What parameters determine the evolution of various stars. The evolution of a star begins in a giant molecular cloud, also called a stellar cradle. From the point of view of physics, a star is a ball of gas

25 nearest stars mV - visual magnitude; r is the distance to the star, pc; L is the luminosity (radiation power) of the star, expressed in units of the luminosity of the Sun (3.86–1026

Types of Stars Compared to other stars in the Universe, the Sun is a dwarf star and belongs to the category of normal stars, in the depths of which hydrogen is converted into helium. One way or another, but the types of stars roughly describe the life cycle of one separately

"LIFE WORLD" (Lebenswelt) is one of the central concepts of Husserl's late phenomenology, formulated by him as a result of overcoming the narrow horizon of a strictly phenomenological method by addressing the problems of world connections of consciousness. Such inclusion of the "global"

Life cycle of a virus Each virus enters a cell in its own unique way. Having penetrated, he must first of all take off his outer clothing in order to expose, at least partially, his nucleic acid and start copying it. The work of the virus is well organized.

Evolution of Stars of Different Masses

Astronomers cannot observe the life of one star from beginning to end, because even the shortest-lived stars exist for millions of years - longer than the life of all mankind. Change over time in physical characteristics and chemical composition stars, i.e. stellar evolution, astronomers study by comparing the characteristics of many stars at different stages of evolution.

The physical patterns connecting the observed characteristics of stars are reflected in the color-luminosity diagram - the Hertzsprung-Russell diagram, on which the stars form separate groupings - sequences: the main sequence of stars, sequences of supergiants, bright and faint giants, subgiants, subdwarfs and white dwarfs.

For most of its life, any star is on the so-called main sequence of the color-luminosity diagram. All other stages of the evolution of a star before the formation of a compact remnant take no more than 10% of this time. That is why most of the stars observed in our Galaxy are modest red dwarfs with the mass of the Sun or less. The main sequence includes about 90% of all observed stars.

The lifespan of a star and what it turns into at the end life path, is completely determined by its mass. Stars with a mass greater than the sun's mass live much less than the Sun, and the lifetime of the most massive stars is only millions of years. For the vast majority of stars, the lifetime is about 15 billion years. After the star exhausts its sources of energy, it begins to cool and shrink. The end product of the evolution of stars are compact massive objects, the density of which is many times greater than that of ordinary stars.

Stars of different masses end up in one of three states: white dwarfs, neutron stars, or black holes. If the star's mass is small, then the gravitational forces are relatively weak and the star's compression (gravitational collapse) stops. It enters the stable state of a white dwarf. If the mass exceeds a critical value, compression continues. At very high density, electrons combine with protons to form neutrons. Soon, almost the entire star consists of only neutrons and has such an enormous density that a huge stellar mass is concentrated in a very small ball with a radius of several kilometers and the compression stops - a neutron star is formed. If the mass of the star is so great that even the formation of a neutron star does not stop the gravitational collapse, then the final stage in the evolution of the star will be a black hole.

Stars, as you know, get their energy from thermonuclear fusion reactions, and sooner or later every star has a moment when thermonuclear fuel comes to an end. The higher the mass of a star, the faster it burns everything it can and goes to the final stage of its existence. Further events can go according to different scenarios, which one - first of all depends again on the mass.
At the time when the hydrogen in the center of the star “burns out”, a helium core is released in it, which contracts and releases energy. In the future, combustion reactions of helium and subsequent elements may begin in it (see below). The outer layers increase many times under the influence of increased pressure coming from the heated core, the star becomes a red giant.
Depending on the mass of the star, different reactions can take place in it. This determines what composition the star will have by the time the fusion fades.

