U10a2 Life Cycle of the Stars Paper Essay Example | Topics and Well Written Essays - 1250 words

U10a2 Life Cycle of the Stars Paper - Essay Example Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star are determined by its evolutionary history, including diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertzprung-Russell diagrams (H–R diagram), allows the age and evolutionary state of a star to be determined. Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. Depending on the mass of the star, this lifetime ranges from only a few million years (for the most massive) to trillions of years (for the least massive, which is considerably more than the age of the universe). Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at the various points in their life, and by simulating stellar structure with computer models. Stellar Evolution: A nebula is a cloud of gas (hydrogen) and dust in space. Nebulae are the birthplaces of stars. There are different types of nebula. An Emission Nebula which glows brightly because the gas in it is energized by the stars that have already formed within it. In a Reflection Nebula, starlight reflects on the grains of dust in a nebula. The nebula surrounding the Pleiades Cluster is typical of a reflection nebula. Dark Nebula also exists. These are dense clouds of molecular hydrogen which partially or completely absorb the light from stars behind them. 1st stage of a stars life: PROTOSTAR Stellar evolution begins with the gravitational collapse of a giant molecular cloud (GMC). As it collapses, a GMC breaks into smaller and small er pieces. In each of these fragments, the collapsing gas releases gravitational potential energy as heat. As its temperature and pressure increase, a fragment condenses into a rotating sphere of superhot gas known as a prostar. Protostars with masses less than roughly 0.08Â  M (1.6?1029 kg) never reach temperatures high enough for nuclear fusion of hydrogen to begin. These are known as brown dwarfs. For a more massive prostar, the core temperature will eventually reach 10 million kelvins, initiating the proton-proton chain reaction and allowing hydrogen to fuse, first to deuterium and then to helium. The onset of nuclear fusion leads relatively quickly to a hydrostatic equilibrium in which energy released by the core exerts a "radiation pressure" balancing the weight of the star's matter, preventing further gravitational collapse. The star thus evolves rapidly to a stable state, beginning the main sequence phase of its evolution. A new star will fall at a specific point on the mai n sequence of the Hertzprung-Russell diagrams, with the main sequence spectral type depending upon the mass of the star. Small, relatively cold, low mass red dwarfs burn hydrogen slowly and will remain on the main sequence for hundreds of billions of years, while massive, hot super giants will leave the main sequence after just a few million years. A mid-sized star like the Sun will remain on the main sequence for about 10 billion years. . A star of less than about 0.5 solar mass will

General motors Essay Example | Topics and Well Written Essays - 2000 words

General motors - Essay Example The company has its manufacturing bases in 37 countries and has eleven brands under its name. As on September 2013, the overall sale and revenue of the company is 152.84 billion dollars (Yahoo Finance, 2013). The company has its operations all round the world. It is engaged in the manufacturing of electric, mini cars and big vehicles such as trucks. The company also performs servicing functions. Thus, the consumers of General Motors ranges from upper-middle class segment, luxury and premium segment, consumers with agriculture and supply chain business and logistics service providers. So generally the company transfers most of its successful brand to different countries for everyone to avail them. GM has very good human resource policies and it employed about 3,000,000 people around the world. The major brands of General Motors include Chevrolet, Cadillac, GMC, Wuling, Opel and Holden. The company does heavy investment on its technology for producing innovative cars. The management te am of the company is centralized and strong. This ensures that the operational functions of the company were standardized in most of its departments. However, the operations of GM in all its offices around the world are not standardized and the market share of the company is not uniform in all the countries. ... History Founded in the year 1908, William C. Durant was the first controller of the company. At first Durant was into manufacturing of horse driven vehicles, before entering into the automobile industry. Within few years the company went on to acquire many companies such as Cadillac, Oldsmobile etc. After the creation stage, came the acceleration stage. During this time Vauxhall, Opel and Chevrolet brands were introduced which took innovation to a new level. GM vehicles became aspirations and statements and changed the image of vehicles way beyond just transportation. During this time GM also expanded its plants to other states. Globalization of General Motors started during 1980 and 1990s. Majority of joint project and new establishments took place during this time. However, challenges started occurring during 2008, as a result of the global recession and economic downturn. The company had to take loan from US treasury and major restructuring had to be done in the strategy and plann ing. After filing for bankruptcy in 2009, GM emerged as leaner and more competitive organization (General Motors, 2013a). Mission Vision and Values The objective of the company is to be the most successful automaker in a span of 5 years and also ensure that the marketing strategies such as e-commerce technologies are utilized for the overall growth of the organization. The vision of the company is to build, design and sell best vehicles of the world. The company also aims to become the most respected automakers of the world. General Motors has indeed succeeded in moving towards its goals. The company has a unique and comprehensive mission statement which sums up the overall long term and short term goals and