A story about any star. Interesting facts about the stars

Introduction

For millennia, 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 notion that stars are points of light attached to a huge dome. However, the greatest thinkers of antiquity understood that the starry sky with the Sun and the Moon is 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 have become closer to us. We learn more and more about them. But the most ancient science of the stars, astronomy, not only has not exhausted itself, but, on the contrary, has become even more interesting.

Stellar magnitudes

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

But the magnitude scale has been preserved and updated. The brightness of a 1 m star is exactly 100 times greater than the brightness of a 6 m star. Luminaries, the brightness of which exceeds the brightness of stars 1 m, have zero and negative stellar magnitudes. The scale continues towards the stars that are invisible to the naked eye. There are stars 7 m, 8 m, and so on. For a more accurate assessment, 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 stellar magnitudes do not say anything about the luminosities (radiation power) of the stars. Therefore, the concept of "absolute magnitude" is also used. The stellar magnitudes that stars would have if they were at the same distance (10 pc) are called absolute stellar magnitudes (M).

Distance to the stars

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

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

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

Luminosity

Some stars seem brighter to us, others fainter. But this does not yet speak about the true radiation power of the stars, since they are located at different distances. Thus, the apparent magnitude in itself cannot be a characteristic of the star, since it depends on the distance. The true characteristic is luminosity, that is, the total energy that a star emits per unit of time. The luminosities of the stars are extremely diverse. One of the giant stars, S Dorado, has a luminosity of 500,000 times that of the Sun, and the luminosity of the faintest dwarf stars is about the same times less.

If the absolute stellar 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 stellar magnitude of the Sun.

Mass of stars

Another important characteristic of a star is its mass. The masses of the stars are different, but, in contrast to the luminosities and sizes, they are different within relatively narrow limits. The main method for determining the masses of stars is provided by the study of binary 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 semi-major axis of the earth's orbit.

A relationship was also found 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 the masses of single stars from the luminosity, 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. By the spectrum of a star, you can find out its luminosity (and hence the distance to it), its temperature, size, 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 whether near her another, invisible star, together with which she revolves around their common center of gravity.

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

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

Among cool red stars, besides the class M, there are two other varieties. In the spectrum of some, instead of the molecular absorption bands of titanium oxide, bands of carbon monoxide and cyanogen are characteristic (in the spectra, denoted by the letters R and N), and among others, 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 various classes are different: O and B are bluish stars, A are white, F and G are yellow, K are orange, M are red.

The above classification 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 the density of the gas in the atmosphere, surface area, and luminosity. These differences are reflected in the spectra of the stars. There is a new, two-dimensional classification of stars. According to this classification, in addition to the spectral class, each star also has a luminosity class. It is denoted by Roman numerals from I to V. I - supergiants, II-III - giants, IV - subgiants, V - dwarfs. For example, the spectral type of the star Vega looks like A0V, Betelgeuse - M2I, Sirius - A1V.

All of the above applies to normal stars. However, there are many non-standard 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 denoted by the letter “e” after the spectral type. So, there are stars Be, Ae, Me. The presence of certain emission lines in the spectrum of the star O is designated as Of. 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 of their energy in the invisible infrared region of the spectrum.

Giant and dwarf stars

Among the stars, there are giants and dwarfs. The largest among them are red giants, which, despite their weak radiation from a square meter of the surface, shine 50,000 times more powerful than the Sun. The largest giants are 2,400 times the size of 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 about twice the diameter of the Sun.

But there are many dwarf stars. They are mostly red dwarfs with a diameter of half or even one-fifth of 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 the stars. But they will be discussed later, as the final stage in the evolution of an ordinary star.

Variable stars

Variable stars are stars that change in brightness. In some variable stars, the brightness changes periodically, in others, there is an erratic brightness change. To designate variable stars, Latin letters are used with the indication of 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.

