From time immemorial, Man tried to give names to the objects and phenomena that surrounded him. This also applies to celestial bodies. First, the brightest, clearly visible stars were given names, and over time, others were given names.

Some stars are named according to the position they occupy in the constellation. For example, the star Deneb (the word translates as “tail”) located in the constellation Cygnus is actually located in this part of the body of an imaginary swan. One more example. The star Omicron, better known as Mira, which translates from Latin as “amazing,” is located in the constellation Cetus. Mira has the ability to change its brightness. For long periods it completely disappears from view, meaning observations with the naked eye. The name of the star is explained by its specificity. Basically, stars received names in the era of antiquity, so it is not surprising that most of the names have Latin, Greek, and later Arabic roots.

The discovery of stars whose apparent brightness changes over time led to special designations. They are designated by capital Latin letters, followed by the name of the constellation in the genitive case. But the first variable star discovered in a certain constellation is not designated by the letter A. The countdown is from the letter R. The next star is designated by the letter S, and so on. When all the letters of the alphabet are exhausted, a new circle begins, that is, after Z, A is used again. In this case, letters can be doubled, for example “RR”. "R Leo" means it is the first variable star discovered in the constellation Leo.

HOW A STAR IS BORN.

Stars are born when a cloud of interstellar gas and dust is compressed and compacted by its own gravity. It is believed that this process leads to the formation of stars. Using optical telescopes, astronomers can see these zones; they look like dark spots against a bright background. They are called "giant molecular cloud complexes" because hydrogen is present in molecular form. These complexes, or systems, along with globular star clusters, are the largest structures in the galaxy, sometimes reaching 1,300 light-years in diameter.

Younger stars, called "stellar population I", were formed from the remnants resulting from the outbursts of older stars, they are called "stellar population II". An explosive flare causes a shock wave that reaches the nearest nebula and provokes its compression.

Bock globules .

So, part of the nebula is compressed. Simultaneously with this process, the formation of dense dark round gas and dust clouds begins. They are called "Bock globules". Bok, an American astronomer of Dutch origin (1906-1983), was the first to describe globules. The mass of the globules is approximately 200 times the mass of our Sun.

As the Bok globule continues to condense, its mass increases, attracting matter from neighboring regions due to gravity. Due to the fact that the inner part of the globule condenses faster than the outer part, the globule begins to heat up and rotate. After several hundred thousand years, during which compression occurs, a protostar is formed.

Evolution of a protostar.

Due to the increase in mass, more and more matter is attracted to the center of the protostar. The energy released from the gas compressed inside is transformed into heat. The pressure, density and temperature of the protostar increase. Due to the increase in temperature, the star begins to glow dark red.

The protostar is very large, and although thermal energy is distributed over its entire surface, it still remains relatively cold. In the core, the temperature rises and reaches several million degrees Celsius. The rotation and round shape of the protostar change somewhat, it becomes flatter. This process lasts millions of years.

It is difficult to see young stars, since they are still surrounded by a dark dust cloud, due to which the brightness of the star is practically invisible. But they can be viewed using special infrared telescopes. The hot core of a protostar is surrounded by a rotating disk of matter with a strong gravitational force. The core gets so hot that it begins to eject matter from the two poles, where resistance is minimal. When these emissions collide with the interstellar medium, they slow down and disperse on either side, forming a teardrop-shaped or arched structure known as a Herbic-Haro object.

Star or planet?

The temperature of a protostar reaches several thousand degrees. Further developments depend on the dimensions of this celestial body; if the mass is small and is less than 10% of the mass of the Sun, this means that there are no conditions for nuclear reactions to occur. Such a protostar will not be able to turn into a real star.

Scientists have calculated that for a contracting celestial body to transform into a star, its minimum mass must be at least 0.08 of the mass of our Sun. A gas-containing cloud of smaller sizes, condensing, will gradually cool and turn into a transitional object, something between a star and a planet, this is the so-called “brown dwarf”.

The planet Jupiter is a celestial object too small to become a star. If it were larger, perhaps nuclear reactions would begin in its depths, and it, along with the Sun, would contribute to the emergence of a system of double stars.

Nuclear reactions.

If the mass of a protostar is large, it continues to condense under the influence of its own gravity. The pressure and temperature in the core increase, the temperature gradually reaches 10 million degrees. This is enough to combine hydrogen and helium atoms.

Next, the “nuclear reactor” of the protostar is activated, and it turns into an ordinary star. A strong wind is then released, which disperses the surrounding shell of dust. Light can then be seen emanating from the resulting star. This stage is called the "T-Taurus phase" and can last 30 million years. The formation of planets is possible from the remnants of gas and dust surrounding the star.

The birth of a new star can cause a shock wave. Having reached the nebula, it provokes the condensation of new matter, and the star formation process will continue through gas and dust clouds. Small stars are faint and cold, while large ones are hot and bright. For most of its existence, the star balances in the equilibrium stage.

CHARACTERISTICS OF STARS.

Observing the sky even with the naked eye, you can immediately notice such a feature of the stars as brightness. Some stars are very bright, others are fainter. Without special instruments, in ideal visibility conditions, about 6,000 stars can be seen. Thanks to binoculars or a telescope, our capabilities increase significantly; we can admire millions of stars in the Milky Way and outer galaxies.

Ptolemy and the Almagest.

The first attempt to compile a catalog of stars, based on the principle of their degree of luminosity, was made by the Hellenic astronomer Hipparchus of Nicaea in the 2nd century BC. Among his numerous works was the Star Catalog, containing a description of 850 stars classified by coordinates and luminosity. The data collected by Hipparchus, who, in addition, discovered the phenomenon of precession, was worked out and further developed thanks to Claudius Ptolemy from Alexandria in the 2nd century. AD He created the fundamental opus “Almagest” in thirteen books. Ptolemy collected all the astronomical knowledge of that time, classified it and presented it in an accessible and understandable form. The Almagest also included the Star Catalog. It was based on observations made by Hipparchus four centuries ago. But Ptolemy's Star Catalog contained about a thousand more stars.

Ptolemy's catalog was used almost everywhere for a millennium. He divided stars into six classes according to the degree of luminosity: the brightest were assigned to the first class, the less bright to the second, and so on.

The sixth class includes stars that are barely visible to the naked eye. The term “luminosity of celestial bodies” is still used today to determine the measure of brilliance of celestial bodies, not only stars, but also nebulae, galaxies and other celestial phenomena.

Magnitude in modern science.

In the middle of the 19th century. English astronomer Norman Pogson improved the method of classifying stars based on the principle of luminosity, which had existed since the times of Hipparchus and Ptolemy. Pogson took into account that the difference in luminosity between the two classes is 2.5. Pogson introduced a new scale according to which the difference between stars of the first and sixth classes is 100 AU. That is, the brightness ratio of stars of the first magnitude is 100. This ratio corresponds to an interval of 5 magnitudes.

Relative and absolute magnitude.

Magnitude, measured using special instruments mounted in a telescope, indicates how much light from a star reaches an observer on Earth. Light travels the distance from the star to us, and, accordingly, the further away the star is, the fainter it appears. That is, when determining stellar magnitude, it is necessary to take into account the distance to the star. In this case we are talking about relative magnitude. It depends on the distance.

There are very bright and very faint stars. To compare the brightness of stars, regardless of their distance from the Earth, the concept of “absolute stellar magnitude” was introduced. It characterizes the brightness of a star at a certain distance of 10 parsecs (10 parsecs = 3.26 light years). To determine the absolute magnitude, you need to know the distance to the star.

The color of the stars.

The next important characteristic of a star is its color. Looking at the stars even with the naked eye, you can see that they are not all the same.

There are blue, yellow, orange, red stars, not just white ones. The color of stars tells a lot to astronomers, primarily depending on the temperature of the star's surface. Red stars are the coldest, their temperature is approximately 2000-3000 o C. Yellow stars, like our Sun, have an average temperature of 5000-6000 o C. The hottest are white and blue stars, their temperature is 50000-60000 o C and higher .

Mysterious lines.

If we pass starlight through a prism, we get a so-called spectrum; it will be intersected by lines. These lines are a kind of “identification card” of the star, since astronomers can use them to determine the chemical composition of the surface layers of stars. The lines belong to different chemical elements.

By comparing the lines in the stellar spectrum with lines made in the laboratory, it is possible to determine which chemical elements are included in the composition of stars. In the spectra, the main lines are hydrogen and helium; it is these elements that make up the main part of the star. But there are also elements of the metal group - iron, calcium, sodium, etc. In the bright solar spectrum, lines of almost all chemical elements are visible.

HERZSPRUNG-RUSSELL DIAGRAM.

Among the parameters characterizing a star, there are two most important ones: temperature and absolute magnitude. Temperature indicators are closely related to the color of the star, and the absolute magnitude is closely related to the spectral class. This refers to the classification of stars according to the intensity of the lines in their spectra. According to the classification currently used, stars are divided into seven main spectral classes according to their spectra. They are designated by the Latin letters O, B, A, F, G, K, M. It is in this sequence that the temperature of stars decreases from several tens of thousands of degrees of class O to 2000-3000 degrees of type M stars.

Absolute magnitude, i.e. A measure of brightness that indicates the amount of energy emitted by a star. It can be calculated theoretically, knowing the distance of the star.

Outstanding idea.

The idea to connect the two main parameters of a star came to the minds of two scientists in 1913, and they carried out work independently of each other.

We are talking about the Dutch astronomer Einar Hertzsprung and the American astrophysicist Henry Norris Russell. Scientists worked at a distance of thousands of kilometers from each other. They created a graph that linked together the two main parameters. The horizontal axis reflects the temperature, the vertical axis – the absolute magnitude. The result was a diagram that was given the names of two astronomers - the Hertzsprung-Russell diagram, or, more simply, the H-R diagram.

Star is a criterion.

Let's see how the G-R diagram is made. First of all, you need to select a criterion star. A star whose distance is known, or another with an already calculated absolute magnitude, is suitable for this.

It should be borne in mind that the luminous intensity of any source, be it a candle, a light bulb or a star, changes depending on the distance. This is expressed mathematically as follows: the luminosity intensity “I” at a certain distance “d” from the source is inversely proportional to “d2”. In practice, this means that if the distance doubles, the luminosity intensity decreases fourfold.

Then the temperature of the selected stars should be determined. To do this, you need to identify their spectral class, color and then determine the temperature. Currently, instead of the spectral type, another equivalent indicator is used - the “color index”.

These two parameters are plotted on the same plane with the temperature decreasing from left to right on the abscissa. The absolute luminosity is fixed at the ordinate, an increase is noted from bottom to top.

Main sequence.

On a H-R diagram, stars are located along a diagonal line running from bottom to top and from left to right. This strip is called the Main Sequence. The stars that make up it are called Main Sequence stars. The sun belongs to this group. This is a group of yellow stars with a surface temperature of approximately 5600 degrees. Main Sequence stars are in the most “quiet phase” of their existence. In the depths of their nuclei, hydrogen atoms mix and helium is formed. The Main Sequence phase accounts for 90% of a star's lifetime. Out of 100 stars, 90 are in this phase, although they are distributed in different positions depending on temperature and luminosity.

The main sequence is a “narrow region,” indicating that stars have difficulty maintaining a balance between the force of gravity, which pulls inward, and the force generated by nuclear reactions, which pulls toward the outside of the zone. A star like the Sun, equal to 5600 degrees, must have an absolute magnitude of about +4.7 to maintain balance. This follows from the G-R diagram.

Red giants and white dwarfs.

Red giants are found in the upper right zone, located on the outer side of the Main Sequence. A characteristic feature of these stars is their very low temperature (about 3000 degrees), but at the same time they are brighter than stars that have the same temperature and are located in the Main Sequence.

Naturally, the question arises: if the energy emitted by a star depends on temperature, then why do stars with the same temperature have different degrees of luminosity. The explanation should be sought in the size of the stars. Red giants are brighter because their emitting surface is much larger than that of Main Sequence stars.

It is no coincidence that this type of star is called “giant”. Indeed, their diameter can exceed the diameter of the Sun by 200 times, these stars can occupy a space of 300 million km, which is twice the distance from the Earth to the Sun! Using the statement about the influence of the size of a star, we will try to explain some aspects in the existence of other stars - white dwarfs. They are located at the bottom left of the H-R diagram.

White dwarfs are very hot, but very dim stars. At the same temperature as the large and hot blue-white stars of the Main Sequence, white dwarfs are much smaller in size. These are very dense and compact stars, they are 100 times smaller than the Sun, their diameter is approximately the same as that of Earth. A striking example of the high density of white dwarfs is that one cubic centimeter of the matter they consist of must weigh about one ton!

