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What will
a forming star look like in HR diagram?
•Temperature
changes relatively simple
–Starts
out large and relatively cool Must
be on red side of diagram
–It
heats up as it contracts Must
towards the blue
•Luminosity
more complicated because it depends on T and R
–Not
much energy to start with Luminosity
must start out low
–Collapse
releases grav. energy Luminosity
will rise
–Fusion
begins, releases more energy Luminosity
at a peak
–Collapse
slows, only have fusion now Luminosity
declines
•Finally
stabilizes on the main sequence
From our text: Horizons, by Sees