Hertz-sprung-Russell diagram is a disperse chart of stars correlating the stars luminosities against their spectral types and effectual temperature. Through this diagram, temperatures are measured in Kelvin’s ranging from 3000 to 30,000. Similarly, the magnitudes of the stars range from +15 to -10.
The stars luminosity and effective temperature are plotted along the vertical and horizontal axis respectively on the diagram. Similarly, the horizontal axis contains a third scale, the spectral scale, plotted on it. Stars are grouped in spectral classes depending on their characteristics.
Characteristics of the four main groupings of stars on the diagram
When one plots the diagrams of the nearest stars to earth, the stars will appear randomly on the chart in four distinct groups suggesting that there is a relationship between the stars temperatures and luminosities. The four groups noted are identified as group A, B, C, and D. Group A stars comprise of the cool and dim stars on the lower right side of the graph to the very bright stars on the top left corner.
Group B stars comprises of cooler and more luminous stars than group A stars. Their size is immensely larger compared to the group A stars. Similarly, group C stars comprise of the much larger and luminous stars than group B stars. Finally, the chart contains the representation of group D stars. These stars, as seen from the diagram, are very hot and dim. This suggests that the stars must be very tiny as compared to other groups of stars, and are referred to as white dwarfs.
Formation of stars
Astronomers have established that stars, like people, have a life cycle. They use the relationship between the young stars and cloud stars to analyze and explain stars formation. The space between the stars comprises of gases and dust known interstellar medium. Of this medium, hydrogen gas constitutes 75 percent of the mass while helium constitutes 25 percent (Seeds and Michael 154). Similarly, traces of carbon, oxygen, and nitrogen are present on this medium.
Certain conditions are crucial in ensuring that the interstellar cloud gas remains in equilibrium. These include the kinetic and potential energy balance. The failure in this regard causes the clouds to undergo gravitational collapse. The viral theorem, that asserts that for equilibrium to persist the internal energy must be half the potential energy, explains this collapse (Moché and Dina 121).
The nebulae clouds and dust remain cold and inactive until excited by an external disturbance from a comet or shockwave originating from a distant supernova. The external force shearing through the cloud particles causes particles’ collision leading to the formation of clumps. With time, a clump accumulates more mass and progressively attains a stronger gravitational pull. With increased gravitational pull, the clump attracts more particles from the surrounding clouds as it increases in size.
Because of the clump’s increase in size and density, its center begins to grow hotter and denser. Over the span of more than a million years, a clump can transform into a small body referred to as a proto-star. Similarly, proto-stars, like the clumps, continue to attract more particles and dust from the surrounding clouds and grow hotter.
Eventually, when the proto-star attains a temperature of 7 million Kelvin’s, hydrogen fusion occurs resulting in the production of helium and massive energy (Seeds and Michael 321). During the initial stages, the strong inward gravitational pull compromises the outflow of the fusion energy. Subsequently, as more materials accumulate in the proto-stars, their mass and heat increases.
Over millions of years, proto-stars attain enough mass and heat to support the solar mass to collapse into the proto-star (Seeds and Michael 321). As this collapse occurs, bipolar flow occurs as enormous gas jets erupt through the proto-stars detonating the remaining particles on the surface. During this stage, the stabilization of a young star occurs with the outward hydrogen fusion thwarting the inward gravitational force.
Death of stars
Billions of years after their formation, stars die ending their life cycle. The death of stars significantly depends on the type of the stars involved. A star’s lifetime will depend on the availability of hydrogen in its core and other factors such as the rate of nuclear burning. Once a star drains its hydrogen supply, it increases in size and luminosity (Seeds and Michael 184).
Death of low stellar mass stars
The exhaustion of the core hydrogen triggers the death of a medium star. This exhaustion thwarts the star’s source of heat causing distortion in the stellar equilibrium (Abell and George 221). Eventually, the star’s core collapses under the gravitational pull resulting in the burning of helium at the expense of hydrogen.
A star will then use helium as its main source of energy until it is exhausted. At this stage, the star’s outer surface expands and extends outwards resulting in an increase in the size of the star involved. This phase lasts for thousands of years leading to a massive loss of the star’s winds. Ultimately, the medium star loses its entire mass envelope and exposes its hot core. The ionization of the nebulas results from the radiation process.
Death of medium and massive stellar mass stars
Over time, massive stars exhaust the hydrogen supply in their cores resorting to the burning of helium. Similarly, with the exhaustion of helium, the nuclear burning cycle continues, but with different elements. First, carbon burns to oxygen followed by the burning of sulfur to iron. Eventually, since iron exists in a stable form, it cannot burn any further thus hampering energy production. With the lack of energy to balance the gravity, the star’s iron core collapses.
Astronomers have noted that the iron core does not completely collapse as the nuclear densities resist any further collapse leading to the core rebound releasing supernova explosions (Fradin and Dennis 67). The supernova explosions are responsible for the injection of carbon, silicon, and oxygen into the space (Gaustad and John 78).
The mass of the parent stars determine the destiny of every hot neutron core. For medium stars, the neutron core cools progressively into a neutron star. Concerning the massive stars, the gravitational pull will be so immense such that the nuclear forces will be overpowered leading to the core collapse and the formation of black holes.
How type I and type II supernovae occur
When massive stars die out, their nuclear reactions turn them into significantly bright and hot bodies that collapse inwardly as they explode by a process called supernova.
This process can be referred to as type I or type II depending on the shape and nature of the spectral lights emitted in the process (Ridpath 56). A type i supernova occurs when the emitted light curves realize sharp maxima with gradual death. The type II supernova is identified with less sharp maxima and a sharp death.
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Fradin, Dennis B.. Astronomy. Chicago: Childrens Press, 1983. Print.
Gaustad, John E., and Michael Zeilik. Study guide to accompany Astronomy, the evolving universe. 3rd ed. New York: Harper & Row, 1982. Print.
Moché, Dinah L., and George Lovi. Astronomy. New York: Wiley, 1978. Print.
Ridpath, Ian. Astronomy. London: Dorling Kindersley, 2006. Print.
Seeds, Michael A.. Horizons: exploring the universe. 5th ed. Belmont, CA: Wadsworth Pub. Co., 1998. Print.