  We calculate the gravitational wave power density emitted by quantum thermal
sources. As particular cases, we calculate the emission of gravitational waves
from the cosmic microwave background and from stellar sources. We study how
treating gravity classically affects the prediction of the thermal emission. We
find that the predicted emitted gravitational wave radiation does not exhibit
an ultraviolet divergence, even if gravity is treated classically, as long as
the fields describing the thermal source are quantum mechanical.
