SUN
the star around which the earth and other planets revolve solar system. The sun plays an exceptional role for humanity as the primary source of most types of energy. Life as we know it would not be possible if the Sun were a little brighter or a little weaker. The sun is a typical small star, there are billions of them. But because of its proximity to us, only it allows astronomers to explore in detail physical structure stars and processes on its surface, which is practically unattainable in relation to other stars, even with the help of the most powerful telescopes. Like other stars, the Sun is a hot ball of gas, mostly hydrogen compressed by its own gravity. The energy radiated by the Sun is born deep in its bowels during thermonuclear reactions that convert hydrogen into helium. Seeping out, this energy is radiated into space from the photosphere - a thin layer of the solar surface. Above the photosphere is the outer atmosphere of the Sun - the corona, which extends for many radii of the Sun and merges with the interplanetary medium. Since the gas in the corona is very rarefied, its glow is extremely weak. Usually imperceptible against the background of a bright daytime sky, the corona becomes visible only during the moments of total solar eclipses. The gas density decreases monotonically from the center of the Sun to its periphery, and the temperature, which reaches 16 million K in the center, decreases to 5800 K in the photosphere, but then rises again to 2 million K in the corona. The transitional layer between the photosphere and the corona, observed as a bright red rim during total solar eclipses, is called the chromosphere. The Sun has an 11-year cycle of activity. During this period, the number of sunspots (dark regions in the photosphere), flares (unexpected brightenings in the chromosphere) and prominences (dense cold clouds of hydrogen condensing in the corona) rises and again decreases again. In this article, we will talk about the areas and phenomena mentioned above on the Sun. After a brief description of the Sun as a star, we will discuss its interior, then the photosphere, chromosphere, flares, prominences, and corona.
The sun is like a star. The Sun is located in one of the spiral arms of the Galaxy at a distance of more than half the galactic radius from its center. Together with neighboring stars, the Sun revolves around the center of the Galaxy with a period of approx. 240 million years. The Sun is a yellow dwarf of spectral type G2 V, belonging to the main sequence in the Hertzsprung-Russell diagram. The main characteristics of the Sun are given in Table. 1. Note that although the Sun is gaseous right up to the very center, its average density (1.4 g/cm3) exceeds the density of water, and in the center of the Sun it is much higher than even that of gold or platinum, which have a density of approx. 20 g/cm3. The surface of the Sun at a temperature of 5800 K radiates 6.5 kW/cm2. The sun rotates around its axis in the direction of the general rotation of the planets. But since the sun is not solid, different areas of its photosphere rotate at different speeds: the rotation period at the equator is 25 days, and at a latitude of 75 ° - 31 days.

Table 1.
CHARACTERISTICS OF THE SUN

INTERNAL STRUCTURE OF THE SUN
Since we cannot directly observe the interior of the Sun, our knowledge of its structure is based on theoretical calculations. Knowing from observations the mass, radius, and luminosity of the Sun, in order to calculate its structure, it is necessary to make assumptions about the processes of energy generation, the mechanisms of its transfer from the core to the surface, and the chemical composition of matter. Geological evidence indicates that the luminosity of the Sun has not changed significantly over the past few billion years. What energy source can sustain it for so long? Conventional chemical combustion processes are not suitable for this. Even gravitational contraction, according to the calculations of Kelvin and Helmholtz, could only keep the Sun glowing for approx. 100 million years. G. Bethe solved this problem in 1939: the source of the Sun's energy is the thermonuclear conversion of hydrogen into helium. Since the efficiency of the thermonuclear process is very high, and the Sun is almost entirely hydrogen, this completely solved the problem. Two nuclear process ensure the luminosity of the Sun: the proton-proton reaction and the carbon-nitrogen cycle (see also STARS). The proton-proton reaction results in the formation of a helium nucleus from four hydrogen nuclei (protons) with the release of 4.3×10-5 erg of energy in the form of gamma rays, two positrons and two neutrinos for each helium nucleus. This reaction provides 90% of the Sun's luminosity. It takes 1010 years for all the hydrogen in the Sun's core to turn into helium. In 1968, R. Davis and colleagues began to measure the flux of neutrinos produced in the course of thermonuclear reactions in the core of the Sun. This was the first experimental test of the solar energy source theory. Neutrino interacts very weakly with matter, so it freely leaves the bowels of the Sun and reaches the Earth. But for the same reason, it is extremely difficult to register it with instruments. Despite the improvement of the equipment and refinement of the solar model, the observed neutrino flux still remains 3 times less than the predicted one. There are several possible explanations: either the chemical composition of the core of the Sun is not the same as at its surface; or mathematical models of the processes occurring in the nucleus are not entirely accurate; either on the way from the Sun to the Earth, the neutrino changes its properties. Further research is needed in this area.
see also NEUTRINO ASTRONOMY. In the transfer of energy from the solar interior to the surface leading role radiation plays, convection is of secondary importance, and thermal conductivity is not important at all. At a high temperature of the solar interior, the radiation is mainly represented by X-rays with a wavelength of 2-10. Convection plays a significant role in the central region of the nucleus and in the outer layer lying directly below the photosphere. In 1962, the American physicist R. Leighton discovered that sections of the solar surface oscillate vertically with a period of approx. 5 minutes. Calculations by R. Ulrich and K. Wolf showed that sound waves excited by turbulent motions of gas in the convective zone lying under the photosphere can manifest themselves in this way. In it, as in an organ pipe, only those sounds are amplified, the wavelength of which exactly fits into the thickness of the zone. In 1974, the German scientist F. Debner experimentally confirmed the calculations of Ulrich and Wolff. Since then, observing the 5-minute oscillations has become a powerful method for studying the internal structure of the Sun. Analyzing them, we managed to find out that: 1) the thickness of the convective zone is approx. 27% of the Sun's radius; 2) the core of the Sun probably rotates faster than the surface; 3) the content of helium inside the Sun is approx. 40% by weight. Oscillations with periods between 5 and 160 min have also been reported. These longer sound waves can penetrate deeper into the interior of the Sun, which will help to understand the structure of the solar interior and, possibly, solve the problem of solar neutrino deficiency.
ATMOSPHERE OF THE SUN
Photosphere. This is a translucent layer several hundred kilometers thick, representing the "visible" surface of the Sun. Since the atmosphere lying above is practically transparent, the radiation, having reached the bottom of the photosphere, freely leaves it and escapes into space. Unable to absorb energy, the upper layers of the photosphere must be colder than the lower ones. Evidence for this can be seen in photographs of the Sun: in the center of the disk, where the thickness of the photosphere along the line of sight is minimal, it is brighter and bluer than at the edge (on the "limb") of the disk. In 1902, the calculations of A. Schuster, and later - E. Milne and A. Eddington, confirmed that the temperature difference in the photosphere is just such as to ensure the transfer of radiation through a translucent gas from the lower layers to the upper ones. The main substance that absorbs and re-radiates light in the photosphere are negative hydrogen ions (hydrogen atoms with an additional attached electron).
Fraunhofer spectrum. Sunlight has a continuous spectrum with absorption lines discovered by J. Fraunhofer in 1814; they indicate that, in addition to hydrogen, many other substances are present in the solar atmosphere. chemical elements. Absorption lines form in the spectrum because the atoms of the upper cooler layers of the photosphere absorb light coming from below at certain wavelengths, and do not radiate it as intensely as the hot lower layers. The distribution of brightness within the Fraunhofer line depends on the number and state of the atoms producing it, i.e. from chemical composition, density and temperature of the gas. Therefore, a detailed analysis of the Fraunhofer spectrum makes it possible to determine the conditions in the photosphere and its chemical composition (Table 2). Table 2.
CHEMICAL COMPOSITION OF THE PHOTOSPHERE OF THE SUN
Element Logarithm of the relative number of atoms

