The passage of light from stars through the solar corona. The mystery of the solar corona. The location of the sun in the galaxy

Has a high fever. On the surface, it is about 5500 degrees Celsius. The sun has an atmosphere called a corona. This area consists of superheated gas - plasma. Its temperature reaches over 3 million degrees. And scientists are trying to understand why the outer layer of the sun is so much hotter than everything that lies beneath it.

The problem that confuses scientists is quite simple. Since the energy source is at the center of the sun, its body should become increasingly cooler as it moves away from the center. But observations suggest otherwise. And so far, scientists cannot explain why the sun's corona is hotter than its other layers.

Old mystery

Despite its temperature, the solar corona is usually not visible to the terrestrial observer. This is due to the intense brightness of the rest of the Sun. Even sophisticated instruments cannot probe it without considering the light emanating from the surface of the Sun. But this does not mean that the existence of the solar corona is a recent discovery. It can be seen in rare but predictable events that have fascinated people for millennia. It's complete.

In 1869, astronomers took advantage of such an eclipse to study the sun's outer layer that was suddenly revealed for observation. They aimed spectrometers at the Sun to study the elusive material in the corona. Researchers have found an unfamiliar green line in the spectrum of the corona. The unknown substance was named coronium. However, seventy years later, scientists realized that it was a familiar element - iron. But heated to unprecedented millions of degrees.

An early theory said that acoustic waves (imagine the sun's material contracting and expanding like an accordion) may be responsible for the temperature of the corona. In many ways, this is similar to how a wave throws water droplets at high speed onto the shore. But the solar probes were unable to find waves with the power to explain the observed coronal temperature.

For almost 150 years, this mystery has been one of the little but interesting mysteries of science, yet scientists are confident that their knowledge of the temperature both on the surface and in the corona is correct enough.

The sun's magnetic field: how does it work?

Part of the problem is that we do not understand many of the small events that take place on the sun. We know how it does its job of warming our planet. But the models of the materials and forces involved in this process simply do not exist yet. We cannot yet get close enough to the Sun to study it in detail.

The answer to most questions about the sun these days boils down to the fact that the sun is a very complex magnet. The earth also has a magnetic field. But, despite the oceans and underground magma, it is still much denser than the Sun. Which is just a big bunch of gas and plasma. The earth is a harder object.

The sun also revolves. But since it is not solid, its poles and equator rotate at different speeds. Matter moves up and down the Sun's layers, like in a pot of boiling water. This effect causes disorder in the magnetic field lines. Charged particles that make up the sun's outer layers travel along lines like high-speed trains. railways... These lines break and reconnect, releasing a tremendous amount of energy (solar flares). Or they produce vortexes full of charged particles that can be freely ejected from these rails into space at colossal speed (coronal mass ejection).

We have many satellites that are already tracking the sun. The Solarer Pro, launched this year, is just beginning its observations. It will continue its work until 2025. Scientists hope that the mission will provide answers to many mysterious questions about the Sun.

If you find an error, please select a piece of text and press Ctrl + Enter.

Eclipses are among the most spectacular astronomical phenomena. However, no technical means can fully convey the sensations arising from the observer. And yet, due to the imperfection of the human eye, he does not see everything at once. The details of this wonderful picture that elude the eye can only be revealed and captured by special photography and signal processing techniques. The variety of eclipses is far from being limited to phenomena in the Sun-Earth-Moon system. Relatively close space bodies regularly cast shadows on each other (you just need to have some powerful source of light radiation nearby). Observing this cosmic shadow theater, astronomers receive a lot of interesting information about the structure of the universe. Photo Vyacheslav Khondyrev

In the Bulgarian resort of Shabla, August 11, 1999 was the most ordinary summer day. Blue sky, golden sand, warm gentle sea. But on the beach, no one went into the water - the audience was preparing for observations. It was here that a hundred-kilometer spot of the lunar shadow was supposed to cross the Black Sea coast, and the duration of the full phase, according to calculations, reached 3 minutes 20 seconds. The excellent weather was consistent with the long-term data, but everyone looked anxiously at the cloud hanging over the mountains.

In fact, the eclipse was already underway, but its particular phases were of little interest to anyone. Another thing is the full phase, before the start of which there was still half an hour. A brand new digital SLR, specially purchased for this occasion, was ready to go. Everything is thought out to the smallest detail, each movement has been rehearsed dozens of times. The weather would not have time to deteriorate, and yet, for some reason, anxiety was growing. Maybe the fact is that the light has noticeably diminished and sharply colder? But this is how it should be with the approach of the full phase. However, the birds cannot understand this - all the birds capable of flying took to the air and screamed out circles over our heads. The wind blew from the sea. He grew stronger every minute, and the heavy camera began to shake on the tripod, which until recently seemed so reliable.