Pulsing stars have smooth brightness variations. They are caused by periodic changes in the radius and temperature of the surface. The periods of pulsating stars vary from fractions of a day (RR Lyrae stars) to tens (Cepheids) and hundreds of days (Mira - stars of the Mira Ceti type). 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, stars like I Gemini, nova-like and symbiotic stars. Eruptive stars include young fast variable stars, IV Ceti 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 taking place 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, the Cepheids. They are a very common and very important type of physical variable stars. They have the features of the star d Cepheus. Its luster is constantly changing. Changes are repeated every 5 days and 8 hours. Gloss rises faster than decreases after maximum. d Cepheus is a periodic variable star. Spectral observations show changes in radial velocities and spectral type. The color of the star also changes. This means that deep changes of a general nature are taking place in the star, the cause of which is the pulsation of the outer layers of the star. Cepheids are non-stationary stars. There is an alternate compression and expansion under the action of two opposing forces: the force of attraction to the center of the star and the force of gas pressure, pushing the substance outward. A very important characteristic of the Cepheids is the period. For each given star, it is constant with great accuracy. Cepheids are giant stars and supergiants with high luminosity.

The main thing is that there is a relationship between the luminosity and the period in Cepheids: the longer the brightness period of the Cepheid, the greater its luminosity. Thus, according to the period known from observations, it is possible to determine the luminosity or absolute magnitude, and then the distance to the Cepheid. Probably, many stars have been 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. The Cepheids also help in determining the size and shape of our Galaxy.

Another type of regular variable is the Mira, a long-period variable star named after the star Mira (about 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 from 80 to 1000 days. The change in luminosity in visual rays for different representatives of this type of stars occurs from 10 to 2500 times. However, the total radiated 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 the Cepheid ones.

As already mentioned, not all physical variable stars exhibit periodic changes. Many stars are known to be classified as semi-regular or irregular variables. In such stars, it is difficult, if not impossible, to notice regularities in the change in brightness.

Let us now consider the third class of variable stars - eclipsing variables. These are binary systems, the orbital plane of which is parallel to the line of sight. When 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 the 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. As long as there is no eclipse, the brightness of the star is practically constant. When the main star is eclipsed, the brightness decreases sharply (main minimum), and when the satellite enters the main star, the brightness decrease is insignificant (secondary minimum) or is not observed at all. From the analysis of the light curve, the radii and luminosities of the components can be calculated.

The second type of eclipsing variable stars are b Lyrae stars. Their brightness continuously and smoothly changes within about two magnitudes. Between the major lows, a shallower secondary low is bound to occur. The periods of variability are from half a day to several days. The components of these stars are massive bluish-white and white giants of spectral types B and A. Due to their significant mass and relative proximity to each other, both components are subject to strong tidal effects, as a result of which they acquired an ellipsoidal shape. In such close vapors, stellar atmospheres penetrate each other, and there is a continuous exchange of matter, part of which goes into interstellar space.

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

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

For about 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 stellar systems in which they are located and the type of their stellar population; distances to distant parts of our Galaxy, as well as to other galaxies. Modern observations have shown that some variable binaries are the source of X-rays.

Stars flowing out of gas

In the collection of stellar spectra, it is possible to trace a continuous transition from spectra with individual thin lines to spectra containing individual unusually wide bands along with dark lines and even without them.

Stars that, according to their spectral lines, could be attributed to stars of spectral class O, but have broad bright bands in the spectrum, are called Wolf-Rayet stars - after two French scientists who discovered and described them in the last century. It was only now possible to unravel the nature of these stars.

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

Such tremendous 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 and atoms of other elements, apparently unable to withstand the pressure of light from below, fly upward with great speed. The speed of their movement under the influence of light pressure is so great that the attraction of the star is unable to keep them. In a continuous stream, they break off the surface of the star and, almost not held back, rush away into world space, forming a kind of atomic rain, but directed not downward, but upward. In such a rain, all life on the planets would be burned if they were surrounded by these stars.

A continuous rain of atoms escaping from the surface of the star forms a continuous atmosphere around it, but continuously scattering into space.

How long can a Wolf-Rayet star expire in 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. Expelling gas at such a rate, the Wolf-Rayet star cannot exist longer than 10 4 -10 5 years, after which nothing will remain of it. Regardless of this, there is evidence that in reality, stars in a similar state have existed for no longer than ten thousand years, rather even much less. Probably, with a decrease in their mass to a certain value, their temperature drops, and the ejection of atoms stops. Currently, only about a hundred of such self-destructing stars are known in the entire sky. Probably only a few of the most massive stars reach such high temperatures in their development when gas loss begins. Perhaps, having thus freed itself from the 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 be also a massive and hot class O or B. Many of these stars are eclipsing binaries. Gas-streaming stars, while rare, have enriched the concept of stars in general.

