The types of stars that exist in the universe

In this article, we will try to address certain star types and basic structures that we can see in the universe.

After a star is born, there is a time period in his life where he experiences a “healthy process”. Astronomers describe this balanced and healthy life part of the stars as the "main phase". In this process, the star produces energy by converting the hydrogen, which forms the majority of the very dense substance in its core, to helium.
When the mainstream stars are classified according to their masses (we take the Sun's mass as "1"), from the heaviest to the lightest; They are symbolized by the letters O, B, A, F, G, K and M. These letters symbolize the mass of the main star and also the type of spectrum.

Depending on the mass of the star at the time of birth, although the duration of the mainstream phase varies, our star, whose youth days eventually end, begins to change and enter a process in which it will evolve into different species.

The general rule is that; The smaller the star's mass (you can think of it by weight, if not the same thing), the longer it lives. Now, let's take a look at the main types of stars one by one:
In this noisy telescope, the bluish glow of a star of the O-B spectral type and the orangeish glow of a K-M spectral star can be seen. This color determines the spectral type of the star.

1- Red Dwarf Stars Like Proxima Centauri (Class M Class)
The time spent in the main phase of the M spectral class red dwarf stars with a mass between 7.5% and 60% of the Sun; Their mass varies from 70 billion years to several trillion years. The ones with the highest mass die at the end of their lives, turning into a white dwarf. The lower mass M-type dwarfs will slowly fade away into a black dwarf.

In the 13.8 billion-year-old universe, no red dwarf star has ever died from the mainstream phase and turned into a black dwarf.

Red dwarf stars are the most numerous in the universe and make up 80 percent of all stars.

2- Orange Stars Similar to Epsilon Eridani (Class K Class)
K-class orange dwarf stars with a mass of 60% to 85% of the Sun spend 20-60 billion years in the main phase, based on their mass. At the end of this period, they first turn into a red giant star, then a planetary nebula, turning into a white dwarf and die.

Throughout the universe's 13.8 billion years of age, no K-class main star has yet to age and die to turn into a red camel.

Orange dwarf stars make up about 8 percent of all stars in the universe.

3- Sun-Like Yellow Stars (G Spectrum)
G-spectral yellow stars with a mass between 85% of the Sun's mass and 1.1 times the mass remain in the main phase between 8 and 13-15 billion years, depending on their mass. Then the red camel turns. Eventually their life ends by forming a planetary nebula and evolving into the white dwarf.

Almost half of the Sun-like stars that have been formed since the universe existed have either turned into a red camel at the moment, or died in the past by turning into a white dwarf.

Class G stars make up about 3.5 percent of the stars in the universe.

4- Sirius-like White Stars (Class A and F)
The main phase of A and F spectral stars with a mass between 1.5 and 2.5 of the Sun covers a period of approximately 300 million to four billion years, depending on the change in mass. At the end of this period, the star turns into a red camel. Then he dies first by becoming a planetary nebula and eventually into a white dwarf. With the red giant stars that exist today, the vast majority of white dwarfs are the result of the aging and death of type A and F stars.

0.7 percent of the stars in the universe phase that exist today in the universe are A-type and 2 percent are F-type stars.

5- Blue-White Giant Stars Similar to Eta Carinae (O and B Spectrum Class)
For giant stars of type O and B, which have a mass of 3.5 to 120 times the Sun, the main phase is between 1 and 150 million years depending on the change in mass. At the end of this period, the star quickly turns into a red camel, followed by a supernova explosion - the neutron star or black hole. On the other hand, those with lower mass form a planetary nebula after the red giant phase and die as a white dwarf.

These stars are the least number of stars in the universe, and only 0.1 percent of all stars are B, 0.00001 percent are O-typhoid.

6- Red Giant Stars Similar to Betelgeuse
When the hydrogen in the core of the aging star reaches the end of the main sequence, the radiation pressure that counteracts gravity, which forces the star to collapse since the day it was born, decreases and the hydrostatic balance of the star is disturbed.

Due to this impaired balance, the gravitational force becomes dominant, and the substance that forms the star begins to squeeze in under its own weight.
As the star collapses, the pressure and heat increase in the compressed core region. When the heat created by pressure and compression reaches 100 million degrees Celsius in the core, Helium atoms accumulated in the core begin to combine to form carbon atoms.

At the same time, all hydrogen, which remained around the nucleus but whose reaction stopped, also reacted. This sudden and enormous energy that emerges prevents the star from collapsing, but it also causes something else: The star begins to expand. We call these expanding stars the "red giant."

A typical red giant star can reach 100 to several thousand times its diameter in the mainstream phase, relative to its starting mass.

7- Dead Stars
The main types of stars that we count in this article are seen in the processes that “the stars still generate energy and continue to shine”. Neutron star and White Dwarf stars are now dead, dead stars, and it is not right to classify them under the name of star types. We recommend that you read our "Death of the Stars" article series to learn about them.

In addition, celestial bodies called "Brown Dwarf" are not stars. However, they are sometimes described as stars in a way that causes misunderstanding. For information on brown dwarfs, you should check out this article.
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