What are galaxies, and what are they?

Those who like to look at the night starry sky, probably noticed a wide band, densely strewn with a variety of (bright, barely noticeable, blue, white, etc.) stars. This cluster is a galaxy.

What are galaxies? One of the greatest mysteries of the universe is that an infinite number of stars are not scattered chaotically in outer space, but are grouped into galaxies. Almost the same way people inhabit cities, leaving the space between settlements empty.

Our planet enters the Milky Way galaxy. Some names of galaxies are well known to us: Big and Small Magellanic Clouds, Andromeda Nebula. We can consider them with the naked eye, while others are very far from the Earth. For quite a long time, it was not possible to consider separate stars in them, it only happened in the 20th century.

"What are galaxies?" - this question was of interest to scientists for a long time. But a real breakthrough in this area occurred at the end of the twentieth century, when the Hubble telescope was created and launched into space.

The dimensions of our galaxy are so huge that it is impossible even to imagine. One hundred thousand earth years will need a light beam to get from one edge to the other. In its center there is a core, from which several spiral lines filled with stars branch off. "Density" is only apparent, in fact they are very rarely located.

Various types of galaxies are known. They differ in shape, mass, size, and also in the substances contained in them. They all contain gas and stardust. There are spiral, elliptical, irregular, sphere-like and other forms of galaxies.

What are galaxies? What is their age? How are they arranged? What processes are taking place in them? Their age is approximately equal to the age of the universe. For scientists, it remains a mystery what the nucleus of a galaxy is. It was found that some nuclei are 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 vary in some galactic nuclei in a few months. This means that they release a colossal amount of energy (much more than a supernova explosion) in a short time.

In 1963, completely new objects with a starlike appearance were identified. They were called quasars. Their luminosity, as it turned out later, far exceeds the luminosity of galaxies. It's amazing that the brightness of quasars can vary.

The formation of galaxies is a natural process of the evolution of the universe, proceeding under the influence of gravitational forces. The variety of species and forms of galaxies is explained by the variety of conditions in which they originated. The compression of the galaxy can last 3 billion years. At this time, the gas is transformed into a stellar system. It is by compressing the gas cloud that stars are formed (when a certain density and temperature is reached sufficient for thermonuclear processes).

Gradually, the interstellar gas reserves are depleted, and the formation of stars becomes less intense. When all the resources have been exhausted, the spiral galaxy is transformed into a lenticular, consisting entirely of red stars. This stage is passed by elliptical galaxies, whose gas resources were consumed another 15-20 billion years ago.

For many people, the idea of what galaxies are is formed from many fantastic films whose characters adore traveling through space, visiting unknown planets and galaxies. In fact, this is not planned in the foreseeable future. Even if we move with the speed of light (which is also impossible), we will reach the Nebula of Andromeda (the nearest galaxy) only after 2.5 million years. Although (according to the calculations of astronomers), it approaches us and after 4-5 billion years will face our Milky Way, which will lead to the formation of a new elliptical galaxy.