Hydrogen _________12.00
Helium ___________11.20
Carbon __________8.56
Nitrogen _____________7.98
Oxygen _________9.00
Sodium ___________6.30
Magnesium ___________7.28
Aluminum _________6.21
Silicon __________7.60
Sulfur _____________7.17
Calcium __________6.38
Chrome _____________6.00
Iron ___________6.76

The most abundant element after hydrogen is helium, which gives only one line in the optical spectrum. Therefore, the content of helium in the photosphere is not measured very accurately, and it is judged from the spectra of the chromosphere. No variations in the chemical composition of the Sun's atmosphere have been observed.
see also RANGE .
Granulation. Photographs of the photosphere taken in white light under very good observation conditions show small bright dots - "granules" separated by dark gaps. Granule diameter approx. 1500 km. They constantly appear and disappear, remaining 5-10 minutes. Astronomers have long suspected that the granulation of the photosphere is associated with convective motions of gas heated from below. Spectral measurements by J. Beckers proved that in the center of the granule, hot gas really floats up with speed. OK. 0.5 km/s; then it spreads to the sides, cools down and slowly descends along the dark borders of the granules.
Supergranulation. R. Leighton discovered that the photosphere is also divided into much larger cells with a diameter of approx. 30,000 km - "supergranules". Supergranulation reflects the movement of matter in the convective zone under the photosphere. In the center of the cell, the gas rises to the surface, spreads to the sides at a speed of about 0.5 km/s, and falls down at its edges; each cell lives for about a day. The movement of gas in supergranules constantly changes the structure magnetic field in the photosphere and chromosphere. Photospheric gas is a good conductor of electricity (because some of its atoms are ionized), so the magnetic field lines appear to be frozen into it and are transferred by the movement of gas to the boundaries of supergranules, where they are concentrated and the field strength increases.
Sun spots. In 1908, J. Hale discovered a strong magnetic field in sunspots, which emerges from the depths to the surface. Its magnetic induction is so great (up to several thousand gauss) that the ionized gas itself is forced to subordinate its motion to the configuration of the field; in spots, the field slows down the convective mixing of the gas, which causes it to cool. Therefore, the gas in the spot is colder than the surrounding photospheric gas and looks darker. The spots usually have a dark core - a "shadow" - and a lighter "penumbra" surrounding it. Typically, their temperature is 1500 and 400 K, respectively, lower than in the surrounding photosphere.

