تصنيف النجوم وفقا لأطيافها الضوئية .. كتاب في سبيل موسوعة علمية .. الدكتور أحمد ذكي

Classification of stars according to their optical spectra

Astronomers analyze the light arriving from a star into its spectrum, the spectrum with colors from red to violet that we mentioned, and from it they deduce everything they know about the star, as we said. From this, they saw that some stars showed lines in their spectrum indicating the presence of helium gas in abundance, while there were less abundant hydrogen lines. This is evidence that the surface of the star (the spectrum of which is this) is very hot. This is consistent with the color of the light, which tends to be bluish. Examples of this include (the man of Orion) (the left man of Gemini).

Next in the classification is the spectrum in which the adrogen lines are most apparent. This means that the surface of the star has a lower temperature than that of first-class stars. This is consistent with the less blue color of the light. Examples of this include: Sirius.

Thus, we graduate into a classification of spectra, which indicate lower temperatures on the surfaces of stars, so the color seen by the eye tends from blue to yellow. Then lines of elements and compounds begin to appear in the spectra, and with this we descend to the stars with surfaces and minimum temperatures. It is accompanied by its red color that the eye sees. An example of this is “Munkab.”
Gemini » .

They made these categories six. They returned and divided each type into smaller categories.
What is important in this is the continuity of this relationship.

This gradation in the spectrum, down from the blue color to the red color, or if you like, from the surface temperature of the large star to the small one, is gradually descending from the upper levels of absolute star brightness to the lower levels.

This uniformity includes stars close to us. Nearby
From the sun in our galaxy.

Giant stars and dwarf stars:

We mentioned the members of the spectrum class, for the stars near us,
With its luminosity, the spectrum class expresses the surface temperature of the star, and this expresses the color of the star, whether it is bluish or reddish.

This means that stars of the same type in terms of spectrum have similar or similar temperatures on their surfaces. That is, a square mile of this surface gives the same or similar amount of heat.

But there are other types of stars other than these types, the sizes of which are very large, and they are included in terms of the spectrum category in the previous categories that we mentioned, but the degree of their luminosity greatly exceeds them, and this is evidence that they have a great surface that greatly exceeds their surfaces, and therefore a large size that exceeds their sizes.

These are the giant stars, an example of which is the red giant in Orion, whose diameter is a few hundred times the diameter of the sun.

Just as there are giants, there are dwarves. White dwarfs are the smallest stars. Despite the whiteness of its brilliance, and although its surface is bluer than the sun and has a higher temperature, it is barely visible and is no larger than some of the sun’s planets. An example is the small star that accompanies the star Sirius.

(It happens that some stars that are not dangerous, but not very bright in the sky, suddenly turn, and suddenly shine with tremendous brightness, which continues to increase for a few days. The size of the star, which was dim and could hardly be seen, imposes itself on the one looking at the sky. Then it calms down. Slowly. Slowly, the star usually returns to its smallness and dimness, and this takes a period of time, months or years. And because these stars appear after they were not visible, it appears to people that a new star has been found where there was no star. That is why they called it Nova, which means new. And from The Arabs called it a supernova, and you can see in the picture the star called Nova Aquilae, how it graduated from dimness to brightness, like an explosion.)

Stars have a long life, then they are emptied of energy, they decay, and then they die:

Stars are great sources of energy and great sources of nuclear fire. Every fire must be extinguished. Then life empties. This is when all the “coal” turns into “ash” and the heavenly stoves begin to cool down.

This is how astronomers imagine what happened
And it is.

Let us give a very brief example of what some of them say. The sky is full of cosmic dust, which to our eyes appears as clouds, varying in density from a leaf, blocking from us the heavenly bodies behind them.

A star is born by beginning to condense this cosmic dust, which is... The closer its parts become, the more confused it becomes. It becomes more and more heated until its matter dissolves, that is, it becomes a gas. It gets hotter than that, and it sparkles and a light comes out of it. It is then a big red giant star.

As its content increases, and perhaps also with successive transformations that create energies, the red giant star comes close to being a star like most of the stars in the sky, entering into the six categories that we previously mentioned, and by entering them, its gigantism disappears, its redness disappears, and the life of a stable star begins. It is life whose mainstay is the production of atomic energy from hydrogen gas, which converts it into helium gas.

After a long life, the star's supply of fuel from hydrogen reaches its limit. The star reaches its maximum temperature. He begins to grow and enter the role of dwarf white stars. Those that may combine to become the size of some of the sun's planets, such as Saturn, for example.

One of the characteristics of these white dwarfs is their small luminosity, which is consistent with their small diameters and sizes. But the density of its matter had reached an enormous amount, and it combined until what would fill a box of matches weighed a few tons.

White dwarf stars are the goal at which stars end. There are stars in which there is nothing left of the atomic nuclear transformation, and they are undoubtedly diminishing.

Dwarf stars are the images that all stars end up with, and they are all their paths to the graves and death.