Massive stars are found, and, because of their age, are probably formed,
in cluster cores. When the stars begin to shine, strong stellar
winds of ≳ 103 km s-1 exert a tremendous force on any remaining gas,
which has at the same time been heated and expands at the sound speed
(~10 km s-1). The gas will be rapidly expelled from
cluster core in much less than a core crossing time. This reduces the
potential of the core, dramatically affecting the dynamics of the core
stars. This process is simulated using NBODY2 to follow the
distributions of massive stars over a few crossing times for various
initial gas fractions. The core of massive stars is found to remain
intact for a core gas fraction of 4 (or equivalently, a star formation
effeciency of 20%). The space and velocity distributions are also
investigated.