The spot begins its growth from a small dark "pore" with a diameter of 1500 km. Most of the pores disappear in a day, but the spots grown from them persist for weeks and reach a diameter of 30,000 km. The details of the growth and decay of sunspots are not fully understood. For example, it is not clear whether the magnetic tubes of the spot are compressed by the horizontal movement of gas or whether they are already ready to "emerge" from under the surface. R. Howard and J. Harvey discovered in 1970 that spots move towards the general rotation of the Sun faster than the surrounding photosphere (by about 140 m/s). This indicates that the spots are associated with the subphotospheric layers, which rotate faster than the visible surface of the Sun. Usually from 2 to 50 spots are combined into a group, often having a bipolar structure: at one end of the group there are spots of one magnetic polarity, and at the other - of the opposite one. But there are also multipolar groups. The number of spots on the solar disk changes regularly with a period of approx. 11 years. At the beginning of each cycle, new spots appear at high solar latitudes (± 50°). As the cycle develops and the number of sunspots increases, they appear at ever lower latitudes. The end of the cycle is marked by the birth and decay of several sunspots near the equator (± 10°). During the cycle, most of the "leading" (western) sunspots in bipolar groups have the same magnetic polarity, and it is different in the northern and southern hemispheres of the Sun. In the next cycle, the polarity of the leading spots reverses. Therefore, one often speaks of a full 22-year cycle of solar activity. There is still a lot of mystery in the nature of this phenomenon.
magnetic fields. In the photosphere, a magnetic field with an induction of more than 50 G is observed only in sunspots, in active regions surrounding sunspots, and also at the boundaries of supergranules. But L. Stenflo and J. Harvey found indirect indications that the magnetic field of the photosphere is actually concentrated in thin tubes with a diameter of 100-200 km, where its induction is from 1000 to 2000 gauss. Magnetically active regions differ from quiet regions only in the number of magnetic tubes per unit surface. Probably, the solar magnetic field is generated in the depths of the convective zone, where the seething gas twists the weak initial field into powerful magnetic bundles. The differential rotation of matter lays these bundles along parallels, and when the field in them becomes strong enough, they float up into the photosphere, breaking through upwards in separate arches. This is probably how spots are born, although there is still much unclear about this. The process of spot decay has been studied much more fully. The supergranules floating up at the edges of the active region capture the magnetic tubes and pull them apart. Gradually the general field weakens; accidental connection of tubes of opposite polarity leads to their mutual destruction.
Chromosphere. Between the relatively cold, dense photosphere and the hot, rarefied corona lies the chromosphere. The weak light of the chromosphere is usually not visible against the background of the bright photosphere. It can be seen as a narrow strip above the limb of the Sun when the photosphere is closed naturally (at the time of a total solar eclipse) or artificially (in a special telescope - a coronograph). The chromosphere can also be studied over the entire solar disk if observations are made in a narrow range of the spectrum (about 0.5) near the center of a strong absorption line. The method is based on the fact that the higher the absorption, the smaller the depth to which our gaze penetrates into the atmosphere of the Sun. For such observations, a spectrograph of a special design is used - a spectroheliograph. Spectroheliograms show that the chromosphere is inhomogeneous: it is brighter above sunspots and along supergranular boundaries. Since it is in these regions that the magnetic field is enhanced, it is obvious that energy is transferred from the photosphere to the chromosphere with its help. Probably, it is carried by sound waves excited by the turbulent movement of gas in granules. But the mechanisms of heating of the chromosphere are not yet understood in detail. The chromosphere strongly radiates in the hard ultraviolet range (500-2000), which is inaccessible to observation from the Earth's surface. Since the early 1960s, many important measurements of ultraviolet radiation have been made using high-altitude rockets and satellites. upper atmosphere Sun. More than 1000 emission lines of various elements were found in its spectrum, including lines of multiply ionized carbon, nitrogen and oxygen, as well as the main series of hydrogen, helium and the helium ion. The study of these spectra showed that the transition from the chromosphere to the corona occurs over a segment of only 100 km, where the temperature increases from 50,000 to 2,000,000 K. It turned out that the heating of the chromosphere to a large extent comes from the corona by thermal conduction. Near sunspot groups in the chromosphere, bright and dark fibrous structures are observed, often elongated in the direction of the magnetic field. Above 4000 km, uneven, jagged formations are visible, evolving rather quickly. When observing the limb in the center of the first Balmer line of hydrogen (Ha), the chromosphere at these heights is filled with many spicules - thin and long clouds of hot gas. Little is known about them. The diameter of an individual spicule is less than 1000 km; she lives ok. 10 minutes. With a speed of approx. At 30 km/s, spicules rise to a height of 10,000-15,000 km, after which they either dissolve or fall down. Judging by the spectrum, the temperature of the spicules is 10,000-20,000 K, although the corona surrounding them at these altitudes is heated to at least 600,000 K. It seems that spicules are sections of a relatively cold and dense chromosphere, temporarily rising into a hot rarefied corona. Counting within the boundaries of supergranules shows that the number of spicules at the level of the photosphere corresponds to the number of granules; there is probably a physical connection between them.
Flashes. The chromosphere above a group of sunspots can suddenly become brighter and shoot out a portion of gas. This phenomenon, called "flash", is one of the most difficult to explain. Flashes emit powerful power over the entire range electromagnetic waves - from radio to X-ray, and also often emit beams of electrons and protons at a relativistic speed (ie, close to the speed of light). They excite shock waves in the interplanetary medium that reach the Earth. Flares more often occur near groups of sunspots with a complex magnetic structure, especially when a new sunspot begins to grow rapidly in a group; such groups produce several outbreaks per day. Weak outbreaks happen more often than strong ones. The most powerful flares occupy 0.1% of the solar disk and last several hours. The total energy of the flare is 1023-1025 J. The X-ray spectra of the flares obtained by the SMM (Solar Maximum Mission) satellite made it possible to better understand the nature of the flares. The onset of the flare may mark an X-ray burst with a photon wavelength of less than 0.05, caused, as its spectrum shows, by a stream of relativistic electrons. In a few seconds, these electrons heat up the surrounding gas to 20,000,000 K, and it becomes a source of X-ray radiation in the 1-20 range, hundreds of times greater than the flux in this range from the quiet Sun. At this temperature, iron atoms lose 24 of their 26 electrons. Then the gas cools down, but still continues to emit x-rays. The flash also emits in the radio range. P. Wild from Australia and A. Maxwell from the USA studied the development of a flare using the radio analogue of a spectrograph - a "dynamic spectrum analyzer" that registers changes in the power and frequency of radiation. It turned out that the frequency of the radiation in the first few seconds of the flash drops from 600 to 100 MHz, indicating that a perturbation propagates through the corona at a speed of 1/3 the speed of light. In 1982, US radio astronomers, using the VLA radio interferometer in pcs. New Mexico and data from the SMM satellite resolved fine details in the chromosphere and corona during the outburst. Not surprisingly, these turned out to be loops, probably of a magnetic nature, in which energy is released, which heats the gas during the flash. At the final stage of the flare, the relativistic electrons captured by the magnetic field continue to radiate highly polarized radio waves, moving in a spiral around the magnetic field lines above the active region. This radiation can continue for several hours after the flash. Although gas is always ejected from the flare region, its speed usually does not exceed the speed of escape from the surface of the Sun (616 km/s). However, flares often emit streams of electrons and protons that reach the Earth in 1–3 days and cause auroras and magnetic field disturbances on it. These particles with energies reaching billions of electron volts are very dangerous for astronauts in orbit. So astronomers try to predict solar flares, studying the configuration of the magnetic field in the chromosphere. The complex structure of the field, with twisted field lines ready to reconnect, indicates the possibility of a flare.
Prominences. Solar prominences are relatively cold masses of gas that appear and disappear in a hot corona. When observed with a coronagraph in the Ha line, they are visible on the limb of the Sun as bright clouds against a dark background of the sky. But when observed with a spectroheliograph or Lyot interference filters, they look like dark filaments against the background of a bright chromosphere.

