AST 309 Lecture Notes - Lecture 5: Jeans Instability, Protostar, Solar Mass
Document Summary
Molecular clouds & first stages of star formation. Cloud begins to collapse once gravity wins over pressure. Since the mass of large molecular clouds could easily exceed the jeans mass, it seems possible the stars can form with very large masses, possibly up to the initial mass of the cloud (100 solar masses) We see lots of stars around 1 solar mass or less. Fragmentation: occurs in molecular clouds once the collapse process starts. Clouds can fragment, which leads to new stars being born in the denser fragmented clumps. A typical cloud can break up into tens, hundred, or even thousands of fragments. With each fragment shrinking and contracting faster and faster. But the whole process from a single stable cloud to many collapsing fragments can take millions of years. A fragment that will eventually turn into a star like our sun, prbably contains around 2 solar masses of material at this stage.