New stars

Stars are called new if their brightness suddenly increases hundreds, thousands, even millions of times. Having reached the highest brightness, the new star begins to extinguish and returns to a calm state. The more powerful the outbreak of a new star, the faster its brightness decreases. In terms of the rate of decrease in brightness, new stars are classified either as “fast” or “slow”.

All new stars eject gas during a burst, which scatters at high speeds. The largest mass of gas ejected by new stars during an outburst is contained in the main envelope. This envelope is visible decades after the outburst 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, there is a flow of gas from the surface of a normal star to the surface of a white dwarf. There is a hypothesis for new outbreaks. The outbreak occurs as a result of a sharp acceleration of thermonuclear reactions of hydrogen burning 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. The flashes can be repeated. The interval between them is from 10,000 to 1,000,000 years.

The closest relatives of novae are dwarf novae. Their outbursts are thousands of times weaker than the outbreaks of new stars, but they occur thousands of times more often. In appearance, new stars and dwarf novae in a quiescent state do not differ from each other. And it is still not known what physical reasons lead to such a 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 outbreak 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 like 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 dissipates to accelerate matter: it scatters in all directions at tremendous speeds (up to 20,000 km / s). Supernova remnants are now observed as expanding nebulae with unusual properties (the Crab Nebula). Their energy is equal to the energy of a supernova explosion. After an outburst, a neutron star or pulsar remains in place of a supernova.

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

Double stars

Binary 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, quadruple stars; they are called multiple stars.

Systems in which components can be seen through a telescope are called visual binaries. But sometimes they are only randomly located in the same direction for the terrestrial observer. In space, they are separated by great distances. These are optical binaries.

Another type of binaries is made up of those stars that, when moving, alternately block each other. These are eclipsing binary 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. With the help of multicolor photoelectric photometry, binary stars can be detected that do not otherwise manifest themselves. They are photomeric binaries.

Stars with invisible satellites can also be classified as binaries.

Spectroscopic binaries are stars whose duality is revealed only by studying their spectra.

Star clusters

These are groups of stars linked by gravity and common origin. They number from several tens to hundreds of thousands of stars. Distinguish between 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. Concentrate towards the equatorial plane of the Galaxy. There are more than 1000 known clusters in our Galaxy.

Globular star clusters number hundreds of thousands of stars, have a clear 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, and there should be about 500.

Globular clusters appear to have formed from huge gas clouds early in the formation of the Galaxy, retaining their elongated orbits. The formation of open clusters began later from gas that “settled” towards the galactic plane. In the densest clouds of gas, 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 types O and B and type T. Taurus. In their characteristics, stellar associations are similar to large, very young open clusters, but differ from them, apparently, in a lesser 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 feeds the stars?

How do the stars expend such monstrous amounts of energy? Various hypotheses have been put forward at different times. So, it was believed that the energy of the Sun is supported by the fall of meteorites on it. But there should be a lot of them on the Sun, which would noticeably increase its mass. The energy of the Sun could be replenished due to its contraction. However, if the Sun were once infinitely large, then in this case, too, its compression to its present 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 for much longer.

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

The theory of nuclear reactions 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 of the hydrogen has been converted to helium, the star can still exist by converting helium into heavier elements, up to and including 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 the gas and light pressures directed from the inside tend to push it away from the center. Since the star exists as a stable body, then, therefore, there is some kind of balance between the conflicting forces. For this, the temperature of different layers in the star should be set such that in each layer the energy flow outward leads to the surface all the energy that has arisen under it. 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 the most diverse forms and states. Since the forms of existence of matter change, then, consequently, various and diverse objects could not have arisen all at the same time, but were formed in different epochs and therefore have their own definite 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 shrinking pieces. The theory of the formation of clumps of matter from which stars are formed was developed in 1902 by the English astrophysicist J. Jins. This theory also explains the origin of the Galaxies. In an initially homogeneous environment of constant temperature and density, compaction can occur. If the force of mutual gravitation in it exceeds the force of gas pressure, then the medium will contract, and if gas pressure prevails, then the substance will dissipate 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 the stars

