Astronomers already knew that other galaxies exist at the beginning of the 20th century. Despite the fact that the first of the discovered galaxies were already known to scientists, at first they were called nebulae, attributing them to our galaxy - the Milky Way. Scientists have suggested that these nebulae may constitute separate stellar systems. However, such hypotheses did not withstand criticism from the scientific world. This was due to the imperfection of the technique for observation.
Galaxy research
In 1922, an astronomer from Estonia, Ernst Epik, was able to calculate the approximate distance that separates the solar system from the Andromeda nebula. The data that the astronomer received is 0.6 of those figures that scientists now have - and this is an even more accurate calculation than that of E. Hubble. Edwin Hubble himself in 1924 used the largest telescope at that time. Its diameter was 254 cm. Hubble also made calculations of the distance to Andromeda. Now scientists have more accurate data, which is three times smaller than the ones made by Hubble - however, this distance is so great that the nebula can in no way be part of our galaxy. So the Andromeda nebula became the first separate galaxy.
Clusters of galaxies
Like stars, galaxies form groups of different sizes. Moreover, such a property is expressed in them much more than in stars. Most stars are not parts of the cluster, being part of the general field of our galaxy. The group of galaxies, which includes the Milky Way (local galaxy), has 40 galaxies. Such a grouping is very common in the vastness of the universe.
Observed galaxy groups
A known part of the galaxy cluster is called the “Metagalaxy” - it can be observed using astronomical methods. The composition of the Metagalaxy includes about one billion galaxies, the observation of which is available using telescopes. The Milky Way is one of the stellar systems that is part of the Metagalaxy. Our galaxy and about 1.5 dozen galaxies are part of a galactic group called the local galaxy group.
Opportunities to explore the Metagalaxy appeared mainly in the late twentieth century. Astronomers have found that in intergalactic space are cosmic and electromagnetic radiation, individual stars, as well as intergalactic gas. Thanks to scientific advances, it has become possible to study different types of galaxies - quasars, radio galaxies.
Metagalaxy Properties
Sometimes astronomers like to call the Metagalaxy "Big Universe." With the improvement of technology and telescopes, an increasing part of it becomes available for observation. Astronomers believe that the Milky Way and the next 10-15 galaxies are members of one galactic cluster. In the Metagalaxy, clusters of galaxies are very common, the number of which is from 10 to several dozen members. Such groups are poorly distinguishable by astronomers at large distances. The reason is that dwarf galaxies are not accessible for observation, and giant ones in such groups, as a rule, are only a few.
According to Einstein's theory of relativity, large masses are able to bend space around themselves. Therefore, the provisions of the Euclidean geometry in this space are not justified. Only on a huge scale of the Metagalaxy can you see the differences between two scientific approaches - Newtonian mechanics and Einstein mechanics. The so-called redshift law also operates in the Metagalaxy. This means that all the galaxies around us are moving away in different directions. Moreover, the further they are removed, the greater their speed becomes.
Types of galaxies in shape
Galactic clusters can be open, or have a spherical shape. They may include tens or even thousands of different galaxies. The closest galaxy to us is located in the constellation Virgo and is 10 million parsecs away. Clusters of galaxies, called regular, have a spherical shape. The constituent galaxies tend to concentrate at one point - the center of the galactic cluster. Correct clusters are already characterized by a high density of galaxies, but in their center the concentration reaches a maximum. However, regular clusters also have differences, manifested mainly in their density and different numbers of galaxies that make up their composition.
Highest density galaxies
For example, a group of Veronica Hair galaxies is characterized by a large number of components, and the galaxies that make up Pegasus are distinguished by their density. It is especially high in the central area of Pegasus. Here, the density reaches 2 thousand galaxies per 1 cubic megaparsec. Nearby galaxies practically touch each other, and their density is almost 40 thousand times higher than the density in the Metagalaxy. Also, high density is characteristic of the groups of galaxies of the Northern Crown.
Where did the galaxies come from?
So far, scientists can not give an exact answer to this question. However, according to the Big Bang theory, the young Universe was full of hydrogen and helium. From this thick cloud under the influence of dark matter (and subsequently gravitational forces) the first stars and star clusters began to form.
When did the first stars appear in the universe?
According to some astronomers, stars appeared quite early - already 30 million years after the Big Bang. Others are convinced that this figure is 100 million years. Studies using modern technology show that luminaries were formed simultaneously in several pieces - often this amount reached even hundreds. This was facilitated by gravitational forces that affect the gas filling the Universe. Gas clouds swirled into disks, and seals gradually formed in them, then became stars. In the young Universe, the first stars were really gigantic - because for them there was a lot of “building material”.
The largest galaxy cluster discovered by astronomers is called SPT-CL J0546-5345. Its mass is almost equal to the mass of 800 trillion Suns. Scientists were able to detect a giant galaxy using the astronomical effect of Sunyaev-Zeldovich - it lies in the fact that the temperature of microwave radiation falls when it interacts with giant objects of the Universe. This cluster is 7 billion light-years distant from us. In other words, astronomers observe it as it was 7 billion years ago - and this is 6.7 billion years after the Big Bang.
In the far reaches of the Universe, another cluster of galaxies was discovered, forming a separate space system - ACT-CL J0102-4915. This huge group of galaxies was called by the astronomers El Gordo, which means “fat man” in Spanish. Its distance to Earth is 9.7 billion light years. The mass of this group of galaxies exceeds the mass of the Sun in 3 million billion.
Veronica's hair
Veronica's Hair Cluster is one of the most interesting galactic groups in the Metagalaxy. It has about several thousand galaxies. They are located several hundred million light-years from the Milky Way. Most galaxies are elliptical. Veronica's hair does not differ in bright stars - even the alpha, called the Diadem, is small. In this constellation, one can observe an accumulation of faintly luminous "Coma" stars, which means "hair" in Latin. The ancient Greek scientist Eratosthenes called this cluster "Hair of Ariadne." Ptolemy attributed it to the composition of the star cluster of Leo.
One of the most beautiful galaxies in the constellation is NGC 4565, or the Needle. From the surface of our planet is visible from the edge. It is located 30 million light years from the Sun. And the diameter of the galaxy is more than 100 thousand light years. There are two interacting galaxies in the Hair of Veronica - NGC 4676, or, as this group is also called, “Mice”. They are 300 million light-years distant from Earth. Studies have shown that already once these galaxies passed through each other. Scientists suggest that the "Mice" will collide more than once, until they turn into one galaxy.