What is the temperature of the red stars. Sizes, masses, stars density. Spectral classes of stars

The substance of our universe is structurally organized and forms a large variety of phenomena of various scale with very highly discharged physical properties. One of the most important such properties is the temperature. Knowing this indicator and using theoretical models, one can judge the many characteristics of a body - about its condition, structure, age.

The variation of the temperature values \u200b\u200bin various observed components of the universe is very large. So, the lowest amount of it in nature is fixed for the BMERANG nebula and is only 1 K. And what are the highest temperatures in the universe, known today, and what features of various objects testify? For a start, let's see how scientists determine the temperature of remote cosmic bodies.

Spectra and temperature

All information about distant stars, nebulae, galaxies scientists receive, exploring their radiation. By what frequency range of the spectrum accounts for a maximum of radiation, the temperature is determined as an average indicator kinetic energywhich is the body particles, because the radiation frequency is associated with a direct dependence with energy. So the highest temperature in the universe should reflect, respectively, the greatest energy.

The higher the high frequencies is characterized by a maximum of the radiation intensity, the hotter the body under study. However, the full range of radiation is distributed through a very wide range, and according to the features of the visible region ("color") you can make certain general conclusions about the temperature, for example, the stars. The final assessment is made on the basis of the study of the entire spectrum, taking into account the lanes of emissions and absorption.

Spectral classes of stars

Based on spectral features, including color, the so-called Harvard classification of stars was developed. It includes seven basic classes denoted by letters O, B, A, F, G, K, M, and several additional. Harvard classification reflects the surface temperature of stars. The sun, whose photosphere is heated to 5780 K, refers to the class of yellow g2 stars. The hottest blue stars class O, the coldest - red - belong to the class M.

Harvard classification complements the Yerkskaya, or the Classification of Morgan-Kinana-Kellman (ICR - by the names of developers), the subdivision stars on eight luminosity classes from 0 to VII, closely related to the mass of the luminaries - from hypergigants to white dwarfs. Our sun is the dwarf class V.

Applied together, as axes for which color values \u200b\u200bare postponed - temperature and absolute value - Luminativity (testifying about the mass), they made it possible to build a graph, widely known as the Herzshprung-Russell diagram, which reflects the main characteristics of stars in their relationship.

The hottest stars

The diagram shows that the hottest blue giants, supergingants and hypergigiants are the hottest. These are extremely massive, bright and short-lived stars. Thermonuclear reactions in their depths proceed very intensively, generating the monstrous luminosity and the highest temperatures. Such stars refer to classes B and O either to a special class W (differs by wide emission lines in the spectrum).

For example, this Big Mesmen. (located at the "end of the handle" of the bucket) when mass, 6 times higher than the solar, shines 700 times more powerful and has a surface temperature of about 22,000 K. Orion Zeta - Stars Alnitata - which is a massive sun of 28 times, external layers of heated up to 33,500 K. and hypergigant temperature with the highest known mass and luminosity (at least 8.7 million times more powerful than our Sun) - R136A1 in a large magtellane cloud - estimated at 53,000 K.

However, the photospheres of stars, no matter how much dispersion, they will not give us ideas about the highest temperature in the universe. In search of hot regions need to look at the bowl.

Thermonuclear heating of cosmos

In the cores of massive stars embezzlened with colossal pressure, there are really high temperatures sufficient for nucleosynthesis elements up to iron and nickel. So, the calculations for blue giants, supergigants and very rare hypergigids give for this parameter to the end of the life of the star Order of the value of 10 9 k - a billion degrees.

The structure and evolution of such objects are not yet well understood, respectively, and the models are still far from full. It is clear, however, that all the stars of large masses should have very hot kernels, to any spectral classes they belong to, for example, red superdgigants. Despite the undoubted differences in the processes occurring in the depths of stars, the key parameter that determines the temperature of the kernel is the mass.

