The Hertzsprung-Russel Diagram is a spread out graph of stars which shows the relationship that occurs between the absolute magnitude of the stars or luminosity in respect to their types of spectra or classifications and the effectual temperatures (Harding, 1999). The Hertzsprung-Russel Diagram (H-R diagram or HRD) was made in circa in the year 1910 by Henry N. Russell and Ejnar Hertzsprung. This represents a big step in helping understand the stellar evolution which is otherwise referred to as the the stars lives. This essay seeks to explain the Hertzsprung-Russel Diagram and the theories of stars that surrounding it in matters of the stars lifetime and distance to the stars.
The reflection done on the diagram made astronomers to give speculations that it could show evolution of stellar, the main contribution being that these body of stars collapsed from deep red giants to very small (dwarf) bodies of stars, then moving progressively down along the main sequence line in the period of their lifetimes. Stars were believed to radiate energy by converting the energy of gravity into radiation as given by the contractions of Kelvin-Helmholtz. The mechanism led to an age meant for the sun that was only tens of millions period of years, and generating a conflict which occurred over the period of solar system amongst the astronomers and many other scientists. These scientists were of the opinion that the earth was far much older than that. A solution came about in 1930 when the process of nuclear fusion was stated as the source and origin of stellar energy (Sekiguchi Fukugita, 2000).
Following Hertzsprung-Russel Diagram, the hypothesis that thermonuclear energy as well as the energy of the stars majorly comprised of hydrogen was yet to be discovered. Again in line with Hertzsprung-Russel
Diagram, dwarf stars were found to stay fundamentally in a static point on the main sequence for most of their lives (Longair, 2006).
With the information about the fusion of hydrogen, the theory of evolution from these forms to red giants as well as the white dwarfs which was physically-based came to being. The Hertzsprung-Russel Diagram in the beginning only allowed the evolution of stellar to be presented in a graph. Many of the stars inhabit the area on the Hertzsprung-Russel Diagram along the line referred to as main sequence. At this point, the stars fuse hydrogen inside their cores (Porter, 2003). Stars consequently are found to concentrate on the branch that rests horizontally where there is the fusion of helium and hydrogen in the stars core in the shell immediately around the core.
The absolute amount of energy possible from a star by the process of nuclear fusion is always limited by the hydrogen fuel most likely to be consumed at the region of the core. At equilibrium, the energy generated at the core should not be less than the radiated energy from the surface. Luminosity is a measure of the amount of energy produced from the radiations in a unit time. With this information, the whole life span of the star can be roughly estimated. The first approximation in this case is arrived at by dividing the total energy liberated by the luminosity of the star (Sekiguchi Fukugita, 2000).
A star whose solar masses is 0.5, when the supply of hydrogen is exhausted and grows to be red giant, can begin to fuse the atoms of helium to make carbon. The output of energy from the fusion process of helium for every mass is roughly a tenth the output of energy from the hydrogen process (Smith, 1995). The luminosity therefore of the particular stars consequently increases. This amounts to a shorter duration at the stage in comparison to the lifetime at the main sequence. The sun for instance is predicted to have spent 130 million years in the process of burning helium as opposed to the 12 billion years it has done so in burning hydrogen. Most of the stars above solar masses of 0.5 will be found on the main sequence.
Averagely, the main sequence stars are entirely known to have the tendency of following the experimental mass-luminosity relationship. Therefore, the luminosity (L) is more or less proportional to the collective mass (M) of the star as in the power law below.
The above law is only applicable to stars of the main sequence with solar masses between 0.1-50. The fuel amount available for fusion is also found to be in proportion to the stars mass. Consequently, the lifetime of a star on the main sequence can be estimated by giving a comparison to the models of solar evolution. For instance, the sun has been the major sequence star now for almost 4.5 billion years and is expected to become red giant in roughly 6.5 billion years for the entire lifetime in main sequence of approximately 1010 years and therefore.
This line graph shows the relation between mass and luminosity (relative to the respective values of the sun) for zero age main sequence stars.
Determining Distances to the Stars
The stars temperature is used to determine the type of spectral of the star through the effect of the star on the physical characteristics of plasma as in its sphere of light. The emission of the energy of the star is a function of the wavelength contributed by the stars composition and temperature. The major indicator of the distribution of energy is provided by the index of color, B-V which measures the magnitude of the star in blue (B) and green-yellow (V) light by way of filters.
