the research mobilized expertise in stellar astrophysics, the formation and evolution of galaxies, gravitational waves and other more specific branches of astrophysics.

To achieve their result, the Italian researchers applied a methodology that combines the state-of-the-art stellar and binary evolution code called SEVN, with an approach based on probability calculations. Dr. Mario Spera, one of the SISSA researchers, developed SEVN specifically for the project.

Most of the calculation was then done taking into account the properties of the galaxies, the rate of star formation in each of them, the amount of stellar mass and the metallicity of the interstellar medium (the part of its mass that does not consist of helium and hydrogen).

Once these ingredients were listed and brought together, the group of researchers applied a self-consistent approach, that is to say taking into account each element that makes up all the structures. Their new very advanced calculation method, integrating all these data, then made it possible to identify all three stellar blacks 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 metal enrichment in individual galaxies. This is one of the first and most robust ab initio calculations of the mass function of stellar black holes throughout cosmic history. “, explains in a communicated Alex Sicilia, PhD student in astrophysics and cosmology at SISSA and lead author of the study.

Focus on the origin of the most massive stellar black holes

SISSA’s research did not stop at just estimating the number of stellar black holes. Indeed, the study looked at many other fascinating questions, such as the formation of black holes of different masses, single stars, binary star systems and star clusters. Among other things, it is shown that the most massive stellar black holes come largely from dynamical events within stellar clusters.

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

The Italian researchers even think they have found a good lead on the formation of light seeds of supermassive black holes, which emit in the upper part of the red wavelengths. These “seeds” would be intermediate black holes, which play a key role in the formation and evolution of galaxies, and more particularly in the formation of supermassive black holes. The SISSA study would thus open the way to identifying the origin of the “heavy seeds”.

Source : The Astrophysical Journal

⇧ [VIDÉO] You might also like this partner content (after ad) The black holes, these ultramassive cosmic objects, which let neither matter nor light escape, fascinate the whole world. Yet they still remain, to a large extent, a mystery to physicists. In an effort to understand them a little more, researchers from the Scuola Internazionale…

⇧ [VIDÉO] You might also like this partner content (after ad) The black holes, these ultramassive cosmic objects, which let neither matter nor light escape, fascinate the whole world. Yet they still remain, to a large extent, a mystery to physicists. In an effort to understand them a little more, researchers from the Scuola Internazionale…

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