Globular star clusters.

When compiling HR diagrams of globular star clusters, and they contain mainly old stars, it is very difficult to determine the Main Sequence. Its traces are recorded mainly in the lower zone, where cooler stars are concentrated. This is due to the fact that hot and bright stars have already passed the stable phase of their existence and are moving to the right, into the red giant zone, and if they have passed it, then into the white dwarf zone. If people were able to trace all the evolutionary stages of a star over its life, they would be able to see how it changes its characteristics.

For example, when hydrogen in the core of a star stops burning, the temperature in the outer layer of the star decreases, and the layer itself expands. The star is leaving the Main Sequence phase and heading to the right side of the diagram. This applies primarily to stars that are large in mass and the brightest; it is this type that evolves faster.

Over time, stars move out of the Main Sequence. The diagram records a “turning point”, thanks to which it is possible to quite accurately calculate the age of the stars in clusters. The higher the “turning point” is on the diagram, the younger the cluster, and, accordingly, the lower it is on the diagram, the older the star cluster.

The meaning of the chart.

The Hertzsprung-Russell diagram is of great help in studying the evolution of stars throughout their existence. During this time, the stars undergo changes and transformations, and in some periods they are very profound. We already know that stars differ not in their own characteristics, but in the types of phases in which they are at one time or another.

Using this diagram you can calculate the distance to the stars. You can select any star located in the Main Sequence with an already determined temperature and see its progress on the diagram.

DISTANCE TO THE STARS.

When we look at the sky with the naked eye, stars, even the brightest ones, seem to us to be shiny points located at the same distance from us. The vault of heaven spreads out above us like a carpet. It is no coincidence that the positions of the stars are expressed in only two coordinates (right ascension and declination), and not in three, as if they are located on the surface and not in three-dimensional space. With the help of telescopes, we cannot obtain all the information about the stars; for example, from photographs of the Hubble Space Telescope, we cannot accurately determine at what distance the stars are located.

Depth of space.

People learned relatively recently that the Universe also has a third dimension – depth. Only at the beginning of the 19th century, thanks to the improvement of astronomical equipment and instruments, scientists were able to measure the distance to some stars. The first was the star 61 Cygni. Astronomer F.V. Bessel found that it was at a distance of 10 light years. Bessel was one of the first astronomers to measure the "annual parallax". Until now, the “annual parallax” method has been the basis for measuring the distance to stars. This is a purely geometric method - just measure the angle and calculate the result.

But the simplicity of the method does not always correspond to effectiveness. Due to the great distance of the stars, the angles are very small. They can be measured using telescopes. The parallax angle of the star Proxima Centauri, the closest of the triple system Alpha Centauri, is small (0.76 exact version), but from this angle you can see a hundred lire coin at a distance of ten kilometers. Of course, the further the distance, the smaller the angle becomes.

Inevitable inaccuracies.

Errors in terms of determining parallax are quite possible, and their number increases as the object moves away. Although, with the help of modern telescopes, it is possible to measure angles with an accuracy of one thousandth, there will still be errors: at a distance of 30 light years they will be approximately 7%, 150 light years. years - 35%, and 350 St. years – up to 70%. Of course, large inaccuracies render measurements useless. Using the “parallax method”, it is possible to successfully determine the distances to several thousand stars located in an area of ​​approximately 100 light years. But in our galaxy there are more than 100 billion stars, the diameter of which is 100,000 light years!

There are several variations of the annual parallax method, such as secular parallax. The method takes into account the movement of the Sun and the entire solar system in the direction of the constellation Hercules, at a speed of 20 km/sec. With this movement, scientists have the opportunity to collect the necessary database to carry out a successful parallax calculation. In ten years, 40 times more information has been obtained than was previously possible.

Then, using trigonometric calculations, the distance to a particular star is determined.

Distance to star clusters.

It is easier to calculate the distance to star clusters, especially open ones. The stars are located relatively close to each other, therefore, by calculating the distance to one star, you can determine the distance to the entire star cluster.

In addition, in this case, statistical methods can be used to reduce the number of inaccuracies. For example, the method of “converging points”, it is often used by astronomers. It is based on the fact that during long-term observation of stars in an open cluster, those moving towards a common point are identified, which is called a convergent point. By measuring the angles and radial velocities (that is, the speed of approaching and moving away from the Earth), you can determine the distance to the star cluster. Using this method there is a possible 15% inaccuracy at a distance of 1500 light years. It is also used at distances of 15,000 light years, which is quite suitable for celestial bodies in our Galaxy.

Main Sequence Fitting – establishment of the Main Sequence.

To determine the distance to distant star clusters, for example to the Pleiades, you can proceed as follows: construct a G-R diagram, on the vertical axis note the apparent stellar magnitude (and not the absolute magnitude, since it depends on the distance), which depends on temperature.

Then you should compare the resulting picture with the G-R Iad diagram; it has many common features in terms of Main Sequences. By combining the two diagrams as closely as possible, it is possible to determine the Main Sequence of the star cluster whose distance must be measured.

Then the equation should be used:

m-M=5log(d)-5, where

m – apparent magnitude;

M – absolute magnitude;

d – distance.

In English this method is called “Main Sequence Fitting”. It can be used for open star clusters such as NGC 2362, Alpha Persei, III Cephei, NGC 6611. Astronomers have attempted to determine the distance to the famous double open star cluster in the constellation Perseus ("h" and "chi"), where many stars are located -supergiants. But the data turned out to be contradictory. Using the “Main Sequence Fitting” method, it is possible to determine distances up to 20,000-25,000 light years, this is a fifth of our Galaxy.

Light intensity and distance.

The further away a celestial body is, the weaker its light appears. This position is consistent with the optical law, according to which the intensity of light "I" is inversely proportional to the distance squared "d".

For example, if one galaxy is located at a distance of 10 million light years, then another galaxy located 20 million light years away has a brightness four times smaller than the first. That is, from a mathematical point of view, the relationship between the two quantities “I” and “d” is precise and measurable. In the language of astrophysics, the intensity of light is the absolute magnitude of the stellar magnitude M of some celestial object, the distance to which should be measured.

Using the equation m-M=5log(d)-5 (it reflects the law of change in brightness) and knowing that m can always be determined using a photometer, and M is known, the distance “d” is measured. So, knowing the absolute magnitude, using calculations it is not difficult to determine the distance.

Interstellar absorption.

One of the main problems associated with distance measuring methods is the problem of light absorption. On its way to Earth, light travels vast distances, passing through interstellar dust and gas. Accordingly, part of the light is adsorbed, and when it reaches telescopes installed on Earth, it already has a non-original strength. Scientists call this “extinction,” the weakening of light. It is very important to calculate the amount of extinction when using a number of methods, such as candela. In this case, the exact absolute magnitudes must be known.

It is not difficult to determine the extinction for our Galaxy - just take into account the dust and gas of the Milky Way. It is more difficult to determine the extinction of light from an object in another galaxy. To the extinction along the path in our Galaxy, we must also add part of the absorbed light from another.

EVOLUTION OF STARS.

The internal life of a star is regulated by the influence of two forces: the force of gravity, which counteracts the star and holds it, and the force released during nuclear reactions occurring in the core. On the contrary, it tends to “push” the star into distant space. During the formation stage, a dense and compressed star is strongly influenced by gravity. As a result, strong heating occurs, the temperature reaches 10-20 million degrees. This is enough to start nuclear reactions, as a result of which hydrogen is converted into helium.

Then, over a long period, the two forces balance each other, the star is in a stable state. When the nuclear fuel in the core gradually runs out, the star enters an instability phase, two forces opposing each other. A critical moment comes for a star; a variety of factors come into play - temperature, density, chemical composition. The mass of the star comes first; the future of this celestial body depends on it - either the star will explode like a supernova, or turn into a white dwarf, a neutron star or a black hole.

How does hydrogen run out?

Only the very largest among celestial bodies become stars, the smaller ones become planets. There are also bodies of average mass, they are too large to belong to the class of planets, and too small and cold for nuclear reactions characteristic of stars to occur in their depths.

So, a star is formed from clouds of interstellar gas. As already noted, the star remains in a balanced state for quite a long time. Then comes a period of instability. The further fate of the star depends on various factors. Consider a hypothetical small star whose mass is between 0.1 and 4 solar masses. A characteristic feature of stars with low mass is the absence of convection in the inner layers, i.e. The substances that make up the star do not mix, as happens in stars with a large mass.

This means that when the hydrogen in the core runs out, there are no new reserves of this element in the outer layers. Hydrogen burns and turns into helium. Little by little the core heats up, the surface layers destabilize their own structure, and the star, as can be seen from the H-R diagram, slowly leaves the Main Sequence. In the new phase, the density of matter inside the star increases, the composition of the core “degenerates”, and as a result a special consistency appears. It is different from normal matter.

Modification of matter.

When matter changes, pressure depends only on the density of the gases, not on temperature.

In the Hertzsprung-Russell diagram, the star moves to the right and then upward, approaching the red giant region. Its dimensions increase significantly, and because of this, the temperature of the outer layers drops. The diameter of a red giant can reach hundreds of millions of kilometers. When our sun enters this phase, it will “swallow” both Mercury and Venus, and if it cannot capture the Earth, it will heat it up to such an extent that life on our planet will cease to exist.

During the evolution of a star, the temperature of its core increases. First, nuclear reactions occur, then, upon reaching the optimal temperature, helium begins to melt. When this happens, the sudden increase in core temperature causes a flare and the star quickly moves to the left side of the H-R diagram. This is the so-called “helium flash”. At this time, the core containing helium burns together with hydrogen, which is part of the shell surrounding the core. On the H-R diagram, this stage is recorded by moving to the right along a horizontal line.

The last phases of evolution.

When helium is transformed into a hydrocarbon, the core is modified. Its temperature rises until the carbon begins to burn. A new outbreak occurs. In any case, during the last phases of the star’s evolution, a significant loss of its mass is noted. This can happen gradually or suddenly, during an outburst, when the outer layers of the star burst like a large bubble. In the latter case, a planetary nebula is formed - a spherical shell, spreading in outer space at a speed of several tens or even hundreds of km/sec.

The final fate of a star depends on the mass remaining after everything that happens to it. If during all transformations and flares it ejected a lot of matter and its mass does not exceed 1.44 solar masses, the star turns into a white dwarf. This one is called the “Chandrasekhar limit” after the Pakistani astrophysicist Subrahmanyan Chandrasekhar. This is the maximum mass of a star at which a catastrophic end may not occur due to the pressure of electrons in the core.

After the outbreak of the outer layers, the core of the star remains, and its surface temperature is very high - about 100,000 o K. The star moves to the left edge of the H-R diagram and goes down. Its luminosity decreases as its size decreases.

The star is slowly reaching the white dwarf zone. These are stars of small diameter, but very high density, one and a half million times the density of water.

A white dwarf represents the final stage of star evolution, without outbursts. She is gradually cooling down. Scientists believe that the end of the white dwarf is very slow, at least since the beginning of the Universe, it seems that not a single white dwarf has suffered from “thermal death”.

If the star is large and its mass is greater than the Sun, it will explode like a supernova. During a flare, a star may collapse completely or partially. In the first case, what will be left behind is a cloud of gas with residual substances of the star. In the second, a celestial body of the highest density will remain - a neutron star or a black hole.

VARIABLE STARS.

According to Aristotle's concept, the celestial bodies of the Universe are eternal and permanent. But this theory underwent significant changes with the appearance in the 17th century. the first binoculars. Observations carried out over subsequent centuries demonstrated that, in fact, the apparent constancy of celestial bodies is explained by the lack of observation technology or its imperfection. Scientists have concluded that variability is a common characteristic of all types of stars. During evolution, a star goes through several stages, during which its main characteristics - color and luminosity - undergo profound changes. They occur during the existence of a star, which is tens or hundreds of millions of years, so a person cannot be an eyewitness to what is happening. For some classes of stars, changes occurring are recorded in short periods of time, for example, over several months, days or part of a day. The star's changes and its luminous fluxes can be measured many times over subsequent nights.

Measurements.

In fact, this problem is not as simple as it seems at first glance. When carrying out measurements, it is necessary to take into account atmospheric conditions, and they change, sometimes significantly within one night. In this regard, data on the luminous fluxes of stars vary significantly.

It is very important to be able to distinguish real changes in the light flux, and they are directly related to the brightness of the star, from apparent ones, which are explained by changes in atmospheric conditions.

To do this, it is recommended to compare the light fluxes of the observed star with other stars - landmarks visible through a telescope. If the changes are apparent, i.e. associated with changes in atmospheric conditions, they affect all observed stars.