Forms of prominences are extremely diverse, but several main types can be distinguished. Sunspot prominences are like curtains up to 100,000 km long, 30,000 km high and 5,000 km thick. Some prominences have a branched structure. Rare and beautiful loop-shaped prominences have a rounded shape with a diameter of approx. 50,000 km. Almost all prominences have a fine structure of gaseous filaments, probably repeating the structure of the magnetic field; the true nature of this phenomenon is not clear. The gas in prominences usually flows downward at a speed of 1–20 km/s. The exception is "sergi" - prominences that fly up from the surface at a speed of 100-200 km / s, and then fall back more slowly. Prominences are born at the edges of sunspot groups and can persist for several revolutions of the Sun (i.e. several Earth months). The spectra of prominences are similar to the spectra of the chromosphere: bright lines of hydrogen, helium and metals against the background of weak continuous radiation. Usually the emission lines of quiet prominences are thinner than the chromospheric lines; this is probably due to the smaller number of atoms in the line of sight in the prominence. An analysis of the spectra indicates that the temperature of quiet prominences is 10,000-20,000 K, and the density is about 1010 at./cm3. Active prominences show lines of ionized helium, indicating a much higher temperature. The temperature gradient in the prominences is very large, since they are surrounded by a corona with a temperature of 2,000,000 K. The number of prominences and their distribution in latitude during an 11-year cycle repeats the distribution of sunspots. However, at high latitudes there is a second belt of prominences, which shifts poleward during the cycle maximum. Why prominences form and what sustains them in a rarefied corona is not entirely clear.
Crown. The outer part of the Sun - the corona - shines weakly and is visible to the naked eye only during total solar eclipses or with the help of a coronograph. But it is much brighter in X-rays and in the radio range.
see also EXTRAATMOSPHERIC ASTRONOMY. The corona shines brightly in the X-ray range, because its temperature is from 1 to 5 million K, and at the moments of outbreaks it reaches 10 million K. X-ray spectra of the corona have recently begun to be obtained from satellites, and optical ones have been studied for many years during the period of total eclipses. These spectra contain lines of multiply ionized atoms of argon, calcium, iron, silicon, and sulfur, which are formed only at temperatures above 1,000,000 K.