The condensations that have arisen in the gas-dust environment of the Galaxy and continue to contract under the action of their own gravitation are called protostars. As it contracts, the density and temperature of the protostar increases, and it begins to emit abundant infrared radiation. The duration of the compression of protostars is different: with a mass less than the solar mass - hundreds of millions of years, and for massive ones - only hundreds of thousands of years. When the temperature in the interior of the protostar rises to several million Kelvin, thermonuclear reactions of the conversion of hydrogen into helium begin in them. At the same time, a huge energy is released, which prevents further compression and heats up the substance to self-luminescence - the protostar turns into an ordinary star. So, the stage of compression is replaced by a stationary stage, accompanied by a gradual “burnout” of hydrogen. In the stationary stage, a star spends most of its life. It is in this stage of evolution that the stars are located, which are located on the "spectrum-luminosity" main sequence. The time spent by a star on the main sequence is proportional to the mass of the star, since the supply of nuclear fuel depends on this, and is inversely proportional to the luminosity, which determines the rate of consumption of nuclear fuel.

When all the hydrogen in the central region has been converted to helium, a helium core will form 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 nucleus boundary. In more massive stars, the temperature of the core during compression rises above 80 million Kelvin, and thermonuclear reactions of the transformation of helium into carbon, and then into other heavier chemical elements, begin in it. The energy escaping from the core and its environs 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 is now spreading over a larger area than before. As a result, the temperature of the photosphere decreases. The star leaves the main sequence, gradually transforming into a red giant or supergiant depending on its mass, and becomes an old star. Passing the stage of a yellow supergiant, a star can turn out to be a pulsating, that is, a physical variable star, and remain so in the stage of a red giant. The swollen 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 scattering of the envelope, only the hot core of the star - a white dwarf - remains.

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

A star, the mass of which is more than twice the mass of the Sun, having lost its balance and beginning to shrink, will either turn into a neutron star, or will not be able to reach 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 that they have giant densities compared to normal stars. Due to the enormous density, the gas in the bowels of white dwarfs is in an unusual state - degenerate. The properties of such a degenerate gas are not at all similar to those of ordinary gases. Its pressure, for example, is practically independent of temperature. The stability of the white dwarf is supported by the fact that the pressure of the degenerate gas in its interior is opposed to the tremendous gravitational force that squeezes it.

White dwarfs are at the final stage of the evolution of stars of not very large masses. There are no more nuclear sources in the star, and it shines for a very long time, slowly cooling down. White dwarfs are stable if their mass does not exceed approximately 1.4 times the mass of the Sun.

Neutron stars

Neutron stars are very small, superdense celestial bodies. Their diameter is on average no more than a few tens of kilometers. Neutron stars are formed after the exhaustion of the sources of thermonuclear energy in the interior of an ordinary star, if its mass by this time exceeds 1.4 solar masses. Since there is no source of thermonuclear energy, stable equilibrium of the star becomes impossible and a catastrophic contraction 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 split second. It can be followed either by the leakage of the remaining stellar envelope onto a hot neutron star with the emission of neutrinos, or ejection of the envelope due to the thermonuclear energy of “unburned” matter or the energy of rotation. Such an ejection occurs very quickly and from the Earth it looks like a supernova explosion. Observed neutron stars - 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 and trillions of times stronger than the earth's magnetic field.

Pulsars

Pulsars are sources of electromagnetic radiation that changes 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 radiation properties of which differ significantly from the properties of radio pulsars.

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

Most pulsars are formed in 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 established that black holes must arise as a result of a very strong compression of any mass, in which the gravitational field increases so strongly that it does not release light or any other radiation, signals or bodies.

In order to overcome gravity and escape from the black hole, it would take a second cosmic speed, greater light speed. According to the theory of relativity, no body can develop 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 appear at the end of the evolution of fairly massive stars.

The effects that arise when the surrounding matter falls into the field of a black hole are most pronounced when the black hole is part of a binary stellar system, in which one star is a bright giant, and the second component is a black hole. In this case, gas from the envelope of the giant star flows to the black hole, twists around it, forming a disk. Layers of gas in the disk rub against each other, slowly approach the black hole along spiral orbits and eventually fall into it. But even before this fall, at the edge of the black hole, the gas is heated by friction to a temperature of millions of degrees and radiates in the X-ray range. From this radiation, astronomers are trying to detect black holes in binary stellar 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 induce specific quantum processes of the “creation” of particles from the vacuum. With the flow of these nascent particles, small black holes in the universe can be detected.

Quantum processes of particle production 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 on the Universe. M.: 1980

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

Astronomy textbook for grade 11. M.: 1994

Frolov V.P. Introduction to the physics of black holes.

