Stars are celestial bodies that are in a constant process of modification. This phenomenon is characterized as star evolution, which consists in observing the transformations of stars during their life cycle. This sequence of changes occurs slowly and can take billions of years, so the studies are based on analyzes elaborated with computer models.
The first step in star evolution is the birth of a star. Normally, this fact occurs in a region called the stellar nursery, where there are gigantic molecular clouds formed by gas and dust. The action of gravity is responsible for the junction of gases with dust, causing the loss of the denser parts of the molecular cloud.
Later, a piece of this junction of gases and dust gains density and heat, becoming a kind of disk. After millions of years, this disk reaches a temperature and density so high that its hydrogen atoms turn into helium. This step marks the beginning of nuclear fusion and the emergence of the star.
Nuclear fusions do not cease and are responsible for the structural change of the stars. Hydrogen is the main "fuel" for the reactions in these celestial bodies, however, when it runs out, the helium starts to perform this function, causing the expansion and increase of energy inside the stars. With a very heated core, they increase in size and have a reddish luminosity, being known as the red giant.
Then, size will determine the fate of these stars. For those with a mass equal to the Sun, the end of the cycle is the transformation into a white dwarf star, made up of carbon and oxygen. For celestial bodies larger than the Sun, the end of the life cycle can have two different outcomes: the star's thermonuclear explosion can cause a black hole or neutron stars to appear.
By Wagner de Cerqueira and Francisco
Graduated in Geography
Brazil School Team
Curiosities - geography - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/geografia/evolucao-estrelar.htm