Obtaining correct data about the state of the star at some stage is the first step. Next, a “light curve” should be drawn up to record possible changes in brightness. It will show the change in magnitude.

Variables or not.

Stars whose magnitude is not constant are called variables. For some of them, variability is only apparent. These are mainly stars belonging to the binary system. Moreover, when the orbital plane of the system more or less coincides with the observer’s line of sight, it may seem to him that one of the two stars is completely or partially eclipsed by the other and is less bright. In these cases, the changes are periodic; periods of change in the brightness of eclipsing stars are repeated at intervals that coincide with the orbital period of the binary star system. These stars are called "eclipsing variables."

The next class of variable stars is “internal variables”. The amplitudes of the brightness fluctuations of these stars depend on the physical parameters of the star, such as radius and temperature. For many years, astronomers have been observing the variability of variable stars. In our Galaxy alone, 30,000 variable stars have been recorded. They were divided into two groups. The first category includes “eruptive variable stars.” They are characterized by single or repeated outbreaks. Changes in stellar magnitudes are episodic. The class of “eruptive variables,” or explosive ones, also includes novae and supernovae. The second group includes everyone else.

Cepheids.

There are variable stars whose brightness changes strictly periodically. Changes occur at certain intervals. If you draw a light curve, it will clearly record the regularity of changes, while the shape of the curve will mark the maximum and minimum characteristics. The difference between the maximum and minimum fluctuations defines a large space between the two characteristics. Stars of this type are classified as “pulsating variables.” From the light curve we can conclude that the star's brightness increases faster than it decreases.

Variable stars are divided into classes. The prototype star is taken as a criterion; it is this star that gives the name to the class. An example is the Cepheids. This name comes from the star Cepheus. This is the simplest criterion. There is another one - stars are divided according to their spectra.

Variable stars can be divided into subgroups according to different criteria.

DOUBLE STARS.

Stars in the firmament exist in the form of clusters, associations, and not as individual bodies. Star clusters can be very densely populated with stars or not.

Closer connections can exist between stars; we are talking about binary systems, as astronomers call them. In a pair of stars, the evolution of one directly affects the second.

Opening.

The discovery of double stars, as they are now called, was one of the first discoveries made using astronomical binoculars. The first pair of this type of stars was Mizar from the constellation Ursa Major. The discovery was made by the Italian astronomer Riccioli. Considering the huge number of stars in the Universe, scientists came to the conclusion that Mizar was not the only binary system among them, and they were right; observations soon confirmed this hypothesis. In 1804, the famous astronomer William Herschel, who devoted 24 years of scientific observations, published a catalog containing descriptions of approximately 700 double stars. At first, scientists did not know for sure whether the components of the binary system were physically connected to each other.

Some bright minds believed that double stars were affected by the stellar association as a whole, especially since the brightness of the components in the pair was not the same. In this regard, it seemed that they were not nearby. To determine the true position of the bodies, it was necessary to measure the parallactic displacements of the stars. This is what Herschel did. To the greatest surprise, the parallactic displacement of one star relative to another during the measurement gave an unexpected result. Herschel noticed that instead of oscillating symmetrically with a period of 6 months, each star followed a complex ellipsoidal path. In accordance with the laws of celestial mechanics, two bodies connected by gravity move in an elliptical orbit. Herschel's observations confirmed the thesis that double stars are connected physically, that is, by gravitational forces.

Classification of double stars.

There are three main classes of double stars: visual binaries, photometric binaries, and spectroscopic binaries. This classification does not fully reflect the internal differences between the classes, but gives an idea of ​​the stellar association.

The duality of visual double stars is clearly visible through a telescope as they move. Currently, about 70,000 visual binaries have been identified, but only 1% of them have had an accurately determined orbit.

This figure (1%) should not be surprising. The fact is that orbital periods can be several decades, if not entire centuries. And building a path along the orbit is a very painstaking work, requiring numerous calculations and observations from different observatories. Very often, scientists have only fragments of the orbital movement; they reconstruct the rest of the path deductively, using the available data. It should be borne in mind that the orbital plane of the system may be inclined to the line of sight. In this case, the reconstructed orbit (apparent) will differ significantly from the true one.

If the true orbit is determined, the period of revolution and the angular distance between the two stars are known, it is possible, by applying Kepler's third law, to determine the sum of the masses of the system components. The distance of the double star to us should also be known.

Double photometric stars.

The duality of this system of stars can be judged only by periodic fluctuations in brightness. When moving, such stars alternately block each other. They are also called "eclipsing double stars." These stars have orbital planes close to the direction of the line of sight. The larger the area the eclipse occupies, the more pronounced the brilliance. If you analyze the light curve of double photometric stars, you can determine the inclination of the orbital plane.

Using the light curve, you can also determine the orbital period of the system. If, for example, two eclipses are recorded, the light curve will have two decreases (minimum). The time period during which three successive decreases along the light curve are recorded corresponds to the orbital period.

The periods of photometric binary stars are much shorter compared to the periods of visual binary stars and last for several hours or several days.

Spectral dual stars.

Using spectroscopy, one can notice the splitting of spectral lines due to the Doppler effect. If one of the components is a weak star, then only a periodic oscillation of the positions of single lines is observed. This method is used when the components of a double star are very close to each other and are difficult to identify with a telescope as visual double stars. Binary stars determined using a spectroscope and the Doppler effect are called spectral binaries. Not all double stars are spectral. The two components of binary stars can move away and approach in a radial direction.

Observations indicate that double stars are found mainly in our Galaxy. It is difficult to determine the percentage of double and single stars. If we use the subtraction method and subtract the number of identified double stars from the entire stellar population, we can conclude that they constitute a minority. This conclusion may be erroneous. In astronomy there is the concept of “selection effect”. To determine the binarity of stars, it is necessary to identify their main characteristics. This requires good equipment. Binary stars can sometimes be difficult to identify. For example, visual double stars cannot always be seen at a great distance from the observer. Sometimes the angular distance between components is not recorded by the telescope. In order to detect photometric and spectroscopic binaries, their brightness must be strong enough to collect modulations of the light flux and carefully measure the wavelengths in the spectral lines.

The number of stars suitable in all respects for research is not so large. According to theoretical developments, it can be assumed that double stars make up from 30% to 70% of the stellar population.

NEW STARS.

Variable explosive stars consist of a white dwarf and a Main Sequence star, like the Sun, or a post-sequence star, like a red giant. Both stars follow a narrow orbit every few hours. They are located at a close distance from each other, and therefore they interact closely and cause spectacular phenomena.

Since the mid-19th century, scientists have recorded the predominance of violet color at certain times in the optical band of variable explosive stars; this phenomenon coincides with the presence of peaks in the light curve. Based on this principle, the stars were divided into several groups.

Classic novae.

Classical novae differ from explosive variables in that their optical outbursts do not have a repeating character. The amplitude of their light curve is more clearly expressed, and the rise to the maximum point occurs much faster. They usually reach maximum brightness in a few hours, during which time the new star acquires a magnitude of approximately 12, that is, the luminous flux increases by 60,000 units.

The slower the process of rising to maximum, the less noticeable the change in brightness. The nova does not remain at its maximum position for long; this period usually lasts from several days to several months. The shine then begins to decrease, quickly at first, then more slowly to normal levels. The duration of this phase depends on various circumstances, but its duration is at least several years.

In new classical stars, all these phenomena are accompanied by uncontrolled thermonuclear reactions occurring in the surface layers of the white dwarf, which is where the “borrowed” hydrogen from the second component of the star is located. New stars are always binary, one of the components is necessarily a white dwarf. When the mass of the star component flows to the white dwarf, the hydrogen layer begins to compress and heats up, accordingly the temperature rises, and the helium heats up. All this happens quickly, sharply, resulting in an outbreak. The emitting surface increases, the star's brightness becomes bright, and a burst is recorded in the light curve.

During the active flare phase, the nova reaches its maximum brightness. The maximum absolute magnitude is on the order of -6 to -9. in new stars this figure is reached more slowly, in variable explosive stars it is achieved faster.

New stars also exist in other galaxies. But what we observe is only their apparent magnitude; the absolute magnitude cannot be determined, since their exact distance to the Earth is unknown. Although, in principle, it is possible to find out the absolute magnitude of a nova if it is in maximum proximity to another nova, the distance to which is known. The maximum absolute value is calculated using the equation:

M=-10.9+2.3log (t).

t is the time during which the light curve of the nova drops to 3 magnitudes.

Dwarf novae and repeating novae.

The closest relatives of novae are dwarf novae, their prototype “U Gemini”. Their optical flares are almost similar to the flares of new stars, but there are differences in the light curves: their amplitudes are smaller. There are also differences in the frequency of flares - in new dwarf stars they occur more or less regularly. On average once every 120 days, but sometimes every few years. The optical flashes of the novae last from several hours to several days, after which the brightness decreases over several weeks and finally reaches normal levels.

The existing difference can be explained by different physical mechanisms that provoke the optical flash. In Gemini U, flares occur due to a sudden change in the percentage of matter on the white dwarf - an increase in it. The result is a huge release of energy. Observations of dwarf novae during the eclipse phase, that is, when the white dwarf and the disk surrounding it are obscured by a component star of the system, clearly indicate that it is the white dwarf, or rather its disk, that is the source of light.

Recurring novae are a cross between classical novae and dwarf novae. As the name suggests, their optical flares repeat regularly, which makes them similar to new dwarf stars, but this happens after several decades. The increase in brightness during a flare is more pronounced and amounts to about 8 magnitudes; this feature brings them closer to classical novae.

OPEN STAR CLUSTERS.

Open star clusters are not difficult to find. They are called galaxy clusters. We are talking about formations that include from several tens to several thousand stars, most of which are visible to the naked eye. Star clusters appear to the observer as a section of the sky densely dotted with stars. As a rule, such areas of concentration of stars are clearly visible in the sky, but it happens, quite rarely, that the cluster is practically indistinguishable. In order to determine whether any part of the sky is a star cluster or whether we are talking about stars simply located close to each other, one should study their movement and determine the distance to the Earth. The stars that make up the clusters move in the same direction. In addition, if stars that are not far from each other are located at the same distance from the solar system, they are, of course, connected to each other by gravitational forces and form an open cluster.

Classification of star clusters.

The extent of these star systems varies from 6 to 30 light years, with an average extent of approximately twelve light years. Inside star clusters, stars are concentrated chaotically, unsystematically. The cluster does not have a clearly defined shape. When classifying star clusters, one must take into account angular measurements, the approximate total number of stars, their degree of concentration in the cluster, and differences in brightness.

In 1930, American astronomer Robert Trumpler proposed classifying clusters according to the following parameters. All clusters were divided into four classes based on the concentration of stars and were designated by Roman numerals from I to IV. Each of the four classes is divided into three subclasses based on the uniformity of stellar brightness. The first subclass includes clusters in which the stars have approximately the same degree of luminosity, the third - with a significant difference in this regard. Then the American astronomer introduced three more categories for classifying star clusters according to the number of stars included in the cluster. The first category “p” includes systems with less than 50 stars. The second “m” is a cluster with from 50 to 100 stars. The third - those with more than 100 stars. For example, according to this classification, a star cluster designated in the catalog as “I 3p” is a system consisting of less than 50 stars, densely concentrated in the sky and having varying degrees of brightness.

Uniformity of stars.

All stars belonging to any open star cluster have a characteristic feature - homogeneity. This means that they were formed from the same gas cloud and at first they had the same chemical composition. In addition, there is an assumption that they all appeared at the same time, that is, they are the same age. The differences between them can be explained by the different course of development, and this is determined by the mass of the star from the moment of its formation. Scientists know that large stars have a shorter lifespan compared to small stars. Large ones evolve much faster. In general, open star clusters are celestial systems consisting of relatively young stars. This type of star clusters is located mainly in the spiral arms of the Milky Way. These areas were active star formation zones in the recent past. The exceptions are the clusters NGC 2244, NGC 2264 and NGC6530, their age is several tens of millions of years. This is a short time for the stars.

Age and chemical composition.

Stars in open star clusters are connected by gravity. But because this connection is not strong enough, open clusters can disintegrate. This happens over a long period of time. The dissolution process is associated with the influence of gravity from single stars located near the cluster.

There are practically no old stars in open star clusters. Although there are exceptions. This primarily applies to large clusters, in which the connection between stars is much stronger. Accordingly, the age of such systems is greater. Among them is NGC 6791. This star cluster includes approximately 10,000 stars and is about 10 billion years old. The orbits of large star clusters take them far from the galactic plane for long periods of time. Accordingly, they have less opportunity to encounter large molecular clouds, which could lead to the dissolution of the star cluster.

