Astronomy 1021 Lecture Notes - Lecture 13: Supernova Remnant, Planetary Nebula, White Dwarf
3 Apr 2016
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Document Summary
Stars are born in cold, dense clouds of gas whose pressure cannot resist gravitaional contracion. The coldest, densest clouds are called molecular clouds because they are cold enough and dense enough to allow atoms to combine and form molecules. Many stars can be birthed at once, which is why stars are usually born in clusters. A protostar is a clump of gas that will become a new star. A molecular cloud fragment heats up as gravity makes it contract, producing a protostar at its centre. A disk forms around the protostar because collisions between gas paricles cause the c loud fragment to laten along its rotaion axis, and the disk keeps spinning because angular momentum must be conserved. Conservaion of angular momentum ensures that protostars rotate rapidly and are surrounded by spinning disks of gas. Many young protostars ire high-speed streams of gas, or jets into interstellar space.