white dwarfs

For stars with masses up to about 10 MC, the core weighs less than 1.5 MC. After the completion of thermonuclear reactions, the radiation pressure stops, and the nucleus begins to shrink under the influence of gravity. It is compressed until the pressure of the degenerate electron gas, due to the Pauli principle, begins to interfere. The outer layers are shed and dissipate, forming a planetary nebula. The first such nebula was discovered by French astronomer Charles Messier in 1764 and cataloged as M27.
What came out of the core is called a white dwarf. White dwarfs have a density greater than 10 7 g/cm 3 and a surface temperature of about 10 4 K. The luminosity is 2-4 orders of magnitude lower than that of the Sun. Thermonuclear fusion does not take place in it, all the energy emitted by it was accumulated earlier. Thus, white dwarfs slowly cool down and cease to be visible.
A white dwarf still has a chance to be active if it is part of a binary star and draws the mass of a companion onto itself (for example, the companion has become a red giant and filled its entire Roche lobe with its mass). In this case, either hydrogen synthesis can begin in the CNO cycle using the carbon contained in the white dwarf, ending with the shedding of the outer hydrogen layer (“new” star). Or the mass of a white dwarf can grow so much that its carbon-oxygen component will light up, a wave of explosive combustion coming from the center. As a result, heavy elements are formed with the release of a large amount of energy:

12 С + 16 O → 28 Si + 16.76 MeV
28 Si + 28 Si → 56 Ni + 10.92 MeV

The luminosity of the star increases strongly for 2 weeks, then rapidly decreases for another 2 weeks, after which it continues to fall by about 2 times in 50 days. The main energy (about 90%) is emitted in the form of gamma quanta from the nickel isotope decay chain. This phenomenon is called a type 1 supernova.
There are no white dwarfs with a mass of 1.5 or more solar masses. This is explained by the fact that for the existence of a white dwarf, it is necessary to balance the gravitational compression with the pressure of the electron gas, but this happens at masses no more than 1.4 M C , this limitation is called the Chandrasekhar limit. The value can be obtained as a condition of equality of pressure forces to gravitational contraction forces under the assumption that the momenta of electrons are determined by the uncertainty relation for the volume they occupy, and they move at a speed close to the speed of light.

neutron stars

In the case of more massive (> 10 M C) stars, things happen a little differently. The high temperature in the core activates energy-absorbing reactions, such as knocking out protons, neutrons and alpha particles from the nuclei, as well as e-capture of high-energy electrons that compensate for the mass difference two cores. The second reaction creates an excess of neutrons in the nucleus. Both reactions lead to its cooling and general contraction of the star. When the energy of nuclear fusion ends, the contraction turns into an almost free fall of the shell onto the contracting core. This sharply accelerates the rate of fusion in the outer falling layers, which leads to the emission of a huge amount of energy in a few minutes (comparable to the energy that light stars emit in their entire existence).
Due to the high mass, the collapsing nucleus overcomes the pressure of the electron gas and contracts further. In this case, reactions p + e - → n + ν e occur, after which there are almost no electrons that interfere with compression in the nucleus. Compression occurs to sizes of 10 − 30 km, corresponding to the density determined by the pressure of the neutron degenerate gas. The matter falling on the nucleus receives the shock wave reflected from the neutron nucleus and part of the energy released during its compression, which leads to a rapid ejection outer shell to the sides. The resulting object is called a neutron star. Most (90%) of the energy released from gravitational contraction, carry away neutrinos in the first seconds after the collapse. The above process is called a Type II supernova explosion. The energy of the explosion is such that some of them are (rarely) visible to the naked eye even in daytime. The first supernova was recorded by Chinese astronomers in 185 AD. Currently, several hundred outbreaks are recorded per year.
The resulting neutron star has a density ρ ~ 10 14 − 10 15 g/cm 3 . The conservation of angular momentum during the contraction of the star leads to very short revolution periods, usually in the range from 1 to 1000 ms. For ordinary stars, such periods are impossible, because Their gravity will not be able to counteract the centrifugal forces of such rotation. A neutron star has a very large magnetic field, reaching 10 12 -10 13 gauss at the surface, which results in strong electromagnetic radiation. A magnetic axis that does not coincide with the axis of rotation leads to the fact that a neutron star sends periodic (with a rotation period) pulses of radiation in a given direction. Such a star is called a pulsar. This fact helped their experimental discovery and is being used for discovery. It is much more difficult to detect a neutron star by optical methods due to its low luminosity. The period of revolution gradually decreases due to the transition of energy into radiation.
The outer layer of a neutron star is composed of crystalline matter, mainly iron and its neighboring elements. Most of the rest of the mass is neutrons, pions and hyperons can be in the very center. The density of the star increases towards the center and can reach values ​​much greater than the density of nuclear matter. The behavior of matter at such densities is poorly understood. There are theories about free quarks, including not only the first generation, at such extreme densities of hadronic matter. Superconducting and superfluid states of neutron matter are possible.
There are 2 mechanisms for cooling a neutron star. One of them is the emission of photons, as everywhere else. The second mechanism is neutrino. It prevails as long as the core temperature is above 10 8 K. It usually corresponds to a surface temperature above 10 6 K and lasts 10 5 −10 6 years. There are several ways to emit neutrinos:

