The sun – the central body of the solar system – is a hot plasma ball. The sun is the star closest to Earth. The light from it reaches us in 8.3 minutes. The sun has decisively influenced the formation of all the bodies of the solar system and created the conditions that led to the emergence and development of life on Earth. Its mass is 333,000 times the mass of the Earth and 750 times the mass of all other planets combined. Over the 5 billion years of the sun’s existence, already about half of the hydrogen in its central part has turned into helium. As a result of this process, the amount of energy that the sun radiates into world space is released. The radiation power of the Sun is very large: about 3.8 * 10 20 degrees MW. An insignificant part of solar energy, about half a billionth of a billion, falls on Earth. It maintains the earth’s atmosphere in a gaseous state, constantly heats the land and water bodies, provides energy to winds and waterfalls, and ensures the livelihoods of animals and plants. Part of the solar energy stored in the bowels of the earth in the form of coal, oil and other minerals. The diameter of the Sun visible from the Earth varies slightly due to the ellipticity of the orbit and is, on average, 1,392,000 km (which is 109 times the diameter of the Earth). The distance to the Sun is 107 times its diameter. The sun is a spherically symmetric body in equilibrium. Everywhere at equal distances from the center of this ball, the physical conditions are the same, but they noticeably change as one approaches the center. Density and pressure rapidly increase in depth, where the gas is more strongly compressed by the pressure of the overlying layers. Consequently, the temperature also rises as it approaches the center. Depending on the change in physical conditions, the Sun can be divided into several concentric layers, gradually turning into each other. In the center of the sun, temperature is 15 million degrees, and pressure exceeds hundreds of billions of atmospheres. Gas is compressed here to a density of about 150,000 kg / m3. Almost all of the energy of the sun is generated in the central region with a radius of about 1/3 of the solar. Through the layers surrounding the central part, this energy is transmitted outward. Over the last third of the radius there is a convection zone. The reason for the occurrence of mixing (convection) in the outer layers of the Sun is the same as in a boiling kettle: the amount of energy coming from the heater is much more than that which is removed by thermal conductivity. Therefore, the substance is forced to move and begins to transfer heat itself. The core and convection zone are practically not observable. Their existence is known either from theoretical calculations, or based on indirect data. Directly observed layers of the Sun, called its Atmosphere, are located above the convective zone. They are better studied since their properties can be judged from observations.
1a). The solar atmosphere also consists of several different layers. The deepest and thinnest of them is the photosphere, directly observed in the visible continuous spectrum. The thickness of the photosphere is about 300 km. The deeper the photosphere layers, the hotter they are. In the outer colder layers of the photosphere, Fraunhofer absorption lines form against the background of the continuous spectrum. During the greatest calm of the Earth’s atmosphere, one can observe the characteristic granular structure of the photosphere. The alternation of small light spots – granules – about 1000 km in size, surrounded by dark gaps, gives the impression of a cellular structure – granulation. The occurrence of granulation is associated with convection under the photosphere. Individual granules are several hundred degrees hotter than the gas surrounding them, and within a few minutes their distribution over the solar disk changes. Spectral measurements indicate the movement of gas in granules, similar to convective: in granules, gas rises, and between them it drops. This movement of gases gives rise to acoustic waves in the solar atmosphere, similar to sound waves in the air. Propagating into the upper atmosphere, waves that arise in the convective zone and in the photosphere transfer part of the mechanical energy of convective motions to them and produce heating of the gases of the subsequent atmospheric layers – the chromosphere and corona. As a result, the upper layers of the atmosphere with a temperature of about 4,500 K turn out to be the “coldest” on the Sun. Both deep and up from them, the temperature of the gases increases rapidly. The layer located above the photosphere is called the chromosphere, during total solar eclipses in those minutes when the moon completely covers the photosphere, it is visible as a pink ring surrounding a dark disk. At the edge of the chromosphere, protruding flames of the flame are observed – chromospheric spicules, which are elongated columns of compacted gas. Then you can observe the spectrum of the chromosphere, the so-called flash spectrum. It consists of bright emission lines of hydrogen, helium, ionized calcium and other elements that suddenly flash during the complete dimming phase.