The stars usually seem immobile to us. But it's just the visibility. So, it seems to us that the Sun is moving in the sky relative to the stationary Earth, but in fact, our planet is revolving around the daylight. It seems to us that the Sun and Moon are about the same size, and in fact the Sun is many times larger than the natural satellite of the Earth but is located far beyond the Moon...
Stars also move. But in order to notice their movement, one should compare the position of stars in the sky at sufficiently long intervals, for example, after tens of years.
One of the most grandiose physical processes in the Universe is the outbreak of so-called new and supernovae stars. In fact, a star exists before the outbreak. But at some point, under the influence of rapid physical processes, such a star suddenly increases in volume, "blows up", drops its gas shell and within a few days emits monstrous energy, shining like billions of suns. Then, having exhausted its resources, the star gradually fades away, and there remains a gas nebula at the site of the outbreak.
Our Sun is a "lonely" star. It is devoid of hot-looking satellites. But in the universe, there are double, triple and more complex star systems, whose members are connected by mutual attraction and turn around the common center of masses. Some clusters contain tens, hundreds and thousands of stars. And the number of stars in large ball clusters reaches even hundreds of thousands.
Interstellar space is not empty either. It is filled with gas and dust particles, which in some places form giant clouds - nebulae, light, and dark.
The stars that make up the Galaxy move around its center in very complex orbits. With a great speed - about 250 km/sec. rushes in the world space and our Sun, carrying with it their planets. The solar system makes one full revolution around the galactic center for 180 million years.
The nearest star systems to our galaxy are about 150 thousand light-years away from us. They are visible in the sky of the Southern Hemisphere as small fog spots.
Our Galaxy and other nearby star systems form the Local Galaxy System. It consists of 16 galaxies and has a cross-section of 2 million light-years. Studies show that star islands and galaxies are typical objects of the Universe. Astronomers now know a great number of galaxies in all parts of the celestial sphere.
Galaxies have a variety of shapes and structures. There are ball and elliptical galaxies, disc-shaped galaxies, spiral galaxies, like our own, finally, galaxies of irregular shape. There are billions of galaxies in the field of astronomical research available today. Scientists have called them Metagalactics.
The universe is not a simple set of celestial bodies, it is constantly experiencing extremely complex and diverse physical processes.
And it is from this point of view that the study of the universe is of the greatest interest for modern natural science. Cosmos is an infinitely diverse laboratory where one can study such states of matter, such as physical conditions, and processes that are unattainable on Earth.
Rapid progress of science and technology in the period of scientific and technical revolution, the contemporaries of which we are, leads to new and new discoveries, deeper and deeper penetration into the most intimate secrets of nature, to further knowledge of the fundamental laws of the universe. And the Universe in our time is becoming an increasingly important source of unique information about the phenomena of nature.
Galaxies run away from us in all directions, and the further a galaxy is, the more rapidly it moves. There is a general expansion of Metagalactica, which is carried out in such a way that the speed of mutual removal of the two-star systems is higher, the greater the distance between them.
The picture of galaxy reciprocal dispersal can be reversed in our minds, and then we will come to the conclusion that in the distant past, about 15-20 billion years ago, matter was in a different state than in our era. Then there were no stars, no planets, no nebulae, no galaxies. All matter was concentrated in a very dense, compact hot plasma clot - a mixture of elementary particles of matter and radiation. Then the clot exploded and began to expand, forming first atoms and then stars, galaxies, and all other space objects.
This is how the theory of the expanding universe emerged, one of the most impressive scientific theories of the twentieth century. The notions of an immutable, stationary universe have given way to new notions of the universe, changing over time. It was a new, extremely important step in understanding the properties of the world around us. Further research has shown that various non-stationary phenomena, in general, play an important role in the modern universe.