Black holes

If the mass of the original star exceeded 30 solar masses, then the core formed in the supernova explosion will be heavier than 3 M C . With such a mass, the pressure of the neutron gas can no longer restrain gravity, and the core does not stop at the stage of a neutron star, but continues to collapse (nevertheless, experimentally discovered neutron stars have masses no more than 2 solar masses, not three). This time, nothing will prevent the collapse, and a black hole is formed. This object has a purely relativistic nature and cannot be explained without GR. Despite the fact that the matter, according to the theory, collapsed into a point - a singularity, a black hole has a non-zero radius, called the Schwarzschild radius:

R W \u003d 2GM / c 2.

The radius denotes the boundary of the gravitational field of a black hole, which is insurmountable even for photons, called the event horizon. For example, the Schwarzschild radius of the Sun is only 3 km. Outside the event horizon, a black hole's gravitational field is the same as that of an ordinary object of its mass. A black hole can only be observed by indirect effects, since it itself does not radiate any noticeable energy.
Despite the fact that nothing can leave the event horizon, a black hole can still create radiation. In the quantum physical vacuum, virtual particle-antiparticle pairs are constantly born and disappear. The strongest gravitational field of a black hole can interact with them before they disappear and absorb the antiparticle. In the event that the total energy of the virtual antiparticle was negative, the black hole loses mass, and the remaining particle becomes real and receives energy sufficient to fly away from the black hole field. This radiation is called Hawking radiation and has a blackbody spectrum. It can be assigned a certain temperature:

The influence of this process on the mass of most black holes is negligible compared to the energy they receive even from the CMB. The exception is relic microscopic black holes that could have formed on early stages evolution of the universe. Small sizes speed up the evaporation process and slow down the mass gain process. The last stages of evaporation of such black holes must end in an explosion. No explosions matching the description have ever been recorded.
Matter falling into a black hole heats up and becomes a source of x-rays, which serves as an indirect sign of the presence of a black hole. When matter falls into a black hole big moment momentum, it forms a rotating accretion disk around it, in which particles lose energy and angular momentum before falling into the black hole. In the case of a supermassive black hole, there are two preferred directions along the axis of the disk, in which the pressure of the emitted radiation and electromagnetic effects accelerate the particles that have escaped from the disk. This creates powerful jets of matter in both directions, which can also be registered. According to one theory, this is how the active nuclei of galaxies and quasars are arranged.
A spinning black hole is a more complex object. With its rotation, it “captures” a certain region of space beyond the event horizon (“Lense-Thirring effect”). This area is called the ergosphere, its boundary is called the static limit. The static limit is an ellipsoid coinciding with the event horizon at the two poles of the black hole's rotation.
Rotating black holes have an additional mechanism of energy loss through its transfer to particles that have fallen into the ergosphere. This loss of energy is accompanied by a loss of angular momentum and slows down the rotation.

Bibliography

1. S.B. Popov, M.E. Prokhorov "Astrophysics of single neutron stars: radio-quiet neutron stars and magnetars" SAI MSU, 2002
2. William J. Kaufman "The Cosmic Frontiers of Relativity" 1977
3. Other Internet sources

December 20 10 y.

Each of us at least once in our lives looked at the starry sky. Someone looked at this beauty, experiencing romantic feelings, the other tried to understand where all this beauty comes from. Life in space, unlike life on our planet, flows at a different speed. Time in outer space lives by its own categories, distances and sizes in the Universe are colossal. We rarely think about the fact that the evolution of galaxies and stars is constantly taking place before our eyes. Every object in the vast space is a consequence of certain physical processes. Galaxies, stars, and even planets have major phases of development.