Star residues

From the mass in general, the fate of the star depends on how she graduates his life path. Malomissive stars of the type of sun, having exhausted the supply of hydrogen, lose the external layers, after which the degenerate kernel remains from the shining, in which thermonuclear synthesis can no longer go, - White Dwarf. Outer slim layer of young white Dwarf It usually has a temperature of up to 200,000 k, and the isothermal kernel is deeper, heated to tens of millions of degrees. Further evolution of dwarf is to gradually cooled.

The giant stars are waiting for a different fate - a supernova explosion, accompanied by an increase in temperature already before values \u200b\u200bof about 10 11 K. Nucleosynthesis of heavy elements becomes possible during the explosion. One of the results of such a phenomenon is neutron Star - Very compact, superlit, with a complex structure of the remainder of the dead star. At birth, it is as hot - up to hundreds of billion degrees, but rapidly cools due to the intensive radiation of neutrino. But, as we will see further, even a newborn neutron star is not the place where the temperature is the highest in the universe.

Far exotic objects

There is a class of space objects, sufficiently remote (and therefore ancient), characterized by completely extreme temperatures. According to modern views, the quasar is the possessing a powerful accretionary disk formed by a decorated with a substance - gas or, more precisely, plasma. Actually, this is an active galactic core in the formation stage.

The speed of the plasma movement in the disk is so high that, due to friction, it is warmed up to ultrahigh temperatures. Magnetic fields Collect radiation and part of the disk substance into two polar beams - jet ejected by a quasar into space. This is an extremely high-energy process. The luminosity of the quasar on average is six orders of magnitude higher than the luminosity of the most powerful R136A1 star.

Theoretical models are allowed for quasars an effective temperature (that is, inherent in an absolutely black body emitting with the same brightness) not more than 500 billion degrees (5 × 10 11 K). However, the recent studies of the nearest quasar 3C 273 led to an unexpected result: from 2 × 10 13 to 4 × 10 13 k - tens of trillion Kelvinov. Such a value is comparable to temperatures achieved in phenomena with the highest well-known energy release - in gamma bursts. To date, it is the highest temperature in the universe that was ever registered.

Hotter all

It should be borne in mind that Kvasar 3C 273 we see as it was about 2.5 billion years ago. So, given that, the farther we look into space, the more distant epochs of the past we observe, in search of the hottest object, we have the right to look around the universe not only in space, but also in time.

If you go back to the very moment of its birth - approximately 13.77 billion years ago, it is impossible to observe, - we will find a completely exotic universe, when describing how cosmology approaches the limit of its theoretical possibilities associated with the borders of the applicability of modern physical theories.

The description of the Universe becomes possible, starting from the age corresponding to the plank time of 10 -43 seconds. The hottest object in this era is our universe itself, with a plane temperature of 1.4 × 10 32 K. and this, according to the modern model of its birth and evolution, the maximum temperature in the universe from everyone ever achieved and possible.

The spectra of stars are their passports with a description of all stellar features. Stars consist of the same chemical elements that are known on Earth, but percentage of them are dominated by light elements: hydrogen and helium.

The spectra of stars are their passports with a description of all stellar features.

According to the spectrum of the star, you can learn its luminosity, distance to the star, temperature, size, chemical composition of its atmosphere, speed of rotation around the axis, the features of the movement around the total center of gravity.

The spectral apparatus installed on the telescope lays the light of the star along the wavelengths of the spectrum. According to the spectrum you can find out which energy comes from a star on various wavelengths and evaluate it very precisely its temperature. The color and range of stars is associated with their temperature. In cold stars with a photosphere temperature of 3000 K radiation in the red spectrum region prevails. There are many lines of metals and molecules in the spectra of such stars. In hot blue stars with a temperature of over 10,000-15000 to most of the atoms of ionisovan. Fully ionized atoms do not give spectral lines, so there are few lines in the spectra of such stars.

Based on numerous snapshots of the spectra of stars obtained in the United States at the Harvard Observatory, at the beginning of the XX century. A detailed classification of stellar spectra was developed, which was based on a modern spectral classification.

