Astronomers have studied three unusually bright objects from a period just 600-800 million years after the Big Bang. They thought their unusual radiation was explained by dust clouds, but they turned out to be galaxies densely packed with old stars.

Stars about 13 billion years old fly on the outskirts of the centers of the most powerful galaxies of the modern universe. These luminaries have a high content of elements that usually form in very massive stars and fly outwards as a result of the collapse of the core and the emergence of a supernova. It turns out that these objects must have formed during a burst of star formation when the age of the universe was less than 1.2 billion years.

Scientists have already managed to find potential “ancestors” of modern large galaxies from the moment when 3.3 billion years have passed since the Big Bang. With the help of the “James Webb” space telescope, it was possible to examine many candidates from the time when the universe was formed only 1.2 billion years ago. It is clear that at least some of these star clusters must have formed even earlier.

In the “James Webb” observations, astronomers discovered numerous compact, massive and extremely “red” galactic emissions from the first billion years after the Big Bang. The problem arose in the interpretation of their red radiation. This could be due both to a population of sufficiently old stars that scientists are looking for, as well as interstellar dust, an active galactic nucleus, or other effects.

The authors of a new study published in the journal Astrophysics Journal Lettersanalyzed the emission of three such “red dots” and tried to understand all possible scenarios and models for the appearance of this type of light.

Objects RUBIES-EGS-49140, 55604 and 966323, discovered in the RUBIES spectroscopic survey, were the subject of the study. We see them as they were 600-800 million years after the Big Bang (redshift from 6.7 to 8.4).

After studying the intensity of its radiation at different wavelengths, scientists concluded that most likely it is a cluster of really “old” stars for such a young universe. The light is several hundred million years old.

“We did not expect to find old stars in a very young universe. Although standard models of cosmology and galaxy formation are incredibly successful, these bright objects do not fit well with accepted theories.” explained Bingjie Wang from Pennsylvania State University (USA), lead author of the new study.

If we assume that star clusters formed very quickly and “efficiently” in the first billion years after the Big Bang, objects can be “fit” into accepted cosmological theories. The total mass of the stars in these clusters should have reached tens of millions of solar masses.

At most, scientists have found signs of the existence of black holes at the centers of some of the objects studied, with masses hundreds or even a thousand times greater than the typical central black holes in galaxies of similar mass in the modern universe. These black holes present a problem: They may account for some of the visible radiation from these objects. But the authors are confident that the real “culprits” are still old stars.

Ultimately, scientists were stunned by the size of the systems; It was only a few hundred years in diameter. It turns out that there are almost the same number of stars there as in the Milky Way, but they are located in an area a thousand times smaller in size. According to study co-author Joel Leja, associate professor of Astronomy and Astrophysics at the University of Pennsylvania (USA), if our galaxy were to be compressed to these dimensions, it would be the closest star to the Sun. It will be almost inside our Solar System. And the supermassive black hole at the center of the galaxy would be only 26 light-years away. We would see its surroundings as a bright column of light in the sky.

The stars in these galaxies had to form under conditions that do not exist in the modern universe. A few billion years after the Big Bang, such objects stopped appearing. We haven’t yet found out why this happened. Scientists will continue to collect and analyze James Webb data to understand the formation history of stars, clusters, galaxies, and supermassive black holes in the early universe.