ESS102H1 Lecture : Lecture 4

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30 Oct 2010
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Currently it is thought that expansion started with a cataclysmic explosion j big bang j between. The further away the galaxy is, the faster it is retreating j expanding universe. Hot cloud containing only h (98%) and he(2%) Collapse of nebulae leads to formation of protostars. The high pressures and temperatures reached within protostars lead to nuclear fusion processes (fusion of hydrogen atoms to create helium atoms) Most mass concentrated in centre of rotation cloud of gas and duse. When a very massive star runs out of fuel, a very energetic explosion occurs, so that elements heavier than fe are formed (supernova) When a star dies, it sends the heavy elements into the universe. A subsequent generatio of stars containing a larger proportion of heavier elements forms out of the more compositionally diverse nebulae. Today 99% of the mass of the universe consists of h and he (only 1% is heavy elemental matter)

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