1. The problem statement, all variables and given/known data If the exponent, α, in the mass-luminosity relationship is 3.0, estimate the lifetime of the above star. (You can assume that the Sun’s lifetime is 1 x 10^10 years). 2. Relevant equations L*/Lsun = (M*/Msun)^α lifetime ∝ M/L ∝ M^-2 3. The attempt at a solution The solution is given as: For a 20Msun star Lifetime = 20^-2 x 1 x 10^10 yrs = 25 x 10^6 yrs Could anyone explain to me how this solution has been arrived at? Thank you.