THE STELLAR EVOLUTION
The LifeCyycle of a star begins with a Stella Nebula, where Gravity is compressing matter (gas and dust). The compression of this matter is the beginning of nuclear fusion
Nuclear fusion is where protons fuse, losing mass and creating energy in the form of light and heat. The compressed matter is referred to as a protostar (very hot and dense). Depending on the mass (how much matter was compressed) of the protostar, it will either evolve to form an average star or a massive star. When a protostar evolves into an average star the fusion of hydrogen (which creates helium) begins, in average stars it can take up to 10 billion years for the star to finish fusing hydrogen. Once the fusion of hydrogen finishes the outer layers of the star expand to become a red giant. The helium core of a red giant is now hot enough to begin fusing carbon and oxygen. A red giant can not fuse any further than this due to the helium core expanding and forcing the radiative and convective zones outward, into the cooler region of this star. When theses zones, which basically create the energy the sun needs to survive, become cooler and unstable, gravity causes the sun to contract which heats the areas of the sun where before fusion was impossible. Gravity continues to compress the star until it can not be compressed anymore. At this point the outer shells of the star seperate from the core becoming a planetary nebular (a cloud of gas and dust). Over time the gaseous she'll drifts away leaving. Very hot and dense core, , this is a white dwarf. The second path of a star is where a protostar of a larger mass, forms a massive star. In massive stars it takes only millions of years for the star to finish fusing hydrogen, compared to the 10 billion years it takes an average star. Once the fusion of hydrogen to helium has finished the outer layers of the massive star expand becoming a red super giant. The star now continues to fuse until iron. Now the star has an iron core and can no longer fuse any other elements. The core collapses and the outer layers explode, this is a supernova. From a super nova there are two paths a star can take. First is a black hole, where gravity is pulling all matter inwards. Second is a neutron star where gravity compressed the remains of the supernova into a star. This is the stellar evolution. |
The Stellar Nebular.
Protostar.
Average Star.
Red Giant.
Planetary Nebular.
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