The formation of cosmic strings causes a change in the metric of space-time. This change in the gravitational field creates particles, including photons, neutrinos, and gravitons. An estimate is made of the power and total energy output per unit length of string formed. For a grand-unification-scale string the total energy output is about ${10}^{30}$ ergs ${\mathrm{cm}}^{\mathrm{-}1}$, with a power output during the time of formation of about ${10}^{68}$ ergs ${\sec }^{\mathrm{-}1}$ ${\mathrm{cm}}^{\mathrm{-}1}$.

• Received 1 June 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.1369