  We have used existing data on the one-proton-removal cross section of 9C at
285 MeV/u and Glauber model calculations to extract the asymptotic
normalization coefficient for the wave function of the last proton in the
ground state of 9C. The calculations are done first using folded potentials
starting from two different effective nucleon-nucleon interactions and second
in the optical limit using three nucleon-nucleon interactions, and the results
are found to be consistent, with no new parameters adjusted. We find
C^2(p3/2)+C^2(p1/2)=1.22+/- fm-1. From this result we obtain the astrophysical
factor for the proton radiative capture reaction 8B(p,gamma)9C as
S_18(0)=46+/-6 eVb. The calculated energy dependence of the astrophysical
S-factor for the energy region Ecm=0-0.8 MeV and the reaction rates for T_9=0-1
are included. PACS no(s): 26.65.+7; 25.60.Dz,25.60.Gc; 24.10.-i; 27.20.+n
