Many creatures and objects, which are found in the universe, undergo the process of evolution. They change from one state to another because of various factors or in order to fit in certain situations. Scientist have discovered the evolution process of many living and non-living things. The solar system has also its evolution process. This paper looks at stellar evolution, which is the evolution process, which the stars undergo.
Stellar evolution is a process by which stars form, then burn for an extended period and then eventually dies. In the process along the way stars struggle with gravity and consumption of fuel so that they can maintain equilibrium. The process of stellar revolution starts when a star is formed. The stars form in giant molecular clouds, particles and swirling masses of gases. During their lifetime starts goes through gravitational collapse. They generate protostars and celestial bodies, which have the potential of becoming stars. The type of start, which is formed from a protostar, is determined by the chemical composition of the protostar. When the stars pull together there is a series of chemical reactions, which starts to occur which, and then makes the star to gain luminosity. As time goes, a star consumes its fuel and then collapses. It then sets another chain of reactions of events, which makes the start to burn brought and hot. The start can turn become a white dwarf, neutron star or it becomes a white hole when it dies. The stellar revolution constantly occurs around the universe as stars comes and go.
Therefore, stellar evolution can be termed to as the process by which star goes through a sequence of radical changes in its lifetime. Stellar revolution is learned by observing the life of numerous stars at various points on their life. This is also done by simulation of the stellar structure by use of computer models. The process starts when there is a gravitational collapse of giant molecular cloud. In the process of collapse, the giant molecular cloud breaks into smaller and smaller particles. In each of the fragments, the gas, which collapses, release gravitational potential energy in form of heat. In the process of temperature and pressure increase, the fragment usually condenses to become rotating sphere of very hot gas, which is called protostar. The protostar with high masses their temperature usually reaches ten million Kelvin, which leads to initiation of the proton- proton chain reaction. They allow the fusion of hydrogen to become deuterium and then changes to become helium. The start of nuclear fusion usually leads to hydrostatic equilibrium which makes the energy that is released by the co exerts have a balance with the weight of the matter of the start, which prevents more gravitational collapse. Therefore, the star evolves in a rapid manner to a stable state. This is where a star starts the main sequence in its evolution process. Red dwarfs which are small in size and relatively cold with a low mass usually burn hydrogen in a slow pace. They remain on the same sequence for billions of years. The supergiant stars, which have high mass usually, leave the main sequence after a few million years. Stars, which are medium in size such as the sum, usually remain in the same sequence for almost ten billion years.
The continuous process by which hydrogen fuses to become helium cause there to be build up of helium in the core. This pace of the process is determined on the initial mass of the star, which ranges from millions to billions of years. The stars, which are hotter and large, produce helium in a more rapid rate that the smaller starts which are usually cool. When the helium accumulates in the core, it causes a gradual increase in the rate of fusion. This also leads to gravitational self-compression because helium is denser than hydrogen. In order to resist the increase in gravitational compression and to maintain a steady state, there is the need for the attainment of high temperatures. As time passes by the core exhausts its oxygen supply. A start, which has a solar mass, less than 0.5. is not able to fuse helium even after the core cease the fusion of hydrogen. There are red dwarfs, which live more time than the sun. It is estimated that red dwarfs which have 0.1 solar mass can stay in the main sequence for more than six trillion years. They also take several hundred billion of years in order to collapse slowly to become a white dwarf.
When the core of a star becomes stagnant, as is the case with the sun, it becomes surrounded by hydrogen, which the star usually draws upon. If the star is fully convective as in the case with lowest mass star, it does not have such as hydrogen surrounding it. If in any case it has such a surrounding it develops to become a red giant. However, they do not fuse helium as in its normal case. What is does is that it contracts until the time when electron degeneracy pressure halts its collapse. In this case, it becomes a white dwarf. At the same time a star that is start the fusion of helium or halting the fusion of helium because of hydrostatic equilibrium, which results because of electron degeneracy pressure and the increased fusion in the layer, which contains hydrogen, makes the star to expand. This makes the outer layer of the star to be lifted from the core. This leads to reduction of gravitational pull on them and expand at a higher rate than the increase of energy production. This makes them to cool and make them to become redder than how it is when it is in the main sequence. These are the stars, which are known as the red giants. A star with few solar masses usually develops a helium core, which is supported by electron degeneracy pressure. The helium core developed is still surrounded by layers, which contain hydrogen. The gravity which it contains compress the hydrogen which is found above it which then makes it to fuse faster than how hydrogen fuse in a main sequence stars with the same mass.
