The collapse of a star is not the only mechanism that leads to the formation of a black hole, especially if it is as old as the Universe itself. Black holes are dating back to only 690 million years after the observation of Big Bang. During this time, the stars present than did not have enough time to collapse into a black hole. The mechanism of direct collapse explains the formation of mega massive black holes born in the early stages of life in the Universe. A new study by two researchers from Western University in Ontario (Canada) clarified the operation of this model, providing an analytical and physically motivated description.
The model of direct collapse requires that supermassive black holes have formed very quickly in a short space of time and that then, almost suddenly, their growth has been interrupted. The research defines a new mathematical model to explain this exponential growth and the rapid formation of these ancient cosmic monsters.
Mega massive black holes are believed to be at the center of each galaxy, including the Milky Way, but their nature is difficult to understand. It can be illustrated their origin In most cases in terms of stellar collapse. Giant stars collapse on themselves to the point where a gravitational singularity is formed: a “black hole” is born, which will capture other stars with the result of continuously increasing its mass.
This mechanism cannot explain the formation of black holes at the center of the quasars, formed a hundred million years after the Big Bang. Their enormous intrinsic brightness is believed to originate from the continuous growth of material in the central supermassive black hole. For these black holes, the explanation of stellar collapse is no longer valid, and over the years, an introduction of a model of the direct collapse.
The growth of black holes through direct collapse could have started when about 400 million years had passed since the Big Bang and would have continued for another 150 million years. During this time, the growth of the black hole occurs under the super-Eddington limit regime.
The Eddington limit defines the maximum value of brightness that an object can reach when the pressure towards the outside, caused by the emitted radiation, counterbalances the gravitational force that tends to make it collapse. It is possible that in the most extreme cases, such as for supermassive black holes, exceeded limits where reached. There is, therefore, talk of the super-Eddington regime, and for these objects, the only possible destiny is the gravitational collapse.
However, the growth in the super-Eddington regime abruptly stops when, in the cloud that houses the black hole, the radiation emitted by the organic matter ionizes the molecules of the cloud dispersing the gas.
Supermassive black holes have only had a short period in which they have been able to proliferate, and then, at some point, due to all the radiation in the universe created by other black holes and stars, their production is the authors of the research explained.
These results can be verified by future observations, in particular by the promising James Webb Telescope, to study further the history and origin of the gigantic black holes born when the Universe was still in its infancy.