The white light of the corona, which during an eclipse is visible up to a distance of 4 solar radii, is formed as a result of the scattering of photospheric radiation by free electrons in the corona. Therefore, the change in the brightness of the corona with height indicates the distribution of electrons, and since the main element is fully ionized hydrogen, so is the distribution of gas density. Coronal structures are clearly divided into open (rays and polar brushes) and closed (loops and arches); ionized gas exactly repeats the structure of the magnetic field in the corona, because cannot move across the lines of force. Since the field exits the photosphere and is associated with an 11-year sunspot cycle, appearance the crown changes during this cycle. During the period of minimum, the corona is dense and bright only in the equatorial belt, but as the cycle develops, coronal rays appear at higher latitudes, and at maximum they can be seen at all latitudes. From May 1973 to January 1974, the corona was continuously observed by 3 crews of astronauts on board orbital station"Skylab". Their data showed that dark coronal "holes", where the temperature and density of the gas are significantly reduced, are areas from which gas flies out into interplanetary space at high speed, creating powerful streams in the calm solar wind. Magnetic fields in coronal holes are "open", i.e. extended far into space, allowing the gas to escape the corona. These field configurations are quite stable and can persist during the period of minimum solar activity for up to two years. The coronal hole and the flow associated with it rotate together with the surface of the Sun with a period of 27 days and, if the flow hits the Earth, each time they cause geomagnetic storms. Energy balance the outer atmosphere of the sun. Why does the Sun have such a hot corona? Until we know it. But there is a fairly reasonable hypothesis that sound and magnetohydrodynamic (MHD) waves, which are generated by turbulent motions of gas under the photosphere, transfer energy to the outer atmosphere. Getting into the upper rarefied layers, these waves become shock waves, and their energy dissipates, heating the gas. sound waves heat the lower chromosphere, and MHD waves propagate along the magnetic lines of force further into the crown and heat it up. Part of the heat from the corona due to thermal conductivity goes into the chromosphere and is radiated into space there. The rest of the heat maintains coronal radiation in closed loops and accelerates solar wind flows in coronal holes.
see also

- the only star in the solar system: description and characteristics with photos, interesting facts, composition and structure, location in the galaxy, development.

The sun is the center and source of life for our solar system. The star belongs to the class of yellow dwarfs and occupies 99.86% of the total mass of our system, and gravity prevails in strength over all celestial bodies. In ancient times, people immediately understood the importance of the Sun for earthly life, so the mention of a bright star is found in the very first texts and rock paintings. It was the central deity, ruling over all.

Let's learn the most interesting facts about the Sun - the only star in the solar system.

A million Earths fit inside

• If we fill our Sun star, then 960,000 Earths will fit inside. But if they are compressed and deprived of free space, then the number will increase to 1300000. The surface area of ​​the Sun is 11990 times larger than the earth's.

Holds 99.86% of system weight

• It is 330,000 times more massive than Earth's. Approximately ¾ is assigned to hydrogen, and the rest is helium.

Almost perfect sphere

• The difference between the equatorial and polar diameters of the Sun is only 10 km. This means that we have one of the closest celestial bodies to the sphere.

The temperature in the center rises to 15 million ° C

• In the core of the Sun, this temperature is possible due to fusion, where hydrogen is transformed into helium. Usually, hot objects expand, so our star could explode, but is held back by powerful gravity. The temperature of the Sun's surface is "only" 5780 °C.

One day the sun will swallow the earth

• When the Sun has used up the entire hydrogen reserve (130 million years), it will switch to helium. This will cause it to grow in size and consume the first three planets. This is the red giant stage.

One day it will reach the size of the earth

• After the red giant, it will collapse and leave a compressed mass in an Earth-sized ball. This is the white dwarf stage.

Sunbeam reaches us in 8 minutes

• The Earth is 150 million km away from the Sun. The speed of light is 300,000 km/s, so the beam takes 8 minutes and 20 seconds. But it's also important to understand that it took millions of years for photons of light to travel from the core of the sun to the surface.

The speed of the Sun - 220 km / s

• The sun is 24,000-26,000 light years away from the galactic center. Therefore, it spends 225-250 million years on the orbital path.

The Earth-Sun distance varies throughout the year

• The Earth moves along an elliptical orbital path, so the distance is 147-152 million km (astronomical unit).

This is a star with a middle age

• The age of the Sun is 4.5 billion years, which means that it has already burned about half of its hydrogen reserve. But the process will continue for another 5 billion years.

There is a strong magnetic field

• Solar flares are released during magnetic storms. We see this as the formation of sunspots where the magnetic lines and spin like earth tornadoes.

A star forms the solar wind

• The solar wind is a stream of charged particles passing through the entire solar system at an acceleration of 450 km/s. The wind appears where the magnetic field of the Sun propagates.

Name of the Sun

• The word itself comes from the Old English meaning "south". There are also Gothic and German roots. Before 700 AD Sunday was called "sunny day". Translation also played a role. The original Greek "heméra helíou" became the Latin "dies solis".

Characteristics of the Sun

The Sun is a G-type main sequence star with absolute value 4.83, which is brighter than about 85% of other stars in the galaxy, many of which are red dwarfs. With a diameter of 696,342 km and a mass of 1.988 x 1030 kg, the Sun is 109 times larger than the Earth and 333,000 times more massive.

This is a star, so the density varies depending on the layer. The average value reaches 1.408 g/cm 3 . But closer to the core it increases to 162.2 g/cm 3 , which is 12.4 times greater than the Earth's.

It appears yellow in the sky, but the true color is white. Visibility is created by the atmosphere. The temperature increases as you get closer to the center. The core heats up to 15.7 million K, the corona heats up to 5 million K, and the visible surface heats up to 5778 K.