This makes the star to be more luminous and expand. The rate of expansion is more that the increase of luminosity which leads to decrease of the effective temperature. For all the stars except the lowest mass stars the material, which is fused, remain deep in the stellar before this point. The convecting envelop makes the fusion products to be seen on the surface of the star for the first time. During this stage of the stellar evolution, the results are usually subtle. At this point, the largest effect that is the alteration to the hydrogen isotopes and helium are unobservable. When the hydrogen, which is found at the core, is totally consumed, it usually expands to become a red giant. It then sheds its envelop to become planetary nebula and then degenerates into white dwarf. When the hydrogen found around the core is consumed, then the core absorbs the helium, which results. This makes it to contract, which then makes hydrogen to fuse at a faster rate. There is the helium fusion, which is ignited in the core. In stars, which have, more than 0.5 solar masses helium fusion is delayed for millions of years because of electron de3generacy. In more massive stars this delay does not occur because of the combined weight of helium core and the layers which overly. This means that such pressure sufficient to cause any delay in the process. The change of energy output makes the star to change in temperature and size for some periods. There is the shift of the energy output to lower frequency emission. There is increase mass loss through stellar winds that are powerful and violent pulsations. Stars, which are in this phase, are known as late type stars. The expelled gas has high amount of elements, which are created inside the star. The elements mostly contain oxygen and carbon but it depends with the type of the star.
Massive stars expand and cool and they do not have a lot of brightness as the less massive stars. The stars do not survive as the red giants do. This is because they destroy themselves as supernovae type II. Extremely massive stars which more than 40 solar masses have great lamination. This makes them have rapid stellar winds and loss their masses so rapidly. This makes them fail to expand to become red supergiants.They retain their high surface temperatures from their main sequence period onwards. Stars normally cannot have more than one twenty solar masses. This is because their outer layer would be expelled by the extreme radiation, which occurs. Despite that fact that lower mass stars do not burn off their outer layer in a rapid way, they can advised to become red supergiants is the have rapid rotation. This would make the convection extend from the core up to the surface. This would result to the absence of a core that is separate and envelop because of the thorough mixing, which occurs in the process.
There are stellar remnants, which are produced after star has burned out of its supply of fuel. The remnants take three forms determined by the mass of the star during its lifetime. They make the form of white dwarfs, neutron stars and black holes. For stars with solar mass of one they resultants white dwarf of about 0.6 solar mass. The white dwarfs are stable because of the inward pull of gravity, which is balanced by degeneracy pressure of the electrons of the star. There is the neutron star, which is formed when stellar core collapses. The pressure leads to the capture of electrons, which convert the great majority of protons to become neutrons. The neutron stars are small and are phenomenally dense. The black hole results if the mass of the stellar remnants is high. Therefore, the neutron degeneracy pressure will be insufficient to prevent collapse. The stellar remnants then become a black hole.
Stellar evolution is a process by which stars form, then burn for an extended period and then eventually dies. In the process along the way stars struggle with gravity and consumption of fuel so that they can maintain equilibrium. The process of stellar revolution starts when a star is formed. The stars form in giant molecular clouds, particles and swirling masses of gases. During their lifetime starts goes through gravitational collapse. They generate protostars and celestial bodies, which have the potential of becoming stars. The type of start, which is formed from a protostar, is determined by the chemical composition of the protostar. When the stars pull together there is a series of chemical reactions, which starts to occur which, and then makes the star to gain luminosity. As time goes, a star consumes its fuel and then collapses. It then sets another chain of reactions of events, which makes the start to burn brought and hot. The start can turn become a white dwarf, neutron star or it becomes a white hole when it dies. The stellar revolution constantly occurs around the universe as stars comes and go.
Therefore, stellar evolution can be termed to as the process by which star goes through a sequence of radical changes in its lifetime. Stellar revolution is learned by observing the life of numerous stars at various points on their life. This is also done by simulation of the stellar structure by use of computer models. The process starts when there is a gravitational collapse of giant molecular cloud. In the process of collapse, the giant molecular cloud breaks into smaller and smaller particles. In each of the fragments, the gas, which collapses, release gravitational potential energy in form of heat. In the process of temperature and pressure increase, the fragment usually condenses to become rotating sphere of very hot gas, which is called protostar. The protostar with high masses their temperature usually reaches ten million Kelvin, which leads to initiation of the proton- proton chain reaction. They allow the fusion of hydrogen to become deuterium and then changes to become helium. The start of nuclear fusion usually leads to hydrostatic equilibrium which makes the energy that is released by the co exerts have a balance with the weight of the matter of the start, which prevents more gravitational collapse. Therefore, the star evolves in a rapid manner to a stable state. This is where a star starts the main sequence in its evolution process. Red dwarfs which are small in size and relatively cold with a low mass usually burn hydrogen in a slow pace. They remain on the same sequence for billions of years. The supergiant stars, which have high mass usually, leave the main sequence after a few million years. Stars, which are medium in size such as the sum, usually remain in the same sequence for almost ten billion years.
