Astrophysical implications of new light Higgs bosons

We explore the consequences of the existence of a new light pseudoscalar particle, such as the axion. Thermal energy can be converted into axions through annihilation ($e^{+}{e}^{-}\to \gamma h$), photoproduction ($\gamma e\to \mathrm{he}$), and plasma decay (${\gamma }_p\to \gamma h$). Explicit expressions for the cross sections and decay lifetimes are given. We conclude that axion production can occur in advanced stages of stellar evolution and in the big-bang creation of the universe. The most dramatic effect, however, is expected during gravitational collapse of massive stars where axions may help trigger a supernova explosion.