40 quintillion stellar-mass black holes lurk in the universe

(ORDO NEWS) — Scientists have estimated the number of “small” black holes in the universe – and it is amazing!

Using a new method, a team of astrophysicists has obtained a new estimate for the number of stellar-mass black holes – that is, black holes with masses between 5 and 10 solar masses – in the universe.

And that figure is astonishing – 40,000,000,000,000,000,000, or 40 quintillion, stellar-mass black holes inhabit the observable part of the universe, which is about 1 percent of the mass of all normal matter, according to this new estimate.

But how did scientists get this number? By tracking the evolution of stars in our universe, they estimated the frequency with which stars – either alone or in binary systems – turn into black holes, said study lead author Alex Sicilia, an astrophysicist at the International School for Advanced Study in Trieste, Italy. .

To make this assessment, astrophysicists modeled not only the life of stars, but also the time intervals preceding their birth.

Using known statistics for various galaxies, such as size, elemental composition, and parent star cloud sizes for these galaxies, the team built a model of the universe that accurately reproduced the formation of stars of various sizes and their frequency of occurrence.

After establishing the rate of formation of stars that could eventually turn into black holes, the team modeled the life and death of these stars, using data such as their masses and metallicities – the abundances of elements heavier than hydrogen or helium – to find the fraction of candidate stars that could turn into black holes.

Into black holes. Also taking into account the stars that make up binary systems, and calculating the frequency with which such black holes meet and combine with each other, the researchers ensured that there was no duplication of black holes in the calculation.

With the results of this calculation in hand, the researchers created a model that tracks changes in the population and size distribution of stellar-mass black holes over time and provides a general estimate of the number of such black holes.

Then, by comparing the obtained calculation data with the data obtained on the basis of the analysis of gravitational waves, the authors confirmed the good agreement of their model with the observational data.


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