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Scientists have turned their attention to a young group of small galaxies that is just forming - the so-called protocluster, the "germ" of a huge galaxy cluster. As it turned out, some galaxies in it are shrouded in such dense clouds of gas and dust that they are not visible at all in visible light. We are in the Local Group of galaxies, which by and large consists of the Milky Way, the larger Andromeda galaxy, the smaller Triangulum galaxy and numerous dwarf satellite galaxies.
Among them fly intergalactic clouds with a mass of hundreds of millions of Suns each, very slowly moving matter from one galaxy to another. The neighboring galactic "street" called the Virgo Cluster is much larger and more densely populated: more than a thousand galaxies, many comparable to ours. All this is part of the Local Supercluster, which stretches for 200 million light years and contains about 30 thousand galaxies.
And the resulting picture was not always so large-scale, it is the result of long billions of years of evolution of the Universe, and once upon a time the huge Virgo cluster was a small group of young galaxies - a protocluster. to find many such protoclusters.
Recently, an international team of astrophysicists examined one of them from where the light traveled to us more than 12 billion years ago. This means that it looks as it did about a billion and a half years after the Big Bang. As the scientists write in an article published on the Cornell University preprint server (USA), the cluster contains 13 galaxies, and their total mass is about the same as that of one of our Milky Way galaxies, if not less — about hundreds of billions of Suns.
Of particular interest were two galaxies that were first noticed during observations through a radio telescope. Later, they were also observed in some other radiation ranges, but not in the visible or even in the near infrared. According to the collected data, the total "weight" of all the stars in them is about 100 and 50 billion solar masses. For comparison: 50 billion is about the same mass as the Triangulum galaxy.
At the same time, “dark” galaxies are very rich in intergalactic gas — its mass significantly exceeds the total mass of all stars. In the Milky Way, the gas “weighs” an order of magnitude less than the stars combined. This suggests that our mature galaxy has mostly used up all its source material for star formation, so it produces a few new stars per year. In distant dark galaxies, it is estimated that thousands of them light up every year. After all, these galaxies are not visible in visible light because they are in a very dense environment and are shaded by it.