The HRD can be used to determine how far a cluster of star is from the earth. This arrived at by comparing the complete magnitudes of the stars which have known distances. The experimental group is consequently shifted in the vertical sense till both main sequences overlap. The discrepancy in magnitude bridged to go with both groups is referred to as the distance modulus and taken as the direct measure meant for the stars distance. This method is known as the main sequence fitting or parallax of spectroscopic (Longair, 2006).
The reflection done on the diagram made astronomers to give speculations that it could show evolution of stellar, the main contribution being that these body of stars collapsed from deep red giants to very small (dwarf) bodies of stars, then moving progressively down along the main sequence line in the period of their lifetimes. Stars were believed to radiate energy by converting the energy of gravity into radiation as given by the contractions of Kelvin-Helmholtz. The mechanism led to an age meant for the sun that was only tens of millions period of years, and generating a conflict which occurred over the period of solar system amongst the astronomers and many other scientists. These scientists were of the opinion that the earth was far much older than that. A solution came about in 1930 when the process of nuclear fusion was stated as the source and origin of stellar energy (Sekiguchi Fukugita, 2000).
Following Hertzsprung-Russel Diagram, the hypothesis that thermonuclear energy as well as the energy of the stars majorly comprised of hydrogen was yet to be discovered. Again in line with Hertzsprung-Russel
Diagram, dwarf stars were found to stay fundamentally in a static point on the main sequence for most of their lives (Longair, 2006).
With the information about the fusion of hydrogen, the theory of evolution from these forms to red giants as well as the white dwarfs which was physically-based came to being. The Hertzsprung-Russel Diagram in the beginning only allowed the evolution of stellar to be presented in a graph. Many of the stars inhabit the area on the Hertzsprung-Russel Diagram along the line referred to as main sequence. At this point, the stars fuse hydrogen inside their cores (Porter, 2003). Stars consequently are found to concentrate on the branch that rests horizontally where there is the fusion of helium and hydrogen in the stars core in the shell immediately around the core.
The absolute amount of energy possible from a star by the process of nuclear fusion is always limited by the hydrogen fuel most likely to be consumed at the region of the core. At equilibrium, the energy generated at the core should not be less than the radiated energy from the surface. Luminosity is a measure of the amount of energy produced from the radiations in a unit time. With this information, the whole life span of the star can be roughly estimated. The first approximation in this case is arrived at by dividing the total energy liberated by the luminosity of the star (Sekiguchi Fukugita, 2000).
A star whose solar masses is 0.5, when the supply of hydrogen is exhausted and grows to be red giant, can begin to fuse the atoms of helium to make carbon. The output of energy from the fusion process of helium for every mass is roughly a tenth the output of energy from the hydrogen process (Smith, 1995). The luminosity therefore of the particular stars consequently increases. This amounts to a shorter duration at the stage in comparison to the lifetime at the main sequence. The sun for instance is predicted to have spent 130 million years in the process of burning helium as opposed to the 12 billion years it has done so in burning hydrogen. Most of the stars above solar masses of 0.5 will be found on the main sequence.
Averagely, the main sequence stars are entirely known to have the tendency of following the experimental mass-luminosity relationship. Therefore, the luminosity (L) is more or less proportional to the collective mass (M) of the star as in the power law below.
The above law is only applicable to stars of the main sequence with solar masses between 0.1-50. The fuel amount available for fusion is also found to be in proportion to the stars mass. Consequently, the lifetime of a star on the main sequence can be estimated by giving a comparison to the models of solar evolution. For instance, the sun has been the major sequence star now for almost 4.5 billion years and is expected to become red giant in roughly 6.5 billion years for the entire lifetime in main sequence of approximately 1010 years and therefore.
This line graph shows the relation between mass and luminosity (relative to the respective values of the sun) for zero age main sequence stars.
Determining Distances to the Stars
The stars temperature is used to determine the type of spectral of the star through the effect of the star on the physical characteristics of plasma as in its sphere of light. The emission of the energy of the star is a function of the wavelength contributed by the stars composition and temperature. The major indicator of the distribution of energy is provided by the index of color, B-V which measures the magnitude of the star in blue (B) and green-yellow (V) light by way of filters.
The HRD can be used to determine how far a cluster of star is from the earth. This arrived at by comparing the complete magnitudes of the stars which have known distances. The experimental group is consequently shifted in the vertical sense till both main sequences overlap. The discrepancy in magnitude bridged to go with both groups is referred to as the distance modulus and taken as the direct measure meant for the stars distance. This method is known as the main sequence fitting or parallax of spectroscopic (Longair, 2006).
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