There is nothing to do - a few minutes before the calculated moment, risking ruining everything, I went down from the sandy hill to its foot, where the bushes were extinguishing the wind. A few movements, and literally at the last moment, the technique is re-tuned. But what is this noise? Dogs bark and howl, sheep bleat. It seems that all animals capable of making sounds are doing it like the last time! The light dims with every second. Birds are no longer visible in the darkened sky. Everything subsides at once. The filamentous sun crescent illuminates the seashore no brighter than the full moon. Suddenly it goes out too. Whoever watched him in the last seconds without a dark filter, in the first moments, probably does not see anything.

My fussy excitement was replaced by a real shock: the eclipse, which I dreamed of all my life, has already begun, precious seconds are flying, and I can't even raise my head and enjoy the rarest spectacle - photography first of all! Each time the button is pressed, the camera automatically takes a burst of nine shots (bracketing). One more. More and more. While the camera clicks the shutter, I still dare to tear myself away and look at the crown through binoculars. From the black moon, many long rays scattered in all directions, forming a pearl crown with a yellowish-cream shade, and bright pink prominences flare up at the very edge of the disk. One of them flew unusually far from the edge of the moon. Spreading out to the sides, the rays of the crown gradually fade and merge with the dark blue background of the sky. The effect of the presence is as if I was not standing on the sand, but flying in the sky. And time seemed to have disappeared ...

Suddenly a bright light hit the eyes - it was the edge of the Sun that floated out from behind the Moon. How quickly it was all over! The prominences and rays of the crown are visible for a few more seconds, and the shooting continues until the last. The program has been completed! A few minutes later, the day flares up again. The birds immediately forgot their fear from the extraordinary fleeting night. But for many years now, my memory has kept a sense of the absolute beauty and grandeur of the cosmos, a sense of belonging to its secrets.

How the speed of light was first measured

Eclipses occur not only in the Sun-Earth-Moon system. For example, the four largest moons of Jupiter, discovered by Galileo Galilei in 1610, played an important role in the development of navigation. In that era, when there were still no accurate marine chronometers, it was possible to recognize the Greenwich time, which was necessary to determine the longitude of the vessel, far from their native shores. Eclipses of satellites in the Jupiter system occur almost every night, when one or the other satellite enters the shadow cast by Jupiter, or hides from our view behind the disk of the planet itself. Knowing the pre-calculated moments of these phenomena from the nautical almanac and comparing them with the local time obtained from elementary astronomical observations, you can determine your longitude. In 1676, the Danish astronomer Ole Christensen Römer noticed that the eclipses of Jupiter's moons deviated slightly from the predicted times. The Jupiterian clock either went ahead by a little over eight minutes, then, after about six months, it lagged behind by the same amount. Roemer compared these fluctuations with the position of Jupiter relative to the Earth and came to the conclusion that the whole point is in the delay in the propagation of light: when the Earth is closer to Jupiter, the eclipses of its satellites are observed earlier, when farther - later. The difference, which was 16.6 minutes, corresponded to the time it took for the light to travel the diameter of the earth's orbit. This is how Roemer measured the speed of light for the first time.

Meetings at the Heavenly Nodes

By a surprising coincidence, the apparent sizes of the Moon and the Sun are almost the same. Due to this, in rare minutes of total solar eclipses, one can see prominences and the solar corona - the outermost plasma structures of the solar atmosphere, constantly "flying away" into outer space. If the Earth had such a large satellite, for the time being, no one would have guessed about their existence.

The visible paths across the sky of the Sun and the Moon intersect at two points - the nodes through which the Sun passes about once every six months. It is at this time that eclipses become possible. When the Moon meets the Sun at one of the nodes, a solar eclipse occurs: the top of the cone of the lunar shadow, resting on the surface of the Earth, forms an oval shadow spot, which moves at high speed along the earth's surface. Only people caught in it will see the lunar disk, which completely overlaps the solar one. For the observer of the full phase strip, the eclipse will be partial. Moreover, in the distance it may not even be noticed - after all, when less than 80-90% of the solar disk is covered, the decrease in illumination is almost imperceptible to the eye.

The bandwidth of the full phase depends on the distance to the Moon, which, due to the ellipticity of its orbit, varies from 363 to 405 thousand kilometers. At the maximum distance, the cone of the lunar shadow falls slightly short of the Earth's surface. In this case, the apparent dimensions of the Moon turn out to be slightly smaller than the Sun, and instead of a total eclipse, an annular eclipse occurs: even in the maximum phase, a bright rim of the solar photosphere remains around the Moon, preventing the corona from being seen. Astronomers, of course, are primarily interested in total eclipses, in which the sky darkens enough to observe a radiant corona.

Lunar eclipses (from the point of view of a hypothetical observer on the Moon, they will, of course, be solar) occur during the full moon, when our natural satellite passes the node opposite to where the Sun is and falls into the cone of the shadow cast by the Earth. There are no direct sunlight inside the shadow, but the light refracted in the earth's atmosphere still hits the surface of the moon. Usually it paints it reddish (and sometimes brownish-greenish) due to the fact that in the air long-wave (red) radiation is absorbed less than short-wave (blue) radiation. One can imagine the horror that led to primitive man the suddenly darkened ominously red disk of the moon! What can we say about solar eclipses, when the daylight, the main deity for many peoples, suddenly began to disappear from the sky?