Encyclopedic Dictionary of the Young Astronomer.

There is hardly a person who has never admired the stars, looking into the twinkling night sky. You can admire them forever, they are mysterious and attractive. In this thread, you will get acquainted with unusual facts about the stars and learn a lot of new things.

Did you know that most of the stars you view at night are double stars? Two stars circle each other, creating a point of gravity, or a smaller star orbits a large “main star”. Sometimes these major stars pull matter from the smaller ones as they approach each other. There is a limit to the mass a planet can handle without causing a nuclear reaction. If Jupiter were large, it might have turned into a brown dwarf, a kind of half-star, many moons ago.

Such processes often occur in other solar systems, as evidenced by the lack of planets in them. Most of the matter that is in the gravitational field of the main star gathers in one place, eventually forming a new star and a binary system. There may be more than two stars in one system, but still binary number systems are more widespread.

White Dwarfs, the so-called "dead stars". After a giant red phase, our own star, the Sun, will also become a white dwarf. White dwarfs have a planet's radius (like Earth, not like Jupiter), but the density of a star. Such specific gravity is possible due to electrons separating from the atomic nuclei that surround them. As a result, the amount of space that these atoms occupy increases and a large mass is created with a small radius

If you could hold the nucleus of an atom in your hand, then the electron would circle around you at a distance of 100 meters or more. In the case of electron degeneration, this space remains free. As a result, the White dwarf cools down and stops emitting light. These massive bodies cannot be seen and no one knows how many there are in the universe.

If the star is large enough to avoid the final white dwarf phase, but too small to avoid becoming a black hole, an exotic type of star known as a neutron star will be formed. The process of formation of neutron stars is somewhat similar to White dwarfs, in which they also gradually degrade - but in a different way. Neutron stars form from the degrading matter called the neutron, when all electrons and positively charged protons are eliminated and only neutrons form the base of the star. The density of a neutron star is comparable to that of the nuclei of an atom.

Neutron stars can have a mass similar to our Sun or slightly higher, but their radius is less than 50 kilometers: usually 10-20. A teaspoon of this neutron is 900 times the mass of the Great Pyramid at Giza. If you observed a neutron star directly, you would see both poles, because a neutron star works like a gravitational lens, bending light around itself due to powerful gravity. A special case of a neutron star is the pulsar. Pulsars can spin at 700 revolutions per second, emitting flashing radiation - hence their name

Eta Carinae is one of the largest stars discovered so far. It is 100 times heavier than our Sun and has approximately the same radius. Eta Carinae can shine a million times brighter than the Sun. Usually, these hypermassive stars have a very short life because they literally burn themselves up, which is why they are called Supernova. Scientists believe the limit is 120 times the mass of the Sun - no star can weigh any more.

The Pistol star is a hypergiant like Eta Carinae that has no way of cooling itself. The star is so hot that it is barely held together by its gravity.

As a result, the star Pistol emits a so-called "solar wind" (high energy particles that, for example, create the Aurora Borealis). It shines 10 billion times stronger than our Sun. Due to massive radiation levels, it is impossible to even imagine that life will ever exist in this star system.

In this thread, I have laid out the most interesting facts about the stars that I could find. I hope you were interested

For centuries, people have observed star patterns in the night sky. constellations.

When studying the starry sky, astronomers of the ancient world divided the sky into regions. Each region was divided into groups of stars called constellations.

Constellations- these are areas into which the celestial sphere is divided for the convenience of orientation in the starry sky. Translated from Latin, "constellation" means "a group of stars." They serve as great landmarks to help you find stars. One constellation can contain from 10 to 150 stars.

A total of 88 constellations are known. 47 are ancient, known for several millennia. Many of them bear the names of the heroes of ancient Greek myths, for example Hercules, Hydra, Cassiopeia and cover the region of the sky accessible to observations from the south of Europe. The 12 constellations are traditionally called zodiacal constellations. These are well-known: Sagittarius, Capricorn, Aquarius, Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Ves-sy and Scorpio. The rest of the modern constellations were introduced in the 17th and 18th centuries as a result of the study of the southern sky.

It was possible to determine your location by finding a certain constellation in the sky in one place or another in the sky. The selection of certain pictures in the mass of stars helped in the study of the starry sky. Astronomers of the ancient world divided the sky into regions. Each region was divided into groups of stars called constellations.

