Solar luminosity. The structure of the sun The luminosity of the sun is

The closest star to us is of course the Sun. The distance from the Earth to it in terms of cosmic parameters is very small: from the Sun to the Earth, the sunlight takes 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. It is a star formed after several supernova explosions, around which a planetary system was formed. Due to the location close to ideal conditions, life arose on the third planet Earth. The Sun is already five billion years old. But let's see why it shines? What is the structure of the Sun and what are its characteristics? What does the future hold for him? How significant does it have on the Earth and its inhabitants? The Sun is a star around which all 9 planets of the solar system revolve, including ours. 1 a.u. (astronomical unit) \u003d 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), meteoric bodies and interplanetary gas and dust. Our Sun is in the center of all this.

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 Sun's surface changed by at least 10%, and on Earth, all living things 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 respected him, because without him 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 stellar body is small - 1.4 times more 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 inner diameter of the Sun, and the radius is about 140 thousand km. Moving away from the center, the photons lose their energy under the influence of the collision. This phenomenon is called the convection phenomenon. This is similar to the process that takes place in a boiling kettle: the energy coming from the heating element is much greater than the amount that is removed by conduction. Hot water in the vicinity of the fire rises, and colder water goes down. This process is called convention. The meaning of convection is that a denser gas spreads over the surface, cools and goes back 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, one can see its granular structure - granulation. It feels like it is made of granules! This is due to convection under 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 the Earth. For the first time the granules on the photosphere were photographed by the Frenchman Janssen in 1885. The average granule has a size of 1000 km, moves at a speed of 1 km / s and lasts about 15 minutes. Dark formations in the photosphere can be observed in the equatorial part, and then they shift. The strongest magnetic fields are the hallmark of such spots. And the dark color is due to the lower temperature relative to the surrounding photosphere.

Chromosphere of the Sun

The sun's chromosphere (colored sphere) is a dense layer (10,000 km) of the solar atmosphere that lies just 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 that resemble long glowing filaments. The prominences rise to a huge distance, reaching the diameter of the Sun (1.4 mlm km), moving at a speed of about 300 km / s, while 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 \u200b\u200bof several diameters of the sun. On the question of where exactly it ends, scientists have not yet received a definite answer.

The composition of the solar corona is a discharged, highly ionized plasma. It contains heavy ions, electrons with a helium nucleus, 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 flow of matter (plasma) from the outer shell of the solar atmosphere. It is composed of protons, atomic nuclei and electrons. The solar wind speed can vary from 300 km / s to 1500 km / s, in accordance with the processes taking place on the Sun. The solar wind spreads throughout the entire 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

All stars are colored. From red dwarfs and red giants to white and yellow stars, to blue giants and supergiants. The color of the star depends on the temperature. When photons burst from within a star into space, they have different amounts of energy. can emit infrared, red, blue and ultraviolet light at the same time. They even emit X-rays and.

If the star is cold, less than 3,500 Kelvin, its color will be red. This is due to the fact that more red photons are emitted than any other in visible light. If the star is very hot, over 10,000 Kelvin, its color will be blue. Again, because there are more blue photons streaming out of the star.

The Sun's temperature is approximately 6,000 Kelvin. The sun, and stars like our sun, appear white. This is due to the fact that we observe all the different colored photons coming out of the Sun at the same time. When you add these colors together, you get pure white.

The white inside this black square is approximately the color of the Sun.

So why does the Sun look yellow here on Earth? Earth's atmosphere scatters sunlight, removing shorter wavelengths of light - blue and violet. Once you remove these colors from the spectrum of light coming from the Sun, it looks yellow. But if you were to fly and view the Sun from space, the color of the Sun would be pure white.

Sun temperature

The sun's surface, the part that we see, is called the photosphere. Photons streaming from the surface of the Sun vary in temperature from 4500 Kelvin to over 6000 Kelvin. The average temperature of the Sun is about 5800 Kelvin. In other units, the Sun is 5500 ° C or 9.900 ° F.

Photosphere of the Sun. Credit: NASA / SOHO.

But this is only the average temperature. Individual photons can be colder and redder, or hotter and blue. The color of the Sun that we see here on Earth is, on average, all the photons streaming from the Sun.

But this is only the surface. The sun is held together by the mutual gravity of its mass. If you could go down the sun, you would feel the temperature and pressure increase all the way to the core. And down to the core, temperatures reach 15.7 million Kelvin. At this pressure and temperature, hydrogen nuclear fusion can already take place. This is where hydrogen atoms combine to form helium, releasing photons of gamma radiation. These photons are released and absorbed by atoms in the Sun as they slowly make their way into space. It may take 100,000 years for a photon from the core to eventually reach the photosphere and jump into space.

