1. The problem statement, all variables and given/known data I have to find the average luminosity of a 9 solar mass protostar as it contracts. What I know about the star M = 1.79x10^34 g (Mass) R = 2.94x10^11 km (Radius) p = 1.67x10^-16 g/cm^3 (Initial number Density) Tff = 2.07x10^13 s <---(Gravitational free-fall) 2. Relevant equations What equation am I suppose to use? 3. The attempt at a solution I have looked around and can only find http://books.google.ca/books?id=2QVm...um=3&ct=result [Broken] and the standard luminosity equation but I don't know the temperature so I can't use that. I have no idea how to do this. Any help would be appreciated.