Internal structure of the Sun. Structure of the atmosphere: photosphere, chromosphere, corona

A spectral analysis of solar rays showed that our star contains the most hydrogen (73% of the star’s mass) and helium (25%). The remaining elements (iron, oxygen, nickel, nitrogen, silicon, sulfur, carbon, magnesium, neon, chromium, calcium, sodium) account for only 2%. All substances discovered on the Sun are found on Earth and on other planets, which indicates their common origin. The average density of the Sun's matter is 1.4 g/cm3.

How the Sun is studied

The sun is a “” with many layers that have different composition and density, and different processes take place in them. Observing a star in the spectrum familiar to the human eye is impossible, but telescopes, radio telescopes and other instruments have now been created that record ultraviolet, infrared, and X-ray radiation from the Sun. From Earth, observation is most effective during a solar eclipse. During this short period, astronomers around the world study the corona, prominences, chromosphere and various phenomena occurring on the only star available for such detailed study.

Structure of the Sun

The corona is the outer shell of the Sun. It has a very low density, which is why it is visible only during an eclipse. The thickness of the outer atmosphere is uneven, so holes appear in it from time to time. Through these holes, the solar wind rushes into space at a speed of 300-1200 m/s - a powerful flow of energy, which on earth causes northern lights and magnetic storms.

The chromosphere is a layer of gases reaching a thickness of 16 thousand km. Convection of hot gases occurs in it, which, from the surface of the lower layer (photosphere), fall back again. They are the ones who “burn through” the corona and form solar wind streams up to 150 thousand km long.

The photosphere is a dense opaque layer 500-1,500 km thick, in which the strongest fire storms with a diameter of up to 1 thousand km occur. The temperature of the photosphere gases is 6,000 oC. They absorb energy from the underlying layer and release it as heat and light. The structure of the photosphere resembles granules. Gaps in the layer are perceived as sunspots.

The convective zone, 125-200 thousand km thick, is the solar shell in which gases constantly exchange energy with the radiation zone, heating up, rising to the photosphere and, cooling, descending again for a new portion of energy.

The radiation zone is 500 thousand km thick and has a very high density. Here, the substance is bombarded with gamma rays, which are converted into less radioactive ultraviolet (UV) and x-rays (X) rays.

The crust, or core, is the solar “boiler”, where proton-proton thermonuclear reactions constantly occur, thanks to which the star receives energy. Hydrogen atoms transform into helium at a temperature of 14 x 10 °C. Here, titanic pressure is a trillion kg per cubic cm. Every second, 4.26 million tons of hydrogen are converted into helium.

Prominences

The surface of the Sun that we see is known as the photosphere. This is the area where light from the core finally reaches the surface. The photosphere has a temperature of about 6000 K and glows white.

Just above the photosphere, the atmosphere extends for several hundred thousand kilometers. Let's take a closer look at the structure of the Sun's atmosphere.

The first layer in the atmosphere has a minimum temperature, and is located at a distance of about 500 km above the surface of the photosphere, with a temperature of about 4000 K. For a star, this is quite cool.

Chromosphere

The next layer is known as the chromosphere. It is located at a distance of only about 10,000 km from the surface. In the upper part of the chromosphere, temperatures can reach 20,000 K. The chromosphere is invisible without special equipment that uses narrow-band optical filters. Giant solar prominences can rise in the chromosphere to a height of 150,000 km.

Above the chromosphere there is a transition layer. Below this layer, gravity is the dominant force. Above the transition region, the temperature rises quickly because helium becomes fully ionized.

Solar corona

The next layer is the corona, and it extends from the Sun millions of kilometers into space. You can see the corona during a total eclipse, when the disk of the luminary is covered by the Moon. The temperature of the corona is about 200 times hotter than the surface.

While the temperature of the photosphere is only 6000 K, near the corona it can reach 1-3 million degrees Kelvin. Scientists still don’t fully know why it is so high.

Heliosphere

The upper part of the atmosphere is called the heliosphere. It is a bubble of space filled with solar wind and extends out to about 20 astronomical units (1 AU is the distance from the Earth to the Sun). Ultimately, the heliosphere gradually transitions into the interstellar medium.