Surface of the sun

Perhaps the most familiar feature on the sun's surface is sunspots. These are relatively colder regions on the Sun's surface where magnetic field lines pierce the Sun's surface. Sunspots can be the source of solar flares and coronal mass ejections.

View of the surface of the Sun from the Japanese scientific satellite Hinode.

When we look at the Sun, we notice that the Sun's center looks much brighter than the borders. This is called "limb darkening" and happens because we see light that has passed through the sun's surface at an angle and has more obstructions — and therefore is darker.

With a good telescope (and even a better solar filter), it is possible to see that the photosphere is not smooth. Instead, it is covered with convection cells called granules. They are caused by convective plasma currents inside the convection zone of the Sun. Hot plasma rises in pillars through this convection region of the Sun, releases its energy, and then cools and sinks. Imagine bubbles rising to the surface in boiling water. These granules can be 1000 km wide and exist for 8-20 minutes before dispersing.

Huge coronal mass ejections can also be seen firing from the sun's surface. They are created when the sun's curled magnetic field is abruptly cut off and disconnected. This disconnection releases a tremendous amount of energy and propels charged plasma into space. When this plasma reaches Earth, it creates beautiful auroras, best seen at the Earth's poles.

Luminosity of the sun

Astronomers measure the brightness of stars with various instruments, but they need a way to compare. This is where our Sun appears. As everyone knows, the Sun gives off approximately 3.839 x 10 33 erg per second of energy. Other stars in the Universe can only give off a fraction of the solar luminosity, or several multiples of it. Our Sun is the star criterion.

Massive coronal mass ejection. This photo shows the size of the Earth for comparison (top left). Credit: NASA / SDO / J. Major.

Imagine that the Sun is surrounded by rows of transparent spheres - like the layers of an onion. The amount of energy, the solar luminosity passing through each of these spheres every second, is always the same. However, the sphere's surface area gets larger and larger. This is why the farther away you get less light from the star you see.

This is called the inverse square law, and allows astronomers to calculate solar luminosity; in fact, it allows them to calculate the luminosities of all stars. Scientists have sent missions into space that measure the total amount of energy falling on their sensors. From this information, astronomers can calculate how much energy falls on the entire Earth, and then how much comes from the Sun.

And it also works for the stars. The spacecraft detects the luminosity of another star, factors in distance, and helps calculate the star's initial luminosity.

Although our Sun is stable, it undergoes minor changes in solar luminosity. These changes are caused by sunspots, which darken regions, and bright structures on the solar disk during the 11-year solar cycle. Detailed measurements over the past 30 years have found that they are not sufficient to lead to the acceleration of global warming that we find here on Earth.

Visually, the stars for an earthly observer look different: some shine brighter, others dimmer.

However, this does not yet speak about the true power of their radiation, since the stars are at different distances.

For example, the blue Rigel from the constellation Orion has an apparent magnitude of 0.11, and the brightest Sirius located nearby in the sky has an apparent magnitude of minus 1.5.

Nevertheless, Rigel emits 2200 times more energy in visible light than Sirius, and it seems weaker only because it is 90 times farther from us compared to Sirius.

Thus, the apparent magnitude in itself cannot be a characteristic of the star, since it depends on the distance.

The true characteristic of the radiation power of a star is its luminosity, that is, the total energy that the star emits per unit time.

Luminosity in astronomy, the total energy emitted by an astronomical object (planet, star, galaxy, etc.) per unit of time. Measured in absolute units: watts (W) - in the International SI system; erg / s - in the CGS system (centimeter-gram-second); or in units of the luminosity of the Sun (the luminosity of the Sun L s \u003d 3.86 · 10 33 erg / s or 3.8 · 10 26 W).

Luminosity does not depend on the distance to the object, only the apparent magnitude depends on it.

Luminosity is one of the most important stellar characteristics, which makes it possible to compare different types of stars with each other on the “spectrum - luminosity” and “mass - luminosity” diagrams.

where R is the radius of the star, T is the temperature of its surface, σ is the Stefan-Boltzmann constant.

The luminosities of stars, it should be noted, are very different: there are stars whose luminosity is 500,000 times that of the Sun, and there are dwarf stars whose luminosity is about the same times less.

The luminosity of a star can be measured in physical units (say, in watts), but astronomers often express the luminosities of stars in terms of the luminosity of the Sun.

You can also express the true luminosity of a star using absolute magnitude.

Let's imagine that we have placed all the stars side by side and we are viewing them from the same distance. Then the apparent stellar magnitude will no longer depend on the distance and will be determined only by the luminosity.