It is not surprising that the search for patterns in the eclipse schedule became one of the first difficult astronomical problems. Assyrian cuneiform tablets dating back to 1400-900 BC e., contain data on systematic observations of eclipses in the era of the Babylonian kings, as well as mention of a remarkable period of 65851/3 days (saros), during which the sequence of lunar and solar eclipses is repeated. The Greeks went even further - by the shape of the shadow crawling on the moon, they concluded that the earth was spherical and that the sun was much larger than it.

How the masses of other stars are determined

Alexander Sergeev

Six hundred "sources"

With distance from the Sun, the outer corona gradually dims. Where in photographs it merges with the background of the sky, its brightness is a million times less than the brightness of prominences and the inner corona surrounding them. At first glance, it is impossible to photograph the corona along its entire length from the edge of the solar disk to merging with the sky background, because it is well known that the dynamic range of photographic matrices and emulsions is thousands of times smaller. But the pictures with which this article is illustrated prove the opposite. The problem has a solution! Only you need to go to the result not ahead of time, but bypassing: instead of one “ideal” frame, you need to take a series of shots with different exposures. Different images will reveal areas of the corona at different distances from the Sun.

Such images are first processed separately, and then they are combined with each other according to the details of the corona rays (it is impossible to combine the images on the Moon, because it is rapidly moving relative to the Sun). Digital processing of photographs is not as easy as it seems. However, our experience shows that any images of one eclipse can be brought together. Wide-angle with telephoto, low and long exposure, professional and amateur. These images show particles of labor of twenty-five observers who photographed the 2006 eclipse in Turkey, the Caucasus and Astrakhan.

Six hundred original images, having undergone many transformations, turned into just a few separate images, but what kind! Now they have all the smallest details of the corona and prominences, the chromosphere of the Sun and stars up to the ninth magnitude. Such stars are visible even at night only with good binoculars. The corona beams "worked out" to a record 13 solar disk radii. And more color! Everything that can be seen in the final images has a real color that coincides with the visual sensations. And this was achieved not by artificial tinting in Photoshop, but by using strict mathematical procedures in the processing program. The size of each image approaches a gigabyte - you can make prints up to one and a half meters wide without any loss of detail.

How the orbits of asteroids are refined

Eclipsing variable stars are called close binary systems in which two stars revolve around a common center of mass so that the orbit is turned edge-on to us. Then the two stars regularly eclipse each other, and the terrestrial observer sees periodic changes in their total brightness. The most famous eclipsing variable star is Algol (Beta Perseus). The circulation period in this system is 2 days 20 hours and 49 minutes. During this time, two minima are observed on the light curve. One is deep, when the small but hot white star Algol A is completely hidden behind the dim red giant Algol B. At this time, the binary's combined brightness drops by almost 3 times. A less noticeable decrease in brightness - by 5-6% - is observed when Algol A passes against the background of Algol B and slightly weakens its brilliance. A careful study of the light curve allows you to learn a lot of important information about the star system: the size and luminosity of each of the two stars, the degree of elongation of their orbits, the deviation of the shape of the stars from spherical under the influence of tidal forces, and most importantly, the mass of the stars. Without this information, it would be difficult to create and test a modern theory of the structure and evolution of stars. Stars can be eclipsed not only by stars, but also by planets. When the planet Venus passed across the disk of the Sun on June 8, 2004, few people thought to talk about an eclipse, since a tiny dark speck of Venus had almost no effect on the brightness of the Sun. But if a gas giant of the Jupiter type were in its place, it would obscure about 1% of the area of ​​the solar disk and reduce its brightness by the same amount. This can already be registered with modern instruments, and today there are already cases of such observations. And some of them are made by amateurs of astronomy. In fact, "exoplanetary" eclipses are the only way available to amateurs to observe planets near other stars.

Alexander Sergeev

Moon shadow panorama

The extraordinary beauty of a solar eclipse is not limited to the sparkling crown. After all, there is also a glowing ring along the entire horizon, which creates unique illumination at the moment of the full phase, as if the sunset occurs immediately from all directions of the world. Only few people manage to take their eyes off the crown and look at the amazing colors of the sea and mountains. And here panoramic photography comes to the rescue. Several shots joined together will show everything that has escaped sight or is not engraved in memory.

The panoramic shot in this article is special. Its horizontal coverage is 340 degrees (almost a full circle), and vertically - almost to the zenith. Only on it we later examined cirrus clouds, which almost spoiled our observations - they are always to a change in weather. Indeed, the rain began within an hour after the Moon left the Sun's disk. The contrails of the two planes visible in the picture do not actually end in the sky, but simply go into the lunar shadow and because of this they become invisible. On the right in the panorama, the eclipse is in full swing, and on the left edge of the image, the full phase has just ended.

