Those who like to look at the night starry sky must have noticed a wide band densely strewn with a variety of (bright, barely noticeable, blue, white, etc.) stars. This cluster is the galaxy.
What are galaxies? One of the greatest mysteries of the Universe is that countless stars are not scattered randomly in outer space, but are grouped into galaxies. In much the same way that people populate cities, leaving the space between settlements empty.
Our planet enters the Milky Way galaxy. Some names of galaxies are well known to us: Large and Small Magellanic Clouds, Andromeda Nebula. We can see them with the naked eye, while others are very far from the Earth. For quite a long time it was not possible to consider individual stars in them, this was done only in the 20th century.
"What are galaxies?" - this question has interested scientists for a long time. But the real breakthroughthis region occurred at the end of the twentieth century, when the Hubble telescope was created and launched into space.
The size of our galaxy is so huge that it is impossible to even imagine. One hundred thousand Earth years will take a light beam to get from one end of it to the other. In its center is the core, from which several spiral lines filled with stars branch off. This "density" is only apparent, in fact they are located quite rarely.
Different types of galaxies are known. They differ in shape, mass, size, as well as in the substances they contain. They all contain gas and stardust. There are spiral, elliptical, irregular, spherical and other forms of galaxies.
What are galaxies? What is their age? How are they arranged? What processes take place in them? Their age is approximately equal to the age of the Universe. For scientists, it still remains a mystery what the core of the galaxy is. Some nuclei have been found to be quite active. This was a surprise, because before this discovery it was believed that the core is a dense cluster of hundreds of millions of stars. Radiation (both optical and radio) can change in some galactic nuclei over several months. This means that they release an enormous amount of energy (much more than in a supernova explosion) in a short time.
In 1963, completely new objects with a star-like appearance were identified. They were called quasars. Their luminosity, as it turned out later, far exceeds the luminositygalaxies. Surprisingly, the brightness of quasars can change.
The formation of galaxies is a natural process of evolution of the Universe, proceeding under the influence of gravitational forces. The variety of types and forms of galaxies is explained by the variety of conditions in which they originated. The contraction of the galaxy can continue for 3 billion years. At this time, the transformation of gas into a star system takes place. It is through the compression of a gas cloud that stars are formed (when a certain density and temperature are reached, sufficient for thermonuclear processes).
Gradually, the reserves of interstellar gas are depleted, and the formation of stars becomes less intense. When all resources are exhausted, the spiral galaxy will transform into a lenticular galaxy consisting entirely of red stars. Elliptical galaxies, whose gas resources were used up 15-20 billion years ago, go through this stage.
For many people, the idea of what galaxies are is formed from numerous science fiction films, the heroes of which love to travel through space, visit unknown planets and galaxies. In fact, this is not expected in the foreseeable future. Even if we move at the speed of light (which is also impossible so far), then we will reach the Andromeda Nebula (the galaxy closest to us) only after 2.5 million years. Although (according to astronomers' calculations) it is approaching us and in 4-5 billion years it will collide with our Milky Way, which will lead to the formation of a new elliptical galaxy.
