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