Average diameter	1.392 10 9 m
Equatorial	6.9551 10 8 m
Equator circumference	4.370 10 9 m
polar contraction	9 10 −6
Surface area	6.078 10 18 m²
Volume	1.41 10 27 m³
Weight	1.99 10 30 kg
Average density	1409 kg/m³
Acceleration free fall at the equator	274.0 m/s²
Second space velocity (for surface)	617.7 km/s
Effective temperature surfaces	5778 K
Temperature crowns	~1,500,000 K
Temperature nuclei	~13,500,000 K
Luminosity	3.85 10 26 W (~3.75 10 28 Lm)
Brightness	2.01 10 7 W/m²/sr

The sun is made of plasma, therefore it is endowed with high magnetism. There are north and south magnetic poles, and the lines form the activity observed on the surface layer. Dark spots mark cool spots and lend themselves to cyclicity.

Coronal mass ejections and flares occur when magnetic field lines realign. The cycle takes 11 years, during which activity rises and subsides. The largest number sunspots occur at peak activity.

The apparent magnitude reaches -26.74, which is 13 billion times brighter than Sirius (-1.46). The Earth is 150 million km away from the Sun = 1 AU. To overcome this distance, the light beam needs 8 minutes and 19 seconds.

Composition and structure of the Sun

The star is filled with hydrogen (74.9%) and helium (23.8%). Among more heavy elements oxygen (1%), carbon (0.3%), neon (0.2%), and iron (0.2%) are present. The inner part is divided into layers: core, radiation and convection zones, photosphere and atmosphere. The core is endowed with the highest density (150 g / cm 3) and occupies 20-25% of the total volume.

It takes a month for a star to rotate its axis, but this is a rough estimate, because we have a plasma ball in front of us. The analysis shows that the core rotates faster than the outer layers. While the equatorial line takes 25.4 days to rotate, it takes 36 days at the poles.

At the core celestial body solar energy is formed due to nuclear fusion, which transforms hydrogen into helium. It creates almost 99% of thermal energy.

Between the radiation and convective zones there is a transition layer - tacholine. It shows a sharp change in the uniform rotation of the radiation zone and differential rotation of the convection zone, which causes a serious shift. The convective zone is 200,000 km below the surface, where the temperature and density are also lower.

The visible surface is called the photosphere. Above this ball, light can freely spread into space, releasing solar energy. It covers hundreds of kilometers in thickness.

The upper part of the photosphere is inferior in heating to the lower one. The temperature rises to 5700 K, and the density rises to 0.2 g/cm 3 .

The atmosphere of the Sun is represented by three layers: the chromosphere, the transitional part and the corona. The first stretches for 2000 km. The transition layer occupies 200 km and warms up to 20,000-100,000 K. The layer has no clear boundaries, but a halo with constant chaotic movement is noticeable. The corona warms up to 8-20 million K, which is influenced by the solar magnetic field.

The heliosphere is a magnetic sphere extending beyond the heliopause (50 AU from the star). It is also called the solar wind.

Evolution and the future of the Sun

Scientists are convinced that the Sun appeared 4.57 billion years ago due to the collapse of part of the molecular cloud, represented by hydrogen and helium. At the same time, it started rotating (due to angular momentum) and began to heat up with increasing pressure.

Most of the mass was concentrated in the center, and the rest turned into a disk that would later form the planets we know. Gravity and pressure led to the growth of heat and nuclear fusion. There was an explosion and the sun appeared. In the figure, you can trace the stages of the evolution of stars.

The star is currently in the main sequence phase. Inside the nucleus, more than 4 million tons of matter are transformed into energy. The temperature is constantly rising. The analysis shows that over the past 4.5 billion years, the Sun has become brighter by 30% with an increase of 1% for every 100 million years.

It is believed that eventually it will begin to expand and turn into a red giant. Due to the increase in size, Mercury, Venus and, possibly, the Earth will die. It will stay in the giant phase for about 120 million years.

Then the process of reducing the size and temperature will begin. It will continue to burn the remaining helium in the core until the reserves run out. After 20 million years, it will lose stability. The earth will be destroyed or inflamed. In 500,000 years only half will remain solar mass, and the outer shell will create a nebula. As a result, we will get white dwarf, which will live for trillions of years and only then turn black.

Location of the sun in the galaxy

The Sun is closer to the inner edge of the Orion Arm in the Milky Way. The distance from the galactic center is 7.5-8.5 thousand parsecs. It is located inside the local bubble - a cavity in the interstellar medium with hot gas.

The solar system resides in the galactic habitable zone. This area is endowed with special characteristics that can support life. solar movement is directed towards Vega in Lyra territory and at an angle of 60 degrees from the galactic center. Among the nearest 50 systems, our Sun is in 40th place in terms of massiveness.

It is believed that the orbital path is elliptical with the presence of perturbation from the galactic spiral arms. Spends 225-250 million years for one orbital flight. Therefore, to date, only 20-25 orbits have been completed. Below is a map of the surface of the Sun. If you wish, use our telescopes online in real time to admire the star of the system. Don't forget to track space weather for magnetic storms and solar flares.

solar neutrinos

Physicist Evgeny Litvinovich about neutrino particles flying from the Sun, the standard solar model and the problem of metallicity:

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Clear description sun for children: interesting facts about the star of the solar system, how more earth with a photo, how the Sun appeared, what it consists of, spots.