The Sun, the central body of the Solar System, is a very hot plasma ball. The sun is the closest star to the earth. The light from it reaches us in 8 1/3 minutes. The Sun had a decisive influence on the formation of all bodies in the Solar System and created the conditions that led to the emergence and development of life on Earth.

The radius of the Sun is 109 times, and the volume is approximately 1,300,000 times greater than the radius and volume of the Earth, respectively. The mass of the Sun is also great. It is approximately 330,000 times the mass of the Earth and almost 750 times the total mass of the planets moving around it.

The Sun probably arose along with other bodies of the Solar System from a gas and dust nebula. About 5 billion years ago. At first, the substance of the Sun became very hot due to gravitational compression, but soon the temperature and pressure in the depths increased so much that nuclear reactions began to occur spontaneously. As a result of this, the temperature in the center of the Sun rose very much, and the pressure in its depths increased so much that it was able to balance the force of gravity and stop the gravitational compression. This is how the modern structure of the Sun arose. This structure is maintained by the slow conversion of hydrogen into helium occurring in its depths. Over the 5 billion years of the Sun's existence, about half of the hydrogen in its central region has already turned into helium. As a result of this process, the amount of energy that the Sun emits into space is released.

The radiation power of the Sun is very high: it is equal to 3.8×10 20 MW. A tiny fraction of solar energy reaches the Earth, amounting to about half a billionth. It maintains the earth's atmosphere in a gaseous state, constantly heats land and water bodies, gives energy to winds and waterfalls, and ensures the vital activity of animals and plants. Part of the solar energy is stored in the bowels of the Earth in the form of coal, oil and other minerals.

The sun is a spherically symmetrical body in equilibrium. Everywhere at the same distances from the center of this ball, the physical conditions are the same, but they change noticeably as you approach the center. Density and pressure quickly increase in depth, where the gas is more strongly compressed by the pressure of the layers above. Consequently, the temperature also increases as it approaches the center. Depending on changes in physical conditions, the Sun can be divided into several concentric layers, gradually transforming into each other.

At the center of the Sun, the temperature is 15 million degrees, and the pressure exceeds hundreds of billions of atmospheres. The gas is compressed here to a density of about 1.5x10 5 kg/m 3. Almost all of the Sun's energy is generated in a central region with a radius of approximately 1/3 that of the Sun. Through the layers surrounding the central part, this energy is transferred outward. Over the last third of the radius there is a convective zone. The reason for 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 greater than that removed by thermal conductivity. Therefore, the substance is forced to move and begins to transfer heat on its own.

The layers of the Sun are virtually unobservable. Their existence is known either from theoretical calculations or on the basis of indirect data. Above the convective zone are the directly observable layers of the Sun, called its atmosphere. They are better studied, since their properties can be judged from observations.

The internal structure of the Sun is layered, or shell-like, it is differentiated into spheres, or regions. In the center is core, then radial energy transfer region, Further convective zone and finally atmosphere. A number of researchers include three external areas: photosphere, chromosphere and corona. True, other astronomers consider only the chromosphere and corona to be the solar atmosphere.

Core- the central region of the Sun with ultra-high pressure and temperature, ensuring the flow of nuclear reactions. They release enormous amounts of electromagnetic energy in extremely short wavelength ranges.

Region of beam energy transfer is located above the core. It is formed by practically motionless and invisible ultra-high-temperature gas. The energy generated in the core is transferred through it to the outer spheres of the Sun by beam method, without moving gas. This process should be imagined something like this. From the core to the region of radiation transfer, energy enters in extremely short-wave ranges - gamma radiation, and leaves in longer-wave x-rays, which is associated with a decrease in gas temperature towards the peripheral zone.

Convective region is located above the previous one. It is also formed by invisible hot gas in a state of convective mixing. It is due to the position of the region between two environments that differ sharply in the pressure and temperature prevailing in them. The transfer of heat from the solar interior to the surface occurs as a result of local uplifts of highly heated air masses under high pressure to the periphery of the star, where the temperature of the gas is lower and where the light range of the Sun's radiation begins. The thickness of the convective region is estimated to be approximately 1/10 of the solar radius.

To get acquainted with the internal structure of the Sun, let us now take an imaginary journey from the center of the star to its surface. But how will we determine the temperature and density of the solar globe at different depths? How can we find out what processes take place inside the Sun?

