After the Big Bang, everything happened very quickly. An international team of astronomers has just published, in the journal Nature, the discovery of the oldest known black hole and it was already there more than 13 billion years ago, just 400 million years after the explosion. In such a short time (on the cosmic scale) it had been able to accumulate the mass of several million suns. The discovery, possible thanks to the space telescope James Webb, It tests theories that try to explain how these objects form and grow.
The discovery occurred in the center of the galaxy GN-z11, discovered by the space telescope Hubble and until recently the oldest known. Although 25 times smaller than the Milky Way and with only 1% of the stars, it was creating them 20 times faster. Its intense brightness suggested that a powerful black hole could be found inside, as happens in galaxies like ours. Although these objects cannot be observed directly, the gas that accumulates in their vicinity heats up and releases ultraviolet rays that reveal their presence.
Roberto Maiolino, professor at the Kavli Institute of Cosmology in Cambridge, does not believe that these results, surprising as they may be, will require new cosmological theories. “At least, not yet,” points out the leader of this study. “The discovery of hypermassive black holes, with masses exceeding billions of solar masses, which were already there in the first billion years after the Big Bang, has been a puzzling result for 20 years,” he explains. The new observations identify the smaller progenitors of those objects that had grown at a rate that already seemed excessive.
One of the theories about the origin of black holes says that they appear when a star one hundred times larger than the sun exhausts its nuclear fuel and collapses under its own gravitational force. Then, feeding on their environment, they begin to accumulate mass, but to reach the size of the object observed in the galaxy GN-z11 at the growth rate seen in nearby black holes, billions of years would be needed. And the galaxy only has 400 million.
Among the models that can make sense of these black holes, some experts say that, although they were born small, in that early universe there was much more gas available to fuel their growth and they could grow up to five times faster than was thought possible. An alternative suggests that they could also have emerged as giants, the result of the gravitational collapse of primordial gas clouds. The capacity of James Webb to transport us to the infancy of the universe and discover more primitive black holes will serve in the coming years to reconstruct the lineage of these influential cosmic monsters.
“The presence of supermassive black holes in galaxies is very important, because we see that their properties are related to the properties of the galaxy,” says Michele Perna, co-author of the study and researcher at the Center for Astrobiology in Madrid. “This is strange, because a black hole is very small compared to the size of the galaxy, like a euro compared to the size of the Earth, and its mass is also a fraction of that of the galaxy, like 1% or less. ”, he indicates. Despite these differences, there is a connection between the activity of the black hole and its galaxy, in how this object, small in comparison, determines the rate at which stars are born in the galaxy or when star formation stops.
In the case of GN-z11, astronomers believe that the black hole may be harming its development, because part of the gas it consumes voraciously shoots towards the galaxy, like a hurricane, and can stop star formation. If this were to happen, it would suck life from the galaxy and ruin its food source.
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