Our planet and we all depend on our luminary. How long will the Sun delight us with its warmth, breathing life into the solar system? What awaits us in the future in millions and billions of years? In this regard, it is curious to learn more about what are the stages of the evolution of astronomical objects, where the stars come from and how the life of these wonderful luminaries in the night sky ends.

Origin, birth and evolution of stars

The evolution of stars and planets inhabiting our galaxy Milky Way and the entire universe, for the most part well studied. In space, the laws of physics are unshakable, which help to understand the origin of space objects. In this case, it is customary to rely on the theory of the Big Bang, which is now the dominant doctrine about the process of the origin of the Universe. The event that shook the universe and led to the formation of the universe is lightning fast by cosmic standards. For the cosmos, moments pass from the birth of a star to its death. Huge distances create the illusion of the constancy of the universe. A star that has flared up in the distance has been shining for us for billions of years, at which time it may no longer exist.

The theory of the evolution of the galaxy and stars is a development of the Big Bang theory. The doctrine of the birth of stars and the emergence of star systems differs in the scale of what is happening and the time frame, which, unlike the Universe as a whole, can be observed modern means Sciences.

Studying the life cycle of stars, you can use the example of the closest luminary to us. The sun is one of the hundreds of trillions of stars in our field of vision. In addition, the distance from the Earth to the Sun (150 million km) provides a unique opportunity to study the object without leaving the solar system. The information obtained will allow us to understand in detail how other stars are arranged, how quickly these giant heat sources are depleted, what are the stages of star development, and what will be the finale of this brilliant life - quiet and dim or sparkling, explosive.

After the Big Bang, the smallest particles formed interstellar clouds, which became the "maternity hospital" for trillions of stars. It is characteristic that all stars were born at the same time as a result of contraction and expansion. Compression in the clouds of cosmic gas arose under the influence of its own gravity and similar processes in new stars in the neighborhood. The expansion resulted from the internal pressure of the interstellar gas and from the magnetic fields inside the gas cloud. In this case, the cloud freely rotated around its center of mass.

The clouds of gas formed after the explosion are 98% composed of atomic and molecular hydrogen and helium. Only 2% of this massif is accounted for by dust and solid microscopic particles. Previously, it was believed that in the center of any star lies the core of iron, heated to a temperature of a million degrees. It was this aspect that explained the gigantic mass of the star.

In the confrontation of physical forces, compression forces prevailed, since the light resulting from the release of energy does not penetrate into the gas cloud. The light, together with part of the energy released, propagates outwards, creating a sub-zero temperature and a zone inside the dense accumulation of gas. low pressure. Being in this state, the cosmic gas is rapidly compressed, the influence of the forces of gravitational attraction leads to the fact that the particles begin to form stellar matter. When an accumulation of gas is dense, intense compression causes star clusters to form. When the size of the gas cloud is small, compression leads to the formation of a single star.

A brief description of what is happening is that the future luminary goes through two stages - fast and slow compression to the state of a protostar. Speaking simple and plain language, rapid contraction is the fall of stellar matter towards the center of the protostar. Slow contraction occurs already against the background of the formed center of the protostar. Over the next hundreds of thousands of years, the new formation shrinks in size, and its density increases millions of times. Gradually, the protostar becomes opaque due to the high density of stellar matter, and the continued compression triggers the mechanism of internal reactions. The growth of internal pressure and temperatures leads to the formation of a future star of its own center of gravity.

In this state, the protostar stays for millions of years, slowly giving off heat and gradually shrinking, decreasing in size. As a result, the contours of a new star appear, and the density of its matter becomes comparable to the density of water.

On average, the density of our star is 1.4 kg / cm3 - almost the same as the density of water in the salty Dead Sea. At the center, the Sun has a density of 100 kg/cm3. The stellar matter is not in a liquid state, but is in the form of plasma.

Under the influence of enormous pressure and temperature of approximately 100 million K, thermonuclear reactions of the hydrogen cycle begin. Compression stops, the mass of the object increases, when the energy of gravity turns into thermonuclear combustion of hydrogen. From that moment on, the new star, radiating energy, begins to lose mass.