IN Harvard classification Spectral types (classes) are denoted by the letters of the Latin alphabet: o, in, a, f, g, to and m. Since in the era of the development of this classification, the connection between the type of spectrum and the temperature was not yet known, then after establishing the corresponding dependence, I had to change the order of spectral classes, which originally coincided with the alphabetic location of the letters.

Main (Harvard) Spectral Star Classification

Inside the class of stars are divided into subclasses from 0 (the hottest) to 9 (the coldest). In the class of subclasses begin with O5. The sequence of spectral classes reflects the continuous drop in the temperature of the stars as it transitions to increasingly late spectral classes.

The overwhelming majority of stars belong to the sequence from about to M. This sequence is continuous: the characteristics of the stars are smoothly changed during the transition from one class to another.

The characteristic feature of the star spectra is also the presence of a huge number of absorption lines belonging to various elements. A subtle analysis of these lines allowed us to obtain particularly valuable information about the nature of the outer layers of stars. Chemical composition The outer layers of stars, from where their radiation directly comes, is characterized by a complete predominance of hydrogen. In second place is helium, and the number of other elements is quite small. Approximately every ten thousand hydrogen atoms account for a thousand helium atoms, about 10 oxygen atoms, slightly less carbon and nitrogen and only one iron atom. Impurities of the rest of the elements are completely insignificant. Without exaggeration, it can be said that the stars consist of hydrogen and helium with a small admixture of heavier elements.

A good temperature indicator of the outer stars of the star is its color. Hot stars of spectral classes o and in blue color; Stars similar to our Sun (whose spectral class G2) are represented by yellow, the stars of the spectral classes to and m - red. In astrophysics there is a carefully designed and quite objective system of colors. It is based on the comparison of the observed star values \u200b\u200bobtained through various strictly elephant light filters. The quantitative color of the stars is characterized by the difference in two values \u200b\u200bobtained through two filters, one of which passes predominantly the blue rays ("B"), and the other has a spectral sensitivity curve similar to the human eye (V "). The technique of measuring the color of the stars is so high that according to the measured b-V value You can determine the spectral class of the stars with an accuracy of the subclass. For weak stars, the color analysis is the only possibility of their spectral classification.

Harvard spectral classification is based on or absence, as well as the relative intensity of certain spectral lines. In addition to those listed in the table of the main spectral classes, for relatively cold stars there are still classes N and R (carbon molecules absorption bands C2, CN and carbon monoxide CO), class S (TIO titanium and zirconia strips), as well as for the coldest Stars - Class L (Hydride Stride CRH, Rubidia Lines, Cezia, Potassium and Sodium). For objects of subside-end type - "brown dwarfs", intermediate by weight between stars and planets, a special spectral class T (water absorption bands, methane and molecular hydrogen is recently introduced).

Spectral classes O, B, and often referred to as hot or early, classes F and G - sunny, and classes to and M - cold or late spectral classes.

Since one Harvard spectral class can correspond to the stars with the same temperature of the photosphere, but different classes of luminosity (that is, differing in orders of lights), then taking into account the luminosity was developed yerk Spectral Classification (called another ICC - on the initials of its authors, U. Morgan, F. Kinana and E. Kelman).

In accordance with this classification, the star attributes the Harvard spectral class and class of luminosity.

Distinguish the following classes of luminosity

Thus, if the Harvard classification determines the abscissa of the Herzshprung chart - Russell, then Yerkskaya is the position of the star on this diagram. An additional advantage of the Yerk classification is the possibility of the type of the spectrum of the star to estimate its luminosity and, accordingly, according to the visible value - the distance (method of spectral parallax).

The sun, being yellow dwarf, has a Jerk spectral class G2V.

Stars of the same (or relatives) luminosity classes form on the Herzshprung chart - Russell sequence (branches), for example, the branch of red giants or white dwarfs.

Herzshprung Russell diagram
(in different ideas)

The diagram was proposed by Astronoma Einar Herzshprung and Henry Russell, independently from each other in about 1910.

Using a diagram, astronomers are able to trace the life cycle of stars, from young hot protosts, through the main phases of development, up to the phase of the dying red giant. The diagram also shows the temperature and color of the stars from various stages of their life cycle.