Mercury is located to the right and below the crown - it never goes far from the Sun, and not everyone can see it. Venus shines even lower, and Mars is on the other side of the Sun. All the planets are located along one line - the ecliptic - the projection onto the sky of the plane, near which all the planets revolve. Only during an eclipse (and also from space) can one see our planetary system, surrounding the Sun, from an edge-on. The constellations Orion and Auriga are visible in the central part of the panorama. The bright stars Capella and Rigel are white, while the red supergiant Betelgeuse and Mars are orange (visible when magnified). Hundreds of people who watched the eclipse in March 2006 now think they saw it all with their own eyes. But the panoramic photo helped them - it has already been posted on the Internet.

How should you take pictures?

On March 29, 2006, in the village of Kemer on the Mediterranean coast of Turkey, in anticipation of the beginning of a total eclipse, experienced observers shared their secrets with beginners. The most important thing about eclipse is to remember to open your lenses. This is not a joke, it does happen. Also, don't duplicate each other by making the same frames. Let everyone shoot what exactly with his equipment can turn out better than others. For observers armed with wide-angle cameras, the main target is the outer crown. We must try to make a series of her shots with different shutter speeds. Telephoto owners can get detailed images of the middle crown. And if you have a telescope, then you need to photograph the area at the very edge of the lunar disk and not waste precious seconds working with other equipment. And the appeal was then heard. And immediately after the eclipse, the observers began to freely exchange files with images in order to assemble a kit for further processing. This later led to the creation of a bank of original images of the 2006 eclipse. Everyone now understood that it was still very, very far from the initial images to a detailed image of the entire crown. The days when any sharp photo of an eclipse was considered a masterpiece and the final result of observations are irrevocably gone. Upon returning home, everyone was expected to work at the computer.

Active sun

The sun, like other stars similar to it, is distinguished by periodically advancing states of activity, when many unstable structures arise in its atmosphere as a result of complex interactions of a moving plasma with magnetic fields. First of all, these are sunspots, where part of the thermal energy of the plasma is converted into the energy of the magnetic field and into the kinetic energy of the movement of individual plasma streams. The sunspots are colder environment and look dark against the background of a brighter photosphere - the layer of the solar atmosphere from which comes to us most of visible light. Around the sunspots and throughout the active region, the atmosphere, additionally heated by the energy of damped magnetic fields, becomes brighter, and structures called torches (visible in white light) and floccules (observed in monochromatic light of individual spectral lines, for example, hydrogen), arise.

Above the photosphere are located more rarefied layers of the solar atmosphere 10-20 thousand kilometers thick, called the chromosphere, and above it the corona extends for many millions of kilometers. Extended clouds often appear above groups of sunspots, and sometimes away from them - prominences, clearly visible during the total eclipse phase at the edge of the solar disk in the form of bright pink arcs and ejections. The corona is the most rarefied and very hot part of the Sun's atmosphere, which, as it were, evaporates into the surrounding space, forming a continuous flow of plasma receding from the Sun, called the solar wind. It is he who gives the sun's crown a radiant appearance that justifies its name.

From the movement of matter in the tails of comets, it turned out that the speed of the solar wind gradually increases with distance from the Sun. Having moved away from the star by one astronomical unit (the value of the radius of the earth's orbit), the solar wind "flies" at a speed of 300-400 km / s with a particle concentration of 1-10 protons per cubic centimeter. Encountering obstacles in the form of planetary magnetospheres on its way, the flow of the solar wind forms shock waves that affect the atmospheres of the planets and the interplanetary medium. Observing the solar corona, we get information about the state of space weather in the outer space around us.

The most powerful manifestations of solar activity are plasma explosions called solar flares... They are accompanied by strong ionizing radiation, as well as powerful ejections of hot plasma. Passing through the corona, plasma flows noticeably affect its structure. For example, helmet-like formations are formed in it, turning into long rays. In fact, these are elongated tubes of magnetic fields, along which streams of charged particles (mainly energetic protons and electrons) propagate at high speeds. In fact, the visible structure of the solar corona reflects the intensity, composition, structure, direction of movement and other characteristics of the solar wind constantly affecting our Earth. At the moments of flares, its speed can reach 600-700, and sometimes more than 1000 km / s.

In the past, the corona was observed only during total solar eclipses and exclusively near the Sun. In total, about an hour of observations has accumulated. With the invention of the extra-eclipse coronagraph (a special telescope in which an artificial eclipse is arranged), it became possible to constantly monitor the inner regions of the corona from the Earth. It is also always possible to register radio emission from the corona, even through clouds and at large distances from the Sun. But in the optical range, the outer regions of the corona are still visible from Earth only in the total phase of a solar eclipse.