The standard distance is 10 ps (parsec).

The apparent stellar magnitude (m) that a star would have at this distance is called absolute stellar magnitude (M).

Thus, the absolute stellar magnitude is a quantitative characteristic of an object's luminosity, equal to the stellar magnitude that an object would have at a standard distance of 10 parsecs.

Since the illumination is inversely proportional to the square of the distance, then

where E is the illumination created by the star, which is r parsec from the Earth; E 0 - illumination from the same star from the standard distance r 0 (10 pc).

Using Pogson's formula, we get:

m - M \u003d -2.5lg (E / E 0) \u003d -2.5lg (r 0 / r) 2 \u003d -5lgr 0 + 5lgr.

this implies

M \u003d m + 5lgr 0 - 5lgr.

For r 0 \u003d 10 pc

M \u003d m + 5 - 5lgr. (1)

If in (1) r \u003d r 0 \u003d 10 pcthen M \u003d m - by determining the absolute magnitude.

The difference between the apparent (m) and absolute (M) stellar magnitudes is called the distance modulus

m - М \u003d 5 lgr - 5.

While M depends only on the star's own luminosity, m also depends on the distance r (in ps) to it.

For example, let's calculate the absolute magnitude for one of the brightest and closest stars to us - Centauri.

Its apparent magnitude is -0.1, the distance to it is 1.33 ps. Substituting these values \u200b\u200binto formula (1), we get: M \u003d -0.1 + 5 - 5lg1.33 \u003d 4.3.

That is, the absolute stellar magnitude a Centauri is close to the absolute stellar magnitude of the Sun, equal to 4.8.

One should also take into account the absorption of the star's light by the interstellar medium. Such absorption weakens the star's brightness and increases the apparent magnitude m.

In this case: m \u003d M - 5 + 5lgr + A (r), where the term А (r) takes into account interstellar absorption.

Luminosity
Visible and absolute stellar magnitudes
Wikipedia

To represent the luminosity of the stars. Equal to the luminosity of the Sun, which is 3.827 × 10 26 W or 3.827 × 10 33 Erg / s.

Calculating a constant

You can calculate the amount of solar energy hitting the Earth by comparing the area of \u200b\u200ba sphere with a radius equal to the Earth's distance from the Sun (the center is in a star) and a sectional area made so that the planet's axis of rotation belongs to the section plane.

• The radius of the Earth is 6.378 km.
• Cross-sectional area of \u200b\u200bthe Earth: S Earth \u003d π × radius² \u003d 128.000.000 km²
• Average distance to the Sun: R Sun \u003d 150,000,000 km. (1 au)
• Area of \u200b\u200ba sphere: S Sun \u003d 4 × π × R Sun ² \u003d 2.82 × 10 17 km².
• The amount of energy per unit of time that hits the Earth: P Earth \u003d P Sun × S Earth / S Sun \u003d 1.77 × 10 17 W.
  • The amount of energy (per unit of time) per square meter: P Earth / S Earth \u003d 1387 W / m² (Solar constant)
  • Humanity consumes approximately 12 × 10 12 watts. How much space is needed to ensure energy consumption? The best solar panels have an efficiency of about 33%. The required area is 12 × 10 12 / (1387 × 0.33) \u003d 26 × 10 9 m² \u003d 26000 km², or a square of ~ 160 × 160 km. (In fact, a larger area is required, since the sun is not always at its zenith and, in addition, some of the radiation is scattered by clouds and the atmosphere.)

Links

• I.-J. Sackmann, A. I. Boothroyd (2003). "Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars". The Astrophysical Journal 583 (2): 1024-1039.

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See what "Luminosity of the Sun" is in other dictionaries:

In astronomy, the total energy emitted by a source per unit of time (in absolute units or in units of the luminosity of the Sun; the luminosity of the Sun \u003d 3.86 · 1033 erg / s). Sometimes one speaks not of complete S., but of S. in a certain wavelength range. For example, in ... ... Astronomical Dictionary

Luminosity is a term used to refer to certain physical quantities. Contents 1 Photometric luminosity 2 Luminosity of a celestial body ... Wikipedia

The luminosity of a star, the intensity of the star's light, that is, the magnitude of the luminous flux emitted by the star, enclosed in a single solid angle. The term "luminosity of a star" does not correspond to the term "luminosity" of general photometry. S. stars can be referred to as ... Great Soviet Encyclopedia

At a point on the surface. one of the luminous quantities, the ratio of the luminous flux emanating from a surface element to the area of \u200b\u200bthis element. The unit C. (SI) is lumens per square meter (lm / m2). A similar value in the energy system. quantities called ... ... Physical encyclopedia

LUMINANCE, the absolute brightness of a STAR, the amount of energy emitted by its surface per second. It is expressed in watts (joules per second) or in terms of the brightness of the sun. Bolometric luminosity measures the total power of a star's light at ... ... Scientific and technical encyclopedic dictionary

LUMINANCE, 1) in astronomy, the total amount of energy emitted by a space object per unit of time. Sometimes they talk about luminosity in a certain wavelength range, for example, radio luminosity. Usually measured in erg / s, W or in units of ... ... Modern encyclopediaWikipedia

How did it become known how much energy the sun emits?

