Rice. 5. Solar eclipse.

Let's look closely at this general educational picture of the origin of a solar eclipse.

The direction of the Earth's movement is counterclockwise, from west to east red arrow.
If the Moon were static, then the shadow of the Moon during the rotation of the Earth would shift in the opposite direction, to the west, along black shooters.
However, the Moon is moving in the direction of the Earth's rotation ( along the red arrow), its orbital speed is more than twice the speed of its rotation. That is why the movement of the moon's shadow on the earth's surface from west to east is observed. But with what speed should the shadow move away from the observer on the ground to the left, i.e. towards the east (observer facing south) - the question is open? … open for discussion!

So, let's sum up some results in our study of the motion of the Moon.

The Moon moves to the left of the fixed stellar sphere (for an observer from the earth facing south), from west to east, in the direction of the rotation of the Earth itself, but faster, at a rate of one rotation in 27.3 days, 13.2 ° per day or 1,023 km/s D lights up the Sun and "runs" on it from the right during a solar eclipse. This happens because the Sun moves along the signs of the zodiac also to the east, making a full circle in 365.24 days, slower than 1 ° per day.

The shadow of the Moon moves to the left, overtakes the rotation of the Earth, passes along the earth's surface from west to east.

For the observer from the Earth (in the northern hemisphere), the picture of the eclipse itself, the displacement of the luminaries of the Sun and the Moon will occur to the right, to the west, i.e. from sunrise to sunset. This movement is connected with the rotation of the Earth around its axis from west to east.

Some questions raised in the topic remain open, I will be glad to hear answers and justifications.

I myself will try in the next part to clarify these issues, based on the actual rotation of the moon.
To be continued…

Already this Saturday, August 11, 2018, a new mission to study the Sun - the Parker Solar Probe (or the Parker solar probe) will go into space. In a few years, the device will come closer to the Sun than any man-made object has yet managed to do. Editorial N+1 with the help of Sergei Bogachev, chief researcher Laboratory of Solar X-Ray Astronomy FIAN, decided to find 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 that can be observed from Earth. It is these huge shining gas balls that are produced in their thermonuclear "furnaces" by many chemical elements heavier than hydrogen and helium, without which our planet, and all life on it, and ourselves would not exist.

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

The sun is much closer to us than it seems at first glance. In a certain sense, the Earth is located inside the Sun - it is constantly washed by the flow of the solar wind coming from the corona - the outer part of the star's atmosphere. It is the streams of particles and radiation from the Sun that control the "space weather" near the planets. The emergence of auroras and disturbances in the magnetospheres of the planets depends on these streams, while 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 solar corona and the inner heliosphere allows us to better navigate the behavior of the plasma "ocean" surrounding the Earth.

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 can be measured with an ordinary thermometer on Earth, are determined for the Sun and stars in a much more complicated way - by their radiation spectrum. This also applies to more complex characteristics, such as the magnetic field. The magnetic field is able to influence the radiation spectrum, splitting the lines in it - this is the so-called Zeeman effect. And it is precisely due to the fact that the field changes the radiation spectrum of the star that 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 directly fly up to a star, ”says Sergey Bogachev.

“But this method also has limitations - take at least 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 or 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, already at a distance of one solar radius from its surface, such measurements are impossible. And there are many such examples. How to be in such a situation? The answer is very simple: you need 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, though less known than those of space telescopes, which make remote observations and provide much more spectacular data (such as photographs) than probes that produce boring streams of numbers and graphs. But if we talk about science, then, of course, few remote observations can be compared in strength and persuasiveness with the study of an object that is located nearby, ”continues Bogachev.

Mysteries of the Sun

Observations of the Sun have been made since 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 to space observatories operating today, such as SDO, SOHO or STEREO, have closely monitored (and are monitoring) 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 anomalous 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 (the photosphere), above 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 not enough to provide these temperatures, which means that other coronal heating mechanisms are at work here.

The corona of the Sun during the 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 one, magnetoacoustic waves and Alfven waves are responsible for heat transfer from the convective zone and photosphere of the Sun to the chromosphere and corona, which, being scattered in the corona, increase the plasma temperature. However, this version has a number of disadvantages, for example, magnetoacoustic waves cannot ensure the transfer of a sufficiently large amount of energy to the corona due to scattering and reflection back to the photosphere, and Alfven waves convert their energy into thermal plasma energy relatively slowly. In addition, for a long time no direct evidence of wave propagation through solar corona simply did not exist - it was not until 1997 that the SOHO space observatory first detected magnetoacoustic solar waves at a frequency of one millihertz, which provide only ten percent of the energy needed to heat the corona to observable temperatures.

