I am trying to solve a set of four coupled equations through NDSolve. However, I am getting the error "NDSolve::ndsz: step size is effectively zero; singularity or stiff system suspected.." I think this is a common error when there exists very large or very big numbers, but I can't see any such numbers in my system. So, I am worried what could be the reason ? The set of equations are given below :
eqn1 = M'[a] +
Log[10]/Sqrt[1/3 (B[a] 10^(-3 a) + R [a] 10^(-4 a) )] (1/M[a]) ^2;
eqn2 = R'[a] + 10^a/M[a] M'[a] B[a];
eqn3 = B'[a] - 1/M[a] M'[a] B[a];
eqn4 = s'[a] + 3 s[a] Log[10] +
1/ (s[a]^((1/3))) B[a]/(M[a] 10^a) M'[a];
sol1 = NDSolve[{eqn1 == 0 , eqn2 == 0, eqn3 == 0,
eqn4 == 0, M[2] == 2, R[2] == 1,
B[2] == 0.001, s[2] == 0.1}, {M, R, B , s}, {a, 2, 8}]