Constellations are imaginary figures that the stars form in the firmament. The night sky is a canvas dotted with paintings of dots. People have found pictures in the sky since ancient times.

The constellations were given names, legends and myths were formed about them. Different peoples divided the stars into constellations in different ways.

Some of the constellation stories have been extremely bizarre. Here, for example, what picture the ancient Egyptians saw in the constellation surrounding the Big Dipper Bucket. They saw a bull, a man was lying next to him, a man was dragged along the ground by a hippo, who walked on two legs and carried a crocodile on his back.

People saw in the sky what they wanted to see. Hunting tribes saw star-filled images of the wild animals they hunted. European navigators found constellations that resemble a compass. Indeed, scientists believe that the main area of ​​use of the constellations was to learn how to navigate the sea while sailing.

There is a legend that tells that the wife of the Egyptian pharaoh Berenice (Veronica) offered her luxurious hair as a gift to the goddess Venus. But the hair was stolen from the halls of Venus and ended up in the sky as a constellation. In summer, the constellation Hair of Veronica can be seen in the Northern Hemisphere below the handle of the Big Dipper Bucket.

Many constellation stories have their origins in Greek myths. Here is one of them. The goddess Juno was jealous of her husband Jupiter, the servant Callisto. To protect Callisto, Jupiter turned her into a bear. But this created a new problem. One day, Callisto's son went hunting and saw his mother. Thinking that this is an ordinary bear, he raised his bow and aimed, Jupiter intervened and, in order to prevent the murder, turned the young man into a little bear cub. This is how, according to the myth, a big bear and a little bear cub appeared in the sky. Now these constellations are called Ursa Major and Ursa Minor.

The position of the stars in relation to each other is constant, but they all revolve around a certain point. In the northern hemisphere this point corresponds Polar Star... If you point a camera on a fixed tripod at this star and wait an hour, you can make sure that each of the stars photographed has circumscribed a part of a circle.

When looking at the sky from the northern hemisphere, the Pole Star is in the center, and the Ursa Minor is above it. Ursa Major is located on the left, between the two Dippers the Dragon "squeezed". Under Ursa Minor, in the shape of an inverted M, is the constellation Cassiopeia.

In the southern hemisphere there is no central star that could serve as a reference point (axis) around which, as it seems to us, all stars revolve. Above the center is South Cross, and above him, in turn, the Centaur, as if surrounding him. The South Triangle is visible on the left, and below it is the Peacock. Even lower is the constellation Toucan.

Since the Earth revolves around the Sun in a year, its position relative to the stars is constantly changing. Each night the sky is slightly different from what it was yesterday. In the northern hemisphere in summer, the Ursa Minor is visible in the center, and above it is visible the Dragon, as if surrounding it, and below, on the right, the zigzag of Cassiopeia, above it is the constellation Cepheus, on the left is the Big Dipper.

In winter, in the northern hemisphere, another part of the sky is visible from the Earth. On the right, one of the most beautiful constellations, Orion, is discernible, and in the middle is Orion's Belt. Below you can see the small constellation of the Hare. If you draw a line down from Orion's Belt, you will notice the brightest star in the sky, Sirius, which never rises high above the horizon at our latitudes.

It seems that the stars in the constellations are close to each other, in fact, this is an illusion.

The stars of the constellations are trillions of kilometers apart. But stars farther away can be brighter and look the same as farther less bright stars. From Earth, we see the constellations flat.

Stars are like people, they are born and die. They are in constant motion. Therefore, over time, the outlines of the constellations change. A million years ago, the current Big Dipper Bucket was not like a bucket, but a long spear. Perhaps in a million years, people will have to come up with new names for the constellations, because their shape will undoubtedly change.

Perhaps, somewhere, there is a planetary system with which our Sun looks like a small star, a part of some constellation, in the outlines of which the inhabitants of a distant planet see the silhouette of their native exotic animal.

ESSAY

pupils of 4 "B" class

MBOU SOSH # 3

them. Ataman M.I. Platov

Golovacheva Lydia

Classroom teacher:

Udovitchenko

Lyudmila Nikolaevna

on the topic:

"Stars and constellations"

1. Concept-constellations, types of constellations.

2. The history of the names of the constellations.

3. Star maps.

Bibliography:

1.Universe: An Encyclopedia for Children / Per. with fr. N. Klokovoi M .: Egmont Russia LTD., 2001 /

Interesting facts about the stars, some of which you may already know, and some may be heard for the first time.

