Our Universe Probably Has 40 Billion Billions of Black Holes

Black holes have long been a fairly enigmatic entity within our universe. Discovered in the ’60s, the first black hole wasn’t formally confirmed until the ’70s. And it wasn’t until 2019 that we saw the first image of a black hole. But it turns out there are likely a lot of them. A team of scientists at Scuola Internazionale Superiore di Studi Avanzati studying the demographics of stellar mass black holes are releasing a series of papers with their findings, and their first paper delivers a supernova-sized bombshell.

In their (very well-studied) estimation, our universe has 40 billion billions of black holes. Yes, billion billions. Forty of them, in fact. This is what it looks like in number form, to help get a sense of just how monumental that number is: 40,000,000,000,000,000,000. Just so many zeroes.

An illustration of a black hole
M. Helfenbein, Yale University/OPAC

The paper was recently published in The Astrophysical Journal. (We first saw this at Gizmodo.) Alex Sicilia, a SISSA Ph.d student, leads the team, which consists of supervisors and a series of collaborators both at the institution and around the world. So how did the team come up with that astonishing number? Using SEVN, a stellar evolution code and combining it with relevant data on stars in galaxies. Specifically, stars’ metallicity, mass, and formation rates.

“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,” Sicila said in a press release. “This is one of the first, and one of the most robust, ab initio computation of the stellar black hole mass function across cosmic history.”

Concept art of a supermassive black hole

Part of their study also looked at the ways in which black holes, especially those of differing mass sizes, form. As stated above, their research focused on stellar black holes, one of the four categories of black hole. They examined isolated stars, binary systems, and stellar clusters. And it’s the latter, per their findings, that contribute to the formation of massive stellar black holes.

So there are a hell of a lot of black holes out in the universe. And, to think about it, this is just the first of presumably several papers. If this is what they’re starting with, we’re very curious to see what the SISSA team publishes next.

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