For almost a century and a half, astronomers and geophysicists have spent a lot of effort in order to determine solar constant.This is the name of the total amount of energy of solar radiation of all wavelengths falling on an area of \u200b\u200b1 cm 2, placed perpendicular to the sun's rays outside the earth's atmosphere and at the average distance of the earth from the sun. Determining the solar constant seems like a fairly straightforward task. But this is only at first glance. In reality, however, the researcher is faced with two serious difficulties.

First of all, it is necessary to create a radiation detector that would perceive all colors of visible light, as well as ultraviolet and infrared rays - in a word, the entire spectrum of electromagnetic waves with the same sensitivity. Let us remind the reader that visible light, ultraviolet and x-ray radiation, gamma rays, infrared radiation and radio waves are in a certain sense the same nature. Their difference from each other is due only to the frequency of oscillations of the electromagnetic field or wavelength. Table 2 indicates the wavelengths of lambda different regions of the spectrum of electromagnetic radiation, as well as the frequency v in hertz and the energy of quanta hv in electron volts).

As the table shows. 2, the visible region, with a length of slightly less than an octave, constitutes a very small part of the entire spectrum of electromagnetic radiation, extending from gamma rays with wavelengths of thousandths of a nanometer to meter radio waves, by more than 46 octaves. The sun radiates in almost all of this giant wavelength range, and the solar constant should take into account, as already mentioned, the energy of the entire spectrum. The most suitable for this purpose are thermal detectors, for example, thermoelements and bolometers, in which the measured radiation is converted into heat, and the readings of the device depend on the amount of this heat, i.e., ultimately, on the power of the incident radiation, but not on its spectral composition.

The Angstrem compensation pyrheliometer, invented in 1895 and widely adopted (with minor improvements), is ingeniously arranged. Imagine two identical plates (from manganin) standing next to each other. Both are coated with platinum niello or special black lacquer. One of them is illuminated and heated by the sun's rays, and the other is closed by a curtain. An electric current of such strength (regulated by a rheostat) is passed through the shaded plate so that its temperature is equal to the temperature of the illuminated plate. The current power required for compensationsolar heating (hence the name of the device - compensation pyrheliometer) is a measure of the power of the incident radiation.

The advantage of the Angstrom pyrheliometer is its simplicity, reliability and good reproducibility of indications. That is why it has been used in various countries for over 85 years. Nevertheless, measurements with it require some small, but difficult to determine, corrections. First of all, no amount of blackening (including soot, platinum black, etc.) ensures complete absorption of the incident rays. Some part of them (about 1.5-2%) is reflected, and this share can vary with wavelength. In this regard, cavity devices have been developed in the last two decades. The diagram of one of them (the PAKRAD-3 pyrheliometer, serially produced by the Eppley Laboratory, USA) is shown in Fig. 1.

In the upper receiving cavity l, formed by a cylinder 2, cone 3 double-walled truncated cone 4, sunlight enters through precision diaphragm 5. Thermopile 6 allows you to determine the temperature increase in the upper structure in comparison with similar points of the lower one, which is arranged in exactly the same way as the upper one (only the cone in it is turned 180 ° for compactness). The power of the absorbed radiation is equal to the power of the current, which must be passed through the winding 7, so that when the diaphragm is closed 5 cause an equal rise in temperature.

As the sun's rays can come out of the cavity 1 only after several reflections, the cavity, blackened from the inside with the same varnish as the plates of the Angstrom pyrheliometer, has a high absorption coefficient. It is 0.997-0.998, and in some cases it reaches 0.9995. This is the advantage of widespread cavity devices.

The second difficulty in determining the solar constant is caused by the earth's atmosphere. The latter attenuates any radiation, and the attenuation is highly dependent on the wavelength. Blue and violet rays are attenuated much more than red ones, and ultraviolet ones are attenuated even more. Radiation with a wavelength of less than 300 nm is generally completely blocked by the earth's atmosphere, like most infrared rays. In addition, the optical properties of the atmosphere are extremely variable, even in clear, cloudless weather.