1. The sun is the closest star.

The Sun, located only 150 million km from the Earth, and by the standards of space is an average star. It is classified as a main sequence yellow dwarf G2. It has been converting hydrogen to helium for 4.5 billion years now, and will likely continue to do so for another 7 billion years. When it runs out of fuel, it will become a red giant, the bulge will increase its current size many times. When it expands, it will engulf Mercury, Venus, and possibly even Earth.

2. All luminaries are made of the same material.

Its birth begins in a cloud of cold molecular hydrogen, which begins to gravitationally contract. When a cloud collapses and fragmented, many of the pieces will form into individual stars. The material is collected in a ball, which continues to contract under the influence of its own gravity, until the temperature in the center reaches a temperature capable of igniting nuclear fusion. The original gas was formed during the Big Bang and consists of 74% hydrogen and 25% helium. Over time, they convert some of the hydrogen into helium. This is why our Sun has a composition of 70% hydrogen and 29% helium. But initially they consist of 3/4 hydrogen and 1/4 helium, with impurities of other trace elements.

3. The star is in perfect balance

Any luminary, as it were, is in constant conflict with themselves. On the one hand, the entire mass by its gravity constantly compresses it. But the hot gas exerts tremendous pressure from the center outward, pushing it away from gravitational collapse. Nuclear fusion, in the nucleus, generates a tremendous amount of energy. The photons travel from the center to the surface in about 100,000 years before escaping. As the star gets brighter, it expands and turns into a red giant. When nuclear fusion in the center stops, then nothing can restrain the growing pressure of the overlying layers and it collapses, turning into a white dwarf, a neutron star or a black hole.

4. Most of them are red dwarfs

If we were to put them all together and put them in a pile, then the largest pile would certainly be with red dwarfs. They have less than 50% of the mass of the Sun, and red dwarfs can weigh even 7.5%. Below this mass, gravitational pressure will not be able to compress the gas in the center to initiate nuclear fusion. They are called brown dwarfs. Red dwarfs emit less than 1 / 10,000 of the Sun's energy, and can burn for tens of billions of years.

5. Mass is equal to its temperature and color

The stars can vary in color from red to white or blue. Red is the coldest color with temperatures less than 3500 Kelvin. Our luminary is yellowish-white, with an average temperature of about 6000 Kelvin. The hottest are blue, with surface temperatures above 12,000 Kelvin. Thus, temperature and color are related. The mass determines the temperature. The greater the mass, the larger the core will be and the more active nuclear fusion will occur. This means more energy reaches its surface and raises its temperature. But there is an exception, these are red giants. A typical red giant can have the mass of our Sun, and be a white star throughout its life. But as it approaches the end of its life, it increases and the luminosity increases 1000 times and seems unnaturally bright. Blue giants are just big, massive, and hot luminaries.

6. Most of them are double

Many are born in pairs. These are binary stars, where two stars orbit around a common center of gravity. There are other systems with 3, 4 and even more participants. Just think what beautiful sunrises can be seen on the planet in a four-star system.

7. The size of the largest suns is equal to the orbit of Saturn

Let's talk about red giants, or more precisely, about red supergiants, against which our star looks very small. The red supergiant is Betelgeuse, in the constellation Orion. It is 20 times the mass of the Sun and at the same time 1000 times more. The largest known star is VY Canis Major. It is 1800 times larger than our Sun and would fit into the orbit of Saturn!

8.The most massive luminaries have a very short life

As mentioned above, the low mass of a red dwarf can last tens of billions of years of combustion before running out of fuel. The converse is also true for the most massive ones we know. Giant luminaries can be 150 times the mass of the Sun and emit a huge amount of energy. For example, one of the most massive stars we know of is Eta Carinae, located about 8000 light years from Earth. It emits 4 million times more energy than the Sun. While our Sun can safely burn fuel for billions of years, Eta Carinae can only shine for a few million years. And astronomers expect Eta Carinae to explode at any time. When it goes out, it will become the brightest object in the sky.

9. There are a huge number of stars

How many stars are there in the Milky Way? You may be surprised to learn that there are on the order of 200-400 billion pieces in our galaxy. Each may have planets, and on some, life is possible. There are about 500 billion galaxies in the universe, each of which may have as many or even more than the Milky Way. Multiply these two numbers together and you will see how many there are approximately.

