In ancient times, people thought that the stars were the souls of people, living ones, or nails that held up the sky. They came up with many explanations for why the stars glow at night, and the Sun was for a long time considered an object completely different from the stars.
The problem of thermal reactions occurring in stars in general and on the Sun, the closest star to us, in particular, has long worried scientists in many areas of science. Physicists, chemists, and astronomers tried to figure out what leads to the release of thermal energy, accompanied by powerful radiation.
Chemists believed that exothermic chemical reactions occur in stars, resulting in the release of large amounts of heat. Physicists did not agree that reactions between substances occur in these cosmic objects, since no reactions could produce so much light for billions of years.
When Mendeleev wrote his famous table, a new era in the study of chemical reactions began - radioactive elements were found and soon it was the radioactive decay reactions that were the main cause of radiation from stars.
The debate stopped for a while, as almost all scientists recognized this theory as the most suitable.
Modern theory about stellar radiation
In 1903, the already established idea of why stars shine and emit heat was overturned by the Swedish scientist Svante Arrhenius, who developed the theory of electrolytic dissociation. According to his theory, the source of energy in stars is hydrogen atoms, which combine with each other and form heavier helium nuclei. These processes are caused by strong gas pressure, high density and temperature (about fifteen million degrees Celsius) and occur in the inner regions of the star. This hypothesis began to be studied by other scientists, who came to the conclusion that such a fusion reaction is enough to release the colossal amount of energy that stars produce. It is also likely that hydrogen fusion would allow stars to shine for several billion years.
In some stars, helium synthesis has ended, but they continue to shine as long as they have enough energy.
The energy released in the interior of stars is transferred to the outer regions of the gas, to the surface of the star, from where it begins to be emitted in the form of light. Scientists believe that light rays travel from the cores of stars to the surface for many tens or even hundreds of thousands of years. After this, the radiation reaches the Earth, which also takes a lot of time. Thus, the radiation of the Sun reaches our planet in eight minutes, the light of the second closest star, Proxima Centrauri, reaches us in more than four years, and the light of many stars that can be seen with the naked eye in the sky has traveled several thousand or even millions of years.
> What are stars?
What are stars?
Each star is a huge ball of hot gases. Typically, hydrogen makes up about 90%, helium a little less than 10%, and the rest comes from admixtures of other gases. At the center of the star there must be a temperature of about 6,000,000°C for a thermonuclear reaction to occur. During a thermonuclear reaction, hydrogen is converted into helium, releasing a colossal amount of energy. This energy, breaking out, prevents the star from shrinking due to its own gravitational forces and is emitted into space in the form of light. The smallest stars are about 10 times smaller than the Sun. The largest known stars are 150 times larger than the Sun.
How can we reach the stars?
The closest star to us is Proxima from the Alpha Centauri system. The distance to it is 4.22 light years. To fly to it at the speed that is now achievable will take several thousand years. To do this, it is necessary to come up with a spaceship that would ensure the life of several generations of people. There are no technologies that would provide this yet. On the other hand, it is possible to develop a spacecraft that could fly at a speed as close as possible to the speed of light. But such a ship does not yet exist. People have long dreamed of flying to the stars. Scientists have been working on this problem for many years, but a lot of time will pass before it is finally solved.
Why do stars glow?
A star is a celestial body that is seen from Earth as a luminous point in the night sky. In general, stars are huge balls of hot gases. In their central part the temperature reaches 6,000,000°C. At this temperature, a thermonuclear reaction occurs, converting hydrogen into helium. This releases a colossal amount of energy. This energy from the center of the star breaks through to the surface and is emitted into space in the form of light. Interestingly, stars are often called the main bodies of the Universe, because they contain the bulk of luminous matter in nature.
How were stars formed?
If you look through a telescope at the starry sky, you will notice that in addition to stars, there are various types and forms of nebula that can become birthplaces of new stars. At some point in its development, any gas-dust cloud of a nebula may begin to become denser. It is compressed into a ball and heated to a high temperature. At the moment when the temperature reaches approximately 6,000,000°C, a thermonuclear reaction begins. During the reaction, hydrogen is converted into helium and a huge amount of energy is released, which breaks through to the surface and is emitted into space in the form of light. This is exactly what our Sun is now.
What types of stars are there?
Among the stars there are white and red dwarfs, novae and supernovae, and neutron stars. Scientists call them one way or another depending on their mass, composition, and characteristics of the light they emit.
In addition, astronomers divide stars into classes, which are designated by letters: O, B, A, F, G, K, M. To remember this sequence, they came up with a special formula, where the first letter of each word (in the English version) is the name of the class of stars: One Shaved Englishman Chewed Dates Like Carrots. Stars of different classes differ in color, brightness and mass.
What are neutron stars?
A large star shines for approximately 30 billion years. Then it turns into a supergiant and pulsates for another 70 billion years. When the fuel burns completely and all thermonuclear reactions that hold the outer layers of the star stop, the star turns into a neutron star. And for a long time waves of hot gas are visible around it, diverging from it in different directions. The sizes of neutron stars are small: rarely more than 20 kilometers in diameter. The density is 100 million times higher than the density of Earth. The gravity on the surface of a neutron star is about 100 billion times greater than what we have on Earth.
What is a black hole?
Black holes are astronomical objects with amazing properties. They attract everything to themselves with very great force: even the light of the stars cannot escape from their “trap”, so the holes themselves seem black to us. The peculiarity of black holes is their very large mass with fairly small sizes. Moreover, the heavier the black hole, the lower its density. So a black hole with a mass equal to the mass of the Earth would have a size of about 9 millimeters, and supermassive black holes have a density of only about 20 kg/m3 much less than the density of water. Black holes usually form from large stars where thermonuclear reactions have stopped. These stars begin to collapse until a black hole is formed.
What is a double star?
Many of the luminaries we know are multiples, that is, they consist of several stars revolving around each other. The closest multiple star to us is the triple system Alpha Centauri. It has three parts: Alpha A Centauri, Alpha B Centauri and Proxima. The brightest multiple star system is Sirius. There are two parts in it: Sirius A and Sirius B. Moreover, the latter has an unusually large mass in relation to its size. It was the first white dwarf to be discovered in the sky. Some double stars are called eclipsing variables. These are systems of two luminaries in which one periodically blocks the other. When one star eclipses the other, the brightness decreases; when both are visible, the brightness is greatest.
Each star is a huge glowing ball of gas, like our Sun. A star shines because it releases a colossal amount of energy. This energy is generated as a result of so-called thermonuclear reactions.
Each star is a huge glowing ball of gas, like our Sun. A star shines because it releases a colossal amount of energy. This energy is generated as a result of so-called thermonuclear reactions.Each star contains many chemical elements. For example, the presence of at least 60 elements has been discovered on the Sun. Among them are hydrogen, helium, iron, calcium, magnesium and others.
Why do we see the Sun so small? Yes, because it is very far from us. Why do stars look so tiny? Remember how small our huge Sun seems to us - just the size of a football. This is because it is very far from us. And the stars are much, much further away!
Stars like our Sun illuminate the Universe around them, warm the planets around them, and give life. Why do they glow only at night? No, no, during the day they also shine, you just can’t see them. In the daytime, our sun illuminates the blue atmosphere of the planet with its rays, which is why space is hidden, as if behind a curtain. At night, this curtain opens, and we see all the splendor of space - stars, galaxies, nebulae, comets and many other wonders of our Universe.
