Did you know there were 40,000,000,000,000,000,000,000,000 black holes? 40,000,000,000,000,000,000 make up 1% of the observable universe, study estimates

  • This calculation comes from the International School for Advanced Studies, Italy
  • They factored in data on properties such as stellar evolution and formation rates
  • The finding could help us better understand the evolution of supermassive holes

The observable universe contains 40,000,000,000,000,000,000 stellar-mass black holes — that’s 40 quintillion, or 40 billion billions, a study has estimated.

Stellar-mass Black Holes are black holes that formed after the death of large stars. Their masses range from a few to a few hundredths of that of the sun.

Experts from the International School for Advanced Studies (SISSA) used a new computational approach to estimate how many of these holes should have formed.

Moreover, they said, these black holes account for 1 per cent of all the ordinary, or ‘baryonic’, matter in the observable universe, which is 93 billion light years across.

According to the team, these findings will help us understand how supermassive black hole formation might occur in stellar- and intermediate mass black holes.

The observable universe contains 40,000,000,000,000,000,000 stellar-mass black holes ¿ that's 40 quintillion, or 40 billion billions, a study has estimated. Pictured: a simulated view of a black hole in front of the Large Magellanic Cloud

The observable universe contains 40,000,000,000,000,000,000 stellar-mass black holes — that’s 40 quintillion, or 40 billion billions, a study has estimated. A simulation of a black spot in front the Large Magellanic Cloud.


In their study, astrophysicist Alex Sicilia and colleagues calculated the number of stellar-mass black holes not in the whole universe — but the ‘observable’ portion.

The spherical area, centring on Earth’s surface, is bound by faraway distances. These are the closest we can possibly see using ground or space telescopes.

Beyond this boundary — dubbed the ‘particle horizon — nothing can be detected. The diameter of our observable universe at the moment is approximately 93 million light years.

The calculation was undertaken by theoretical astrophysicist Alex Sicilia of the Trieste, Italy-based SISSA and his colleagues.

‘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,’ explained Mr Sicilia.

It is described as “ab initio,” and it was one of the strongest. [from first principles]Calculation of the stellar black holes mass function over cosmic time.

To calculate their estimate of the number of black holes in the observable universe, the team combined models of how single and binary star pairs evolve — and thus how many turn into black holes — with data on other relevant galactic properties.

The latter included information on star formation rates, the masses of stars and the metallicity of the interstellar medium — all of which influence the formation of stellar-mass black holes. These data also included information on black hole mergers.

The team was also able calculate the mass distribution of black holes throughout the entire history of the universe.

The researchers not only calculated the number of black hole with stellar masses in the visible universe, but they also investigated the various paths by which different black holes can be formed.

These included looking into possible origins of isolated stars and binary star systems, as well as more populous clusters. 

The team found that the largest stellar-mass black holes typically form from the collision of smaller black holes within stellar clusters — a notion that matches well the observational gravitational wave data on black hole collisions collected to date.

“Our work offers a strong theory of the creation of light.” [stellar-mass] seeds for (super)massive black holes at high redshift,’ said paper author and astrophysicist  Lumen Boco, also of SISSA.

He said that such information “can be used as a point of departure to study the history of heavy seeds.” [intermediate-mass black holes]We will continue to pursue this topic in a future paper.

In fact, with this initially study complete, the researchers are now looking to undertake similar calculations focussed instead on intermediate-mass black holes and then, subsequently, their supermassive counterparts.

The Astrophysical Journal has published all of the findings.


The gravitational pull of black holes is strong enough that they can withstand any form radiation, not light.

These stars act as powerful sources of gravitation, which lift up gas and dust around them. It is believed that their intense gravitational pulling acts as a magnet around which stars orbit in galaxies.

It is not clear how they form. Scientists believe that they form from a cloud of gas, 100,000 times greater than the sun.

Many of these supermassive dark holes are formed when many of the black hole seed merge into one larger black hole. These black holes can be found in every massive galaxy.

Another possibility is that a supermassive dark hole seed might come from a massive star about 100 times larger than the sun. After running out of fuel, it eventually forms into a hole and then collapses.

These giant stars also die and become’supernovae’. This is a massive explosion in which the matter of their outer layers are pushed into deep space.