The life cycle of a star
(Nebula to Black Hole)
When you look at the dark sky, you can see a glimmer of light that extends from one end of the sky to the other. Our Sun is a very common star in the Milky Way galaxy. The number of such galaxies discovered in visible space under the Hubble Space Telescope (the most powerful telescope in the world) is estimated by astronomers to be at least 100 billion (2016 revised estimate of 2 trillion!). Galaxies are composed of a variety of gaseous clouds, the main constituents of which are hydrogen (60%) and helium (30%). It also contains a few other ingredients. When these gaseous clouds become much thicker at one point and form a large area of dense clouds in space, it is called a nebula. This nebula is basically the birthplace of stars.
The region of the nebula in which stars are formed is called the Molecular Cloud. These molecular clouds are basically made up of hydrogen molecules. Such a massive rotating gaseous cloud of hydrogen molecules is compressed and collapses under the influence of a gravitational ball caused by its own mass. The denser the cloud, the more the gas molecules inside it collide with each other, and the faster their velocity increases. Due to these endless collisions and the rapid growth of gas molecules, they become so hot that they no longer collide with each other, but the hydrogen molecules combine to form helium molecules in the process of nuclear fusion. The massive heat generated by this reaction is much like the explosion of a hydrogen bomb. It is because of this huge amount of heat generated that the stars continue to burn in this way. On the other hand, the pressure of the gas inside this extra heat star also increases rapidly. At one point, this pressure is able to equalize with the gravitational ball, causing the gaseous molecules to stop contracting and the star to reach an apparent equilibrium. The star remains in this state until its hydrogen molecules are completely converted into helium molecules.
In this state, the star uses its nuclear energy to generate heat for a long period of time, resisting its own gravitational force and maintaining balance for a long period of time. Eventually, at some point in the normal course, he runs out of all his hydrogen and other nuclear fuel.
Once all the hydrogen in the star's core turns into helium, the star begins to become unstable again. Helium molecules then react with each other to form heavier molecules and produce the heat needed by the star. In this way carbon, oxygen, nitrogen, and finally iron are formed gradually in the center of the star. However, since energy is required for this type of atomic reaction, the degree to which a molecular reaction is possible in the central region of a star depends on the initial mass of the star.
One thing may seem strange, but it is true that the more energy a star has, the faster it will run out of energy. This is because the larger the shape of the star, the more heat will be needed to keep it in balance by resisting the force of gravity. And the more heat it needs to produce, the faster the star will use its nuclear energy to deplete it. For example, our Sun is a medium-sized star. The amount of energy that the sun has can sustain the sun for at least another five thousand million years, but there are many more giant giant stars that could run out of energy in just one hundred million years.
If the star is normal in size (such as the Sun) after the hydrogen fuel of the center has been depleted and turned into helium, it will not be able to hold the relatively light gaseous region on the outside, causing the region to swell and expand and become a giant red giant star. Known as the "Red Giant". If our sun becomes such a red giant, its circumference will cross the earth and reach closer to Mars. Once the star turns into a red giant, it begins to produce heavier molecules, such as carbon, using its central helium molecule to produce energy. But at this stage the star does not remain in equilibrium for a long time and at one stage it is completely broken by the effect of the gravitational ball. The outer gaseous part then forms a small planet-forming nebula, and the inner part shrinks drastically to form a dwarf constellation of very small radius known as the "White Dwarf". Such a white dwarf can have a radius of only a few thousand kilometers (Earth's radius is 8,36.1 km) and a density of up to several hundred tons per cubic inch!
In the case of a star of normal mass, the white dwarf is the final result. A large number of such white dwarfs have already been discovered in space. Such a white dwarf revolves around the brightest star in the sky, Sirius. It is one of the first white dwarf stars to be discovered. According to many scientists, these white dwarfs will cool down to a point where they will no longer be able to radiate a significant amount of light, so they will turn black. This phase of the star is called the "Black Dwarf". However, the amount of time it would take for a star to reach this stage is greater than the age of our universe (approximately 13.6 billion years). So it can be assumed that no such black dwarf has been created in the universe so far.
But, if the star is very large in size and larger than a certain limit, then their result will be different. In that case, they are in the form of the Red Giant in the initial stage, "although they have become the Red Super Giant (since they are much larger in size), but their subsequent situation is dramatically different. Then under the strong pressure of the center of the star, helium will gradually produce carbon, oxygen, neon and finally heavier material iron. During this time, as a result of strong nuclear reactions inside, the star becomes brighter and brighter, and at one point explodes violently. This massive explosion is known as "Supernova". When this supernova explodes, the star becomes billions of times brighter than before. In 1052, Chinese astronomers saw such a supernova explosion. Our famous Crab Nebula was created as a result of this supernova. The brightest supernovae of the current century occurred in a star inside the IC4172 nebula. Although this nebula is made up of billions of stars, the brightness of this supernova was hundreds of times greater than that of all nebulae.
amazing !