The above version of the formation of a star is just a primitive scheme that describes First stage evolution and birth of a star. Today, such processes in our galaxy and throughout the Universe are practically imperceptible due to the intensive depletion of stellar material. In the entire conscious history of observations of our Galaxy, only single appearances of new stars have been noted. On the scale of the Universe, this figure can be increased by hundreds and thousands of times.

For most of their lives, protostars are hidden from the human eye by a shell of dust. Radiation from the nucleus can only be observed in infrared range, which is the only opportunity to see the birth of a star. For example, in the Orion Nebula in 1967, astrophysicists discovered a new star in the infrared range, the radiation temperature of which was 700 degrees Kelvin. Subsequently, it turned out that the birthplace of protostars are compact sources, which are available not only in our galaxy, but also in other corners of the Universe remote from us. In addition to infrared radiation, the birthplaces of new stars are marked by intense radio signals.

The process of studying and the scheme of the evolution of stars

The whole process of knowing the stars can be divided into several stages. At the very beginning, you should determine the distance to the star. Information about how far the star is from us, how long the light comes from it, gives an idea of ​​what happened to the star during all this time. After a person learned to measure the distance to distant stars, it became clear that the stars are the same suns, only of different sizes and with different fates. Knowing the distance to the star, the process of thermonuclear fusion of the star can be traced by the level of light and the amount of radiated energy.

After determining the distance to the star, it is possible, using spectral analysis, to calculate the chemical composition of the star and find out its structure and age. Thanks to the advent of the spectrograph, scientists had the opportunity to study the nature of the light of stars. This device can determine and measure the gas composition of stellar matter, which a star has at different stages of its existence.

Studying the spectral analysis of the energy of the Sun and other stars, scientists came to the conclusion that the evolution of stars and planets has common roots. All cosmic bodies have the same type, similar chemical composition and originated from the same matter that emerged as a result of the Big Bang.

The stellar matter is composed of the same chemical elements(up to iron), as our planet. The difference is only in the number of certain elements and in the processes taking place on the Sun and inside the earth's firmament. This is what distinguishes stars from other objects in the universe. The origin of stars should also be considered in the context of another physical discipline − quantum mechanics. According to this theory, the matter that determines the stellar substance consists of constantly dividing atoms and elementary particles that create their own microcosm. In this light, the structure, composition, structure and evolution of stars is of interest. As it turned out, the bulk of our star and many other stars account for only two elements - hydrogen and helium. A theoretical model describing the structure of a star will make it possible to understand their structure and the main difference from other space objects.

The main feature is that many objects in the Universe have a certain size and shape, while a star can change size as it develops. A hot gas is a combination of atoms that are weakly bonded to each other. Millions of years after the formation of a star, the surface layer of stellar matter begins to cool. A star gives off most of its energy into outer space, decreasing or increasing in size. The transfer of heat and energy comes from interior areas stars to the surface, affecting the intensity of the radiation. In other words, the same star in different periods its existence looks different. Thermonuclear processes based on hydrogen cycle reactions contribute to the conversion of light hydrogen atoms into heavier elements - helium and carbon. According to astrophysicists and nuclear scientists, such a thermonuclear reaction is the most efficient in terms of the amount of heat released.

Why does nuclear fusion of the nucleus not end with the explosion of such a reactor? The thing is that the forces of the gravitational field in it can keep the stellar matter within the stabilized volume. From this we can draw an unambiguous conclusion: any star is a massive body that retains its size due to the balance between the forces of gravity and the energy of thermonuclear reactions. The result of this ideal natural model is a heat source that can work for a long time. It is assumed that the first forms of life on Earth appeared 3 billion years ago. The sun in those distant times warmed our planet in the same way as it does now. Consequently, our star has not changed much, despite the fact that the scale of the radiated heat and solar energy is colossal - more than 3-4 million tons every second.

It is easy to calculate how much our star has lost in weight over the years of its existence. This will be a huge figure, but due to its huge mass and high density, such losses on the scale of the Universe look negligible.

