ASTR 3 Lecture Notes - Lecture 5: Radiation Zone, Noble Gas, Chromosphere
28 Aug 2016
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Thursday, october 22, 2015 chapter 14 from chapter 8: radioactive decay. Big nucleus breaking apart to become more stable-- ssion. Argon is a noble gas that doesn"t condense; it come from decay of potassium-40 energy. Sun has high thermal energy (collective kinetic energy of many particles) Stars start out as a huge, diffuse cloud that collapses under gravity; converts gravitational potential energy into thermal energy as it collapses. Reason why star stops heating up: once hot enough, starts to convert its own mass into energy (e=mc^2) Controlled nuclear reactions (why the sun hasn"t explodednobody has found a way to imitate that) a closer look at the sun. On re? it would last about 10,000 years; was determined unlikely in 1800s. Contracting? (gravitational to thermal energy) would last about 25 million years; accepted explanation from physicists in second half of the 1800s; geologists knew that the earth was older.