Even for the little ones It is no secret that we owe the appearance of life on our planet to the only star in the system - the Sun. Parents or teachers at school can start a story about the Sun and explanation for children since, like the rest of the stars, ours is the center and surpasses all the planets in size. If compared with , then it is 109 times larger than the diameter and occupies 99.8% of the total mass of the system. Interestingly, about a million of the same planets as ours can be placed within the solar volume.

The temperature of the visible part is heated up to 5500°C. And for the Sun, this is not the limit, since its core can heat up to 15 million ° C. Parents should explain to children that in front of them is a real nuclear reactor. To reproduce this amount of energy, it would take 100 billion tons of dynamite to explode every second.

But the Sun can only be called unique because life originated within its system. Children must understand that in milky way There are more than 100 billion stellar objects. Despite being the center of the system, it also orbits the galactic core (25,000 light-years away). One revolution takes as much as 250 million years.

The sun is part of the stellar generation Population I. Such objects are rich in elements that are heavier than helium, and younger than the rest in age. But Population II and, possibly, III are the older generation, whose representatives are still unknown.

The emergence and evolution of the Sun - for children

To begin explanation for children It is possible from the fact that our star was born 4.6 billion years ago. According to the main theory, the entire system was formed from a huge gas and dust cloud that did not stop rotating - the solar nebula. The internal force of gravity activated the processes of destruction, accelerating the formation and pulling it out in the form of a flattened disk. Because of this, a larger volume of particles headed towards the center and formed the Sun. Below, astronomy for children offers a drawing of the development of a star.

The star has a fairly large amount of fuel that will allow it to function normally for another 5 billion years. When it exhausts itself, the Sun will start the process of destruction. The star will grow and become a red giant. Subsequently, the upper layers will be destroyed, and the core will explode, passing into the category of white dwarfs. After a long period of time, it will dim, cool down and become a white dwarf.

Internal structure and atmosphereSun - for children

Should explain to the little ones that any object can have certain zones. The inner part is represented by the core, radiative and convective levels. Sun picture for kids provides a diagram of the composition and structure of a star.

1/4 of the distance from the center to the top goes to the core. With a seemingly small volume (only 2% of the sun), it is 15 times higher than the density of lead and occupies almost half of the entire stellar mass. From the core to the surface (70%) there is a radiation zone (32% of the volume and 48% of the mass). This is where the light from the core decays, so that children should know that it can take millions of years for a photon to get out of this region.

Further, a convection layer (66% of volume and 2% of mass) approaches the surface. Here you can see a lot of "convection cells" with gas rotating inside. Two main types can be distinguished: granulation (1000 km wide) and supergranulation (30,000 km in diameter).

To kid it will be interesting to know that the atmosphere includes the photosphere, chromosphere, transition region, and corona. Among other things, there are also solar winds blowing gas out of the corona.

The lowest layer is the photosphere. The light emitted by it, we perceive as the usual rays of the sun. With a thickness of 500 km, a significant portion of the light comes from the lowest part of the layer. Here the temperature can vary from 6125°C at the bottom to 4125°C at the top.

After it comes the chromosphere. It is much hotter (19725°C) and consists entirely of pointed formations reaching 1,000 km in length and 10,000 km in height. Further on, a transition strip was located for several thousand kilometers. The corona heats it up and also sheds most of the UV rays.

Above is a superhot corona, consisting of loops and flows of ionized gas. Its temperature reaches from half a million to 6 million degrees (sometimes it exceeds this mark, reaching several tens if an outbreak occurs). There is matter on the corona that propagates in the form of solar winds.

Chemical compositionSun - for children

Like other stars, the Sun is filled with hydrogen and helium. But they also read 7 more less voluminous components. For one million hydrogen atoms falls: helium (98000), oxygen (850), carbon (360), neon (120), nitrogen (110), magnesium (40), iron (35) and silicon (35). Despite all these numbers, children should know that hydrogen is the lightest of all, therefore it occupies only 72% of the solar mass, but helium is allocated 26%.

A magnetic field

Parents may explain to children that the Sun's magnetic field is twice that of the Earth's. But what is interesting is that it acts unevenly and in some places it can be 3000 times more active. Such "roughness" is constantly evolving, because the rotation of the star is much faster at the equatorial part than at higher latitudes. Therefore, it turns out that the speed inside is higher than outside. It is because of this that we can observe sunspots, flares and coronal mass ejections. Flares will be the strongest, but a coronal mass ejection, although not as aggressive, will involve a large number of material (up to 20 billion tons of matter can be released at a time). The bottom drawing for children shows the influence of the solar wind and the magnetic field on the Earth, as well as their relationship.

Spots and cycles Sun - for children

Children you may have noticed that in some areas the Sun seems darker, as if with holes. These features are called spots. They reach the shape of a circle and are cooler than the general surface. They appear in those regions where dense clots of magnetic field lines break through.

The total number of sunspots is unstable and depends on the magnetic activity. Usually the maximum reaches 250, but then they disappear to a minimum. This cycle takes about 11 years. At the very end of this process, the magnetic field rapidly changes polarity.

Bright sunlight is a source of excellent mood and cheerfulness. In cloudy weather, many people feel depressed, succumb to depression. Despite this, everyone knows that the bad weather will end soon and the sun will appear in the sky. It has been familiar to people since childhood, and few people think about what this luminary is. The most famous information about the Sun is that it is a star. However, there are many more interesting facts that may be of interest to both children and adults.

What is the Sun?