With the development of extra-atmospheric research methods, it became possible to directly obtain an image of the entire corona in ultraviolet and X-rays. The most impressive images are regularly received from the space-based Solar Orbiting Heliospheric Observatory SOHO, launched in late 1995 jointly by the European Space Agency and NASA. In the SOHO images, the corona beams are very long, and a lot of stars are visible. However, in the middle, in the region of the inner and middle crown, there is no image. The artificial "moon" in the coronagraph is too big and obscures much more than the real one. But it cannot be otherwise - the Sun is shining too brightly. So satellite imagery does not replace observations from Earth. But space and terrestrial images of the solar corona perfectly complement each other.

SOHO also constantly monitors the surface of the Sun, and eclipses do not interfere with it, because the observatory is located outside the Earth-Moon system. Several ultraviolet images taken by SOHO around the 2006 total eclipse were pieced together and placed in place of the moon. Now we can see which active regions in the atmosphere of the closest star are associated with certain features in its corona. It may seem that some "domes" and zones of turbulence in the corona are not caused by anything, but in reality their sources are simply hidden from observation on the other side of the star.

"Russian" eclipse

The next total solar eclipse in the world is already called "Russian", since it will mainly be observed in our country. In the afternoon of August 1, 2008, the full phase strip will stretch from the Arctic Ocean almost along the meridian to Altai, passing exactly through Nizhnevartovsk, Novosibirsk, Barnaul, Biysk and Gorno-Altaisk - right along the federal highway M52. By the way, in Gorno-Altaysk this will be the second eclipse in over two years - it is in this city that the stripes of the 2006 and 2008 eclipses intersect. During an eclipse, the Sun's height above the horizon will be 30 degrees: this is enough for photographing the corona and ideal for panoramic photography. The weather in Siberia at this time is usually good. It's not too late to get a couple of cameras ready and buy a plane ticket.

This eclipse cannot be missed in any way. Following full eclipse will be seen in China in 2009, and then good observation conditions will develop only in the United States in 2017 and 2024. In Russia, the break will last almost half a century - until April 20, 2061.

If you are thinking, here is a good advice for you: observe in groups and exchange the resulting images, send them for joint processing to the Flower Observatory: www.skygarden.ru. Then someone will definitely be lucky with the processing, and then everyone, even those who stayed at home, thanks to you, will see an eclipse of the Sun - a star crowned with a crown.

Already this Saturday, August 11, 2018, a new mission to study the Sun - Parker Solar Probe (or "Parker" solar probe) will go into space. In a few years, the device will approach the Sun as close as no other man-made object has ever been able to do. Editorial staff N + 1 With the help of Sergei Bogachev, chief researcher at the Laboratory of X-ray Astronomy of the Sun of FIAN, she decided to figure out why scientists send the apparatus to such a hot place and what results are expected from it.

When we look at the night sky, we see a huge number of stars - the most numerous category of objects in the Universe available for observations from Earth. It is these huge shining gas balls that produce many chemical elements heavier than hydrogen and helium, without which our planet would not exist, and all life on it, and we ourselves.

Stars are located at great distances from Earth - the distance to the nearest of them, Proxima Centauri, is estimated at several light years. But there is one star whose light reaches us only eight minutes - this is our Sun, and observations of it help us learn more about other stars in the Universe.

The sun is much closer to us than it seems at first glance. In a sense, the Earth is inside the Sun - it is constantly washed by the flow of the solar wind emanating from the corona - the outer part of the star's atmosphere. It is the streams of particles and radiation from the Sun that govern the "space weather" near the planets. The appearance of auroras and disturbances in the magnetospheres of planets depends on these streams, and solar flares and coronal mass ejections disable satellites, affect the evolution of life forms on Earth, and determine the radiation load on manned space missions. Moreover, similar processes occur not only in the solar system, but also in other planetary systems. Therefore, understanding the processes in the sun's corona and the inner heliosphere allows us to better orient ourselves in the peculiarities of the behavior of the plasma "ocean" surrounding the Earth.

The structure of the sun

Wikimedia Commons

“Due to the remoteness of the Sun, we receive almost all information about it through the radiation it generates. Even some simple parameters, such as temperature, which on Earth can be measured with an ordinary thermometer, for the Sun and stars are determined in a much more complex way - by the spectrum of their radiation. This also applies to more complex characteristics, such as the magnetic field. A magnetic field can influence the radiation spectrum by splitting the lines in it - this is the so-called Zeeman effect. And precisely due to the fact that the field changes the spectrum of the star's radiation, we are able to register it. If such an influence did not exist in nature, then we would not know anything about the magnetic field of stars, since there is no way to fly directly to the star, ”says Sergei Bogachev.

“But this method also has limitations - just take the fact that the absence of radiation deprives us of information. If we talk about the Sun, then the solar wind does not emit light, so there is no way to remotely determine its temperature, density and other properties. Does not emit light and magnetic field. Yes, in the lower layers of the solar atmosphere, magnetic tubes are filled with luminous plasma and this makes it possible to measure the magnetic field near the surface of the Sun. However, even at a distance of one radius of the Sun from its surface, such measurements are impossible. And there are quite a few such examples. How to be in such a situation? The answer is very simple: it is necessary to launch probes that can fly directly to the Sun, plunge into its atmosphere and into the solar wind, and take measurements directly on the spot. Such projects are widespread, although less well-known than those of space telescopes, which make remote observations and deliver much more spectacular data (such as photographs) than probes that carry boring streams of numbers and graphs. But if we talk about science, then, of course, few remote observation can be compared in strength and persuasiveness with the study of an object that is nearby, ”continues Bogachev.

