Life Cycle of Stars

Life Cycle of Stars

Stars take millions of years to form and they come in many types and sizes. Many factors must be taken into consideration regarding the birth of stars. This paper will detail the life cycle of stars.

Objects in the Universe remit, reflect and absorb electromagnetic waves in their own unique way. Light or electromagnetic radiation is considered a form of energy. "Visible light is a narrow range of wavelengths of the electromagnetic spectrum." (Anonymous, 1994). In order to learn about the nature of objects, "measurements of the wavelength or frequency of light from these objects" (Anonymous, 1994) should be studied. To transmit information from space, electromagnetic radiation is needed. The human eye is can only see small ranges of wavelengths. Our eyes cannot see most objects in the universe. "Astronomers use telescopes with detection devices that are sensitive to wavelengths other than visible light in order to study objects that emit this radiation" (Anonymous, 1994).

"The universe is the sum total of all matter and energy, encompassing the super clusters and voids and everything within them" (Bennett, Donahue, Schneider, and Voit, 2004). The hierarchy of the universe is as follows planets move around stars. Stars are grouped together and move slowing around the center of the galaxy. Galaxy clusters are formed by galaxies which are held by gravity as they move through the void. Super clusters contain thousands of galaxies. "The super clusters are arranged in filament or sheet-like structures between which there are gigantic voids of seemingly empty space" (Bennett, Donahue, Schneider, and Voit, 2004). The Milky Way is one of the two largest galaxies among about 40 galaxies in the Local Group.

Stars are composed of hydrogen and helium. This cloud is referred to as a nebula. The nuclear fuel of these stars is burned quickly which causes the core to be composed of iron. During the nuclear fusion process, iron cannot be burned as it requires the input of energy to force iron nuclei to fuse with other nuclei. Without nuclear fusion, the star's core can no longer counteract the force of gravity and the star starts to disintegrate resulting in a supernova. As the speed of the particles increase, the gas breaks down. Heat sources are slightly different before and after the main sequence due to the fact that the star is "contracting and is not hot or dense enough to start nuclear reactions" (Lochner, 2004). As the speed of molecules increases, the temperature of the gas rises. The gas gives off more light as the temperature rises. This large ball of hot gas is a protostar. Even though the protostar is very bright due to its large size, it is difficult to see because it is usually hidden within the nebula from which it is forming.

The luminosity of a star is the total amount of power that it radiates into space. A star's luminosity can be determined if the star's distance and apparent brightness is known (Bennett). Stars come in different colors - red, orange, yellow, white and blue. The temperature of stars is determined by their color. The coolest stars are red and the hottest stars are blue. The Sun is a yellow dwarf start. In order to determine the stage in a star's life cycle, astronomers rely on the color and actual brightness.

The mass of a star is the most important property. In order to measure the mass of a star, in binary systems, it must be determined how the stars orbit each other and apply Newton's Laws. "Binary star systems can be classified into several different types. Eclipsing binaries, in which the stars periodically pass in front of each other, are the most useful for measuring stellar masses because we can determine their orbital speeds most directly" (Bennett, Donahue, Schneider, and Voit, 2004).

Main sequence stars burn hydrogen in their cores. The mass of stars is determined by the position of the stars along the main sequence. "Main sequence stars fall along the diagonal line that goes from the upper left to the lower right on the Hertzsprung-Russell Diagram" (Lochner, 2004). The H-R diagram is a much used classification diagram which plots the luminosity versus the surface