Stars are distributed unevenly across the universe. They are combined into clusters, which are commonly called galaxies. However, it will be a mistake to consider that the constellations visible in the sky are star clusters. Those luminaries that a person sees in one part of the sky, in fact, can be removed from each other at a gigantic distance.
Universal Scale Definition
According to the astronomical dictionary, the metagalaxy is a part of the entire Universe that can be observed and investigated using modern scientific methods and instruments. It contains about a billion stellar systems. There is another definition. For example, the Great Soviet Encyclopedia says that a metagalaxy is a collection of galaxies, which includes many galaxies (about 1 billion), which can be observed using telescopes. The more powerful modern technology becomes, the more the boundaries of human knowledge about the unknown Universe expand. The matter of the Universe is the matter of which the entire metagalaxy is composed. Sometimes you can see such a definition: the Universe and the metagalaxy are synonyms.
The concepts of “metagalaxy” and “observable Universe”
To understand in more detail what a metagalaxy is, another term must be explained - the “observable Universe”. Astronomers call this phrase that part of the Universe that a person can observe from the Earth. In this case, scientists can observe and explore its most diverse parts - not only stars and planets, but also waves, and signals - everything that passes relative to our home in the Universe. The Observed Universe is only a part of the vast Space. It has its own border - the cosmological horizon. Scientists believe that the total number of star clusters in the observable Universe exceeds 170 billion.
Since the concept of the observable Universe includes a much larger number of objects than can be seen by a simple person, the concept of a metagalaxy was introduced. Stars and galaxies observed using cutting edge technology are part of the observable Universe. If we are talking about those objects that are beyond this reach, then such objects are called metagalactic. Many astronomers believe that the actual dimensions of the Universe are significantly larger than those available to observation.
But the observable Universe cannot be observed completely by astronomers, because it is limited to special radiation. Because of it, it is almost impossible to observe what is beyond the horizon. This radiation is the farthest object that modern astronomy has “reached”.
Galactic clusters
Galaxies are grouped into clusters of various types in the same way as stars do. There are two types of galactic clusters - globular and open. All stars that can be observed with the naked eye or with the help of telescopes (excluding the most powerful of them) form one system - our Galaxy. Scientists believe that it has about 100 billion components.
Discovery of new galaxies
Beyond the borders of the Milky Way, astronomers have discovered a large number of other stellar systems. They are similar in structure to ours. Similarly, they are made up of billions of stars, some of which are similar to the Sun. The structure of the metagalaxy has become the subject of research at the turn of the XIX and XX centuries. Then, some astronomers were convinced that nebulae are actually stellar systems that are billions of light years distant from the Milky Way.
Andromeda Galaxy - an example of an independent star system
At the beginning of the 20th century, Edwin Hubble proved that such nebulae are actually separate, often gigantic, stellar systems. An example of such a separate galaxy is the cluster of Andromeda stars. You can watch it on a clear, but moonless night. It is visible as a bright foggy spot the size of a moon disk. In many ways, the galaxy is similar to the Milky Way. It is visible to observers slightly tilted with respect to the angle of view. The brightest parts of it are built like a spiral, and it itself is larger than our galaxy. The Andromeda Nebula is more than 1 million light-years from us.
Theory of an expanding universe
This theory is one of the most ambitious in science. Its other names are “the theory of the expanding metagalaxy,” or simply the Big Bang Theory. Its main position is that the Universe was born about 20 billion years ago. This was due to a giant explosion of a cluster of matter of great density. How did this theory come about? Once upon a time, the so-called isotropic models of the Universe were popular. The author of one of them was A. Einstein.
What does this term mean? Each galaxy (and metagalaxy) can be divided into several elementary regions. The same thing can be done with the whole universe. Isotropy means that the properties of the metagalaxy are the same in all such areas. According to the model proposed by Einstein, the metagalaxy is a stationary system in which no changes occur. Subsequently, this theory was refuted by the domestic scientist A. A. Fridman. He proposed a model of an expanding universe.
Quasars are the brightest objects of the Universe
An important contribution to the study of various objects of the metagalaxy is the study of quasars - unusual and fascinatingly beautiful formations. Quasars are fueled by uncharted black holes, with their bright radiance they eclipse neighboring galaxies. Quasars have masses that are billions of times greater than the mass of the sun.
When scientists first obtained data on quasars, they could not believe in their existence. A healthy desire for skepticism forced them to find a scientific explanation for these objects. However, subsequent astronomical studies have shown that the brightest formations of the metagalaxy are actually in front of scientists. Supermassive black holes are the best power sources for quasars. Black holes of this type are areas in outer space whose gravitational forces are so strong that even sunlight cannot escape beyond their boundaries. Supermassive black holes are also a mystery to astronomers. Their size can reach the size of the solar system. How they are formed, none of the scientists can not yet understand.