Stars Hertzsprung-Russell diagram

In trying to understand stars, Hertzsprung –Russell Diagram is the most commonly used tool in stars analysis. Hertzsprung Russell Diagram uses temperature, radii, mass and luminous aspect of stars, in order to find the relationship between their nature and physical elements.  In this, the Hertzsprung Russell Diagram uses both magnitude and spectral nature to construct H-R plot diagram. When using H-R diagram, a star may be classified as a main-sequence star, if they lie within the top left hand corner of the H-R diagram and the down right hand side of the H-R diagram. This mean that, the main sequence stars lies within a hydrogen-burning stage and are being generated into helium.  A Hertzsprung Russell diagram can also be constructed sing the luminous-temperature elements, that is, by plotting L against T diagram. In this, plot diagram, stars with high temperatures or else hot stars lie at the top left side of the diagram and less hot or cool stars lie at the down right hand side of the diagram or at the near end of the main sequence strip. If the Hertzsprung Russell is constructed by using the luminous and radii elements, stars will be classified on the basis of their size. In this case, they will be termed as giant and supergiant. Research has proven that gigantic and supergiant stars have no hydrogen to burn. Therefore, stars that lie below the main sequence strip are small while those above the man sequence strip are referred to as giant stars or supergiant stars depending on the luminosity and magnitude of the star in the L against M (luminous versus magnitude) plot diagram. Examples of a giant and supergiant star are Aldebran and Betelgeuse respectively.

When the H-R diagram is constructed using the radii, another type of stars are derived from this classification; dwarf stars. Dwarf stars are located below and left of main sequence strip in the H-R plot diagram. They are perceived, to have the same radii as that of the earth, that is, small radii. The dwarf stars are sometimes called, the dead stars since they no longer generate hydrogen and have low temperatures. Another property of dwarf stars is that their luminosity is low and only appears as faint and whitish. An example of dwarf star is Sirius B; its luminosity is perceived to be 8.6 years and a magnitude of 8.5 away from the main-sequence strip (Swamy, 2003).

How a star is born

The formation of a star is usually preceded by an existing mass of gas and dust. It is believed that, these two elements have atoms and nuclei if put under certain force, probably by the force of gravity, they are compressed together. This state of nuclei compression is referred as interstellar medium. The interstellar medium has a gas that fuses the elements atoms. If this state is maintained by both force of gravity and the atom fusion force, a star is creation progresses. However, for these elements to compress to a star, they first need achieve a protostar state. In the protostar phase, a nebula must be in state of collapsing. A nebula is termed as a cloud of gas consisting of both hydrogen and helium gases and some organic molecules. In the protostar phase, the nebula gases components are perceived to have varied density that compresses the organic molecules together. Temperature intensifies in this phase resulting to collapse of the nebula. The hydrogen atoms in the core of the nebula breaks at almost 2,000o C and at 10, 000o C a fusion occurs creating a sun like star now referred as a protostar. After the formation of a star, there must be stability of that star and it is achieved through a stellar equilibrium. The stellar equilibrium is achieved at the final star formation phase, that is, nuclear fusion force and the outward pressure must be greater than the gravitational force for the newly formed star to evolve.

 

 

How a star dies

After a star has fully fused its hydrogen atoms into helium, it is possible for the star to die. It is assume that if a star mass is half that of the sun, there is less electron degeneration and starts to exist as a dwarf star. This only happens to stars with low stellar masses. For stars with medium and high stellar mass like giant and supergiant stars, the helium gas fusion sheds off the outer layer of the star’s mass (Seeds, 2008).

Type I and Type II supernovae

White dwarf stars are known to exist in binary form, that is, they could be in type I or type II supernova. Type I supernova occurs, when the white dwarf are made up of carbon and oxygen gases only. There is exception of hydrogen component in white dwarf stars. This type of supernovae occurs during the nuclear fusion, involving high density masses probably from another neutron star. Type II supernovae occur when high mass stars with no nuclear energy explode on their own.

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