It turns out that most of the physical parameters of stars (our Sun is also a star!) are not measured, but are calculated theoretically using computers. The starting points for such calculations are only some general characteristics of the star, for example its mass, radius, as well as the physical conditions prevailing on its surface: temperature, extent and density of the atmosphere, and the like. The chemical composition of a star (in particular, the Sun) is determined spectrally. And based on these data, a theoretical astrophysicist will create a mathematical model of the Sun. If such a model corresponds to the observational results, then it can be considered a fairly good approximation to reality. And we, relying on such a model, will try to imagine all the exotic depths of the great star.

The central part of the Sun is called its core. The matter inside the solar core is extremely compressed. Its radius is approximately 1/4 the radius of the Sun, and its volume is 1/45 (a little more than 2%) of the total volume of the Sun. Nevertheless, almost half of the solar mass is packed into the core of the star. This became possible due to the very high degree of ionization of solar matter. The conditions there are exactly the same as those needed for the operation of a thermonuclear reactor. The Core is a giant controlled power station where solar energy is generated.

Having moved from the center of the Sun to approximately 1/4 of its radius, we enter the so-called radiation energy transfer zone. This most extensive inner region of the Sun can be imagined as like the walls of a nuclear boiler, through which solar energy slowly leaks out. But the closer to the surface of the Sun, the lower the temperature and pressure. As a result, vortex mixing of the substance occurs and energy transfer occurs predominantly by the substance itself. This method of energy transfer is called convection, and the subsurface layer of the Sun where it occurs is called the convective zone. Solar researchers believe that its role in the physics of solar processes is exceptionally great. After all, it is here that various movements of solar matter and magnetic fields originate.

Finally we are at the visible surface of the Sun. Since our Sun is a star, a hot plasma ball, it, unlike the Earth, Moon, Mars and similar planets, cannot have a real surface, understood in the full sense of the word. And if we are talking about the surface of the Sun, then this concept is conditional.

The visible luminous surface of the Sun, located directly above the convective zone, is called the photosphere, which is translated from Greek as “sphere of light.”

The photosphere is a 300-kilometer layer. This is where solar radiation comes to us. And when we look at the Sun from Earth, the photosphere is precisely the layer that penetrates our vision. Radiation from deeper layers no longer reaches us, and it is impossible to see them.

The temperature in the photosphere increases with depth and is estimated on average at 5800 K.

The bulk of the optical (visible) radiation of the Sun comes from the photosphere. Here, the average gas density is less than 1/1000 the density of the air we breathe, and the temperature decreases to 4800 K as we approach the outer edge of the photosphere. Hydrogen under such conditions remains almost completely neutral.

Astrophysicists take the base of the photosphere as the surface of the great star. They consider the photosphere itself to be the lowest (inner) layer of the solar atmosphere. Above it are two more layers that form the outer layers of the solar atmosphere - the chromosphere and the corona. And although there are no sharp boundaries between these three layers, let’s get acquainted with their main distinguishing features.

The yellow-white light of the photosphere has a continuous spectrum, that is, it looks like a continuous rainbow stripe with a gradual transition of colors from red to violet. But in the lower layers of the rarefied chromosphere, in the region of the so-called temperature minimum, where the temperature drops to 4200 K, sunlight experiences absorption, due to which narrow absorption lines are formed in the solar spectrum. They are called Fraunhofer lines, named after the German optician Joseph Frau and Gopher, who carefully measured the wavelengths of 754 lines in 1816.

To date, over 26 thousand dark lines of varying intensity have been recorded in the spectrum of the Sun, arising due to the absorption of light by “cold” atoms. And since each chemical element has its own characteristic set of absorption lines, this makes it possible to determine its presence in the outer layers of the solar atmosphere.

The chemical composition of the Sun's atmosphere is similar to that of most stars formed within the last few billion years (called second-generation stars). Compared to old celestial bodies (stars of the first generation), they contain tens of times more heavy elements, that is, elements that are heavier than helium. Astrophysicists believe that heavy elements first appeared as a result of nuclear reactions that occurred during the explosions of stars, and perhaps even during the explosions of galaxies. During the formation of the Sun, the interstellar medium was already quite well enriched in heavy elements (the Sun itself does not yet produce elements heavier than helium). But our Earth and other planets condensed, apparently, from the same gas and dust cloud as the Sun. Therefore, it is possible that, while studying the chemical composition of our daylight, we are also studying the composition of the primary protoplanetary matter.

