With the invention of radio telescopes, for example, astronomers can "peek" at distances that in the 1940s seemed inaccessible. However, it is necessary to clearly imagine the immense magnitude of this journey and the enormous difficulties we will still face on our way to the stars
One of the most important and complex in astronomy is the study of the structure and evolution of galaxies. Since the seventeenth century, when Galileo saw the Milky Way in the telescope, his most important goal was to study astronomers. Only in the XIX century. managed to understand that the Milky Way is the only system that contains all the visible stars. Our Sun, Earth, and planets enter this system on an equal footing with everyone, and they are located on its outskirts.
The star system, which we call the Milky Way and seen from the inside, has been defined by astronomers as the Galaxy (the Greek "galacticos" means "milky"). Since the beginning of the XX century. galaxies became the subject of cosmogonic exploration when their true nature was established and it turned out to be not nebulae in the form of clouds of gas and dust, but vast worlds of vision at very great distances from us.
It turns out that the Galaxy has a fairly correct structure and shape, consisting of a disk, a halo (from "round") and a crown. The disk is like two closed edges of a plate and is about 100,000 light-years in diameter. It is formed by stars that move in orbiting circular orbits around the center of the galaxy within this formation.
In the galore, they fill a barely flattened spherical expanse and move along not circular but strongly elongated orbits. The planes of these orbits pass through the center of the galaxy and are distributed more or less evenly in different directions. The disk and the surrounding halo are immersed in the crown. The disc and halo radii are almost equal in size.
The crown radius is many times greater than these distances. The crown is colorless and its radius can be determined only by its gravity, which acts on visible stars and clouds of gas that emit light. The mass of the crown is several times the mass of all the stars in the disk and halo. It is very difficult to study the invisible crown because we do not know what it consists of.
Assuming that its mass consists of a neutrino, then physicists first need to find out whether this small particle has a mass of rest, that is, the mass that the particle has in a state when it is not moving but is in place. (Most elementary particles have this mass). If scientists find a mass of neutrino rest, they may calculate the mass of the crown.
In recent decades, much in the field of cosmology has come to light about the history of galaxies and stars, the physical state of the rarefied substance from which they formed. Modern cosmology is based on the idea of Newton - gravitational instability, all particles of matter create one or another condensation of different mass and scale.
In the Universe, for a long time, there was a distribution and movement of matter, until strong heterogeneities were formed - protoscopation, in which the movement of matter became turbulent.
Protoscales due to gravitational instability were decomposed into separate condensations, known as "protogalaxies." The fragmentation of protogalactic clouds due to the action of gravitational instability led to the emergence of the first stars, and the clouds turned into star systems - galaxies. The fastest-rotating ones received a two-component structure: they formed a halo of more or less spherical shape and a disk in which spiral arms appeared, where the birth of vision is still going.
Protogalaxies with slower rotation or complete absence turned into elliptical or irregular galaxies. Simultaneously with this process was the formation of a large-scale structure of the universe - there were clusters of galaxies, connecting their edges like cells of bee cells.
At the beginning of the XX century. Hubble classified the structure of galaxies, which now distinguishes three classes of galaxies.
- Elliptical galaxies (E) - have an ellipsoidal shape. Here is an example of the circular nebula in the constellation Lira, which is 2100 light-years away. It consists of the light-gas that surrounds the central star. This shell was formed when the aging star "released" into space gas covers. Dawn shrunk and went into a state of white dwarf, similar in size to our planet, and in mass - to the Sun.
- Spiral galaxies - two relatively bright, spiral-shaped branches, extending either from a bright nucleus (such galaxies are indicated by S) or from the ends of a light jumper that crosses the nucleus (denoted by SB). An example is the spiral galaxy M51 in the constellation of Hound Dogs, the distance of which is about 8 million light-years. At the end of the spiral branch, there is a thickening - this is an independent irregular galaxy. Some bright stars are in our galaxy.
- Irregular (irregular) galaxies (I) - have irregular shapes. A striking example is the Great Magellanic Cloud, which is 165,000 light-years away from us and is the galaxy closest to us. Next to it is a smaller galaxy - the Small Magellanic Cloud. Both of these galaxies are satellites of our galaxy.