Gravitational bremsstrahlung in plasmas and clusters

We study the gravitational bremsstrahlung owing to collisions mediated by a $1/r$ potential. We combine classical and first order Born approximation results in order to construct an approximate gravitational ``Gaunt factor'' for the total emitted energy. We also obtain the cross section with an angular momentum cutoff and hence the cross section for emission via close hyperbolic encounters in a gravitating cluster. These effects are the dominant source of very high frequency gravitational noise in the Solar System. The total gravitational wave power of the Sun is 76±20 MW.