What do the stars in the sky consist of? Types of stars, their characteristics

With the naked eye in the sky on a moonless night and far away from the city you can see a huge number of stars. With the help of the telescope, you can observe even more luminaries. Professional equipment allows you to determine their color and size, as well as luminosity. The question "what do the stars consist of?" For a long time in the history of astronomy remained one of the most controversial. However, it was resolved. Today, scientists know what the Sun and other stars consist of and how this parameter changes in the evolution of cosmic bodies.

Method

The astronomers learned to determine the composition of luminaries only in the middle of the XIX century. It was then that a spectral analysis appeared in the arsenal of space researchers. The method is based on the properties of atoms of different elements to emit and absorb light at strictly defined resonant frequencies. Accordingly, the spectrum shows dark and light bands located on the ground, characteristic for a given substance.

Different sources of light can be distinguished from the pattern of absorption and emission lines. Spectral analysis is successfully used to determine the composition of stars. His data help researchers understand very many processes that take place within the luminaries and are inaccessible to direct observation.

What does the star in the sky consist of?

The sun and other luminaries are huge hot gas balls. The stars consist mainly of hydrogen and helium (73 and 25%, respectively). Still about 2% of the substance falls on heavier elements: carbon, oxygen, metals and so on. In general, today's known planets and stars consist of the same material as the entire universe, but the differences in the concentration of individual substances, the mass of objects and internal processes give rise to the diversity of existing cosmic bodies.

In the case of light, the main criteria for the differences between their types are the mass and those very 2% of the elements, which are heavier than helium. The relative concentration of the latter is called metallicity in astronomy. The magnitude of this parameter helps to determine the age of the star and its future.

Internal structure

The "filling" of stars does not scatter over the Galaxy due to the forces of gravitational compression. They also contribute to the distribution of elements in the inner structure of the luminaries in a certain way. In the center, to the core, all metals are rushing (in astronomy, any element heavier than helium is called). The star is formed from a cloud of dust and gases. If only helium and hydrogen are present in it, then the first forms the core, and the second - the shell. At the moment when the mass reaches the critical level, a thermonuclear reaction begins and the star lights up.

Three generations of stars

The nuclei, consisting exclusively of helium, had first-generation luminaries (also called stars of population III). They were formed some time after the Big Bang and were characterized by impressive dimensions comparable with the parameters of modern galaxies. In the process of synthesis, other elements (metals) were gradually formed in their bowels from helium. Such stars ended their lives by exploding into a supernova. Elements synthesized in them, became a building material for the following luminaries. For stars of the second generation (population II), low metallicity is characteristic. The youngest of the luminaries known today belong to the third generation. In their number includes the Sun. The peculiarity of such luminaries is a higher metallicity index in comparison with predecessors. Younger stars were not discovered by scientists, but it can be confidently asserted that they will be characterized by an even larger size of this parameter.

The defining parameter

What the stars are made of, affects the length of their lives. Metals that descend to the core affect the thermonuclear reaction. The more of them, the earlier the star lights up and the smaller the size of its core at that. A consequence of the latter fact is the lower amount of energy radiated by such a luminary per unit time. As a result, such stars live much longer. Their fuel stock is enough for many billions of years. For example, according to scientists, the Sun is now in the middle of its life cycle. It already exists about 5 billion years and the same is still ahead.

The sun, according to theory, was formed from a gas-dust cloud saturated with metals. It refers to the stars of the third generation or, as they are also called, the population I. Metals in its core, in addition to slower combustion of fuel, provide a uniform heat release, which was one of the conditions for the birth of life on our planet.

Evolution of stars

The composition of the stars is unstable. Let's see what stars consist of at different stages of their evolution. But first, let us recall what stages the luminary passes from the moment of appearance to the completion of the life cycle.

At the beginning of the evolution, the stars are located on the main sequence of the Hertzsprung-Russell diagram. At this time, the main fuel in the core is hydrogen, of which four atoms form one helium atom. The star spends most of his life in this state. The next stage of evolution is the red giant. Its dimensions are much larger than the original, and the surface temperature, on the contrary, is lower. Stars like the Sun end their lives in the next stage - they become white dwarfs. More massive luminaries turn into neutron stars or black holes.

The first stage of evolution

Thermonuclear processes in the bowels cause the transition of the star from one stage to another. Combustion of hydrogen leads to an increase in the amount of helium, and hence, the size of the core and the reaction area. As a result, the temperature of the star increases. Hydrogen begins to react in the reaction, previously not involved in it. There is a violation of the balance between the shell and the core. As a consequence, the first begins to expand, and the second - to narrow. At the same time, the temperature rises strongly, which provokes the combustion of helium. From it are formed heavier elements: carbon and oxygen. The star descends from the main sequence and turns into a red giant.

The next part of the cycle

The red giant is an object with a heavily inflated shell. When the Sun reaches this stage, it will occupy the whole space up to the orbit of the Earth. Of course, we can not speak about life on our planet in such conditions. In the depths of the red giant, carbon and oxygen are synthesized. At the same time, the luminary regularly loses mass due to the stellar wind and constant pulsation.

Further events differ for objects with medium and large mass. The pulsations of stars of the first type lead to the fact that their outer shells are dumped and form a planetary nebula. The fuel ends in the core, it cools down and turns into a white dwarf.

Evolution of supermassive lights

Hydrogen, helium, carbon and oxygen are not all that make up stars with huge masses at the last stage of evolution. At the stage of the red giant, the nuclei of such luminaries are compressed with tremendous force. In the conditions of constantly growing temperature, burning of carbon begins, and then of its products. Oxygen, silicon, and iron are successively formed. Further, the synthesis of elements no longer goes on, since the formation of heavier nuclei from the iron with the release of energy is impossible. When the core mass reaches a certain value, it collapses. A supernova lights up in the sky. The further fate of the object again depends on its mass. On the place of the star, a neutron star or a black hole can form.

After the explosion of the supernova, the synthesized elements scatter in the surrounding space. Of these, it is quite possible, after a while, new stars will form.

Examples

A special feeling arises when it turns out not only to recognize the familiar luminaries in the sky, but also to recall to which class they belong, what they consist of. Let's see what stars the Big Dipper consists of. The asterism of the ladle includes seven luminaries. The brightest of them are Aliot and Dubha. The second star is a system of three components. In one of them the burning of helium began. The other two, like Aliot, are located on the main sequence. The same part of the Hertzsprung-Russell diagram includes Fekda and Benetasch, who also make up the bucket.

The brightest star of the night sky, Sirius, consists of two components. One of them refers to the main sequence, the second - a white dwarf. On the branch of the red giants Pollux is located (Alpha Gemini) and Arcturus (Alpha Volopas).

What kind of light does each galaxy consist of? How many stars are the Universe formed? It is rather difficult to answer exactly these questions. Several hundred billion luminaries are concentrated in the Milky Way alone. Many of them have already hit the telescope lenses and new ones are regularly found. The fact that the gases are composed of stars is also generally known to us, however, new luminaries often do not correspond to the established idea. The cosmos has many secrets and many objects and their properties are waiting for their discoverers.