Stars in open star clusters are similar in chemical composition to the Sun and other stars in the galactic disk. The difference in chemical composition depends on the distance from the center of the Galaxy. The farther from the center a star cluster is located, the fewer elements from the metal group it contains. The chemical composition also depends on the age of the star cluster. This also applies to single stars.

Globular star clusters.

Globular star clusters, numbering hundreds of thousands of stars, have a very unusual appearance: they have a spherical shape, and the stars are concentrated in them so densely that even with the help of the most powerful telescopes it is impossible to distinguish single objects. There is a strong concentration of stars towards the center.

Research on globular clusters is important in astrophysics in terms of studying the evolution of stars, the process of galaxy formation, studying the structure of our Galaxy and determining the age of the Universe.

The shape of the Milky Way.

Scientists have found that globular clusters formed at the initial stage of the formation of our Galaxy - the protogalactic gas had a spherical shape. During the gravitational interaction until the compression was completed, which led to the formation of the disk, clumps of matter, gas and dust appeared outside of it. It is from them that globular star clusters were formed. Moreover, they were formed before the appearance of the disk and remained in the same place where they were formed. They have a spherical structure, a halo, around which the plane of the galaxy was later located. This is why globular clusters are distributed symmetrically in the Milky Way.

The study of the problem of the location of globular clusters, as well as measurements of the distance from them to the Sun, made it possible to determine their extent of our Galaxy to the center - it is 30,000 light years.

Globular star clusters are very old in terms of their time of origin. Their age is 10-20 billion years. They represent the most important element of the Universe, and, undoubtedly, knowledge about these formations will provide considerable assistance in explaining the phenomena of the Universe. According to scientists, the age of these star clusters is identical to the age of our Galaxy, and since all galaxies were formed at approximately the same time, it means that the age of the Universe can be determined. To do this, the time from the appearance of the Universe to the beginning of the formation of galaxies should be added to the age of globular star clusters. Compared to the age of globular star clusters, this is a very short period of time.

Inside the cores of globular clusters.

The central regions of this type of cluster are characterized by a high degree of concentration of stars, approximately thousands of times more than in the zones closest to the Sun. Only over the last decade has it become possible to examine the cores of globular star clusters, or rather, those celestial objects that are located in the very center. This is of great importance in the field of studying the dynamics of stars included in the core, in terms of obtaining information about systems of celestial bodies connected by gravitational forces - star clusters belong precisely to this category - as well as in terms of studying the interaction between stars of clusters through observations or data processing on the computer.

Due to the high degree of concentration of stars, real collisions occur and new objects are formed, for example stars, which have their own characteristics. Binary systems can also appear; this happens when the collision of two stars does not lead to their destruction, but mutual capture occurs due to gravity.

Families of globular star clusters.

Globular star clusters of our Galaxy are heterogeneous formations. Four dynamic families are distinguished according to the principle of distance from the center of the Galaxy and according to their chemical composition. Some globular clusters have more metal group chemical elements, others have less. The degree of presence of metals depends on the chemical composition of the interstellar medium from which celestial objects were formed. Globular clusters with fewer metals are older and are located in the halo of the Galaxy. A higher metal composition is characteristic of younger stars, they were formed from an environment already enriched in metals due to supernova explosions - this family includes “disk clusters” found on the galactic disk.

The halo contains "halo-inner star clusters" and "halo-outer star clusters." There are also “star clusters of the peripheral part of the halo”, the distance from which to the center of the Galaxy is greatest.

Environmental influence.

Star clusters are not studied and divided into families for the sake of classification as an end in themselves. Classification also plays an important role in studying the influence of the environment surrounding a star cluster on its evolution. In this case we are talking about our Galaxy.

Undoubtedly, the star cluster is greatly influenced by the gravitational field of the Galaxy's disk. Globular star clusters move around the galactic center in elliptical orbits and periodically cross the galactic disk. This happens once every 100 million years.

The gravitational field and tidal projections emanating from the galactic plane act so intensely on the star cluster that it gradually begins to disintegrate. Scientists believe that some old stars currently located in the Galaxy were once part of globular star clusters. Now they have already collapsed. It is believed that approximately 5 star clusters disintegrate every billion years. This is an example of the influence of the galactic environment on the dynamic evolution of a globular star cluster.

Under the influence of the gravitational influence of the galactic disk on the star cluster, a change in the extent of the cluster also occurs. We are talking about stars located far from the center of the cluster; they are influenced to a greater extent by the gravitational force of the galactic disk, and not by the star cluster itself. Stars “evaporate” and the size of the cluster decreases.

SUPERNOVA STARS.

Stars are also born, grow and die. Their end may be slow and gradual or abrupt and catastrophic. This is typical for very large stars that end their existence with an outburst; these are supernovae.

Discovery of supernovae.

For centuries, the nature of supernovae was unknown to scientists, but observations of them have been carried out since time immemorial. Many supernovae are so bright that they can be seen with the naked eye, sometimes even during the day. The first mentions of these stars appeared in ancient chronicles in 185 AD. Subsequently, they were observed regularly and all data was scrupulously recorded. For example, the court astronomers of the emperors of ancient China recorded many of the discovered supernovae many years later.

Notable among them is the supernova that erupted in 1054 AD. in the constellation Taurus. This supernova remnant is called the Crab Nebula because of its distinctive shape. Western astronomers began to conduct systematic observations of supernovae late. Only towards the end of the 16th century. references to them appeared in scientific documents. The first observations of supernovae by European astronomers date back to 1575 and 1604. In 1885, the first supernova was discovered in the Andromeda galaxy. This was done by Baroness Bertha de Podmanicka.

Since the 20s of the XX century. Thanks to the invention of photographic plates, supernova discoveries follow one after another. Currently, there are up to a thousand of them open. Finding supernovae requires a lot of patience and constant observation of the sky. The star must not only be very bright, its behavior must be unusual and unpredictable. There are not so many “supernova hunters”; a little more than ten astronomers can boast that they have discovered more than 20 supernovae in their lifetime. The leader in this interesting classification belongs to Fred Zwicky - since 1936, he has identified 123 stars.

What are supernovae?

Supernovae are stars that explode suddenly. This flare is a catastrophic event, the end of the evolution of large stars. During flares, the radiation power reaches 1051 erg, which is comparable to the energy emitted by the star throughout its entire life. The mechanisms that cause flares in double and single stars are different.

In the first case, the outburst occurs under the condition that the second star in the binary system is a white dwarf. White dwarfs are relatively small stars, their mass corresponds to the mass of the Sun, and at the end of their “life path” they have the size of a planet. The white dwarf interacts with its pair in a gravitational way; it “steals” matter from its surface layers. The “borrowed” substance heats up, nuclear reactions begin, and an outbreak occurs.

In the second case, the star itself flares up; this happens when there are no longer conditions for thermonuclear reactions in its depths. At this stage, gravity dominates and the star begins to contract at a rapid rate. Due to sudden heating as a result of compression, uncontrolled nuclear reactions begin to occur in the star's core, energy is released in the form of a flash, causing the destruction of the star.

After the flash, a cloud of gas remains and spreads in space. These are “supernova remnants” - what remains from the surface layers of an exploding star. The morphology of supernova remnants is different and depends on the conditions in which the explosion of the “progenitor” star occurred, and on its characteristic internal features. The cloud spreads unequally in different directions, which is due to interaction with interstellar gas, which can significantly change the shape of the cloud over thousands of years.

Characteristics of supernovae.

Supernovae are a variation of eruptive variable stars. Like all variables, supernovae are characterized by a light curve and easily recognizable features. First of all, a supernova is characterized by a rapid increase in brightness, it lasts several days until it reaches a maximum - this period is approximately ten days. Then the shine begins to decrease - first haphazardly, then consistently. By studying the light curve, you can trace the dynamics of the flare and study its evolution. The part of the light curve from the beginning of the rise to the maximum corresponds to the flare of the star, the subsequent descent means the expansion and cooling of the gas envelope.

WHITE Dwarfs.

In the “star zoo” there are a great variety of stars, different in size, color and brilliance. Among them, “dead” stars are especially impressive; their internal structure differs significantly from the structure of ordinary stars. The category of dead stars includes large stars, white dwarfs, neutron stars and black holes. Due to the high density of these stars, they are classified as “crisis” stars.

Opening.

At first, the essence of white dwarfs was a complete mystery; all that was known was that they had a high density compared to ordinary stars.

The first white dwarf to be discovered and studied was Sirius B, a pair of Sirius, a very bright star. Using Kepler's third law, astronomers calculated the mass of Sirius B: 0.75-0.95 solar masses. On the other hand, its brightness was significantly lower than that of the sun. The brightness of a star is related to the square of its radius. After analyzing the numbers, astronomers came to the conclusion that the size of Sirius is small. In 1914, the stellar spectrum of Sirius B was compiled and the temperature was determined. Knowing the temperature and brightness, we calculated the radius - 18,800 kilometers.

First research.

The obtained result marked the discovery of a new class of stars. In 1925, Adams measured the wavelength of some emission lines in the spectrum of Sirius B and determined that they were longer than expected. The red shift fits into the framework of the theory of relativity, discovered by Einstein several years before the events taking place. Using the theory of relativity, Adams was able to calculate the radius of the star. After the discovery of two more stars similar to Sirius B, Arthur Eddington concluded that there are many such stars in the Universe.

So, the existence of dwarfs was established, but their nature still remained a mystery. In particular, scientists could not understand how a mass similar to the sun could fit in such a small body. Eddington concludes that “at such a high density the gas loses its properties. Most likely, white dwarfs consist of degenerate gas."

The essence of white dwarfs.

In August 1926, Enrico Fermi and Paul Dirac developed a theory describing the state of gas under conditions of very high density. Using it, Fowler in the same year found an explanation for the stable structure of white dwarfs. In his opinion, due to its high density, the gas in the interior of the white dwarf is in a degenerate state, and the gas pressure is practically independent of temperature. The stability of a white dwarf is maintained by the fact that the force of gravity is opposed by the gas pressure in the bowels of the dwarf. The study of white dwarfs was continued by the Indian physicist Chandrasekhar.

In one of his works, published in 1931, he makes an important discovery - the mass of white dwarfs cannot exceed a certain limit, this is due to their chemical composition. This limit is 1.4 solar masses and is called the “Chandrasekhar limit” in honor of the scientist.

Almost a ton per cm3!

As their name suggests, white dwarfs are small stars. Even if their mass is equal to the mass of the Sun, they are still similar in size to a planet like Earth. Their radius is approximately 6000 km - 1/100 of the radius of the Sun. Considering the mass of white dwarfs and their size, only one conclusion can be drawn - their density is very high. A cubic centimeter of white dwarf matter weighs almost a ton by Earth standards.

Such a high density leads to the fact that the gravitational field of the star is very strong - about 100 times higher than the solar one, and with the same mass.

Main characteristics.

Although the core of white dwarfs no longer undergoes nuclear reactions, its temperature is very high. Heat rushes to the surface of the star and then spreads out into space. The stars themselves slowly cool down until they become invisible. The surface temperature of “young” white dwarfs is about 20,000-30,000 degrees. White dwarfs are not only white, there are also yellow ones. Despite the high surface temperature, due to its small size, the luminosity is low; the absolute magnitude can be 12-16. White dwarfs cool very slowly, which is why we see them in such large numbers. Scientists have the opportunity to study their main characteristics. White dwarfs are included in the H-R diagram and occupy a small space below the Main Sequence.

NEUTRON STARS AND PULSARS.

The name "pulsar" comes from the English combination "pulsating star" - "pulsating star". A characteristic feature of pulsars, unlike other stars, is not constant radiation, but regular pulsed radio emission. The pulses are very fast, the duration of one pulse lasts from thousandths of a second to, at most, several seconds. The pulse shape and periods are different for different pulsars. Due to the strict periodicity of radio emission, pulsars can be considered as cosmic chronometers. Over time, the periods decrease to 10-14 s/s. Every second the period changes by 10-14 seconds, that is, the decrease occurs over about 3 million years.

Regular signals.

The history of the discovery of pulsars is quite interesting. The first pulsar, PSR 1919+21, was detected in 1967 by Bell and Anthony Husch of the University of Cambridge. Bell, a young physicist, conducted research in the field of radio astronomy to confirm the theses he put forward. Suddenly he discovered a radio signal of moderate intensity in an area close to the galactic plane. The strange thing was that the signal was intermittent - it disappeared and reappeared at regular intervals of 1.377 seconds. They say that Bell ran to his professor to notify him of the discovery, but the latter did not pay due attention to this, believing that it was a radio signal from the Earth.