Riddles of the Sun

Observations of the Sun were carried out in Ancient Greece and in Ancient egypt, and over the past 70 years, more than a dozen space satellites, interplanetary stations and telescopes, ranging from Sputnik-2 and ending with space observatories operating today, such as SDO, SOHO or STEREO, have closely followed (and are following) the behavior of the closest to us the stars and its surroundings. Nevertheless, astronomers still have many questions related to the structure of the sun and its dynamics.

For example, for more than 30 years, scientists have been facing the problem of solar neutrinos, which consists in the lack of registered electron neutrinos produced in the core of the Sun as a result of nuclear reactions, compared with their theoretically predicted number. Another mystery is related to the abnormal heating of the corona. This outermost layer of the star's atmosphere has a temperature of more than a million degrees Kelvin, while the visible surface of the Sun (photosphere), over which the chromosphere and corona are located, is heated to only six thousand degrees Kelvin. This seems strange, because, logically, the outer layers of the star should be colder. Direct heat transfer between the photosphere and the corona is insufficient to provide such temperatures, which means that other mechanisms for heating the corona are at work here.

Corona of the Sun during a total solar eclipse in August 2017.

NASA's Goddard Space Flight Center / Gopalswamy

There are two main theories to explain this anomaly. According to the first, magnetoacoustic waves and Alfven waves are responsible for the transfer of heat from the convective zone and photosphere of the Sun to the chromosphere and corona, which, scattering in the corona, increase the plasma temperature. However, this version has a number of drawbacks, for example, magnetoacoustic waves cannot ensure the transfer of a sufficiently large amount of energy to the corona due to scattering and reflection back into the photosphere, and Alfven waves relatively slowly convert their energy into thermal energy of the plasma. In addition, for a long time there was simply no direct evidence of wave propagation through the solar corona - it was only in 1997 that the SOHO space observatory first recorded magnetoacoustic solar waves at a frequency of one millihertz, which provide only ten percent of the energy required to heat the corona to the observed temperatures.

The second theory associates the anomalous heating of the corona with constantly occurring microflares arising from the continuous reconnection of magnetic lines in local regions of the magnetic field in the photosphere. This idea was proposed in the 1980s by the American astronomer Eugene Parker, whose name is the probe and who also predicted the presence of the solar wind - a stream of high-energy charged particles continuously emitted from the Sun. However, the theory of microflares has not yet been confirmed. It is possible that both mechanisms work on the Sun, but this must be proved, and for this it is necessary to fly up to the Sun at a sufficiently close distance.

Another secret of the Sun is connected with the corona - the mechanism of the formation of the solar wind, which fills the entire solar system. It is on it that space weather phenomena such as the aurora borealis or magnetic storms depend. Astronomers are interested in the mechanisms of the appearance and acceleration of the slow solar wind, which is born in the corona, as well as the role of magnetic fields in these processes. There are also several theories here, with both evidence and flaws, and the Parker probe is expected to help dot the i.

“In general, there are currently well-developed models of the solar wind that predict how its characteristics should change with distance from the Sun. The accuracy of these models is quite high at distances of the order of the Earth's orbit, but how accurately they describe the solar wind at close distances from the Sun is not clear. Perhaps Parker can help with this. Another rather interesting question is the acceleration of particles on the Sun. After flares, streams of a large number of accelerated electrons and protons come to the Earth. It is not completely clear, however, whether they are accelerated directly on the Sun, and then they simply move towards the Earth by inertia, or these particles are additionally (and maybe completely) accelerated on the way to the Earth by an interplanetary magnetic field. Perhaps, when the data collected by the probe near the Sun comes to Earth, this issue can also be dealt with. There are several more similar problems, the solution of which can be advanced in the same way - by comparing analogous measurements near the Sun and at the level of the Earth's orbit. In general, it is precisely on such issues that the mission is aimed. We can only hope that the device will be successful, ”says Sergei Bogachev.

Straight to hell

The Parker probe will be launched on August 11, 2018 from the SLC-37 launch site at the US Air Force base at Cape Canaveral, it will be launched into space by the Delta IV Heavy launch vehicle - this is the most powerful rocket in operation, it can be launched into low orbit almost 29 tons of cargo. It only surpasses it in terms of carrying capacity, but this carrier is still in the testing stage. To get to the center of the solar system, it is necessary to extinguish the very high speed that the Earth (and all objects on it) have relative to the Sun - about 30 kilometers per second. In addition to a powerful rocket, this will require a series of gravitational maneuvers near Venus.