Stages of stellar evolution

The fate of the star in depends on the initial mass of the star and its chemical composition. While the main reserves of hydrogen are concentrated in the core, the star remains in the so-called main sequence. As soon as there is a tendency to increase the size of the star, it means that the main source for thermonuclear fusion has dried up. The long final journey of the transformation of the celestial body began.

The luminaries formed in the Universe are initially divided into three most common types:

• normal stars (yellow dwarfs);
• dwarf stars;
• giant stars.

Stars with low mass (dwarfs) slowly burn their hydrogen reserves and live their lives quite calmly.

Such stars are the majority in the Universe and our star, a yellow dwarf, belongs to them. With the onset of old age, the yellow dwarf becomes a red giant or supergiant.

Based on the theory of the origin of stars, the process of formation of stars in the universe has not ended. Most bright stars in our galaxy are not only the largest, in comparison with the Sun, but also the youngest. Astrophysicists and astronomers call such stars blue supergiants. In the end, they will meet the same fate that trillions of other stars are experiencing. First, a rapid birth, a brilliant and ardent life, after which there comes a period of slow attenuation. Stars the size of the Sun have a long life cycle, being in the main sequence (in the middle of it).

Using data on the mass of the star, we can assume it evolutionary path development. A clear illustration of this theory is the evolution of our star. Nothing is permanent. As a result of thermonuclear fusion, hydrogen is converted into helium, therefore, its initial reserves are consumed and reduced. Someday, very soon, these reserves will run out. Judging by the fact that our Sun continues to shine for more than 5 billion years, without changing in size, mature age stars can still last about the same period.

The depletion of hydrogen reserves will lead to the fact that, under the influence of gravity, the core of the sun will begin to rapidly shrink. The density of the nucleus will become very high, as a result of which thermonuclear processes will move to the layers adjacent to the nucleus. Such a state is called collapse, which can be caused by the passage of thermonuclear reactions in upper layers stars. As a result high pressure thermonuclear reactions involving helium are launched.

The reserves of hydrogen and helium in this part of the star will last for millions of years. It will not be long before the depletion of hydrogen reserves will lead to an increase in the intensity of radiation, to an increase in the size of the envelope and the size of the star itself. As a consequence, our Sun will become very large. If you imagine this picture in tens of billions of years, then instead of a dazzling bright disk, a hot red disk will hang in the sky. giant size. Red giants are a natural phase in the evolution of a star, its transition state into the category of variable stars.

As a result of such a transformation, the distance from the Earth to the Sun will be reduced, so that the Earth will fall into the zone of influence of the solar corona and begin to “fry” in it. The temperature on the surface of the planet will increase tenfold, which will lead to the disappearance of the atmosphere and the evaporation of water. As a result, the planet will turn into a lifeless rocky desert.

Final stages of stellar evolution

Reaching the red giant phase normal star under the influence of gravitational processes becomes a white dwarf. If the mass of a star is approximately equal to the mass of our Sun, all the main processes in it will occur calmly, without impulses and explosive reactions. The white dwarf will die for a long time, burning to the ground.

In cases where the star initially had a mass greater than the solar mass by 1.4 times, the white dwarf will not be the final stage. With a large mass inside the star, the processes of compaction of stellar matter begin at the atomic, molecular level. Protons turn into neutrons, the density of the star increases, and its size rapidly decreases.

Neutron stars known to science have a diameter of 10-15 km. With such a small size, a neutron star has a colossal mass. One cubic centimeter of stellar matter can weigh billions of tons.

In the event that we initially dealt with a star of large mass, the final stage of evolution takes on other forms. The fate of a massive star is a black hole - an object with an unexplored nature and unpredictable behavior. The huge mass of the star contributes to an increase in gravitational forces, setting in motion the forces of compression. It is not possible to stop this process. The density of matter grows until it turns into infinity, forming a singular space (Einstein's theory of relativity). The radius of such a star will eventually become zero, becoming a black hole in outer space. There would be much more black holes if in space most of the space was occupied by massive and supermassive stars.

It should be noted that during the transformation of a red giant into a neutron star or into a black hole, the Universe can experience a unique phenomenon - the birth of a new cosmic object.

