What does all this tell us about the lifetime of stars?
miles until empty = gallons of gas / gallons per mile
lifetime of star = amount of Hydrogen / rate of burning Hydrogen
lifetime of star proportional to (mass of star) / (luminosity of star)
From measuring the masses and luminosity of nearby stars, we know that
so we find that
type Mass Temp Radius Lum (Sun=1) Lifetime ----------------------------------------------------------- O 60.0 50,000 15.0 1,400,000 430,000 B 18.0 28,000 7.0 20,000 9,000,000 A 3.2 10,000 2.5 80 400,000,000 F 1.7 7,400 1.3 6 3,000,000,000 G 1.1 6,000 1.1 1.2 9,000,000,000 K 0.8 4,900 0.9 0.4 20,000,000,000 M 0.3 3,000 0.4 0.04 75,000,000,000 ------------------------------------------------------------