The Life of a Star
One night while little Jimmy was out camping with his father, he asked his father how a star is made? And his father said there are high-mass stars, intermediate-mass stars, and low-mass stars. The life cycles of stars follow three general patterns each associated with a range of initial mass. Much like human beings stars have a life cycle, they go threw birth, evolution, and death. And little Jimmy said how is that possible?
First the star must be born. Many astronomers believe that a star is formed when large compression waves traveling threw gas clouds create dense knots of gas is the cloud. The gravity of these knots then pules the other gas molecules. As the knot grows larger and larger the gravity starts attracting more and more gas molecules. Eventually, the knot coalesces into a growing sphere of compressed gas that reaches internal temperatures of a few million degrees Celsius. At this point the gases in the knot’s interior become so hot that their atomic nuclei begin fusing, creating large amounts of nuclear energy and forming a new star. Pressure from the radiation of new stars in turn causes more, higher-density zones to form in the gas cloud, which initiates the birth of more stars.
Next the evolution and main sequence of a star, it’s going threw puberty. In its earliest stage, a typical star is large and emits infrared light. Within a million years, the gravitational attraction of the star’s material for itself cases the star to shrink to the present size of the sun. The added pressure caused by this collapse in size raises the star’s internal temperature high enough to trigger nuclear reactions in the core. The main sequence stars fall along the diagonal line that goes from the upper left to the lower right on the H-R diagram. During its main-sequence phase, a star gradually exhausts its hydrogen supply.
The next stage of a star’s evolution involves dramatic stages of expansion and contraction the star approaches the end of its life cycle. After the star has used all of its hydrogen in the core, the core begins to shrink, converting hydrogen into helium in ever-larger shells around the inner core. The star’s core shrinks because the outward pressure of heat generated by the nuclear reactions no longer balances the inward gravitational attraction of the stars mass for itself. Although the core of a star gradually shrinks as it exhausts its hydrogen supply, the star itself begins expanding. It resorts to burning the hydrogen in a shell around its helium core, which inflates the outer layers of its atmosphere. Eventually, the star expands into a red giant, possibly attaining a diameter from 10 to 1,000 times the diameter of the sun. The shrinking core increases the star’s internal pressure. The shrinking core increases the star’s internal pressure. The increase in pressure makes the star’s temperature to increase again until it is hot enough to trigger nuclear reactions between previously inert helium nuclei present in the star. At this point, the star’s outer atmosphere begins to contract. When a low to medium mass star exhausts the nuclear fuel in its core, it collapses under the gravitational pressure of its own weight into an extremely compact, dense star known as a white dwarf. As a High Mass star dies it blows off more than half of its outer layer into space as planetary nebula-gas and dust that may provide material for new planets in other new solar systems. After it enters the white dwarf stage it will still shine but slowly dim as it uses up all of its last resources.
In conclusion little Jimmy’s father said now do you see that a star goes threw birth, evolution, and death? And little Jimmy said that yea I under stand now dad thank you. They then went to their tents and lived haply ever after knowing how a star’s life cycle works.