  We suggest to use operator product expansion and QCD sum rule techniques to
estimate the long-distance contribution to the amplitude of the exclusive rare
decay $B\to K^* \gamma$. In contrast to a phenomenological description in terms
of $\psi$ resonances converting into a photon, the virtual charm quark loop
interacting with soft gluons is represented by a new quark-gluon-photon
operator. The matrix element of this operator is calculated in the same
approximation as the matrix element of the leading magnetic penguin operator.
The overall correction is found to be small, not more than about 5%.