Due to the fact that rays of different wavelengths are attenuated by the atmosphere in different ways, the transparency coefficient cannot be found by conducting observations in "white light" on devices such as pyrheliometers, which register radiation of all wavelengths that are not decomposed into a spectrum. A spectrometric instrument is absolutely essential. Observations on it will make it possible to determine the values \u200b\u200bof the atmospheric transparency coefficient separately for a number of wavelengths. Only then can we calculate from them the correction for the atmosphere to the readings of the pyrheliometer.

All this greatly complicates the determination of the solar constant from the surface of the Earth. It is not surprising that the observations made, for example, in the last century, had low accuracy, and different authors obtained values \u200b\u200bthat differ by 2 times or more.

Methodologically, the works begun in 1900 and continued for several decades under the leadership of Ch. Abbott are rightfully considered the best among ground definitions. They showed results that had a 2-3% spread around the average. Abbot himself interpreted this spread as real changes in solar radiation. However, later a more refined analysis of these same observations showed that the scatter was caused by errors associated primarily with insufficient consideration of the instabilities of the earth's atmosphere.

Meanwhile, for meteorology and a number of other earth sciences, as well as for astrophysics (in particular, the physics of planets), both a more accurate knowledge of this quantity and a solution to the question of whether the solar constant is really constant are necessary, i.e. and in what limits the possible fluctuations of solar radiation.

The most radical solution to the problem is provided by the use of artificial earth satellites. Satellites designed to measure the solar constant have been regularly “working” for the last 10-12 years. The removal of instruments outside the atmosphere (of course, along with the improvement of the instruments themselves) makes it possible to determine the flux of solar radiation with an unprecedented accuracy - an absolute value of up to 0.3%, and possible fluctuations up to 0.001% of the average value. Nevertheless, despite the achieved accuracy, the problem of fluctuations in the solar constant has not been fully resolved. It has only been established that their amplitude (if they exist) is not more than 0.1-0.2%. Without going further into the discussion of the stability of solar radiation, we note that with an accuracy of 1%, the solar constant is 137 mW / cm 2, or 1.96 cal (cm 2 min) -1.

Knowing the value of the solar constant, we can get interesting data. Consider a certain area of \u200b\u200bthe earth's surface and assume that the angle of incidence of the sun's rays on it is 60 ° (the height of the Sun above the horizon is 30 °). In this case, quite typical for mid-latitude conditions, about 65% of the total solar radiation flux will reach the Earth's surface, the rest will be delayed by the atmosphere. The illumination of the earth's surface must still be halved due to the oblique incidence of the rays. It is easy to calculate that under these conditions, a power of 22 million kW is supplied from the Sun to an area 5 × 10 km in size (equal to the area of \u200b\u200ban average city), i.e. more than the entire complex of 5 power plants under construction in Ekibastuz will provide. Further, knowing the radius of the globe, equal to 6.371 10 8 cm, it is easy to find the area of \u200b\u200bthe "cross-section" of the Earth (1.275 10 18 cm 2) and calculate that the power of solar radiation falling on the entire half of the earth's surface illuminated by the Sun is enormous - about 1.7 10 14 kW. To present it more clearly, it is enough to say that the solar energy falling on the daytime hemisphere of the Earth is enough to melt a block of ice with a volume of 0.56 km 3 in 1 s (1 km long and 1 km wide and 560 m high) or heat up in 4 hours from 0 to 100 ° C and then evaporate as much water as there is in Lake Ladoga (908 km 3). Finally, in 26 days the Sun sends more energy to the Earth than is contained in all the explored and predicted reserves of coal, oil and gas and other types of fossil fuels. These reserves are estimated at 13 10 12 tons of the so-called standard fuel (ie, fuel with a calorific value of 7000 cal / g, or 29.3 10 6 J / kg).

The energy of all weather phenomena, all natural processes occurring in the earth's atmosphere and hydrosphere, such as wind, evaporation of the oceans, moisture transport by clouds, precipitation, streams and rivers and ocean currents, the movement of glaciers - all this is basically the converted energy of solar radiation that fell to the ground. The development of the biosphere is determined by heat and light, therefore, some types of fuels, as well as all our food, according to the figurative expression of K. A. Timiryazev, "is canned sun rays."

Let's give one more figure. The average distance of the Earth from the Sun (or the semi-major axis of the Earth's orbit) is 149.6 10 6 km. Hence, the total luminosity of the Sun is 3.82 10 23 kW, or 3.82 10 33 erg / s; this value is almost 17 orders of magnitude higher than the capacity of the largest technical power plants, such as our largest hydro and thermal power plants.