Nevertheless, the signal continued to appear regardless of terrestrial radioactivity. This indicated that the source of its appearance had not yet been established. As soon as the data about the discovery were published, numerous speculations arose that the signals were coming from a ghostly extraterrestrial civilization. But scientists were able to understand the essence of pulsars without the help of alien worlds.

The essence of pulsars.

After the first one, many more pulsars were discovered. Astronomers have concluded that these celestial bodies are sources of pulsed radiation. The most numerous objects in the Universe are stars, so scientists decided that these celestial bodies most likely belong to the class of stars.

The rapid movement of the star around its axis is most likely the cause of the pulsations. Scientists measured the periods and tried to determine the essence of these celestial bodies. If a body rotates at a speed exceeding a certain maximum speed, it disintegrates under the influence of centrifugal forces. This means that there must be a minimum value of the rotation period.

From the calculations performed, it followed that for a star to rotate with a period measured in thousandths of a second, its density should be on the order of 1014 g/cm3, like that of atomic nuclei. For clarity, we can give the following example: imagine a mass equal to Everest in the volume of a piece of sugar.

Neutron stars.

Since the thirties, scientists have assumed that something similar exists in the sky. Neutron stars are very small, super-dense celestial bodies. Their mass is approximately equal to 1.5 solar masses, concentrated in a radius of approximately 10 km.

Neutron stars consist mainly of neutrons, particles without an electrical charge that, together with protons, make up the nucleus of an atom. Due to the high temperature in the interior of the star, the matter is ionized, electrons exist separately from the nuclei. At such a high density, all nuclei decay into their constituent neutrons and protons. Neutron stars are the end result of the evolution of a large mass star. After exhausting the sources of thermonuclear energy in its depths, it explodes sharply, like a supernova. The outer layers of the star are thrown into space, gravitational collapse occurs in the core, and a hot neutron star is formed. The collapse process takes a fraction of a second. As a result of the collapse, it begins to rotate very quickly, with periods of thousandths of a second, which is typical for a pulsar.

Radiation of pulsations.

There are no sources of thermonuclear reactions in a neutron star, i.e. they are inactive. The emission of pulsations does not come from the interior of the star, but from the outside, from zones surrounding the surface of the star.

The magnetic field of neutron stars is very strong, millions of times greater than the magnetic field of the Sun, it cuts through space, creating a magnetosphere.

A neutron star emits streams of electrons and positrons into the magnetosphere; they rotate at speeds close to the speed of light. The magnetic field influences the movement of these elementary particles; they move along the lines of force, following a spiral trajectory. Thus, they release kinetic energy in the form of electromagnetic radiation.

The rotation period increases due to the decrease in rotational energy. Older pulsars have a longer pulsation period. By the way, the pulsation period is not always strictly periodic. Sometimes it slows down sharply, this is associated with phenomena called “glitches” - this is the result of “microstarquakes”.

BLACK HOLES.

The image of the firmament amazes with the variety of shapes and colors of celestial bodies. There is so much in the Universe: stars of all colors and sizes, spiral galaxies, nebulae of unusual shapes and colors. But in this “cosmic zoo” there are “specimens” that arouse special interest. These are even more mysterious celestial bodies, as they are difficult to observe. In addition, their nature is not fully understood. Among them, a special place belongs to “black holes”.

Movement speed.

In everyday speech, the expression “black hole” means something bottomless, where a thing falls, and no one will ever know what happened to it in the future. What are black holes really? To understand this, let's go back in history two centuries ago. In the 18th century, the French mathematician Pierre Simon de Laplace first introduced this term while studying the theory of gravitation. As you know, any body that has a certain mass - the Earth, for example - also has a gravitational field; it attracts surrounding bodies.

This is why an object thrown up falls to the Earth. If the same object is thrown forward with force, it will overcome the gravity of the Earth for some time and fly some distance. The minimum required speed is called “movement speed”; for the Earth it is 11 km/s. The speed of movement depends on the density of the celestial body, which creates a gravitational field. The higher the density, the higher the speed should be. Accordingly, one can make the assumption, as Laplace did two centuries ago, that in the Universe there are bodies with such a high density that their speed of movement exceeds the speed of light, that is, 300,000 km/s.

In this case, even light could succumb to the gravitational force of such a body. Such a body could not emit light, and therefore it would remain invisible. We can imagine it as a huge hole, black in the picture. Undoubtedly, the theory formulated by Laplace does not bear the imprint of time and seems too simplified. However, at the time of Laplace, quantum theory had not yet been formulated, and from a conceptual point of view, considering light as a material body seemed nonsense. At the very beginning of the 20th century, with the advent and development of quantum mechanics, it became known that light under certain conditions also acts as material radiation.

This position was developed in Albert Einstein's theory of relativity, published in 1915, and in the work of German physicist Karl Schwarzschild in 1916, he provided a mathematical basis for the theory of black holes. Light can also be subject to gravity. Two centuries ago, Laplace raised a very important problem in terms of the development of physics as a science.

How do black holes appear?

The phenomena we are talking about received the name “black holes” in 1967 thanks to the American astrophysicist John Wheeler. They are the end result of the evolution of large stars whose mass is greater than five solar masses. When all nuclear fuel reserves are exhausted and reactions no longer occur, the death of the star occurs. Further, its fate depends on its mass.

If the mass of a star is less than the mass of the sun, it continues to contract until it goes out. If the mass is significant, the star explodes, then we are talking about a supernova. The star leaves behind traces - when gravitational collapse occurs in the core, all the mass is collected into a ball of compact size with a very high density - 10,000 times more than that of the nucleus of an atom.

Relative effects.

For scientists, black holes are an excellent natural laboratory that allows them to conduct experiments on various hypotheses in terms of theoretical physics. According to Einstein's theory of relativity, the laws of physics are influenced by a local gravitational field. In principle, time flows differently near gravitational fields of different intensities.

In addition, a black hole affects not only time, but also the surrounding space, affecting its structure. According to the theory of relativity, the presence of a strong gravitational field arising from such a powerful celestial body as a black hole distorts the structure of the surrounding space, and its geometric data changes. This means that near a black hole, the short distance connecting two points will not be a straight line, but a curve.

Stars are not only a beautiful glow and a landmark in the night sky, they are also the basis of any life. This is confirmed so far by only one celestial body - our Sun, but it does it confidently, bringing us light and warmth every day for many millions of years. But what interesting facts about stars do we know yet?

1. All stars, no matter how different they are, always consist of the same matter. In their initial state, 74% is occupied by hydrogen, 25% goes under helium, and 1% consists of gaseous impurities of various kinds. Throughout their existence, stars gradually process hydrogen and using the example of the Sun, for which this ratio is already 70% to 29%, it is most convenient to observe this process.

2. Among the interesting facts about stars in space is the balance of their processes. In fact, gravity forces the celestial body to retract into itself, significantly decreasing in size, and this could last for millions of years, until in volume they all became similar to neutron stars, if not for the light. Thanks to a constant thermonuclear reaction, it is produced and emanates from the very center of the star, passing through it for thousands of years, acting as a resistance to gravity.

3. Red dwarfs occupy the largest number of stars. They are, as a rule, half the size of our Sun and produce a correspondingly small amount of energy - about 0.00001 of the capabilities of our luminary. They are called failed, inferior, and their internal supply of hydrogen only lasts for 10 trillion years.

4. Interesting fact about the stars in the sky. We are used to thinking that blue light is cold, while orange and red light, in turn, are more like sources of heat. But in fact, it is the fiery red luminaries that have a minimum temperature - no more than 3,600 Kelvin, and blue ones have a maximum temperature - up to 12,000 Kelvin.

5. At first glance, it seems that each star is on its own. But there are those that form pairs, while having a common gravitational center. But this is not the limit; scientists have found three and four celestial bodies connected into one system. One has only to imagine that instead of one Sun we could have four.

6. The largest planet in our system is Saturn, it is truly huge, but there are luminaries that could absorb it. They are called supergiants and one of the most famous is Betelgeuse, it is 1000 times larger than our Sun. However, this is not the limit, because the most enormous is considered to be VY Canis Majoris, which is twice the size of Betelgeuse itself.

7. An interesting fact about planets and stars: if instead of our Sun there was something a little hotter, in a few million years Mercury would simply turn into steam.

8. Small celestial bodies end their existence, forming white dwarfs, and giants, in turn, leave behind black holes.

9. Despite the incredible number of gaseous giants that surround us, they are all very, very far away. The closest one to us is called Proxima Centauri and is about four and a half light years away from Earth. That is, a beam of light can cover this distance in such a time, as for a person, on the most incredibly fast spaceship it would take him at least 70 thousand years, which makes travel between the stars simply impossible at the moment.

10. How many stars are there in total? It is extremely difficult, and maybe even impossible, to calculate this, because in our galaxy alone their number averages 300 billion. And there may be 500 billion galaxies in total, each with about the same number of gaseous giants, making the total number quite frightening.

Introduction

For thousands of years, the stars were incomprehensible to human consciousness, but they fascinated him. Therefore, the science of stars - astronomy - is one of the most ancient. It took thousands of years for people to free themselves from the naive idea that stars are luminous points attached to a huge dome. However, the greatest thinkers of antiquity understood that the starry sky with the Sun and Moon was something more than just an enlarged semblance of a planetarium. They guessed that planets and stars are separate bodies and float freely in the Universe. With the beginning of the space age, the stars became closer to us. We are learning more and more about them. But the ancient science of stars, astronomy, not only has not exhausted itself, but, on the contrary, has become even more interesting.

Magnitudes

One of the most important characteristics is the magnitude. Previously, it was believed that the distance to stars is the same, and the brighter the star, the larger it is. The brightest stars were classified as stars of the first magnitude (1 m, from the Latin magnitido - magnitude), and those barely visible to the naked eye - as the sixth (6 m). Now we know that magnitude characterizes not the size of a star, but its brilliance, that is, the illumination that the star creates on Earth.

But the magnitude scale has been preserved and refined. The brightness of a star 1 m is exactly 100 times greater than the brightness of a star 6 m. Luminaries whose brilliance exceeds the brilliance of stars 1 m have zero and negative magnitudes. The scale continues towards stars not visible to the naked eye. There are stars 7 m, 8 m and so on. For a more accurate estimate, fractional magnitudes of 2.3 m, 7.1 m, and so on are used.

Since the stars are at different distances from us, their apparent magnitudes do not say anything about the luminosity (radiation power) of the stars. Therefore, the concept of “absolute magnitude” is also used. The magnitudes that stars would have if they were at the same distance (10 pc) are called absolute magnitudes (M).

Distance to stars

To determine the distances to the nearest stars, the parallax method (the amount of angular displacement of an object) is used. The angle (p) at which the average radius of the earth's orbit (a) would be visible from the star, located perpendicular to the direction of the star, is called the annual parallax. The distance to the star can be calculated using the formula

Distance to the star corresponding to a parallax of 1? ? called a parsec.

However, annual parallaxes can only be determined for the nearest stars, located no further than several hundred parsecs. But a statistical relationship was discovered between the type of spectrum of a star and its absolute magnitude. In this way, absolute stellar magnitudes are estimated by the type of spectrum, and then, comparing them with visible stellar magnitudes, distances to stars and parallaxes are calculated. Parallaxes defined in this way are called spectral parallaxes.

Luminosity

Some stars appear brighter to us, others fainter. But this does not yet indicate the true radiation power of the stars, since they are at different distances. Thus, the apparent magnitude itself cannot be a characteristic of the star, since it depends on the distance. The true characteristic is luminosity, that is, the total energy emitted by a star per unit time. The luminosities of stars are extremely varied. One of the giant stars, S Doradus, has a luminosity 500,000 times greater than the Sun, and the luminosity of the faintest dwarf stars is approximately the same number of times less.

If the absolute magnitude is known, then the luminosity of any star can be calculated using the formula

log L = 0.4(Ma -M),

where: L is the luminosity of the star,

M is its absolute magnitude, and

Ma is the absolute magnitude of the Sun.

Mass of stars

Another important characteristic of a star is its mass. The masses of stars are different, but, unlike luminosities and sizes, they vary within relatively narrow limits. The main method for determining the masses of stars is provided by the study of double stars. Based on the law of universal gravitation and Kepler’s laws generalized by Newton, the formula was derived

M 1 + M 2 = -- ,

where M 1 and M 2 are the masses of the main star and its satellite, P is the satellite’s orbital period, and is the semimajor axis of the earth’s orbit.

A relationship was also discovered between the luminosity and the mass of the star: the luminosity increases in proportion to the cube of the mass. Using this dependence, it is possible to determine from the luminosity the masses of single stars for which it is impossible to calculate the mass directly from observations.

