AST 111 Lecture Notes - Lecture 26: Nuclear Fission, Red Giant, Solar Neutrino
6 Jun 2020
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Document Summary
Pressure and temperature increase towards the centre of the sun. Force of gravity is balanced by the gas pressure. Sun"s energy is generated in its core and flows out to the surface. Nuclear fission occurs when nuclei of large atoms (such as uranium) split into two. Nuclear fusion occurs when nuclei of small atoms combine together to make bigger nuclei. Specific type of nuclear fusion reaction that powers the sun is called proton-proton chain. In this reaction four hydrogen nuclei (protons) combine to form a helium nucleus. Reaction requires very high temperatures and pressures that are found at the core of the sun. Enough hydrogen to last for 10 billion years. Uses up its hydrogen fuel slowly increases in luminosity. When it runs out of hydrogen in its core it will swell up to many times its current size forming a red giant. Astronomers often loosely talk about a star like the sun burning hydrogen.