The birth of a supernova is the most impressive final stage in the evolution of stars. A natural law of nature operates here: the cessation of the existence of one body gives rise to a new life. The period of such a cycle as the birth of a supernova mainly concerns massive stars. The spent reserves of hydrogen lead to the fact that helium and carbon are included in the process of thermonuclear fusion. As a result of this reaction, the pressure rises again, and an iron core is formed in the center of the star. Under the influence of the strongest gravitational forces, the center of mass shifts to the central part of the star. The core becomes so heavy that it is unable to resist its own gravity. As a result, a rapid expansion of the core begins, leading to an instantaneous explosion. The birth of a supernova is an explosion, a shock wave of monstrous force, a bright flash in the vast expanses of the Universe.

It should be noted that our Sun is not a massive star, therefore, such a fate does not threaten it, and our planet should not be afraid of such a finale. In most cases, supernova explosions occur in distant galaxies, which is the reason for their rather rare detection.

Finally

The evolution of stars is a process that stretches over tens of billions of years. Our understanding of the ongoing processes is just a mathematical and physical model, a theory. earth time is only a moment in a huge time cycle that our Universe lives on. We can only observe what happened billions of years ago and guess what future generations of earthlings may face.

If you have any questions - leave them in the comments below the article. We or our visitors will be happy to answer them.

It is quite natural that stars are not living beings, but they also go through evolutionary stages similar to birth, life and death. Like a person, a star undergoes radical changes throughout its life. But it should be noted that they obviously live longer - millions and even billions of Earth years.

How are stars born? Initially, or rather after the Big Bang, matter in the universe was unevenly distributed. Stars began to form in nebulae, giant clouds of interstellar dust and gases, mostly hydrogen. Gravity acts on this matter, and part of the nebula is compressed. Then round and dense gas and dust clouds are formed - Bok globules. As such a globule continues to thicken, its mass increases due to the attraction of matter from the nebula towards itself. In the inner part of the globule, the gravitational force is strongest, and it begins to heat up and rotate. This is already a protostar. Hydrogen atoms begin to bombard each other and thereby produce a large number of energy. Eventually the temperature of the central part reaches a temperature of the order of fifteen million degrees Celsius, the core of a new star is formed. The newborn flares up, begins to burn and glow. How long this will continue depends on what was the mass of the born star. What I said at our last meeting. The larger the mass, the shorter the life of the star.
By the way, it depends on the mass whether a protostar can become a star. According to calculations, in order for this contracting celestial body to turn into a star, its mass must be at least 8% of the mass of the Sun. A smaller globule, condensing, will gradually cool down and turn into a transitional object, something in between a star and a planet. Such objects are called brown dwarfs.

The planet Jupiter, for example, is too small to be a star. If Jupiter were more massive, perhaps thermonuclear reactions would begin in its depths, and our solar system would be a double star system. But it's all poetry...

So, the main stage of the life of a star. For most of its existence, the star is in equilibrium. The force of gravity tends to compress the star, and the energy released as a result of thermonuclear reactions occurring in the star forces the star to expand. These two forces create a stable position of equilibrium - so stable that the star lives like this for millions and billions of years. This phase of a star's life secures its place in the main sequence. -

Shining for millions of years big star, that is, a star at least six times heavier than the Sun, begins to burn out. When the core runs out of hydrogen, the star expands and cools, turning into a red supergiant. This supergiant will then contract until it finally explodes in a monstrous and dramatic blazing explosion known as a supernova. It should be noted here that very massive blue supergiants bypass the stage of transformation into a red supergiant and explode much faster in a supernova.
If the remaining supernova core is small, then its catastrophic contraction (gravitational collapse) into a very dense neutron star begins, and if it is large enough, it will contract even more, forming a black hole.

A slightly different death for an ordinary star. Such a star lives longer and dies a more peaceful death. The sun, for example, will burn for another five billion years before the hydrogen in its core runs out. Its outer layers will then expand and cool; a red giant is formed. In this form, a star can exist for about 100 million years on the helium formed during its lifetime in its core. But helium also burns out. To top it off, the outer layers will be blown away - they form a planetary nebula, and a dense white dwarf will shrink from the core. Although the white dwarf is hot enough, eventually it will cool down, turning into a dead star, which is called a black dwarf.