Astronomers have discovered a brood of unusual galaxies in the early universe that grew hundreds of times faster than their modern cousins, which explains the mystery of the existence of giant black holes in the early epochs after the Big Bang, according to an article published in the journal Nature.
RIA Novosti / Alina Polyanina
“We were looking for a completely different thing - we were trying to find traces of star formation in those galaxies where these black holes were found. Instead, we managed to find four other objects right next to them, the stars were forming at a breakneck speed - several hundred solar masses a year,”says Roberto Decarli from the Institute of Astronomy in Heidelberg (Germany).
It is believed that the centers of most massive galaxies are home to supermassive black holes, whose mass can range from a million to billions of times the mass of the Sun. The reasons for the formation of these objects are not yet entirely clear. Scientists initially believed that such objects arose in the same way as their normal "cousins": as a result of the gravitational collapse of stars and the subsequent merger of several large black holes.
Observations of the first galaxies in the Universe made astrophysicists doubt this - it turned out that they were inhabited by black holes with a mass of tens of billions of Suns. Such objects, as calculations show, simply would not have time to grow to such a size if they were born small. Therefore, some scientists began to believe that supermassive black holes are born in more exotic scenarios - as a result of the collapse of giant clouds of "pure" atomic hydrogen or due to clumps of dark matter.
This is how the artist imagined the birth of a black hole in the early universe. Photo: John Wise, Georgia Tech
Decarli and his colleagues found a possible answer to this question by studying the most distant galaxies where these black holes were found using the ALMA radio telescope, built on the Chilean high-altitude plateau Chahnantor. This telescope, the authors explain, can track the movements of even the coldest clouds of gases from which stars are formed, which allows it to be used to directly estimate the frequency of star formation.
The galaxies that Decarli and his colleagues tried to study formed about 13 billion years ago, just a few hundred million years after the Big Bang. The enormous distance to them and the bright light of quasars significantly complicate attempts to carry out a census of stars in them and estimate the mass of "stellar building materials", focusing on traces of carbon in their spectrum.
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For this reason, astronomers were unable to see the stars being born inside the 25 galaxies they initially observed, but they were able to follow this process in the neighboring "star megacities", in which black holes were not so active.
As it turned out, stars in them are formed at an unimaginably high speed - every year several stars are born in them, whose mass is several hundred times higher than that of the Sun. Such rates of star formation and the associated influx of cold matter into galaxies, as the calculations of the authors of the article show, should be enough to explain the formation of giant black holes with a mass of billions of Suns in the first billion years of the life of the Universe.