Astronomy 1021 Lecture : Star Lives
31 Jan 2012
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Document Summary
As a star is generating energy through nuclear fusion its chemical composition is gradually changing (ex: transforming hydrogen into helium, the star is evolving) Stellar evolution is the change in composition but also changes in stellar parameters over time (temperatures, size, ex: how stars change position on the h-r diagram) Note that the timescales involved in stellar evolution are extremely long for human understanding. We have never seen a full evolution of a star. What we know is like taking pictures of thousands of people and figuring out what people look like as they are from them. Understanding stellar evolution comes from understanding what happens to the pressure in a star as it ages. For the purpose of understanding stellar evolution it is useful to divide stars into three groups based on their initial (main sequence mass) Low-mass stars : masses less than 2 msun. Intermediate-mass stars : masses between 2 and8 msun.
