The former unity fractured into evolutionists, who believed life as we see it today developed from smaller and more primitive organisms, and creationists, who kept believing life in all its diversity was created by a higher entity. Each side introduced substantial arguments to support their claims, but at the same time, the counter-arguments of each opponent were also credible. Therefore, the debates between the evolutionists and the creationists seem to be far from ending.
On human timescales, most stars do not appear to change at all, but if we were to look for billions of years, we would see how stars are born, how they age, and finally how they die. The primary factor determining how a star evolves is its mass as it reaches the main sequence.
The following is a brief outline tracing the evolution of a low-mass and a high-mass star. The life of a star Stars are born out of the gravitational collapse of cool, dense molecular clouds.
As the cloud collapses, it fragments into smaller regions, which themselves contract to form stellar cores. These protostars rotate faster and increase in temperature as they condense, and are surrounded by a protoplanetary disk out of which planets may later form. The central temperature of the contracting protostar increases to the point where nuclear reactions begin.
At this point, hydrogen is converted into helium in the core and the star is born onto the main sequence. Once the hydrogen in the core has all been burned to helium, energy generation stops and the core begins to contract. This raises the internal temperature of the star and ignites a shell of hydrogen burning around the inert core.
Meanwhile, the helium core continues to contract and increase in temperature, which leads to an increased energy generation rate in the hydrogen shell. This causes the star to expand enormously and increase in luminosity — the star becomes a red giant.
Eventually, the core reaches temperatures high enough to burn helium into carbon. If the mass of the star is less than about 2. If the star is more massive than this, the ignition of the core is more gentle.
At the same time, the star continues to burn hydrogen in a shell around the core. The star burns helium into carbon in its core for a much shorter time than it burned hydrogen. Once the helium has all been converted, the inert carbon core begins to contract and increase in temperature.
This ignites a helium burning shell just above the core, which in turn is surrounded by a hydrogen burning shell. What happens next depends on the mass of the star Stars less than 8 solar masses The inert carbon core continues to contract but never reaches temperatures sufficient to initiate carbon burning.
However, the existence of two burning shells leads to a thermally unstable situation in which hydrogen and helium burning occur out of phase with each other.
This thermal pulsing is characteristic of asymptotic giant branch stars. The carbon core continues to contract until it is supported by electron degeneracy pressure.
No further contraction is possible the core is now supported by the pressure of electronsnot gas pressureand the core has formed a white dwarf.
Meanwhile, each thermal pulse causes the outer layers of the star to expand, resulting in a period of mass loss.Stellar Evolution Sancho Criado del Rey Stellar evolution is the study of how a star changes throughout its “lifetime”. The major changes which a star in evolution goes through are classified as: * Birth of the star, it’s the first phase of a star’s life.
Jan 25, · Evolution Of Stars Essay Writing – Accueil › Forums › halal › Evolution Of Stars Essay Writing – Ce sujet a 0 réponse, 1 participant et a . May 16, · Evolution Essay Evolution is the theory that all living forms came from ancient ancestors.
Through a series of mutations, genetic drift, migration, and natural selection today’s descendants show an amazing amount of similarities and diversity. - The purpose of this essay is not to prove “Darwinian” evolution, as the writer would be performing a feat already done by others, but to examine a certain track of thought amongst Creation proponents.
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