The continuous process by which hydrogen fuses to become helium cause there to be build up of helium in the core. This pace of the process is determined on the initial mass of the star, which ranges from millions to billions of years. The stars, which are hotter and large, produce helium in a more rapid rate that the smaller starts which are usually cool. When the helium accumulates in the core, it causes a gradual increase in the rate of fusion. This also leads to gravitational self-compression because helium is denser than hydrogen. In order to resist the increase in gravitational compression and to maintain a steady state, there is the need for the attainment of high temperatures. As time passes by the core exhausts its oxygen supply. A start, which has a solar mass, less than 0.5. is not able to fuse helium even after the core cease the fusion of hydrogen. There are red dwarfs, which live more time than the sun. It is estimated that red dwarfs which have 0.1 solar mass can stay in the main sequence for more than six trillion years. They also take several hundred billion of years in order to collapse slowly to become a white dwarf.
When the core of a star becomes stagnant, as is the case with the sun, it becomes surrounded by hydrogen, which the star usually draws upon. If the star is fully convective as in the case with lowest mass star, it does not have such as hydrogen surrounding it. If in any case it has such a surrounding it develops to become a red giant. However, they do not fuse helium as in its normal case. What is does is that it contracts until the time when electron degeneracy pressure halts its collapse. In this case, it becomes a white dwarf. At the same time a star that is start the fusion of helium or halting the fusion of helium because of hydrostatic equilibrium, which results because of electron degeneracy pressure and the increased fusion in the layer, which contains hydrogen, makes the star to expand. This makes the outer layer of the star to be lifted from the core. This leads to reduction of gravitational pull on them and expand at a higher rate than the increase of energy production. This makes them to cool and make them to become redder than how it is when it is in the main sequence. These are the stars, which are known as the red giants. A star with few solar masses usually develops a helium core, which is supported by electron degeneracy pressure. The helium core developed is still surrounded by layers, which contain hydrogen. The gravity which it contains compress the hydrogen which is found above it which then makes it to fuse faster than how hydrogen fuse in a main sequence stars with the same mass.
This makes the star to be more luminous and expand. The rate of expansion is more that the increase of luminosity which leads to decrease of the effective temperature. For all the stars except the lowest mass stars the material, which is fused, remain deep in the stellar before this point. The convecting envelop makes the fusion products to be seen on the surface of the star for the first time. During this stage of the stellar evolution, the results are usually subtle. At this point, the largest effect that is the alteration to the hydrogen isotopes and helium are unobservable. When the hydrogen, which is found at the core, is totally consumed, it usually expands to become a red giant. It then sheds its envelop to become planetary nebula and then degenerates into white dwarf. When the hydrogen found around the core is consumed, then the core absorbs the helium, which results. This makes it to contract, which then makes hydrogen to fuse at a faster rate. There is the helium fusion, which is ignited in the core. In stars, which have, more than 0.5 solar masses helium fusion is delayed for millions of years because of electron de3generacy. In more massive stars this delay does not occur because of the combined weight of helium core and the layers which overly. This means that such pressure sufficient to cause any delay in the process. The change of energy output makes the star to change in temperature and size for some periods. There is the shift of the energy output to lower frequency emission. There is increase mass loss through stellar winds that are powerful and violent pulsations. Stars, which are in this phase, are known as late type stars. The expelled gas has high amount of elements, which are created inside the star. The elements mostly contain oxygen and carbon but it depends with the type of the star.
Massive stars expand and cool and they do not have a lot of brightness as the less massive stars. The stars do not survive as the red giants do. This is because they destroy themselves as supernovae type II. Extremely massive stars which more than 40 solar masses have great lamination. This makes them have rapid stellar winds and loss their masses so rapidly. This makes them fail to expand to become red supergiants.They retain their high surface temperatures from their main sequence period onwards. Stars normally cannot have more than one twenty solar masses. This is because their outer layer would be expelled by the extreme radiation, which occurs. Despite that fact that lower mass stars do not burn off their outer layer in a rapid way, they can advised to become red supergiants is the have rapid rotation. This would make the convection extend from the core up to the surface. This would result to the absence of a core that is separate and envelop because of the thorough mixing, which occurs in the process.
There are stellar remnants, which are produced after star has burned out of its supply of fuel. The remnants take three forms determined by the mass of the star during its lifetime. They make the form of white dwarfs, neutron stars and black holes. For stars with solar mass of one they resultants white dwarf of about 0.6 solar mass. The white dwarfs are stable because of the inward pull of gravity, which is balanced by degeneracy pressure of the electrons of the star. There is the neutron star, which is formed when stellar core collapses. The pressure leads to the capture of electrons, which convert the great majority of protons to become neutrons. The neutron stars are small and are phenomenally dense. The black hole results if the mass of the stellar remnants is high. Therefore, the neutron degeneracy pressure will be insufficient to prevent collapse. The stellar remnants then become a black hole.
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