Spectral classification

The spectra of stars are their passports with a description of all their physical properties. From the spectrum of a star, you can find out its luminosity (and therefore the distance to it), its temperature, size, the chemical composition of its atmosphere, both qualitative and quantitative, the speed of its movement in space, the speed of its rotation around its axis, and even then, no or near it there is another, invisible star, with which it revolves around their common center of gravity.

There is a detailed classification of star classes (Harvard). Classes are designated by letters, subclasses are designated by numbers from 0 to 9 after the letter indicating the class. In class O, subclasses begin with O5. The sequence of spectral types reflects the continuous drop in temperature of stars as they move to increasingly later spectral types. It looks like this:

O - B - A - F - G - K - M

Among cool red stars, in addition to class M, there are two other varieties. In the spectrum of some, instead of the molecular absorption bands of titanium oxide, the bands of carbon monoxide and cyanide are characteristic (in the spectra designated by the letters R and N), and among others, the bands of zirconium oxide (class S) are characteristic.

The vast majority of stars belong to the sequence from O to M. This sequence is continuous. The colors of stars of different classes are different: O and B are bluish stars, A are white, F and G are yellow, K are orange, M are red.

The classification discussed above is one-dimensional, since the main characteristic is the temperature of the star. But among the stars of the same class there are giant stars and dwarf stars. They differ in gas density in the atmosphere, surface area, and luminosity. These differences are reflected in the spectra of stars. There is a new, two-dimensional classification of stars. According to this classification, for each star, in addition to its spectral class, a luminosity class is also indicated. It is designated by Roman numerals from I to V. I are supergiants, II-III are giants, IV are subgiants, V are dwarfs. For example, the spectral class of the star Vega looks like A0V, Betelgeuse - M2I, Sirius - A1V.

All of the above applies to normal stars. However, there are many unusual stars with unusual spectra. First of all, these are emission stars. Their spectra are characterized not only by dark (absorption) lines, but also by light emission lines, brighter than the continuous spectrum. Such lines are called emission lines. The presence of such lines in the spectrum is indicated by the letter “e” after the spectral class. So, there are stars Be, Ae, Me. The presence of certain emission lines in the spectrum of a star O is designated as Оf. There are exotic stars whose spectra consist of broad emission bands against the background of a weak continuous spectrum. They are designated WC and WN; they do not fit into the Harvard classification. Recently, infrared stars have been discovered that emit almost all their energy in the invisible infrared region of the spectrum.

Giant stars and dwarf stars

Among the stars there are giants and dwarfs. The largest among them are the red giants, which, despite their weak radiation from a square meter of surface, shine 50,000 times more powerfully than the Sun. The largest giants are 2400 times larger than the Sun. Inside they could accommodate our solar system up to the orbit of Saturn. Sirius is one of the white stars, it shines 24 times more powerful than the Sun, it is approximately twice the diameter of the Sun.

But there are many dwarf stars. These are mostly red dwarfs with a diameter of half or even one-fifth the diameter of our Sun. The Sun is an average star in size; there are billions of such stars in our galaxy.

White dwarfs occupy a special place among stars. But they will be discussed later, as the final stage of the evolution of an ordinary star.

Variable stars

Variable stars are stars whose brightness varies. Some variable stars change their brightness periodically, while others experience a random change in brightness. To designate variable stars, Latin letters are used indicating the constellation. Within one constellation, variable stars are assigned sequentially one Latin letter, a combination of two letters, or the letter V with a number. For example, S Car, RT Per, V 557 Sgr.

Variable stars are divided into three large classes: pulsating, eruptive (explosive) and eclipsing.

Pulsating stars exhibit smooth changes in brightness. They are caused by periodic changes in the radius and surface temperature. The periods of pulsating stars vary from fractions of a day (RR Lyrae type stars) to tens (Cepheids) and hundreds of days (Mirids - Mira Ceti type stars). About 14 thousand pulsating stars have been discovered.

The second class of variable stars is explosive, or, as they are also called, eruptive stars. These include, firstly, supernovae, novae, repeated novae, type I Gemini stars, novae-like and symbiotic stars. Eruptive stars include young fast variable stars, IV Ceti type stars, and a number of related objects. The number of open eruptive variables exceeds 2000.

Pulsating and eruptive stars are called physical variable stars because changes in their apparent brightness are caused by physical processes occurring on them. This changes the temperature, color, and sometimes the size of the star.

Let us consider in more detail the most interesting types of physical variable stars. For example, Cepheids. This is a very common and very important type of physical variable star. They have the characteristics of the star d Cephei. Its shine is constantly changing. Changes are repeated every 5 days and 8 hours. The gloss increases faster than it decreases after the maximum. d Cephei is a periodic variable star. Spectral observations show changes in radial velocities and spectral class. The color of the star also changes. This means that profound changes of a general nature are occurring in the star, the cause of which is the pulsation of the outer layers of the star. Cepheids are non-stationary stars. Alternate compression and expansion occurs under the influence of two opposing forces: the force of attraction towards the center of the star and the force of gas pressure, pushing the matter out. A very important characteristic of Cepheids is the period. For any given star it is constant with great accuracy. Cepheids are giant and supergiant stars with great luminosity.

The main thing is that there is a relationship between the luminosity and the period of Cepheids: the longer the Cepheid's brightness period, the greater its luminosity. Thus, from the period known from observations, it is possible to determine the luminosity or absolute magnitude, and then the distance to the Cepheid. Many stars are likely to be Cepheids for some time during their lives. Therefore, their study is very important for understanding the evolution of stars. In addition, they help determine the distance to other galaxies, where they are visible due to their high luminosity. Cepheids also help determine the size and shape of our Galaxy.

Another type of regular variables are Miras, long-period variable stars, named after the star Mira (O Ceti). Being huge in volume, exceeding the volume of the Sun by millions and tens of millions of times, these red giants of spectral class M pulsate very slowly, with periods of 80 to 1000 days. The change in luminosity in visual rays for different representatives of this type of star occurs from 10 to 2500 times. However, the total emitted energy changes only 2-2.5 times. The radii of the stars fluctuate around average values ​​in the range of 5-10%, and the light curves are similar to Cepheid ones.

As already mentioned, not all physical variable stars exhibit periodic changes. There are many known stars that belong to semi-regular or irregular variables. For such stars, it is difficult or even impossible to notice patterns in brightness changes.

Let us now consider the third class of variable stars - eclipsing variables. These are binary systems whose orbital plane is parallel to the line of sight. As stars move around a common center of gravity, they alternately eclipse each other, which causes fluctuations in their brightness. Outside of eclipses, light from both components reaches the observer, and during an eclipse, the light is attenuated by the eclipsing component. In close systems, changes in the total brightness can also be caused by distortions in the shape of stars. The periods of eclipsing stars range from several hours to tens of years.

There are three main types of eclipsing variable stars. The first is variable stars of the Algol type (b Perseus). The components of these stars are spherical in shape, with the size of the companion star being larger and the luminosity less than the main star. Both components are either white, or the main star is white and the companion star is yellow. While there is no eclipse, the star's brightness is almost constant. When the main star is eclipsed, the brightness decreases sharply (primary minimum), and when the satellite sets behind the main star, the decrease in brightness is insignificant (secondary minimum) or not observed at all. From light curve analysis the radii and luminosities of the components can be calculated.

The second type of eclipsing variable star is the b Lyrae star. Their brightness varies continuously and smoothly within approximately two magnitudes. Between the main lows, a shallower secondary low necessarily occurs. Periods of variability range from half a day to several days. The components of these stars are massive bluish-white and white giants of spectral classes B and A. Due to their significant mass and relative proximity to each other, both components are subject to strong tidal influences, as a result of which they have acquired an ellipsoidal shape. In such close pairs, the atmospheres of stars penetrate each other, and a continuous exchange of matter occurs, some of which goes into interstellar space.

The third type of eclipsing binary stars are stars called type W Ursa Major stars after this star, whose variability (and orbital) period is only 8 hours. It is difficult to imagine the colossal speed with which the huge components of this star rotate. The spectral types of these stars are F and G.

There is also a small separate class of variable stars - magnetic stars. In addition to a large magnetic field, they have strong inhomogeneities in surface characteristics. Such inhomogeneities during the rotation of the star lead to a change in brightness.

For approximately 20,000 stars the variability class has not been determined.

The study of variable stars is of great importance. Variable stars help determine the age of the star systems where they are found and the type of stellar population they contain; distances to distant parts of our Galaxy, as well as to other galaxies. Modern observations have shown that some variable double stars are sources of X-ray radiation.

Stars bleeding out of gas

In the collection of stellar spectra, one can trace a continuous transition from spectra with individual thin lines to spectra containing individual unusually broad bands along with dark lines and even without them.

Stars that, based on the lines of their spectra, could be classified as stars of spectral class O, but have broad bright bands in the spectrum, are called Wolf-Rayet type stars - after the name of two French scientists who discovered and described them in the last century. It is only now that we have been able to unravel the nature of these stars.

Stars of this class are the hottest among all known. Their temperature is 40-100 thousand degrees.

Such enormous temperatures are accompanied by such a powerful radiation of a stream of ultraviolet rays that light atoms of hydrogen, helium, and at very high temperatures, atoms of other elements, apparently unable to withstand the pressure of light from below, fly up at enormous speed. The speed of their movement under the influence of light pressure is so great that the gravity of the star is unable to hold them. In a continuous stream they fall from the surface of the star and, almost uncontained, rush away into outer space, forming, as it were, atomic rain, but directed not downwards, but upwards. Under such rain, all life on the planets would burn if there were any surrounding these stars.

The continuous rain of atoms falling from the surface of the star forms a continuous atmosphere around it, but continuously dissipating into space.

How long can a Wolf-Rayet star bleed gas? In a year, the Wolf-Rayet star emits a mass of gas equal to one tenth or one hundred thousandth of the mass of the Sun. The mass of Wolf-Rayet stars is on average ten times the mass of the Sun. Exuding gas at such a speed, a Wolf-Rayet star cannot exist longer than 10 4 -10 5 years, after which there will be nothing left of it. Regardless of this, there is evidence that in reality stars in such a state exist no longer than ten thousand years, rather even much less. Probably, as their mass decreases to a certain value, their temperature drops and the emission of atoms stops. Currently, only about a hundred such self-destructing stars are known in the entire sky. It is likely that only a few, the most massive stars, reach such high temperatures in their development that gas loss begins. Perhaps, having thus freed itself from excess mass, the star can continue its normal, “healthy” development.

Most Wolf-Rayet stars are very close spectroscopic binaries. Their partner in a pair always turns out to also be a massive and hot star of class O or B. Many of these stars are eclipsing binaries. Stars oozing gas, although rare, have enriched the understanding of stars in general.

New stars

Novas are stars whose brightness unexpectedly increases hundreds, thousands, even millions of times. Having reached its greatest brightness, the new star begins to fade and returns to a calm state. The more powerful the nova flare, the faster its brightness decreases. Based on the speed at which their brightness decreases, new stars are classified as either “fast” or “slow.”

All new stars eject gas during a flare, which scatters at high speeds. The largest mass of gas ejected by new stars during an outburst is contained in the main shell. This shell is visible tens of years after the explosion around some other stars in the form of a nebula.

All new ones are double stars. In this case, the pair always consists of a white dwarf and a normal star. Since the stars are very close to each other, a flow of gas occurs from the surface of a normal star to the surface of a white dwarf. There is a hypothesis of nova outbreaks. The flare occurs as a result of a sharp acceleration of thermonuclear reactions of hydrogen combustion on the surface of a white dwarf. Hydrogen enters the white dwarf from a normal star. Thermonuclear “fuel” accumulates and explodes after reaching a certain critical value. Outbreaks may recur. The interval between them is from 10,000 to 1,000,000 years.

The closest relatives of novae are dwarf novae. Their flares are thousands of times weaker than novae flares, but they occur thousands of times more often. In appearance, novae and dwarf novae in a quiet state do not differ from each other. And it is still not known what physical reasons lead to such different explosive activity of these outwardly similar stars.

Supernovae

Supernovae are the brightest stars that appear in the sky as a result of stellar flares. A supernova explosion is a catastrophic event in the life of a star, since it can no longer return to its original state. At its maximum brightness, it shines like several billion stars similar to the Sun. The total energy released during the flare is comparable to the energy emitted by the Sun during its existence (5 billion years). Energy is spent accelerating matter: it scatters in all directions at enormous speeds (up to 20,000 km/s). Remnants of supernova explosions are now observed in the form of expanding nebulae with unusual properties (the Crab Nebula). Their energy is equal to the energy of a supernova explosion. After the explosion, a neutron star or pulsar remains in place of the supernova.

