The internal structure of the Sun and main sequence stars and energy sources

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 we still have to dream about their direct investigation. Only the Sun is available for constant observation at a relatively short distance. However, even in the case of the central star of our planetary system, most 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 interior - all these characteristics are derived "at the tip of the pen." However, they are sufficient to explain many of the nuances of behavior not only of our luminary, but also of other stars that are similar to it.

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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. In the chemical composition of the light, hydrogen predominates strongly (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 relationship 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 maintenance of the constancy of all stars.

Thermonuclear boiler

The model of the internal structure of the Sun is formed due to observation, theoretical analysis, spectroscopy and other methods of astronomy. Based on the information gathered in this way, the characteristics of the star are determined. The derived regularities and created theories exist as long as they explain well the visible changes occurring with the luminary and other similar stars of the main sequence.

According to modern concepts, the main source of solar radiation are thermonuclear reactions, constantly flowing in its core. At extremely high temperatures (14 million Kelvin), hydrogen is converted to helium. At the same time, an impressive amount of energy is allocated.

Layers

The internal structure of the Sun is three zones: a core, an isothermal and a convective region. The core of the star occupies about a quarter of its radius and is a very strongly compressed substance. The core mass is almost half of the total solar energy. It is here that reactions of synthesis of elements take place.

Then follows the isothermal zone. Here, the energy formed in the course of the 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 parameters of these parameters, convection processes arise - the next layer of the luminary begins. Here the energy transfer is carried out by the substance itself. The convective zone near the Sun is much less isothermal (the seventh part of the radius).

Close by structure

The internal structure of the Sun and stars of the main sequence is similar. It is somewhat different in the case of blue stars and red dwarfs. The former are characterized by a convective core and a fairly extended radiant transfer zone (isothermal). Red dwarfs are similar in sequence to the stars of the Sun type. However, they dominate the convection zone, and radiant transfer occupies only a relatively small area.

Atmosphere

The sun does not have a familiar surface for us. It, like all the stars, is a glowing gas ball. The surface is allocated conditionally and delineates the convective zone of the light and its atmosphere. It also distinguishes three layers.

The internal structure of the Sun and stars of the main sequence, similar to it, ends with a zone of convection. It is directly adjacent to the photosphere, a 300-meter layer, from where the 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 falls to a value of 4800 K. The photosphere is strongly rarefied. Its density is a thousand times less than the analogous air parameter on Earth. Gradually, it flows into the chromosphere, behind which is the crown of the Sun.

Composition of the atmosphere

The content of certain elements in the outer shells of the light is determined by means of spectral analysis. His data show that according to the chemical composition of the atmosphere, the Sun is analogous to the stars of the second generation (they have been formed during the last several billion years). Unlike their predecessors, they are characterized by a much higher concentration of elemental atoms, heavier than hydrogen and helium. The sun and similar luminaries were formed after the destruction of a part of the first-generation stars, in the bowels of which in the process of thermonuclear fusion heavy elements were formed.

Chromosphere

The internal structure of the Sun and stars is not available for direct observation. The same can be said about the air envelope of the luminary following the photosphere. Significant brightness allows you to see it only during a total solar eclipse. This shell is called "chromosphere", which in translation means "colored sphere". At the moment when the Moon blocks the Sun, it acquires a pinkish hue, the appearance of which contributes to hydrogen. It is this element that makes up an 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 matter. In the upper layers of the chromosphere, the temperature reaches 50,000 kelvins.

Crown

The line of the hydrogen spectrum ceases to be distinguishable at an altitude of 12,000 kilometers above the photosphere. A little further noticeable is the trace of calcium. Its spectral line disappears after another 2,000 km. The height of 14 000 km above the photosphere is considered to be the beginning of the crown, the third outer shell of our luminary.

The higher from the conventional surface of the Sun, the less dense becomes the air and is more significant than the temperature. The crown, 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 crown is 30 solar radii. The farther from the chromosphere, the less dense it becomes. The last layer of it flows into outer space, forming a solar wind.

Future

The inner structure of the Sun, as scientists see it today, will not last forever. Sooner or later, according to forecasts in about 5 billion years, the luminous will run out of fuel. As a result, the internal structure of the Sun will change greatly: the core shrinks to a size that is 100 times smaller than the modern dimensions of the luminary, and its other shells will turn into a slowly cooling atmosphere. Our star will enter the stage of the red giant. In a few tens of thousands of years, the expanding shell of the Sun will dissipate in outer space and the luminary will turn into a white dwarf.

Doubts

The development of the event can go in a different scenario, since the sources of energy and the internal structure of the Sun, as well as similar stars, are still not fully understood. It has been suggested that thermonuclear fusion does not play such an important role as it is credited with. 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 punching ability, that is, they must reach the Earth without hindrance. However, they have not been able to fix them yet.

The data of the group of astronomers under the guidance of Academician A.B. North. According to them, the Sun experiences slight fluctuations. They are possible only if the luminosity is uniform. That is, if it were possible to capture the internal structure of the Sun, the photo would demonstrate a complete uniformity of the layers. In this case, the temperature of the yard of the luminary should be 6.5 million kelvins, which is low for the flow of thermonuclear reactions. While this hypothesis is only gaining momentum.

Thus, the inner structure of the Sun, summarized here, requires further careful study. Perhaps the final understanding of the processes taking place in the bowels of the stars will become available to us only after a significant improvement in the equipment and methods of cognition.