The Sun converts mass into energy ==> available fuel = eff x MSun x
Fuel Consumption rate = Luminosity
===> lifetime = Fuel/L = (0.007)x2x1030x(3x108)/4x1026 = 3.2x1017 s = 100 billion years
The Sun burns only the inner 10 % of its hydrogen during its main sequence lifetime ===> Main Sequence Lifetime = 10 billion years.
lifetime ~ 1010 years / M3
where we measure masses in multiples of the mass of the Sun. We then have:
Star formation can persist in the Milky Way galaxy for several billion more years.