SCI238 Lecture Notes - Reaction Rate, Main Sequence, Cno Cycle
9 Jul 2013
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Document Summary
Born in clouds of interstellar gas, shine with energy produced by nuclear fusion in their cores, and die when they finally exhaust all sources of fuel for fusion. The youngest star clusters are always associated with dark clouds of gas and dust, indicating that stars are born in such clouds. Ir image shows star formation which is hidden in visible light. We therefore expect star-forming clouds to be colder and denser than most other interstellar gas: stars are born within the coldest and densest clouds. Collapse begins: fgrav > pgas (i. e. mcloud > mbalance ) Shock wave from: sn, collision? forming region, cloud. As cloud shrinks n increases, mbalance decreases, a smaller mass limit for contraction could give fragmentation. Fragmentation: higher cloud density -> smaller masses can contract. Many cores formed in a single cloud. Core to protostar gas now falling to central core initially still cools efficiently, gradually heats especially core.
