Stars are the most common bodies in the universe. Many astrophysicists devote their lives to their study. At the same time, all the luminaries are so far removed from our planet that they can only dream of a direct study of them. Only the Sun is available for constant observation at a relatively short distance. However, in the case of the central luminary of our planetary system, most of the parameters are obtained from calculations based on theories and only indirectly confirmed by observations. The internal structure of the Sun, the source of its energy, the features of certain processes occurring in the bowels - all these characteristics are derived "at the tip of the pen." However, they are enough to explain many of the nuances of the behavior of not only our luminary, but also other stars similar to it.
Parameters
The sun is a star of spectral class G2, a yellow dwarf. Its mass is estimated at 2 · 10 30 kg, and the radius is 696 thousand kilometers. Hydrogen predominates in the chemical composition of the star (90%), followed by helium (10%) and heavier elements (less than 0.1%). The sources of energy and the internal structure of the sun are closely related to the ratio and transformation of these atoms.
At each point of the star, the balance of two opposing forces is constantly maintained : gravity and gas pressure. Due to their harmonious correlation, the Sun is a more or less stable cosmic body. A similar mechanism underlies the constancy of all stars.
Thermonuclear boiler
The model of the internal structure of the Sun is formed thanks to the data of observation, theoretical analysis, spectroscopy and other methods of astronomy. Based on the information collected in this way, the characteristics of the star are determined. Derived laws and created theories exist as long as they well explain the visible changes that occur with the star and other similar stars of the main sequence.
According to modern concepts, the main source of solar radiation are thermonuclear reactions that constantly occur in its core. At extremely high temperatures (14 million kelvins), hydrogen is converted to helium. An impressive amount of energy is released.
Layers
The internal structure of the Sun is three zones: the core, the isothermal and convective regions. The core of the star occupies about a quarter of its radius and is a very highly compressed substance. The mass of the nucleus is almost half of the total solar mass. It is here that the reactions of the synthesis of elements proceed.
This is followed by an isothermal zone. Here, the energy generated during reactions in the nucleus is transferred by radiation. This is the longest zone. Energy slowly seeps through it. As it moves forward, the temperature and pressure in the bowels of the Sun decrease. With certain indicators of these parameters, convection processes occur - the next layer of the star begins. Here the energy transfer is carried out by the substance itself. The convective zone of the Sun is much less isothermal (the seventh of the radius).
Similar in structure
The internal structure of the Sun and the stars of the main sequence is similar. It is slightly different in the case of blue stars and red dwarfs. The former are characterized by a convective core and a rather long zone of radiant transfer (isothermal). Red dwarfs are similar in sequence to the arrangement of stars with stars like the Sun. However, the convection zone dominates in them, and the radiative transfer occupies only a relatively small area.
Atmosphere
The Sun has no familiar surface for us. It, like all stars, is a luminous gas ball. The surface stands out conditionally and delimits the convective zone of the star and its atmosphere. It also distinguishes three layers.
The internal structure of the Sun and the main sequence stars similar to it ends with a convection zone. It directly borders the photosphere, a 300-meter layer, from where radiation rushes into space, including the Earth. The average temperature of this part is 5800 K. As it moves away from the convective layer, it drops to a value of 4800 K. The photosphere is very rarefied. Its density is a thousand times less than a similar parameter of air on Earth. Gradually, it flows into the chromosphere, behind which lies the corona of the sun.
Atmosphere composition
The content of certain elements in the outer shells of the luminary is determined using spectral analysis. His data show that the Sun's chemical composition is similar to second-generation stars (they have formed over the past several billion years). Unlike their predecessors, they are characterized by a much higher concentration of element atoms, heavier than hydrogen and helium. The sun and similar luminaries formed after the destruction of some of the stars of the first generation, in the bowels of which heavy elements were formed in the process of thermonuclear fusion.
Chromosphere
The internal structure of the Sun and stars is not available for direct observation. The same can be said of the luminaries following the photosphere. Significant brightness allows you to see it only during a total solar eclipse. This shell is called the "chromosphere", which means "colored sphere". At that moment, when the Moon blocks the Sun, it acquires a pinkish tint, the appearance of which is promoted by hydrogen. It is this element that makes up the impressive part of the highly rarefied chromosphere.
The temperature here is higher than on the previous layer. This phenomenon is explained by a decrease in the density of the substance. In the upper layers of the chromosphere, the temperature reaches 50 thousand Kelvin.
Crown
The line of the hydrogen spectrum ceases to be distinguishable at an altitude of 12 thousand kilometers above the photosphere. A little more noticeable trace of calcium. Its spectrum line disappears after another 2,000 km. A height of 14,000 km above the photosphere is considered to be the beginning of the corona, the third outer shell of our luminary.
The higher the conditional surface of the Sun, the less dense the air becomes and more significant the temperature. The corona, which is a rarefied plasma, is heated to 2 million kelvins. As a result, the substance of the region becomes a constant powerful source of x-ray and ultraviolet radiation.
Studies show that the length of the corona is 30 solar radii. The farther from the chromosphere, the less dense it becomes. Its last layer flows into outer space, forming a solar wind.
Future
The internal structure of the Sun, as scientists see it today, will not last forever. Sooner or later, according to forecasts, after about 5 billion years, the star will run out of fuel. As a result, the internal structure of the Sun will change dramatically: the core will shrink to a size 100 times smaller than the modern dimensions of the star, and its other shells will turn into a slowly cooling atmosphere. Our star will enter the stage of the red giant. After a few tens of thousands of years, the expanding shell of the Sun will dissipate in outer space and the star will turn into a white dwarf.
Doubt
The development of the event can go according to another scenario, since the sources of energy and the internal structure of the Sun, as well as stars similar to it, are still not fully understood. It has been suggested that fusion does not play such an important role as is attributed to it. An indirect confirmation of this is the solar neutrino, more precisely, its absence. These particles are formed in the process of thermonuclear reactions and have a powerful breakdown ability, that is, they must freely reach the Earth. However, they have not yet been able to fix them.
The data of a group of astronomers led by academician A.B. Northern. According to them, the Sun experiences slight fluctuations. They are possible only subject to the uniformity of the star. That is, if it was possible to capture the internal structure of the Sun, the photo would demonstrate the complete uniformity of the layers. At the same time, the temperature of the yard of the star should be 6.5 million Kelvin, which is not enough for thermonuclear reactions to occur. So far, this hypothesis is only gaining strength.
Thus, the internal structure of the Sun, summarized here, requires further careful study. Perhaps a final understanding of the processes occurring in the depths of the luminaries will become available to us only after a significant improvement in the equipment and methods of cognition.