On the Herzshprung-Russell diagram you can see a diagonal line, leading from the upper left corner to the right down. She is known as Home sequence And most stars are these stages in their development. In general, when the star temperature decreases, the star falls and the luminosity. The diagram can also see the branch that is above 100 units. luminosity. These are the red giants that are at the end of their life cycle. They can be simultaneously bright and relatively cold, as they are very big. Usually this stage lasts several million years.

Inclined dashed lines on the bottom diagram determine the size of stars in the radius of the Sun.

Stars are so far that even in the largest telescope they look only in points. How to find out the size of the star?

The moon comes to the aid of astronomers. She slowly moves against the background of the stars, overlapping the light running away from them. Although the corner size of the star is extremely small, the moon flashes it not immediately, but during several hundredths or thousandth fractions of a second. By the duration of the process of reducing the brightness of the star when coating its moon, the angular size of the star is determined. A, knowing the distance to the stars, from the corner size it is easy to get its true dimensions.

But only a small part of the stars in the sky is so successful that moon can be covered. Therefore, other methods of star sizes are usually used. The angular diameter of bright and not very distant luminaries can be directly measured by a special instrument - an optical interferometer. But in most cases, the radius of the star (R) is determined theoretically, based on the estimates of its full luminosity (L) and temperature (T):

R 2 \u003d L / (4πσT 4)

The size of the stars are very different. Stars of supergiant are found, whose radius is thousands of times more solar. On the other hand, the stars of dwarfs are known with a radius of tens of times less than the sun.

The most important characteristic of the star is the mass. The more substance gathered in the star, the higher the pressure and temperature in its center, and this determines almost all other characteristics of the star, as well as the features of her life path.

Direct mass estimates can only be made on the basis of the world of global. The mass of stars varies in much smaller limits: from about 10 28 to 10 32 kilograms. There is a connection between the mass of the star and its luminosity: the greater the mass of the star, the greater its luminosity. The luminosity is proportional to about a fourth grade mass:

The density of stars differ greatly. For example, the density of the red giant of bethelgeuse is one and a half thousand times less indoor air density (meaning the average density; in the center of the star density is much larger than on the surface). By the way, the diameter of this star is 300 times larger than the diameter of the Sun, the volume, respectively, is 27 million times greater, and the mass is only 15 times higher than the sunny. And the density of white dwarf Sirius is 30,000 times the density of water, that is, 1500 times the density of gold. 1 liter of such a substance weighs 30 tons.

1. Variety of stars. Harvard classification of star spectra.

The main method of studying stars is the study of their spectra. The special apparatus, installed on the telescope, with the help of a diffraction lattice lays the light of the star along the wavelengths in the rainbow strip of the spectrum. Astronomers receive a lot of stars information, decrypting their spectra. The star spectrum allows you to determine which energy comes from a star on different wavelengths, and it is more accurate to estimate its temperature than in color. Numerous dark lines crossing the spectral strip are associated with the absorption of light by atoms of various elements in the atmosphere of stars. Since each chemical element It has its own set of lines, the spectrum allows you to determine from which substances a star consists. The spectra of stars can be divided into several basic classes.

Back in the 70s of the XIX century, one of the Pioneers of Astrophysics Director of the Vatican Observatory A. Skits offered the first classification of stellar spectra. Later it was expanded and clarified.

In 1924, the Harvard Observatory completed the publication of the catalog of Drerer, containing a classification of over 225 thousand stars. Modern classification is a refined and augmented version of this classification, generally accepted in modern astronomy.

In the Harvard classification, seven spectral classes, designated by Latin letters O, B, A, F, G, K, M. When moving around the row left, the color of the star changes: O - blue, and - white, G - yellow, m - red . In the same direction, the temperature of the stars is reduced accordingly.

P
two branches were added to the Harvard classification of the spectra and another main classw. As a result, the classification of stellar spectra is now as follows:

In addition, each main class is divided into another ten subclass, such as O1, O2, O3, and so on. Our sun refers to class G2.