Since the temperature in the solar atmosphere varies with altitude, absorption lines at different levels are created by atoms of different chemical elements. This makes it possible to study the various atmospheric layers of the great star and determine their extent.

Above the photosphere is a rarer syllable! atmosphere of the Sun, which is called the chromosphere, which means "colored sphere". Its brightness is many times less than the brightness of the photosphere, so the chromosphere is visible only during short minutes of total solar eclipses, like a pink ring around the dark disk of the Moon. The reddish color of the chromosphere is caused by hydrogen radiation. This gas has the most intense spectral line - Ha - in the red region of the spectrum, and there is especially much hydrogen in the chromosphere.

From spectra obtained during solar eclipses, it is clear that the red line of hydrogen disappears at an altitude of approximately 12 thousand km above the photosphere, and the lines of ionized calcium cease to be visible at an altitude of 14 thousand km. This height is considered as the upper boundary of the chromosphere. As the temperature rises, the temperature increases, reaching 50,000 K in the upper layers of the chromosphere. With increasing temperature, the ionization of hydrogen and then helium increases.

The increase in temperature in the chromosphere is quite understandable. As is known, the density of the solar atmosphere quickly decreases with height, and a rarefied medium emits less energy than a dense one. Therefore, the energy coming from the Sun heats up the upper chromosphere and the corona lying above it.

Currently, heliophysicists using special instruments observe the chromosphere not only during solar eclipses, but also on any clear day. During a total solar eclipse, you can see the outermost layer of the solar atmosphere - the corona - a delicate pearly-silver glow extending around the eclipsed Sun. The total brightness of the corona is about one millionth the light of the Sun or half the light of the full Moon.

The solar corona is a highly rarefied plasma with a temperature close to 2 million K. The density of coronal matter is hundreds of billions of times less than the density of air near the Earth's surface. Under such conditions, atoms of chemical elements cannot be in a neutral state: their speed is so high that during mutual collisions they lose almost all their electrons and are repeatedly ionized. This is why the solar corona consists mainly of protons (hydrogen atomic nuclei), helium nuclei and free electrons.

The exceptionally high temperature of the corona causes its material to become a powerful source of ultraviolet and X-ray radiation. For observations in these ranges of the electromagnetic spectrum, as is known, special ultraviolet and X-ray telescopes installed on spacecraft and orbital scientific stations are used.

Using radio methods (the solar corona intensely emits decimeter and meter radio waves), coronal rays are “viewed” up to distances of 30 solar radii from the edge of the solar disk. With distance from the Sun, the density of the corona decreases very slowly, and its uppermost layer flows into outer space. This is how solar wind is formed.

Only due to the volatilization of corpuscles, the mass of the Sun decreases every second by no less than 400 thousand tons.

The solar wind blows across the entire space of our planetary system. By then the initial speed reaches more than 1000 km/s, but then it slowly decreases. The Earth's orbit has an average wind speed of about 400 km/s. Ohm sweeps away in its path all the gases emitted by planets and comets, the smallest meteoric dust particles and even particles of low-energy galactic cosmic rays, carrying all this “garbage” to the outskirts of the planetary system. Figuratively speaking, we seem to be bathing in the crown of a great star...

The closest star to us is, of course, the Sun. The distance from the Earth to it, according to cosmic parameters, is very small: sunlight travels from the Sun to the Earth in only 8 minutes.

The Sun is not an ordinary yellow dwarf, as previously thought. This is the central body of the solar system, around which the planets revolve, with a large number of heavy elements. This is a star formed after several supernova explosions, around which a planetary system was formed. Due to its location close to ideal conditions, life arose on the third planet Earth. The Sun is already five billion years old. But let's figure out why it shines? What is the structure of the Sun and what are its characteristics? What does the future hold for him? How significant an impact does it have on the Earth and its inhabitants? The Sun is a star around which all 9 planets of the solar system, including ours, revolve. 1 a.u. (astronomical unit) = 150 million km - the same is the average distance from the Earth to the Sun. The Solar System includes nine major planets, about a hundred satellites, many comets, tens of thousands of asteroids (minor planets), meteoroids, and interplanetary gas and dust. At the center of it all is our Sun.