Now everyone knows that the Sun is a star, and not a huge resembling a planet. It is a cloud of gases with a core inside. The main component of this star is hydrogen, which occupies about 92% of its total volume. Approximately 7% is accounted for by helium, and the remaining percentage is divided among other elements. These include iron, oxygen, nickel, silicon, sulfur and others.

Most of a star's energy comes from the fusion of helium from hydrogen. Information about the Sun, collected by scientists, allows us to attribute it to the G2V type according to the spectral classification. This type is called a "yellow dwarf". At the same time, the sun, contrary to popular belief, shines with white light. The yellow glow appears as a result of scattering and absorption by the atmosphere of our planet of the short-wavelength part of the spectrum of its rays. Our luminary - the Sun - is an integral part of the galaxy. From its center, the star is at a distance of 26,000 light years, and one revolution around it takes 225-250 million years.

solar radiation

The Sun and the Earth are separated by a distance of 149,600 km. Despite this, solar radiation is the main source of energy on the planet. Not all of its volume passes through the Earth's atmosphere. The energy of the Sun is used by plants in the process of photosynthesis. In this way, various organic compounds and oxygen is released. Solar radiation is also used to generate electricity. Even the energy of peat reserves and other minerals appeared in ancient times under the influence of the rays of this bright star. The ultraviolet radiation of the Sun deserves special attention. It has antiseptic properties and can be used to disinfect water. UV radiation also affects biological processes in the human body, causing tanning on the skin, as well as the production of vitamin D.

Sun life cycle

Our luminary - the Sun - is a young star belonging to the third generation. It contains a large amount of metals, which indicates its formation from other stars of previous generations. According to scientists, the Sun is about 4.57 billion years old. Given that it is 10 billion years, it is now in its middle. At this stage, thermonuclear fusion of helium from hydrogen occurs in the core of the Sun. Gradually, the amount of hydrogen will decrease, the star will become more and more hot, and its luminosity will be higher. Then the reserves of hydrogen in the core will run out completely, part of it will pass into the outer shell of the Sun, and helium will begin to condense. The processes of star extinction will continue for billions of years, but still lead to its transformation first into a red giant, then into a white dwarf.

sun and earth

Life on our planet will also depend on the degree of solar radiation. In about 1 billion years, it will be so strong that the surface of the Earth will heat up significantly and become unsuitable for most life forms, they can only remain in the depths of the oceans and in the polar latitudes. By the age of the Sun at about 8 billion years, the conditions on the planet will be close to those that are now on Venus. There will be no water at all, it will all evaporate into space. This will lead to complete disappearance. different forms life. As the core of the Sun shrinks and its outer shell increases, the probability of swallowing our planet will increase. outer layers star plasma. This will not happen only if the Earth rotates around the Sun at a greater distance as a result of the transition to another orbit.

A magnetic field

Information about the Sun, collected by researchers, indicates that it is a magnetically active star. created by him, changes its direction every 11 years. Its intensity also varies over time. All these transformations are called solar activity, which is characterized by special phenomena, such as wind, flares. They are the cause and which adversely affect the operation of some devices on Earth, the well-being of people.

solar eclipses

Information about the Sun, collected by the ancestors and survived to this day, contains references to its eclipses since antiquity. A large number of them are also described in the Middle Ages. A solar eclipse is the result of the obscuration of a star by the Moon from an observer on Earth. It can be complete, when at least from one point of our planet the solar disk is completely hidden, and partial. There are usually two to five eclipses per year. At a certain point on the Earth, they occur with a time difference of 200-300 years. Fans of viewing the sky, the Sun can also see an annular eclipse. The moon covers the disk of the star, but due to its smaller diameter, it cannot completely outshine it. As a result, a “fiery” ring remains visible.

It is worth remembering that observing the Sun with the naked eye, especially with binoculars or a telescope, is very dangerous. This can lead to permanent visual impairment. The sun is relatively close to the surface of our planet and shines very brightly. Without a threat to eye health, you can look at it only during sunrises and sunsets. The rest of the time you need to use special dimming filters or project an image obtained with a telescope onto a white screen. This method is the most acceptable.

A story about the Sun for children will tell you how to explain to a child what the Sun is and what its significance is in our life.

A Brief Message about the Sun

The sun is the most important star for humans, which provides and maintains life on planet Earth. All the planets, their satellites, as well as comets and meteorites revolve around it. It is a million times larger than the Earth. The average distance from the Earth to the Sun is 149.6 million km. A light beam reaches the Earth in 8 minutes.

The luminary of the solar system is incredibly hot. On its surface the temperature is 6000°C, and in the center - more than 15 million degrees.

A star called the Sun, formed from a huge cloud of hydrogen and stardust, has been burning for 4.6 billion years. It has enough fuel to burn for a very long time.

It is thanks to him that we live, eat the fruits of the earth (vegetables, fruits, berries), raise livestock, and in general, enjoy life. Why?
First, the sun is light. Without light, plants would not be able to release oxygen into the atmosphere. But we breathe only thanks to oxygen! Without light, a person would have a lack of vitamin D, which is necessary for the strength of our bones. The bones would become brittle and brittle. We would break at every turn.
Second, the sun is warm. Without heat, our earth would turn into a huge ball of ice. Naturally, all life at such a low temperature would have disappeared from the face of the earth.