According to the plan, the process of rapprochement with the Sun will last seven years - with each new orbit (there are 24 of them in total), the apparatus will come closer and closer to the star. The first perihelion will be passed on November 1, at a distance of 35 solar radii (about 24 million kilometers) from the star. Then, after a series of seven gravitational maneuvers near Venus, the device will approach the Sun to a distance of about 9-10 solar radii (about six million kilometers) - this will happen in mid-December 2024. This is seven times closer than the perihelion of the orbit of Mercury, no man-made spacecraft has ever gotten closer to the Sun (the current record belongs to the Helios-B spacecraft, which approached the star by 43.5 million kilometers).

Scheme of the flight to the Sun and the main working orbits of the probe.

The main stages of work in each of the orbits.

The choice of such a position for observation is not accidental. According to scientists' calculations, at a distance of ten radii from the Sun is the Alfven point - an area where the solar wind accelerates so much that it leaves the Sun, and waves propagating in the plasma no longer affect it. If the probe can be close to the Alfven point, then we can assume that it entered the solar atmosphere and touched the sun.

The Parker probe in the assembled state, during installation on the third stage of the launch vehicle.

"The task of the probe is to measure the main characteristics of the solar wind and the solar atmosphere along its trajectory. The scientific instruments on board are not unique, do not have record characteristics (except for the ability to withstand solar radiation fluxes at the perihelion of the orbit). Parker Solar Probe is an apparatus with conventional instruments, but in a unique orbit. Most (and perhaps even all scientific instruments) are planned to be kept disabled in all parts of the orbit, except for perihelion, where the apparatus is closest to the Sun. In a sense, such a scientific program additionally emphasizes that the main the mission is to study the solar wind and the solar atmosphere.When the spacecraft moves away from perihelion, the data from the same instruments will turn into ordinary data, and to preserve the resource of scientific instruments they will simply be switched to the background mode until the next approach. a given trajectory and the ability to to live on it for a given time - these are the factors on which the success of the mission will first of all depend, "says Sergei Bogachev.

The device of the "Parker" thermal shield.

Greg Stanley / Johns Hopkins University

View of the heat shield at the stage of installation on the probe.

NASA / Johns Hopkins APL / Ed Whitman

Parker probe with installed heat shield.

NASA / Johns Hopkins APL / Ed Whitman

To survive close to the star, the probe is equipped with a heat shield that acts as an "umbrella" for all scientific instruments. The front of the shield will withstand temperatures in excess of 1400 degrees Celsius, while the temperature at the back, where scientific instruments are located, should not exceed thirty degrees Celsius. This temperature difference is provided by the special design of this "sun umbrella". With a total thickness of only 11.5 centimeters, it consists of two panels made of carbon-graphite composite, between which there is a layer of carbon foam. The front of the shield has a protective coating and a white ceramic layer that increases its reflectivity.

In addition to the shield, the cooling system is designed to solve the problem of overheating, using 3.7 liters of deionized water under pressure as a refrigerant. The electrical wiring of the device is made using high-temperature materials such as sapphire tubes and niobium, and when approaching the Sun, the solar panels will be removed under the heat shield. In addition to the intense heat, mission engineers will have to account for the strong light pressure from the Sun, which will knock off the probe's correct orientation. To facilitate this work, sunlight sensors are installed on the probe in various places, helping to monitor the protection of scientific equipment from the influence of the sun.

Tools

Almost all of the probe's scientific instruments are "sharpened" for the study of electromagnetic fields and the properties of the surrounding solar plasma. The only exception is optical telescope WISPR (Wide-field Imager for Solar PRobe), the task of which will be to obtain images of the solar corona and solar wind, the inner heliosphere, shock waves and any other structures observed by the apparatus.

Our Sun is a truly unique star, if only because its glow made it possible to create conditions suitable for life on our planet Earth, which, either by an amazing coincidence of circumstances, or by God's brilliant plan, is at an ideal distance from the Sun. Since ancient times, the Sun was under the close attention of man, and if in ancient times the priests, shamans, druids revered our luminary as a deity (in all pagan cults there were solar gods), now the Sun is being actively studied by scientists: astronomers, physicists, astrophysicists. What is the structure of the Sun, what are its characteristics, its age and location in our galaxy, read about all this further.

The location of the sun in the galaxy

Despite its enormous size relative to our planet (and other planets) on a galactic scale, the Sun is far from the largest star, but very small, there are stars much larger than the Sun. Therefore, astronomers classify our star as a yellow dwarf.

As for the location of the Sun in the galaxy (as well as our entire solar system), it is located in the Milky Way galaxy, closer to the edge of the Orion arm. The distance from the center of the galaxy is 7.5-8.5 thousand parsecs. In simple terms, you and I are not that we are on the outskirts of the galaxy, but we are also relatively far from the center - a kind of "sleeping galactic area", not on the outskirts, but not in the center either.

This is what the location of the Sun looks like on the galactic map.

