By the beginning of our century, the borders of the explored Universe had moved so far that they included the Galaxy. Many, if not all, then thought that this huge star system was the whole Universe as a whole.
But in the 1920s, new large telescopes were built, and astronomers opened up completely unexpected horizons. It turned out that the world does not end outside the galaxy. Billions of star systems, galaxies, similar to ours and different from it, are scattered here and there in the vastness of the universe.
Photos of galaxies made with the help of the largest telescopes are striking in their beauty and variety of shapes: these are powerful vortexes of star clouds, regular balls, and other star systems do not detect any specific shapes at all, they are ragged and shapeless. All these types of galaxies – spiral, elliptical, irregular – that got their names in appearance in photographs, were discovered by the American astronomer E. Hubble in the 20-30s of our century.
If we could see our Galaxy from afar, then it would appear before us quite different from the one in the schematic drawing, according to which we got acquainted with its structure. We would not see a disk, or a halo, or, naturally, a crown, which is actually invisible. From great distances only the brightest stars would be visible. And all of them, as it turned out, are collected in wide strips that arc out from the central region of the Galaxy. The brightest stars form its spiral pattern. Only this pattern would be distinguishable from afar. Our Galaxy in a picture taken by an astronomer from some starry world would look very similar to the Andromeda nebula.
Recent studies have shown that many large spiral galaxies have – like our Galaxy – extended and massive invisible crowns. This is very important: because if so, then it means that almost the entire mass of the Universe (or, in any case, the vast majority of it) is a mysterious, invisible, but gravitating “hidden” mass.
Many, maybe even almost all galaxies are assembled in various collectives, which are called groups, clusters and superclusters, depending on how many there are. A group can include only three or four galaxies, and a supercluster up to a thousand or even several tens of thousands. Our Galaxy, the Andromeda nebula and more than a thousand of the same objects are included in the so-called Local supercluster. It does not have a clearly defined form.
Other superclusters lying far away from us, but quite distinctly distinguishable in modern large telescopes, are approximately similarly arranged.
Until recently, astronomers believed that these objects are the largest formations in the Universe and that there are no other large systems. But it turned out that this is not so.
A few years ago, astronomers made an amazing map of the universe. On it, each galaxy is represented only by a dot. At first glance, they are scattered randomly on the map. If you look closely, you can find groups, clusters and superclusters that look like chains of dots here. But most strikingly, the map reveals that some of these chains are connected and intersected, forming some kind of mesh or mesh pattern resembling lace or maybe bee honeycombs with cell sizes of 100-300 million light-years.
Whether such “grids” cover the entire Universe remains to be seen. But several individual cells outlined by superclusters have been studied in detail. There are almost no galaxies inside them, all of them are assembled into “walls”.
A cell is a preliminary, working title for the largest entity in the universe. There are no larger systems in nature. It shows a map of the universe. Astronomy has finally reached the completion of one of its most ambitious tasks: the entire sequence, or, as they say, hierarchy, of astronomical systems is now entirely known. But still…
Sun and Stars.
On a clear moonless night, when nothing interferes with observation, a person with keen eyesight will see in the sky no more than two or three thousand flickering dots. In the list compiled in the 2nd century BC by the famous ancient Greek astronomer Hipparchus and supplemented later by Ptolemy, 1022 stars are listed. Hevelius, the last astronomer to make such calculations without the help of a telescope, brought their number to 1533.
But already in antiquity they suspected the existence of a large number of stars invisible to the eye. Democritus, the great scientist of antiquity, said that the whitish streak that stretches across the sky, which we call the Milky Way, is actually a combination of the light of many individually invisible stars. The debate about the structure of the Milky Way continued for centuries. The decision – in favor of Democritus’ hunch – came in 1610, when Galileo announced the first discoveries made in the sky with a telescope. He wrote with understandable excitement and pride that he was now able to “make available to the eye stars that were never previously visible and whose number is at least ten times the number of stars.