(ORDO NEWS) — American and European astronomers have found in the constellation Sextant a giant ancient galaxy, which in the first epochs of the existence of the Universe managed to form and reach a mass of 20 trillion Suns in just 500 million years – an almost impossible short time by the standards of cosmology. The article with the results of the study was accepted for publication by the Astrophysical Journal.
“Our observations have shown that, thanks to the ultra-fast rate of formation of new stars, the largest galaxies can grow unusually quickly. Now we need to understand whether the galaxy C1-23152 we discovered can be considered an exception or a typical example of what happened in the early Universe,” said Francesco la Barbera, astronomer of the Italian National Astrophysical Institute (INAF).
It is believed that the first galaxies appeared in the Universe about 300-400 million years after the Big Bang. Then its matter had time to cool down to temperatures at which cold clouds of gas can form. Stars are formed within these clouds.
At first, astronomers assumed that the first galaxies were relatively small and grew slowly. Recent discoveries show that this is actually not the case – large galaxies, which are dozens of times larger than the Milky Way, appeared already in the first billion years of the life of the Universe. The fact of their existence has become another big mystery for scientists.
La Barbera and his colleagues found that galaxies in the early universe could grow even faster than Hubble’s observations of the oldest galaxies in the universe indicated, conducting a kind of “census” of stars in several recently discovered ancient galaxies. This conclusion of scientists was prompted by observations of galaxies, the light from which went to the Earth for almost 12 billion years. This means that we see them in the state in which they were approximately 1.93 billion years after the Big Bang.
Astronomers have tried to determine how fast these galaxies formed stars, how often these galaxies collided with neighboring star clusters and consumed them. To do this, scientists analyzed the spectrum of these galaxies using the LBT binocular telescope, which is installed at the top of Mount Graham in the southern United States, as well as their other properties.
Astronomers roughly estimated how many stars were in these galaxies. During the work, scientists unexpectedly found out that one of such objects, the elliptical galaxy C1-23152 from the constellation Sextant, was formed in a very short time – about 500-600 million years.
This is supported, in particular, by the fact that the average age of stars inside C1-23152 does not exceed 400 million years. This is evidenced by some features of the spectrum of this galaxy. They indicate that the stars in C1-23152 were forming at a record speed. On average, tens and hundreds of new stars were formed in it every year, the total mass of which exceeded the solar mass by about 450 times. These rates of star formation are hundreds of times higher than those observed in the Milky Way and its neighbors.
Interestingly, scientists have not found a single hint that over the entire 500 million years of its existence, C1-23152 collided with neighboring galaxies or absorbed them. This suggests that it “alone” reached a mass about 20 trillion times the solar mass. Previously, this was considered impossible in principle. Astronomers suggest that this was due to the fact that C1-23152 was formed as a result of the collision of several superdense clouds of gas, the existence of which was possible only in the first epochs after the Big Bang.
An equally big mystery for scientists was why the star formation processes in this galaxy, about 600 million years after its appearance, abruptly stopped. La Barbera and his colleagues hope that further observations of C1-23152, as well as similar research for other largest galaxies in the early universe, will help answer both of these questions.
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