Characteristics of the Sun

According to the astronomical classification of celestial objects, the Sun is classified as a G-class star, it is brighter than 85% of other stars in the galaxy, many of which are red dwarfs. The diameter of the Sun is 696342 km, and its mass is 1.988 x 1030 kg. If we compare the Sun with the Earth, then it is 109 times larger than our planet and 333,000 times more massive.

Comparative sizes of the Sun and planets.

Although the Sun appears to us to be yellow, its real color is white. The visibility of yellow is created by the atmosphere of the luminary.

The temperature of the Sun is 5778 degrees Kelvin in the upper layers, but as it approaches the core, it rises even more and the core of the Sun is incredibly hot - 15.7 million degrees Kelvin

Also, the Sun has strong magnetism, on its surface there are north and south magnetic poles, and magnetic lines, which are readjusted every 11 years. At the time of such rearrangements, intense solar emissions occur. Also, the Sun's magnetic field affects the Earth's magnetic field.

The structure and composition of the sun

Our Sun is mainly composed of two elements: (74.9%) and helium (23.8%). In addition to them, it is present in small quantities: (1%), carbon (0.3%), neon (0.2%) and iron (0.2%). Inside, the Sun is divided into layers:

• core,
• radiation and convection zones,
• photosphere,
• atmosphere.

The core of the Sun has the highest density and occupies about 25% of the total solar volume.

The structure of the sun is schematic.

It is in the solar core that thermal energy is generated through nuclear fusion, which transforms hydrogen into helium. In fact, the core is a kind of solar motor, thanks to it, our star emits heat and heats all of us.

Why does the sun shine?

Just the same glow of the Sun occurs due to the tireless work of the solar core, or rather, the thermonuclear reaction that constantly takes place in it. The burning of the Sun occurs due to the conversion of hydrogen into helium, this is that eternal thermonuclear reaction that constantly feeds our star.

Sun spots

Yes, there are spots on the Sun too. Sunspots are darker areas on the sun's surface, and they are darker because their temperature is lower than the temperature of the surrounding solar photosphere. The sunspots themselves are formed under the influence of magnetic lines and their readjustment.

sunny wind

The solar wind is a continuous stream of plasma emanating from the solar atmosphere and filling the entire solar system. The solar wind is formed due to the fact that due to the high temperature in the solar corona, the overlying layers cannot balance with the pressure in the corona itself. Therefore, there is a periodic emission of solar plasma into the surrounding space. There is a whole separate article about the phenomenon on our website.

A solar eclipse is a rare astronomical phenomenon in which the Moon is the Sun, in whole or in part.

Schematically, a solar eclipse looks like this.

Evolution of the Sun and its future

Scientists believe that the age of our star is 4.57 billion years. At that distant time, it was formed from a part of the molecular cloud, represented by helium and hydrogen.

How was the sun born? According to one of the hypotheses, the helium-hydrogen molecular cloud, due to the angular momentum, started rotation and at the same time began to intensely heat up as the internal pressure increased. At the same time, most of the mass was concentrated in the center, and turned into the sun itself. Strong and pressure led to an increase in heat and nuclear fusion, thanks to which both the Sun and other stars work.

This is how the evolution of a star, including the Sun, looks like. According to this scheme, our Sun is currently in the phase of a small star, and the current solar age is in the middle of this phase. In about 4 billion years, the Sun will turn into a red giant, expand further and destroy Venus, and possibly our Earth. If the Earth as a planet still survives, then life on it by that time will still be impossible. Since after 2 billion years the glow of the Sun will increase so much that all the earth's oceans will simply boil away, the Earth will be incinerated and turn into a continuous desert, the temperature on the earth's surface will be 70 C, and if life is possible, then only deep underground. Therefore, we still have about a billion plus years to find a new refuge for humanity in the very distant future.

But back to the Sun, having turned into a red giant, it will stay in this state for about 120 million years, then the process of decreasing its size and temperature will begin. And when the remnants of helium in its core are burned up in a constant furnace of thermonuclear reactions, the Sun will lose its stability and explode, turning into a planetary nebula. The Earth at this stage, as well as the neighboring one, will most likely be destroyed by a solar explosion.

After another 500 million years, a white dwarf is formed from the solar nebula, which will exist for another trillion of years.

• Inside the Sun can be placed a million Earths or planets the size of ours.
• The shape of the sun forms an almost perfect sphere.
• 8 minutes and 20 seconds - it is during this time that the sunbeam reaches us from its source, despite the fact that the Earth is 150 million km away from the Sun.
• The very word "Sun" comes from the Old English word meaning "South" - "South".
• And we have bad news for you, in the future the Sun will incinerate the Earth, and then completely destroy it. However, this will not happen earlier than in 2 billion years.

Sun, video

And in conclusion, an interesting scientific documentary from the Discovery Channel - "What the Sun Hides".

When writing the article, I tried to make it as interesting, useful and high-quality as possible. I would be grateful for any feedback and constructive criticism in the form of comments to the article. Also, you can write your wish / question / suggestion to my mail [email protected] or Facebook, sincerely the author.