Mega World Structures
The main structural elements of the mega world are planets and planetary systems; stars and star systems forming galaxies; systems of galaxies forming metagalactics.
Planets are non—self-luminous celestial bodies, similar in shape to a ball, rotating around stars and reflecting their light. Due to its proximity to the Earth, the most studied are the planets of the Solar System moving around it in elliptical orbits. Our Earth, located at a distance of 150 million km from the Sun, also belongs to this group of planets.
Stars are luminous (gas) space objects formed from a gas-dust medium (mainly hydrogen and helium) as a result of gravitational condensation. The stars are separated from each other by huge distances and are thus isolated from each other. This means that the stars practically do not collide, although the motion of each of them is determined by the gravitational force created by all the stars of the Galaxy. The number of stars in the Galaxy is on the order of a trillion. The most numerous of them are dwarfs, whose masses are about 10 times less than the mass of the Sun. Depending on the mass, stars in the process of evolution become either "white dwarfs", or neutron stars, or "black holes".
A "white dwarf" is an electronic post—star formed when a star at the last stage of its evolution has a mass less than 1.2 solar masses. The diameter of the "white dwarf" is equal to the diameter of our Earth, the temperature reaches about a billion degrees, and the density is 10 t / cm3, i.e. hundreds of times more than the earth's density.
Neutron stars arise at the final stage of the evolution of stars with a mass of 1.2 to 2 solar masses. The high temperature and pressure in them create conditions for the formation of a large number of neutrons. In this case, a very rapid compression of the star occurs, during which a rapid development of nuclear reactions begins in its outer layers. At the same time, so much energy is released that an explosion occurs with the scattering of the outer layer of the star, the inner regions of the star are rapidly shrinking. The remaining object is called a neutron star, because it consists of protons and neutrons (they also have the name "pulsars"),
"Black holes" are stars at the final stage of their development, whose mass exceeds 2 solar masses, having a diameter of 10 to 20 km. Theoretical calculations have shown that they have a gigantic mass (1015 g) with an abnormally strong gravitational field. "Black holes" got this name because they do not have a glow, but due to their gravitational field, they capture all cosmic bodies from space and radiation that cannot come back out, "fall" into them as into a hole. Due to the strong gravity, no captured material body can go beyond the gravitational radius of the object, and therefore they appear "black" to the observer.
Star systems (star clusters) are groups of stars connected by gravitational forces, having a common origin, similar chemical composition and including up to hundreds of thousands of individual stars. There are scattered star systems, such as the Pleiades in the constellation Taurus. Such systems do not have the correct form. More than a thousand star systems are known. In addition, the star systems include globular star clusters, consisting of hundreds of thousands of stars. Gravitational forces keep stars in such clusters for billions of years. Scientists know about 150 globular clusters.
Galaxies are aggregations of star clusters. The concept of "galaxy" in modern interpretation means huge star systems. This term comes from the Greek word "milk, milky" and was coined to refer to our star system, which is a light strip with a milky hue stretching across the sky and therefore called the "Milky Way".
Conventionally, the appearance of the galaxy can be divided into three types. Spiral galaxies belong to the first (about 80%). In this species, the nucleus and spiral "sleeves" are clearly observed. The second type (about 17%) includes elliptical galaxies, i.e. those that have the shape of an ellipse. The third type (about 3%) includes irregular-shaped galaxies that do not have a distinct nucleus. In addition, galaxies differ in size, the number of stars included in them, and luminosity. All galaxies are in a state of motion, and the distance between them is constantly increasing, i.e. there is a mutual removal (scattering) of galaxies from each other.
The solar system belongs to the Milky Way Galaxy, which includes at least 100 billion stars, and therefore belongs to the category of giant galaxies. It has a flattened shape, in the center of which there is a core with spiral "sleeves" extending from it. The diameter of our Galaxy is about 100 thousand light—years, the thickness is 10 thousand light-years. Next to us is the Andromeda Nebula galaxy.
Metagalaxy is a system of galaxies that includes all known space objects.
Since the mega world deals with large distances, the following special units have been developed to measure these distances.
