1. The problem statement, all variables and given/known data Consider energy generation in the Sun. Fusion through the pp cycle takes place within its core which has r = 0.2 Rs T = 1.3 x 10 ^ 7 K rho (density) = 1.1 x 10 ^ 5 kg m^-3 X (total mass fraction of hydrogen) = 0.34 The nuclear energy generation rate for the pp cycle (where T6 = T/10^6K and density has units of kg m ^ -3) is Epp = (0.241) (rho) (X^2) (T6 ^ (-2/3) ) exp (-33.8/(T6 ^ 1/3)) W kg ^ -1 Estimate epp per unit mass mass. 2. Relevant equations Epp = (0.241) (rho) (X^2) (T6 ^ (-2/3) ) exp (-33.8/(T6 ^ 1/3)) W kg ^ -1 3. The attempt at a solution I subbed everything in: Epp = (0.241) (1.1 x 10 ^ 5) (0.1156) ( 13 ^ -2/3) exp (-33.8/ (13 ^ 1/3)) (T6 is 13, because it says in the question that T6 = T/10^6K) and I got 3.186 x 10 ^ -4 as my final answer, I assume the unit is W kg ^ -1 because it was given in the formula. The bit I'm confused by is that in the question it specifies "estimate epp PER UNIT MASS MASS." That bit I havent a clue about... did I do it wrong? Thanks for any help!