From the point of view of science, we do not have an answer to the question of how the universe was born. There are many different scientific theories about this, but there is no answer to the question yet. Be that as it may, we consider these theories, trying to explain the history of the life of a star.

A star is a celestial body that emits its own light. The planets, as you know, shine only by reflected light. The planets shine evenly and the stars twinkle. This flickering is due to the fluctuations in the air between the Earth and the stars. The unstable air deflects the beam of light from the star, making it appear to tremble.

Stars vary greatly in size, density, and temperature. On the one hand, we have stars that are called "red supergiants", which are many times larger than our Sun (and it is also a star). On the other hand, there are stars called "white dwarfs", some of which are approximately the size of our planet. Supergiants have a density that is 1,000 times thinner than the air we breathe. White dwarfs are hundreds of thousands of times denser.

One theory says that in the life history of a star, it goes through both of these phases. Stars were formed, according to this theory, from clouds of cosmic dust. The cloud is compressed because the particles are attracted to each other. Gradually, this substance becomes gaseous, begins to glow, and a red supergiant appears.

Further, the compression continues, and the star approaches in size and temperature to our Sun. It remains in this state of "average star" for many billions of years, constantly radiating energy. Energy is released when hydrogen is converted into heavier elements.

When the supply of hydrogen is almost running out, the star collapses. Explosions occur, and the star finally becomes a dense white dwarf. Over time, when the energy reserves are exhausted, the star begins to lose its brightness and eventually ceases to shine.

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