The second theory relates the anomalous heating of the corona to 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 by the Sun. However, the theory of microoutbursts has not yet been confirmed either. It is possible that both mechanisms work on the Sun, but this needs to be proven, and for this it is necessary to fly up to the Sun at a fairly 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 him that such phenomena of space weather as the northern lights or magnetic storms depend. Astronomers are interested in the mechanisms of origin and acceleration of the slow solar wind, born in the corona, as well as the role of magnetic fields in these processes. Here too, there are several theories with both evidence and flaws, and it is expected that the Parker probe will help to dot the i's.

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

Straight into hell

The Parker probe will be launched on August 11, 2018 from the launch complex SLC-37 at Cape Canaveral Air Force Base, it will be launched into space by a heavy launch vehicle Delta IV Heavy - this is the most powerful rocket in operation, it can launch into low orbit almost 29 tons of cargo. In terms of carrying capacity, it is surpassed only by, 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) has 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 approaching the Sun will last seven years - with each new orbit (there are 24 in total), the device will come 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 Mercury's orbit, no man-made spacecraft has ever gotten so close to the Sun (the current record belongs to the Helios-B apparatus, which approached the star at 43.5 million kilometers).

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

The main stages of work on each of the orbits.

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

Probe "Parker" 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, they do not have record characteristics (except for the ability to withstand flows solar radiation at the perihelion of the orbit). The Parker Solar Probe is a conventional instrumented spacecraft in a unique orbit. Most (maybe even all scientific instruments) are planned to be kept off at all parts of the orbit, except for perihelia, where the device is closest to the Sun. In a sense, such scientific program additionally emphasizes that the main task of the mission is to study the solar wind and solar atmosphere. When the device moves away from perihelion, the data from the same instruments will turn into ordinary ones, and in order to save the resource of scientific instruments, they will simply be switched to the background until the next approach. In this sense, the ability to reach a given trajectory and the ability to live on it for a given time are the factors on which the success of the mission will primarily depend,” says Sergey Bogachev.

The device of the heat shield "Parker".

Greg Stanley/Johns Hopkins University

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

NASA/Johns Hopkins APL/Ed Whitman

Probe "Parker" with installed heat shield.

NASA/Johns Hopkins APL/Ed Whitman

To survive near the star, the probe is equipped with a heat shield that acts as an "umbrella" under which all scientific instruments will hide. The front of the shield will withstand temperatures in excess of 1,400 degrees Celsius, while the back of the shield, where the scientific instruments are located, must not exceed thirty degrees Celsius. Such a temperature difference is provided by the special design of this "solar umbrella". With a total thickness of just 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 reflective properties.

In addition to the shield, the cooling system is designed to solve the problem of overheating, using 3.7 liters of pressurized deionized water as a coolant. The electrical wiring of the apparatus is made using high-temperature materials such as sapphire tubes and niobium, and during approaches to the Sun solar panels will be removed under the heat shield. In addition to strong heating, mission engineers will have to take into account strong light pressure from the Sun, which will interfere with the correct orientation of the probe. To facilitate this work, sensors are installed on the probe in different places. sunlight, which help to control the protection of scientific equipment from the influence of the Sun.

Tools

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

- the only star in the solar system: description and characteristics with a photo, Interesting Facts, composition and structure, location in the galaxy, development.

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

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

A million Earths fit inside

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

Holds 99.86% of system weight

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

Almost perfect sphere

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

The temperature in the center rises to 15 million ° C

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

One day the sun will swallow the earth

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

One day it will reach the size of the earth

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

Sunbeam reaches us in 8 minutes

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

The speed of the Sun - 220 km / s

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

The Earth-Sun distance varies throughout the year

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

This is a star with a middle age

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

There is a strong magnetic field

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

A star forms the solar wind

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

Name of the Sun

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

Characteristics of the Sun

The Sun is a G-type main sequence star with an absolute magnitude of 4.83, which is brighter than about 85% of other stars in the galaxy, many of which are red dwarfs. With a diameter of 696342 km and a mass of 1.988 x 1030 kg, the Sun is 109 times larger than the earth and 333,000 times more massive.

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

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

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

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

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

Composition and structure of the Sun

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

A star spends a month per axis rotation, but this is a rough estimate, because we have plasma ball. The analysis shows that the core rotates faster than the outer layers. While the equatorial line takes 25.4 days to rotate, it takes 36 days at the poles.

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

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

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

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

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

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

Evolution and the future of the Sun

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

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

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

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

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

Location of the sun in the galaxy

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

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

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

solar neutrinos

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

Click on the image to enlarge it