The physical nature of the stars. Birth of a star

Space - stars and planets, galaxies and nebulae - a huge mysterious world, which people since ancient times understand. At first astrology, and then astronomy, aspired to learn the laws of life on its expanses. Today we can safely say that we know a lot, but an impressive part of the processes and phenomena has only an alleged explanation. The physical nature of stars is one of the widely discussed issues in astronomy. Today, in general, the picture is clear, but there are gaps in our knowledge of the heavenly bodies.

Countless numbers

Any star is a gas ball that constantly emits light. The forces of gravity and internal pressure prevent its destruction. The physical nature of stars is such that thermonuclear reactions constantly take place in its interior . They cease only at certain stages of the development of the luminary, as will be discussed below.

With good weather conditions and no artificial lighting in the sky, you can see up to 3000 thousand stars in each hemisphere. However, this is only a small part of the amount that fills the cosmos. The closest star to us is the Sun. Studying his behavior, scientists learn a lot about luminaries in general. The closest star outside the solar system is Proxima Centauri. It is separated from us about 4.2 light years.

Options

The science of the stars knows today enough to understand how the main characteristics affect their evolution. The most important parameters for any light are mass and composition. They determine the duration of existence, the features of the passage of different stages and all other characteristics, for example, spectrum, size, gloss. However, due to the huge distance separating us from all the stars, except the Sun, it is not always possible to obtain accurate data about them.

Weight

In modern conditions, more or less accurate data on the mass of stars can be obtained only if they are partners of a binary system. However, such calculations give a sufficiently high error - from 20 to 60%. For the remaining stars, the mass is calculated indirectly. It is derived from various known relationships (for example, mass-luminosity).

The physical nature of stars with a change in this parameter remains the same, but many processes begin to flow in a somewhat different plane. The mass directly affects the thermal and mechanical equilibrium of the entire cosmic body. The larger it is, the greater the gas pressure and temperature in the center of the star, as well as the amount of thermonuclear energy produced. To maintain the thermal equilibrium, the luminary should radiate as much as it was formed in its interior. For this, the diameter of the star changes. Similar changes continue until both types of equilibrium are established.

Chemical composition

The basis of the star is hydrogen and helium. In addition to them, the composition in a different ratio includes more heavy elements. "Full set" indicates the age and generation of the luminary, indicates some of its other properties.

The percentage of heavier elements is extremely small, but it is they that affect the rate of thermonuclear fusion. Its slowing down and acceleration is reflected in the brightness, color and longevity of the luminary. Knowing the chemical composition of the star makes it easy to determine the time of its formation.

Birth of a star

The process of formation of the stars has not been sufficiently studied. A thorough understanding of the picture is hampered by huge distances and the inability to observe directly. However, today there is a generally accepted concept that describes the birth of a star. Let's briefly dwell on it.

Apparently, the luminaries are formed from interstellar gas, compressed by the action of its own gravity. At the same time the energy of gravitation is converted into heat - the temperature of the formed globule grows. This process ends when the nucleus warms up to several million Kelvin and the formation of elements heavier than hydrogen (nucleosynthesis) is triggered. Such a star remains a fairly long time, settling on the main sequence of the Hertzsprung-Russell diagram.

Red giant

The next stage of evolution begins after the exhaustion of the entire fuel. All the hydrogen in the center of the star turns into helium and its burning continues in the outer shells of the star. The cosmic body begins to change. Its luminosity increases, the outer layers expand, while the inner layers are compressed, the brightness decreases temporarily, the surface temperature falls. The star descends from the Main sequence and becomes a red giant. In this state, the luminary spends much less time in its life than in the previous stage.

Irreversible changes

Soon (by space standards), the nucleus again begins to contract, unable to withstand its own weight. The increasing temperature thus stimulates the beginning of the synthesis of helium from heavier elements. On such a fuel, the star can also survive long enough. Further events depend on the initial parameters of the luminary. Massive stars pass through several stages, when carbon first (formed from helium) starts to act as fuel, and then silicon (formed from carbon). As a result of processing the latter, iron is formed. By this time, the final stage of the life of the star comes, when it can be transformed into neutron. However, most of the luminaries after burning out all the hydrogen in the red giant turn into white dwarfs.

Not so new

It should be noted that not every bright star that suddenly flames up in the sky is a "newborn". As a rule, this is the so-called variable - the luminary, whose brightness changes with time. The objects designated in astronomy as a "new star" also do not refer to newly appeared bodies. They are related to the cataclysmic variables, which sharply change their brightness. However, supernovae in this significantly outstrip: the amplitude of change in them can be up to 9 values. However, both these types of luminaries are a topic for individual articles.

The physical nature of stars is largely understandable today, although there is no guarantee that new data will not disprove established theories. The accepted hypotheses and ideas dominate in science only until they can explain the observed phenomena. Each new star, discovered on the expanses of the Universe, reveals the unsolved problems of astronomy. The existing understanding of cosmic processes is far from complete, there are quite large gaps in it, concerning, for example, the formation of black holes, supernovas, and so on. However, regardless of the state of the theory, the heavenly bodies continue to please us at night. In essence, a bright star will not cease to be beautiful if we fully understand its nature. Or, on the contrary, we stop all study.