Astrophysicists Calculate A Staggering 40 Quintillion Stellar Black Holes Permeate The Universe

black hole
A team of astrophysicists have developed a method of estimating the number of stellar-mass black holes, and that number is massive. They estimate that while these black holes only make up 1% of all normal matter, there are an astounding 40,000,000,000,000,000,000 (40 quintillion) of them.

Teams at NASA continue to align the mirrors of the James Webb Space Telescope, so that it can it begin taking pictures of the universe. JWST is expected to reach into space and time, as it sends back pictures that scientists hope will unlock secrets of the universe. Those mysteries include the origin story of how black holes came into existence. The European Southern Observatory's Very Large Telescope Interferometer (ESO's VLTI) recently peered where no telescope has before, and gathered the sharpest images of the region around the supermassive black hole in the center of the Milky Way. More recently, a paper published in The Astrophysical Journal this month by a team of astrophysicists, calculates there is an astonishing 40 quintillion stellar-mass black holes in the known universe.

The paper is a first in what the scientists refer to as, "a series aimed at modeling the black hole (BH) mass function, from the stellar to the intermediate to the (super)massive regime." The first paper explains how the team calculated its estimate of stellar black holes, those with masses 5 to 10 times that of our Sun, in the universe.

stellar black hole
This may seem like a number that is impossible to estimate, being that black holes are not the easiest celestial objects to spot. This is because they are as dark as the space that surrounds them. Black holes can typically only be seen under extreme circumstances, such as when they are bending light around them, consuming the unlucky gases and stars that come too close, or meandering toward collisions that emit gravitational waves.

One may wonder how the scientists came up with their unique way of calculating the number of stellar-mass black holes. It appears they did so by tracking the evolution of stars in our universe, and then estimated how often the stars , either on their own or paired into binary systems, would transform into black holes. The team also implemented a new star evolution code called SEVN into their calculations. Simply math, right? Sure...

Stellar BH Relic Mass Function
Source: The Astrophysical Journal

Alex Sicilia, an astrophysicist at the International School of Advanced Studies (SISSA), and one of the paper's authors, stated, "The innovative character of this work is in the coupling of a detailed model of stellar and binary evolution with advanced recipes for star formation and metal enrichment in individual galaxies." He continued, "This is one of the first, and one of the most robust, ab initio (ground up) computation(s) of the stellar black hole mass function across cosmic history."

The team also investigated how black holes of varying sizes might form. While the origin of supermassive black holes remains a mystery, it is thought that stellar-mass black holes derive from the collapsed core of dead stars. Lumen Boco, an astrophysicist at SISSA and co-author of the paper, says the team's calculations "can constitute a starting point to investigate the origin of 'heavy seeds', that we will pursue in a forthcoming paper."

Astrophysicists are hoping to use the new estimate to investigate some puzzling questions that come about from observations of the early universe. For example, how the early universe became so populated by supermassive black holes so soon after the Big Bang. Researchers hope that by gaining a better understanding of small black holes formed in the early universe, it could help them to discover the origins of supermassive black holes as well.