The expansion of the universe makes black holes grow

A new study suggests that the growth of black holes does not depend on the absorption of material from dead stars: these mysterious structures could grow mainly from the universe’s own constant expansion.

A team of researchers from the University of Hawaii at Mānoa, in collaboration with specialists from the University of Chicago and the University of Michigan in Ann Arbor, has proposed a novel solution to the problem of the growth of black holes, many of which are unexpectedly great for scientific predictions. According to the new theory, black holes grow along with the permanent expansion of the universe.

In his general theory of relativity, Albert Einstein argued that the universe is constantly expanding. Although this idea is widely accepted in the scientific community, until now it has not been suggested that it could directly impact black holes. Now, the new study published in The Astrophysical Journal Letters indicates that black holes get bigger from the expansion of the universe itself.

Do they grow with the universe?
This would explain why many black holes are too big for scientists’ expectations. Originally, physicists expected black holes to have masses on the order of 40 suns at most, because black hole mergers are made from massive stars, which cannot hold together if they grow too large.

In contrast, recent studies conducted with specialized instruments such as the LIGO and Virgo observatories have discovered many black holes with masses greater than 50 suns, some as massive as 100 suns. According to a press release, this characteristic would be explained because black holes would not only grow by incorporating material from dead stars, but would gain mass from the expansion of the universe itself.

Despite not generating light, black hole mergers can be observed by emitting gravitational waves, which are disturbances of space-time produced by an accelerated massive body. These waves, also predicted by Einstein, have made possible a great advance in the observations of these phenomena, especially in recent years.

However, studies based on these new concepts and technologies have faced a scientific dilemma: why do black holes grow so large and how do they grow? Multiple scenarios have been developed to try to explain these unexpected sizes, but none of the theories has managed to satisfy most specialists.

Cosmologically coupled
Apparently, the diversity of observed black hole mergers and the enormous masses that these mysterious cosmic objects can reach could be understood from the incorporation of material through a phenomenon called “cosmological coupling”. According to Kevin Croker, the principal investigator in charge of the new study, this means that the masses of black holes can grow in unison with the universe and its expansion, beyond adding material from their own surroundings.

In other words, this means that black holes are “cosmologically coupled” and gain energy and mass without consuming other stars or incorporating gas. According to American scientists, the universe continued to grow since its formation and the masses of black holes were increasing in line with this expansion, as they spiraled towards each other.

Despite being a shocking theory, the researchers believe that their work still requires new observations and studies, because various aspects of the merger of black holes are not yet known in detail, as well as part of the complex physical processes that take place. develop in these structures.

Cosmologically Coupled Compact Objects: A Single-parameter Model for LIGO – Virgo Mass and Redshift Distributions. Kevin S. Croker et al. The Astrophysical Journal Letters (2021) .DOI: https: //