The sun is the only star in the solar system; all the planets of the system, as well as their satellites and other objects, up to cosmic dust, move around it. If we compare the mass of the Sun with the mass of the entire solar system, then it will be about 99.866 percent.

The Sun is one of the 100,000,000,000 stars in our Galaxy and ranks fourth in size among them. The closest star to the Sun, Proxima Centauri, is located four light years from Earth. From the Sun to planet Earth 149.6 million km, light from the star reaches in eight minutes. The star is located at a distance of 26 thousand light years from the center of the Milky Way, while it rotates around it at a speed of 1 revolution in 200 million years.

Presentation: Sun

According to the spectral classification, the star belongs to the type "yellow dwarf", according to rough estimates, its age is just over 4.5 billion years, it is in the middle of its life cycle.

The sun, which is 92% hydrogen and 7% helium, has a very complex structure. In its center is a core with a radius of approximately 150,000-175,000 km, which is up to 25% of the total radius of the star, in its center the temperature approaches 14,000,000 K.

The nucleus rotates around the axis at a high speed, and this speed is significantly higher than the indicators of the outer shells of the star. Here the reaction of the formation of helium from four protons takes place, as a result of which a large amount of energy is obtained, passing through all layers and emitted from the photosphere in the form of kinetic energy and light. Above the core there is a zone of radiant transfer, where temperatures are in the range of 2-7 million K. Then there is a convective zone about 200,000 km thick, where there is no longer re-radiation for energy transfer, but mixing of the plasma. On the surface of the layer, the temperature is approximately 5800 K.

The atmosphere of the Sun consists of the photosphere, which forms the visible surface of the star, the chromosphere about 2000 km thick and the corona, the last outer solar shell, the temperature of which is in the range of 1,000,000-20,000,000 K. Ionized particles, called the solar wind, emerge from the outer part of the corona. ...

When the Sun reaches an age of about 7.5 - 8 billion years (that is, after 4-5 billion years), the star will turn into a "red giant", its outer shells will expand and reach the Earth's orbit, possibly pushing the planet further away.

Under the influence of high temperatures, life in today's understanding will become simply impossible. The Sun will spend the final cycle of its life in the state of a "white dwarf".

The sun is the source of life on Earth

The sun is the most important source of heat and energy, thanks to which, with the assistance of other favorable factors, there is life on Earth. Our planet Earth rotates on its axis, so every day, being on the sunny side of the planet, we can watch the sunrise and the amazingly beautiful sunset phenomenon, and at night, when part of the planet falls into the shadow side, we can watch the stars in the night sky.

The sun has a huge impact on the life of the Earth, it participates in photosynthesis, helps in the formation of vitamin D in the human body. The solar wind causes geomagnetic storms and it is its penetration into the layers of the earth's atmosphere that causes such a beautiful natural phenomenon as the northern lights, also called polar lights. Solar activity changes in the direction of decrease or increase approximately once every 11 years.

Since the beginning of the space age, researchers have been interested in the sun. For professional observation, special telescopes with two mirrors are used, international programs have been developed, but the most accurate data can be obtained outside the layers of the Earth's atmosphere, therefore, most often research is carried out from satellites, spacecraft. The first such studies were carried out back in 1957 in several spectral ranges.

Today, satellites are launched into orbits, which are miniature observatories, which provide very interesting materials for studying the star. Even in the years of the first space exploration by man, several spacecraft aimed at studying the Sun were developed and launched. The first of these was a series of American satellites, launched in 1962. In 1976, the West German spacecraft Helios-2 was launched, which for the first time in history approached the star at a minimum distance of 0.29 AU. At the same time, the appearance of light helium nuclei during solar flares was recorded, as well as magnetic shock waves covering the range of 100 Hz-2.2 kHz.

Another interesting device is the Ulysses solar probe, launched in 1990. It is launched into a near-solar orbit and moves perpendicular to the strip of the ecliptic. Eight years after launch, the device completed its first orbit around the Sun. He registered the spiral form of the magnetic field of the luminary, as well as its constant increase.

In 2018, NASA plans to launch the Solar Probe +, which will approach the Sun as close as possible - 6 million km (this is 7 times less than the distance reached by Gelius-2) and will occupy a circular orbit. It is equipped with a carbon fiber shield to protect it from the highest temperatures.