The sun has been shining for millions of years, which is confirmed by modern biological research obtained from the remains of blue-green-blue algae. If the temperature of the surface of the Sun changed by even 10%, all life on Earth would die. Therefore, it is good that our star evenly radiates the energy necessary for the prosperity of humanity and other creatures on Earth. In the religions and myths of the peoples of the world, the Sun has always occupied the main place. For almost all peoples of antiquity, the Sun was the most important deity: Helios - among the ancient Greeks, Ra - the sun god of the ancient Egyptians and Yarilo among the Slavs. The sun brought warmth, harvest, everyone revered it, because without it there would be no life on Earth. The size of the Sun is impressive. For example, the mass of the Sun is 330,000 times the mass of the Earth, and its radius is 109 times greater. But the density of our star is small - 1.4 times greater than the density of water. The movement of spots on the surface was noticed by Galileo Galilei himself, thus proving that the Sun does not stand still, but rotates.

Convective zone of the Sun

The radioactive zone is about 2/3 of the internal diameter of the Sun, and the radius is about 140 thousand km. Moving away from the center, photons lose their energy under the influence of collision. This phenomenon is called the phenomenon of convection. This is reminiscent of the process that occurs in a boiling kettle: the energy coming from the heating element is much greater than the amount that is removed by conduction. Hot water close to the fire rises, and colder water sinks. This process is called convention. The meaning of convection is that denser gas is distributed over the surface, cools and again goes to the center. The mixing process in the convective zone of the Sun is carried out continuously. Looking through a telescope at the surface of the Sun, you can see its granular structure - granulations. It feels like it's made of granules! This is due to convection occurring beneath the photosphere.

Photosphere of the Sun

A thin layer (400 km) - the photosphere of the Sun, is located directly behind the convective zone and represents the “real solar surface” visible from Earth. Granules in the photosphere were first photographed by the Frenchman Janssen in 1885. The average granule has a size of 1000 km, moves at a speed of 1 km/sec and exists for approximately 15 minutes. Dark formations in the photosphere can be observed in the equatorial part, and then they shift. Strong magnetic fields are a distinctive feature of such spots. And the dark color is obtained due to the lower temperature relative to the surrounding photosphere.

Chromosphere of the Sun

The solar chromosphere (colored sphere) is a dense layer (10,000 km) of the solar atmosphere that lies directly behind the photosphere. The chromosphere is quite problematic to observe due to its close location to the photosphere. It is best seen when the Moon covers the photosphere, i.e. during solar eclipses.

Solar prominences are huge emissions of hydrogen, resembling long luminous filaments. The prominences rise to enormous distances, reaching the diameter of the Sun (1.4 mm km), move at a speed of about 300 km/sec, and the temperature reaches 10,000 degrees.

The solar corona is the outer and extended layers of the Sun's atmosphere, originating above the chromosphere. The length of the solar corona is very long and reaches values ​​of several solar diameters. Scientists have not yet received a clear answer to the question of where exactly it ends.

The composition of the solar corona is a rarefied, highly ionized plasma. It contains heavy ions, electrons with a helium core, and protons. The temperature of the corona reaches from 1 to 2 million degrees K, relative to the surface of the Sun.

The solar wind is a continuous outflow of matter (plasma) from the outer shell of the solar atmosphere. It consists of protons, atomic nuclei and electrons. The speed of the solar wind can vary from 300 km/sec to 1500 km/sec, in accordance with the processes occurring on the Sun. The solar wind spreads throughout the solar system and, interacting with the Earth's magnetic field, causes various phenomena, one of which is the northern lights.

Characteristics of the Sun

Mass of the Sun: 2∙1030 kg (332,946 Earth masses)
Diameter: 1,392,000 km
Radius: 696,000 km
Average density: 1,400 kg/m3
Axis tilt: 7.25° (relative to the ecliptic plane)
Surface temperature: 5,780 K
Temperature at the center of the Sun: 15 million degrees
Spectral class: G2 V
Average distance from Earth: 150 million km
Age: 5 billion years
Rotation period: 25.380 days
Luminosity: 3.86∙1026 W
Apparent magnitude: 26.75m