Z. rides are mainly approximately the same chemical composition: the main components are hydrogen and helium with small impurities of other substances. Therefore, the variety of spectra is explained by different temperatures of stars.

The hottest stars are the stars of the class W. The temperature of their surface reaches 100,000 K. Their color is blue. Blue also class O. Their temperature from 50000 K and below. Blue-white stars class B have a temperature of 12000 - 25000 K; White stars class A - 11000 K. Yellow stars of classes F and G and yellowish-orange class K have a temperature of about 4500 K. and, finally, the coldest stars - the red stars of class M with a temperature below 3600 K.

In 1905, the Dutch astronomer E. Herzpruung tried to compare the absolute values \u200b\u200bof the stars and their spectral classes. In 1913, the American Russell completed his work. As a result, a famous chart, named by scientists, was turned out.

As can be seen from the diagram, the spectral class of the star and its luminosity are in some dependence: the points corresponding to different stars are grouped into several clusters. These accumulations are called sequences.

The bulk of stars belongs to the main sequence. The hot star of the main sequence, the greater the luminosity it has. In addition to the main sequence, white dwarfs, giants and supergiant are also distinguished.

The diagram shows that the stars of this spectral class cannot have arbitrary luminosity, and vice versa, the stars of certain luminosity cannot have an arbitrary temperature.

Stars belong to the hot objects of the universe. It is the high temperature of our Sun made possible on Earth. But the reason for such strong heating of the stars has remained unknown people for a long time.

The rapid of the high temperature of the star lies inside it. It is understood not only the composition of the luminaries - in the literal sense, the entire rank of stars comes from the inside. - this is a hot heart of a star, in which the synthesis thermonuclear reaction occurs, the most powerful of nuclear reactions. This process is a source of energy for the whole shining - heat from the center rises outside, and then in open space.

Therefore, the temperature of the star varies greatly depending on the measurement location. For example, the temperature in the center of the nucleus of our reaches 15 million degrees Celsius - and already on the surface, in the photoosphere, the heat decreases to 5 thousand degrees.

Why is the temperature of the star so different?

Primary unification of hydrogen atoms - the first step of the nuclear synthesis process

Indeed, differences in the heating of the star kernel and its surfaces are surprised. If all the energy of the sun core will be distributed on the star evenly, the surface temperature of our luminaries will be several million degrees Celsius! No less striking differences in the temperature between stars of different spectral classes.

The thing is that the star temperature is determined by two main factors: the level of the core and the radiating surface area. Consider them in more detail.

Energy radiation nucleus

Although the kernel is raised to 15 million degrees, not all this energy is transmitted to neighboring layers. It is radiated only the heat that was obtained from thermonuclear reaction. Energy, despite its power, remains within the nucleus. Accordingly, the temperature of the upper stars of the star determines only the power of thermonuclear reactions in the kernel.

Differences here can be high-quality and quantitative. If the core is large enough, there is more hydrogen in it. This way of energy is obtained by young and mature stars of the sizes of the Sun, as well as blue giants and supergiant. Massive stars like red giants spend in nuclear "furnace" not only hydrogen, but also helium, or even carbon and oxygen.

The synthesis processes with the kernels of heavy elements gives much more energy. In the framework of the thermalide reaction of the synthesis, the energy is obtained due to the excess mass of the connecting atoms. During that occurs inside the sun, 6 hydrogen nuclei with atomic weight 1 are combined into one helium core with a mass of 4- roughly speaking, 2 unnecessary hydrogen kernels are moving into energy. And when the carbon is "burning", the kernels are faced with a mass of already 12 - respectively, the yield of energy is much more.

Square of emitting surface

However, the stars not only generate energy, but also spend it. Consequently, the more energy the star gives, the less its temperature. And the amount of energy given priority determines the area of \u200b\u200bthe emitted surface.

The truth of this rule can be checked even in everyday life - the underwear will dry faster if it is welded in the rope. And the star surface expands its core. What it is denser, the higher its temperature - and when it is reached with a specific bar, hydrogen is lit outside the stelod.