Concept explainers
Compare the following stages in the lives of a human being and a star: prenatal, birth, adolescence/ adulthood, middle age, old age, and death. What does a star with the mass of our Sun do in each of these stages?
To describe:
The different phasesin the life of a star and compare it with the lives of a human being.
Explanation of Solution
Introduction:
The prenatal period is the development period of the child inside the mother’s womb, where the child is dependent on the mother for food supply.
On the birth of a child, it is capable to produce its own energy from the food that it eats. Later it passes through different phases in its life through adulthood, middle-age, old-age and then dies.
In the prenatal stage, the core of the giant’s molecular clouds collapses due to gravity and becomes a protostar. On protostar’s disk material is continuously falling.
Once a star has reached the main-sequence band in the H-R diagram. The term zero-age is used to name the time whenthe star stops contracting, and it obtains the energy almost entirely from the nuclear fusion reaction (fusion of hydrogen molecule into helium molecule).Scientists say that this is the birth of a star.
When the surface temperature of star increases, the star “moves” to the left in the H-R diagram.As their luminosity, and temperature changes, the point on the H-R diagram also change. All-stars spend most of their lives on the main sequence of the H-R diagram, astronomers like to call this phase as adulthood.
When the star consumesthe entire core’s hydrogen, gravity takes over the pressure and the star startsto contract. Heat released during contraction begins the nuclear reaction in star shell’s hydrogen.The star moves upward from the main sequence in the H-R diagram and becomesa red giant. This phase of the star is the middle age.
After the consumption of the shell’s hydrogen, helium flash occurs which maintains the balance between pressure and gravity. Sooner or later, each star exhausts its store of nuclear energy and dies. A star like sun, dies as a white dwarf unlike massive stars which die as a neutron star or a blackhole.
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