The mechanism of supernova explosions is still not completely clear. Most likely, such a stellar catastrophe is possible only at the end of the “life path” of a star. The most likely sources of energy are: gravitational energy released during the catastrophic compression of a star. Supernova explosions have important consequences for the Galaxy. The star's matter, flying away after the flare, carries energy that feeds the energy of the movement of interstellar gas. This substance contains new chemical compounds. In a certain sense, all life on Earth owes its existence to supernovae. Without them, the chemical composition of the matter in galaxies would be very poor.

Double stars

Double stars are pairs of stars bound into one system by gravitational forces. The components of such systems describe their orbits around a common center of mass. There are triple and quadruple stars; they are called multiple stars.

Systems in which the components can be seen through a telescope are called visual binaries. But sometimes they are only randomly located in one direction for an earthly observer. They are separated in space by enormous distances. These are optical double stars.

Another type of binary is made up of those stars that alternately block each other as they move. These are eclipsing double stars.

Stars with the same proper motion (in the absence of other signs of duality) are also binary. These are the so-called wide pairs. Using multicolor photoelectric photometry, it is possible to detect double stars that otherwise do not show themselves. These are photomeric doubles.

Stars with invisible satellites can also be classified as double stars.

Spectral binary stars are stars whose duality is revealed only by studying their spectra.

Star clusters

These are groups of stars connected by gravity and a common origin. They number from several tens to hundreds of thousands of stars. There are open and globular clusters. The difference between them is determined by the mass and age of these formations.

Open star clusters unite tens and hundreds, rarely thousands of stars. Their sizes are usually several parsecs. They are concentrated towards the equatorial plane of the Galaxy. More than 1000 clusters are known in our Galaxy.

Globular star clusters contain hundreds of thousands of stars and have a distinct spherical or ellipsoidal shape with a strong concentration of stars towards the center. All globular clusters are located far from the Sun. There are 130 known globular clusters in the Galaxy, but there should be about 500.

Globular clusters appear to have formed from huge gas clouds early in the formation of the Galaxy, maintaining their elongated orbits. The formation of open clusters began later from gas that “settled” towards the plane of the Galaxy. In the densest gas clouds, the formation of open clusters and associations continues to this day. Therefore, the age of open clusters is not the same, while the age of large globular clusters is approximately the same and is close to the age of the Galaxy.

Star associations

These are scattered groups of stars of spectral classes O and B and T. Tauri type. In their characteristics, stellar associations are similar to large, very young open clusters, but differ from them, apparently, in a lower degree of concentration towards the center. In other galaxies there are complexes of hot young stars associated with giant clouds of hydrogen ionized by their radiation - superassociations.

What powers the stars?

Why do stars expend such monstrous amounts of energy? At different times, different hypotheses were put forward. Thus, it was believed that the energy of the Sun is supported by the fall of meteorites on it. But there would have to be a significant number of them falling on the Sun, which would noticeably increase its mass. The Sun's energy could be replenished by compressing it. However, if the Sun was once infinitely large, then even in this case its compression to its current size would be enough to maintain energy for only 20 million years. Meanwhile, it has been proven that the earth’s crust exists and is illuminated by the Sun much longer.

Finally, the physics of the atomic nucleus indicated a source of stellar energy that is in good agreement with astrophysics and, in particular, with the conclusion that most of the stellar mass is hydrogen.

The theory of nuclear reactions has led to the conclusion that the source of energy in most stars, including the Sun, is the continuous formation of helium atoms from hydrogen atoms.

When all the hydrogen has turned into helium, the star can still exist by converting helium into heavier elements, up to iron.

Internal structure of stars

We consider a star as a body subject to the action of various forces. The force of gravity tends to pull the matter of the star towards the center, while gas and light pressure, directed from the inside, tend to push it away from the center. Since the star exists as a stable body, it follows that there is some kind of balance between the contending forces. To do this, the temperature of the different layers in the star must be set such that in each layer the outward flow of energy takes all the energy generated underneath it to the surface. Energy is generated in a small central core. For the initial period of a star's life, its compression is a source of energy. But only until the temperature rises so much that nuclear reactions begin.

Formation of stars and galaxies

Matter in the Universe is in continuous development, in a wide variety of forms and states. Since the forms of existence of matter change, then, consequently, different and diverse objects could not all arise at the same time, but were formed in different eras and therefore have their own specific age, counted from the beginning of their origin.

The scientific foundations of cosmogony were laid by Newton, who showed that matter in space under the influence of its own gravity is divided into compressed pieces. The theory of the formation of clumps of matter from which stars are formed was developed in 1902 by the English astrophysicist J. Jeans. This theory also explains the origin of Galaxies. In an initially homogeneous medium with constant temperature and density, compaction may occur. If the force of mutual gravity in it exceeds the force of gas pressure, then the medium will begin to compress, and if gas pressure prevails, then the substance will disperse in space.

It is believed that the age of the Metagalaxy is 13-15 billion years. This age does not contradict the estimates of the age of the oldest stars and globular star clusters in our Galaxy.

Evolution of stars

The condensations that have arisen in the gas and dust environment of the Galaxy, which continue to contract under the influence of their own gravity, are called protostars. As it contracts, the density and temperature of the protostar increases, and it begins to emit abundantly in the infrared range of the spectrum. The duration of compression of protostars is different: for those with a mass less than the Sun - hundreds of millions of years, and for massive ones - only hundreds of thousands of years. When the temperature in the bowels of a protostar rises to several million Kelvin, thermonuclear reactions begin in them, converting hydrogen into helium. In this case, enormous energy is released, preventing further compression and heating the matter to the point of self-luminescence - the protostar turns into an ordinary star. So, the compression stage is replaced by a stationary stage, accompanied by a gradual “burnout” of hydrogen. The star spends most of its life in the stationary stage. It is at this stage of evolution that stars are found that are located on the main “spectrum-luminosity” sequence. The time a star stays on the main sequence is proportional to the mass of the star, since the supply of nuclear fuel depends on this, and inversely proportional to the luminosity, which determines the rate of consumption of nuclear fuel.

When all the hydrogen in the central region is converted to helium, a helium core forms inside the star. Now hydrogen will turn into helium not in the center of the star, but in a layer adjacent to the very hot helium core. As long as there are no energy sources inside the helium core, it will constantly shrink and at the same time heat up even more. Compression of the nucleus leads to a more rapid release of nuclear energy in a thin layer near the boundary of the nucleus. In more massive stars, the temperature of the core during compression becomes above 80 million Kelvin, and thermonuclear reactions begin in it, converting helium into carbon, and then into other heavier chemical elements. The energy escaping from the core and its surroundings causes an increase in gas pressure, under the influence of which the photosphere expands. The energy coming to the photosphere from the interior of the star now spreads over a larger area than before. In this regard, the temperature of the photosphere decreases. The star moves off the main sequence, gradually becoming a red giant or supergiant depending on its mass, and becomes an old star. Passing the yellow supergiant stage, a star may turn out to be a pulsating, that is, a physical variable star, and remain so in the red giant stage. The inflated shell of a star of small mass is already weakly attracted by the core and, gradually moving away from it, forms a planetary nebula. After the final dissipation of the shell, only the hot core of the star remains - a white dwarf.

The fate of more massive stars is different. If the mass of a star is approximately twice the mass of the Sun, then such stars lose stability in the last stages of their evolution. In particular, they can explode as supernovae and then catastrophically shrink to the size of balls with a radius of several kilometers, that is, turn into neutron stars.

A star whose mass is more than twice the mass of the Sun, losing its balance and beginning to contract, will either turn into a neutron star or will not be able to achieve a stable state at all. In the process of unlimited compression, it is likely capable of turning into a black hole.

White dwarfs

White dwarfs are unusual, very small, dense stars with high surface temperatures. The main distinguishing feature of the internal structure of white dwarfs is their gigantic density compared to normal stars. Due to the enormous density, the gas in the interior of white dwarfs is in an unusual state - degenerate. The properties of such a degenerate gas are not at all similar to the properties of ordinary gases. Its pressure, for example, is practically independent of temperature. The stability of the white dwarf is maintained by the fact that the enormous gravitational force compressing it is opposed by the pressure of the degenerate gas in its depths.

White dwarfs are at the final stage of evolution of stars of not very large masses. There are no nuclear sources in the star anymore, and it still shines for a very long time, slowly cooling. White dwarfs are stable unless their mass exceeds about 1.4 solar masses.

Neutron stars

Neutron stars are very small, super-dense celestial bodies. Their diameter on average is no more than several tens of kilometers. Neutron stars are formed after the exhaustion of sources of thermonuclear energy in the bowels of an ordinary star, if its mass at that moment exceeds 1.4 solar masses. Since there is no source of thermonuclear energy, stable equilibrium of the star becomes impossible and a catastrophic compression of the star towards the center begins - gravitational collapse. If the initial mass of the star does not exceed a certain critical value, then the collapse in the central parts stops and a hot neutron star is formed. The collapse process takes a fraction of a second. It can be followed either by the leakage of the remaining star shell onto a hot neutron star with the emission of neutrinos, or by the release of the shell due to the thermonuclear energy of “unburnt” matter or rotational energy. Such an ejection occurs very quickly and from Earth it looks like a supernova explosion. Observed neutron star pulsars are often associated with supernova remnants. If the mass of a neutron star exceeds 3-5 solar masses, its equilibrium will become impossible, and such a star will be a black hole. Very important characteristics of neutron stars are rotation and magnetic field. The magnetic field can be billions to trillions of times stronger than the Earth's magnetic field.

Pulsars

Pulsars are sources of electromagnetic radiation that varies strictly periodically: from fractions of a second to several minutes. The first pulsars were discovered in 1968. as weak sources of pulsed radio emission. Later, periodic sources of X-ray radiation were discovered - the so-called X-ray pulsars, the properties of the radiation of which differ significantly from the properties of radio pulsars.

The nature of pulsars has not yet been fully revealed. Scientists believe that pulsars are rotating neutron stars with a strong magnetic field. Due to the magnetic field, the pulsar's radiation is like a searchlight beam. When, due to the rotation of a neutron star, a beam hits the antenna of a radio telescope, we see bursts of radiation. The “failures” of periods observed in some pulsars confirm predictions about the presence of a solid crust and a superfluid core in neutron stars (“failures” of the period occur when the solid crust is broken - “starquakes”).

Most pulsars are formed from supernova explosions. This has been proven, at least for the pulsar in the center of the Crab Nebula, which also exhibits impulsive emission in the optical range.

Black holes

Some of the most interesting and mysterious objects in the Universe are black holes. Scientists have determined that black holes must arise as a result of very strong compression of some mass, in which the gravitational field increases so strongly that it does not release any light or any other radiation, signals or bodies.

In order to overcome gravity and escape from a black hole, a second escape velocity, greater than light speed, would be required. According to the theory of relativity, no body can reach a speed greater than the speed of light. That is why nothing can fly out of a black hole, no information can come out. After any bodies, any substance or radiation fall under the influence of gravity into a black hole, the observer will never know what happened to them in the future. Near black holes, according to scientists, the properties of space and time should change dramatically.

Scientists believe that black holes can arise at the end of the evolution of sufficiently massive stars.

The effects that arise most strongly when surrounding matter falls into the field of a black hole appear when the black hole is part of a binary star system, in which one star is a bright giant, and the second component is a black hole. In this case, gas from the shell of the giant star flows towards the black hole and swirls around it, forming a disk. The layers of gas in the disk rub against each other, slowly approach the black hole in spiral orbits and eventually fall into it. But even before this fall, at the boundary of the black hole, the gas is heated by friction to a temperature of millions of degrees and emits in the X-ray range. Using this radiation, astronomers are trying to detect black holes in binary star systems.

It is possible that very massive black holes arise in the centers of compact star clusters, in the centers of galaxies and quasars.

It is also possible that black holes could have arisen in the distant past, at the very beginning of the expansion of the Universe. In this case, the formation of very small black holes with a mass much less than the mass of celestial bodies is possible.

This conclusion is especially interesting because near such small black holes, the gravitational field can cause specific quantum processes of “birth” of particles from the vacuum. Using the stream of these nascent particles, small black holes in the Universe can be detected.

Quantum processes of particle creation lead to a slow decrease in the mass of black holes, to their “evaporation.”

Bibliography

Astrophysics, ed. Dagaeva M.M. and Charugina V.M.

Vorontsov-Velyaminov B.A. Essays about the Universe. M.: 1980

Meyer M.V. Universe. S.-P.: 1909

Textbook on astronomy for 11th grade. M.: 1994

Frolov V.P. Introduction to black hole physics.

Encyclopedic Dictionary of a Young Astronomer.

13.04.2014

Stars have been fascinating subjects of study throughout history. From the ancient Greeks to our modern astronomers, people are constantly looking for new stars, other planets and galaxies. AND interesting facts about stars always intrigue us. The universe is constantly expanding and also changing, so every time an astronomer looks through a telescope, he can see something that wasn't there the day before! And in this place, so full of wonder and so much unknown, there are tons of facts about the stars. We would like to present you our top 10 the most interesting facts about stars.

No. 10. Red dwarfs:

The most common stars in the universe are red dwarfs. This is largely due to their low mass, which allows them to live for a very long time before becoming white dwarfs.

No. 9. Chemical composition of stars:

Almost all the stars in the universe have the same chemical composition and the nuclear fusion reaction occurs in each star and is almost identical, determined only by the amount of fuel.

No. 8. Neutron stars:

As we know, like a white dwarf, neutron stars are one of the final processes of stellar evolution, largely arising after a supernova explosion. Previously, it was often difficult to distinguish a white dwarf from a neutron star, but now scientists are using
telescopes found differences in them. A neutron star gathers more light around itself and this is easy to see with infrared telescopes. Eighth place among interesting facts about stars.

No. 7. Black hole:

Due to its incredible mass, according to Einstein's general theory of relativity, a black hole is actually a bend in space such that everything within its gravitational field is pushed towards it. The gravitational field of a black hole is so strong that not even light can escape it.

No. 6. Massive star:

As far as we know, when a star runs out of fuel, the star can grow in size by more than 1000 times, then it turns into a white dwarf, and due to the speed of the reaction, it explodes. This reaction is better known as a supernova. Scientists suggest that due to this long process, such mysterious black holes are formed.

No. 5. Confluence of stars in the sky:

Many of the stars we see in the night sky can appear as just one glimpse of light. However, this is not always the case. Most of the stars we see in the sky are actually two star systems, or binary star systems. They are simply unimaginably far away and it seems to us that we see only one speck of light.

No. 4. Lifespan of stars:

The stars that have the shortest lifespans are the most massive. They are a high mass of chemicals and tend to burn their fuel much faster.

No. 3. Twinkling stars:

Despite the fact that sometimes it seems to us that the Sun and stars are twinkling, in fact this is not the case. The flickering effect is only the light from the star, which at this time passes through the Earth's atmosphere but has not yet reached our eyes. Third place among the most interesting facts about stars.

No. 2. Huge distances to the stars:

The distances involved in estimating how far away a star is are unimaginably huge. Let's consider an example: The closest star to earth is approximately 4.2 light years away, and to get to it, even on our fastest ship, will take about 70,000 years.

No. 1. Temperature of stars:

The coolest known star is the brown dwarf CFBDSIR 1458+10B, which has a temperature of only about 100 °C.
The hottest known star, a blue supergiant in the Milky Way called Zeta Puppis, has a temperature of over 42,000 °C.

>Stars

All information about stars for children: description with photos and videos, interesting facts, how stars are born and die, types, white dwarf, supernova, black hole.

For children and adults, a shooting star seems like an incredibly beautiful and magical event when you can make a wish. However, real stars look like even more interesting objects in the Universe, because before us are giant balls of seething gas with high temperatures. Moreover, their death is just a new stage of life in the form of even more mysterious objects, like black holes or neutron stars. Below you will learn descriptions, characteristics and the most interesting facts about stars with photos, pictures, drawings, videos and diagrams of rotation around the center of the galaxy.

Parents or teachers At school can start explanation for children because these are not just the most common objects in the Universe, but also the main galactic building blocks. Using age, composition and distribution, one can understand the historical dynamics and evolution of a particular galaxy. Also children should know that stars are responsible for the creation and distribution of heavy elements (carbon, oxygen and nitrogen), so their characteristics resemble those of planets.

Star formation - explained for children

Important explain to the children that stars are born from dust and gas clouds, after which they are scattered across galaxies. For example, we can recall the Orion Nebula. So, deep within these clouds lies intense turbulence that creates massive knots that cause dust and gas to collapse due to their own gravity. When the entire cloud begins to collapse, the material at the very center heats up and turns into a protostar. This hot core in the center will soon become a star.

To explanation for children It became clear that computer models demonstrate an interesting thing. During the collapse process, the clouds may split into two or three droplets. This is why most stars are grouped into pairs or clusters.

But not all the material collected by the hot core becomes part of the star. It can form planets, asteroids, comets, or remain dust. In some cases, the cloud may not collapse at a sustainable rate. In 2004, amateur astronomer James McNeill noticed a small nebula that suddenly appeared near the M78 nebula in the constellation Orion. When other astronomers learned about this, they realized that its brightness was changing. Inspection by the Chandra X-ray Observatory made it clear that the magnetic field interacts with the surrounding gas, which leads to an episodic increase in brightness.

Why do stars light up?

Cartoon about the birth of stars, globular clusters and the future of the Milky Way:

Main Sequence Stars - Explained for Kids

For the little ones It is important to realize that a solar-sized star will take approximately 50 million years to go from collapse to adulthood. Our Sun will reach maturity in about 10 billion years.

Stars also feed, although they use nuclear fusion of hydrogen as food to form helium within themselves. An energy flow constantly flows from the central region, generating pressure. Children must understand that it is necessary so that the star does not collapse from the gravity of its own weight and energy.

Main sequence stars span a wide variety of brightnesses and colors. They can even be classified according to these characteristics. The smallest ones are called red dwarfs. They reach only 10% of the solar mass and release 0.01% of energy at a temperature of 3000-4000 K. Despite such miniature size, they outnumber other species and exist for tens of billions of years.

Types of stars - explanation for children

Red dwarfs Red dwarf stars include Proxima Centauri, Gliese 581 and Bernard's Star. Important explain to the children that these are the smallest main sequence stars. They don't have enough heat to fuel nuclear fusion reactions that use hydrogen. But children We must remember that this type is the most common because it has a long lifespan, which even exceeds the age of the Universe itself (13.8 billion years). The reason is the slowness of fusion and efficient circulation of hydrogen due to convective heat transfer.

Yellow dwarfs Yellow dwarfs include the Sun, Kepler-22 and Alpha Centauri A. These stars are now in their prime because they continue to actively burn hydrogen in their core. This process takes them to the next stage, in which most of the stars are. The name "yellow dwarf" is not entirely true, since most of them are, in fact, white. But, if you look through the filter of the earth's atmosphere, they appear yellow.

Blue giants These are large stars with a noticeable blue color. Although definitions may vary. The fact is that only 0.7% of stars are in this category. Not all blue supergiants are main sequence stars. The largest (O-type) burn out very quickly, causing the outer layers to begin to expand and increase in brightness. The presence of high temperature provides them with a long-lasting blue color. But as they cool, they can become red giants, supergiants or hypergiants. Blue supergiants with 30 solar masses can create enormous holes in their outer layers, revealing a hot core. They are called Wolf-Rayet stars. Most likely, they are destined to explode in a supernova before losing temperature and moving on to a later stage of development (red supergiant). The stellar remnant after the supernova will turn into a neutron star or black hole.

Giants This includes Arcturus and Aldebaran. They are located at the end of the evolutionary scale. Previously they were main sequence stars (like the Sun). If a star is less than 0.3-10 solar masses, then it will not become a red giant. The fact is that convective heat transfer will not allow you to gain sufficient density to release the heat needed for expansion. Large stars become red supergiants or hypergiants. Red giants accumulate helium, which causes the core to shrink and increase internal heating. Hydrogen merges in the outer layers, and the star grows in size and shines even brighter. Since the surface area has increased, the temperature becomes lower. Eventually, the outer layers collapse to form a planetary nebula, leaving behind a white dwarf.

Supergiants In this category children And parents Antares and Betelgeuse will be seen. NML Cygni is 1,650 times larger than the Sun and is the largest star in the Universe. Located at a distance of 5300 light years from us. These stars swell due to contraction in their cores, but most often grow into blue giants and supergiants with 10-40 solar masses. If the mass is greater, then they quickly destroy the outer layers and become Wolf-Rayet stars or supernovae. Red giants eventually destroy themselves in a supernova, leaving behind a neutron star or black hole.

The largest are supergiants. They are 100 times larger than the Sun, and their temperature heats up to 30,000K. Energy radiation also exceeds solar radiation by hundreds of thousands of times, but they live only a couple of million years. Although they were common during the early Universe, they are now a rare occurrence. There are only a few of them in our galaxy.

Stars and their fate - explanation for children

For the little ones It has probably already become clear that the larger the star, the shorter it will live. Death occurs at the moment when the entire supply of internal hydrogen is burned. Without the necessary energy, it starts the process of destruction and shines brighter. This shines off the hydrogen that is still available in the shell around the core. The hot core pushes out the outer layers, causing the object to swell and lose temperature. After which we see the red giant.

If the star was massive, then the core heats up to such critical temperatures that it begins to reproduce heavy elements (even iron). But this does not save, it only delays the inevitable. Soon it burns out, continuing to pulsate, shed its outer layers and envelop itself in a gas and dust haze. Subsequent processes already depend on the size of the kernel.

How do stars die?

Cartoon about the evolution of stars, the Main Sequence and the fate of red giants:

Medium stars are white dwarfs

For such stars (our Sun), the process of getting rid of the outer layers continues until the core is revealed. This is a dead, but still dangerous and active hot ball, which is called a white dwarf. Their sizes usually reach the size of the Earth, although they still weigh like a star. But why didn't they collapse? It's all about quantum mechanics.

The star is kept from destruction by rapidly moving electrons that create pressure. The more massive the core, the denser the white dwarf will be (smaller diameter = greater mass). Children should know that in a few billion years our Sun will also enter the white dwarf stage. It will last until it cools down. This fate is reserved for those stars that are approximately 1.4 times the solar mass. If it is greater, then the pressure will not keep the core from collapse.

A white dwarf may become a supernova - an explanation for children

If the white dwarf is located in a binary or multiple star system, it will experience more intense processes. Novas were once simply called new stars. But to be specific, these are old stars that have turned into white dwarfs. If it is located close to its “stellar comrade”, it can begin to steal hydrogen from the outer layers of the unfortunate one. Once enough hydrogen has accumulated, an explosion of nuclear fusion occurs and the white dwarf clears away the remaining material and glows brighter. This lasts several days, after which a repeat cycle of the same operations begins. If the dwarf is large, it can gain so much mass that it collapses and completely recovers as a supernova.

Supernovae bypass neutron stars or black holes

If a star reaches a mass greater than eight solar masses, it is doomed to die and become a supernova. Important explain to the children that this is not just the birth of a new star. In the previous one, the core explodes completely, which gives rise to the formation of iron. When it appears, it means that the star has given up all its energy (heavier elements will absorb it). The object no longer has the ability to support its mass, and the iron core collapses. Just a couple of seconds pass, and the core sharply decreases, increasing the temperature by a million degrees or more.

The outer layers collapse along with the core, bounce off and fly apart. A supernova is an amazing spectacle, as at this moment a colossal amount of energy is released. There is so much of it that it can eclipse the entire galaxy for weeks! On average, such outbreaks occur once every 100 years. Every year you can find 25-50 supernovae that appear, but they are located so far away that you cannot see them without a telescope.

Neutron stars - explanation for children

If the core at the center of the supernova is 1.4-3 solar masses, then the destruction lasts until electrons and protons create neutrons. This is where the formation of a neutron star begins. These are extremely dense objects with a small volume, which generates strong gravity. If it appeared in a multiple star system, it could collect gas from neighboring satellites.

In addition, they have a powerful magnetic field that can increase the speed of atomic particles around the magnetic poles, which is why strong beams of radiation are formed. The star rotates, and these rays, like a spotlight, spread in different directions. If they hit Earth regularly, we will notice pulses appearing every time the magnetic pole sweeps past the line of sight. In this case, the neutron star is called a pulsar.

Black holes - explanation for children

If the collapsing stellar core is three times the stellar mass, it is completely destroyed, creating a black hole. Parents or At school must explain for the youngest children that it is an incredibly dense object with gravity so powerful that it doesn't even let out light. Earthly instruments cannot see it, but we study its size and location due to its influence on neighboring bodies.

Novas and supernovae leave behind dust and debris that merge with dimensional dust and gas to form the building blocks for a new generation of stars.

We hope that the information about stars, their types, varieties, classification and evolution seemed useful and interesting. To help children remember interesting facts better, show them photos, pictures, drawings, videos and documentary cartoons on the website. For the most curious, we have 3D models of not only the Solar System, but also the most famous stars with galaxies, clusters and constellations. You can travel through space online, studying star maps and the surfaces of amazing objects like Alpha Centauri, Eridanus, Polaris, Arcturus or Sirius.

Space objects